Method and apparatus for adjusting the intermediate flexion balance during knee joint replacement surgery

Abstract

A method and apparatus for joint balance adjustment for joint replacement procedures is disclosed. An example of a knee balance adjustment fixture may include a tibial positioning guide and / or at least one balance adjustment assembly configured to be mounted on a tibial reference in a generally medial-lateral orientation at a generally anterior position relative to the knee. The balance adjustment assembly may include a vertical guide configured to be releasably mounted on the tibial positioning guide in a generally downward-upward orientation, at least one posteriorly extending paddle selectively movable vertically along the vertical guide, the paddle configured to selectively engage with the distal femur and / or proximal tibia, and / or at least one pin guide selectively movable vertically along the vertical guide, the at least one pin guide including at least one opening configured to receive at least one of a drill bit and a bone pin.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority to U.S. Patent Application No. 18 / 127,250, filed on March 28, 2023, entitled "METHODS AND APPARATUS FOR MID - FLEXION BALANCING DURING KNEE ARTHROPLASTY", the entire contents of which are hereby incorporated by reference for all purposes.

[0002] Technical Field The present disclosure is directed to surgical devices and methods, and more particularly, to surgical devices for use in joint replacement and related methods for balancing a joint at flexions other than 0 degrees and 90 degrees.

Background Art

[0003] Referring to Figure 1, this disclosure considers that in full extension, the lateral and medial femoral condyles included in a normal human knee joint contact the tibial plateau anterior to the anterior-posterior midline, and the contact of the lateral femoral condyle in full extension is anterior to the contact of the medial femoral condyle. As the knee joint is repositioned from full extension to full flexion (approximately 160 degrees, which varies depending on anatomical constraints and the individual's ability to flex the knee), the contact of the lateral femoral condyle with the tibial plateau moves progressively posteriorly until approximately 120 degrees of flexion is reached. After reaching this amount of flexion, the lateral femoral condyle leaves the tibial plateau and descends slightly along the posterior surface of the tibia. In contrast, the medial femoral condyle first moves posteriorly from full extension to intermediate flexion (ranging from 60 to 80 degrees), and then moves anteriorly as the knee progressively flexes to full knee flexion. Therefore, compared to the lateral femoral condyle, the medial femoral condyle remains more centrally on the tibial plateau throughout knee flexion, primarily due to the medial collateral ligament (MCL) resisting excessive posterior medial condyle movement. This disclosure considers that some total knee arthroplasty (TKA) designs sometimes attempt to induce excessive medial condyle rollback, causing the MCL to become too tight and resist weight-bearing knee flexion. The contact patterns exhibited by the medial and lateral femoral condyles result in a fan-like movement pattern, where the lateral femoral condyle rotates around the medial femoral condyle in a non-circular pattern. As shown in the movement pattern in Figure 1, the movement of both the medial and lateral femoral condyles throughout the flexion range of motion is progressive in nature, excluding sudden, jerky changes in direction.

[0004] This disclosure considers that when arthritis or degeneration causes structural changes to the contact surfaces of the knee joint that the body cannot adequately repair, it may be time for a patient to consider total or partial knee replacement. Knee replacement involves surgical replacement of the contact surfaces of the knee joint with orthopedic implants; partial knee replacement replaces a portion of the contact surfaces, while total knee replacement replaces all of them. The long-standing concept of total knee replacement has yielded superior survival outcomes at follow-up of more than 10 years in both individual surgeon, institution, and large registry data. These concepts may include coronal alignment, resection of the distal femur, proximal tibia, and posterior femur, as well as balancing of the medial and lateral collateral ligaments.

[0005] Regarding Figures 2 and 3, this disclosure considers that when the anterior cruciate ligament (ACL) is resected for posterior cruciate-retaining (PCR) total knee arthroplasty (TKA), the femoral condyles experience highly abnormal or contradictory movement patterns, where the biomechanics are often the opposite of those of a normal knee, and the knee often experiences sliding due to progressive knee flexion rather than rollback. Figure 2 shows the lateral condyle movement patterns for five subjects underwent PCR TKA, and Figure 3 shows the medial condyles for the same subjects. These subjects experienced highly erratic movement patterns, the opposite of normal knee movement patterns. In posterior cruciate-retaining (PCR) TKA, the ACL is sacrificed while the posterior cruciate ligament (PCL) remains intact. Without the ACL, the PCL no longer has the counterforce to ensure a smooth movement pattern. In posterior stabilized (PS) total knee arthroplasty (TKA) and posterior cruciate sacrificing (PCS) TKA, both the ACL and PCL are sacrificed. The cruciate ligaments in PS and PCS TKA, as well as the sacrificed ACL in PCR TKA, can cause the femoral condyles to slide and move in abnormal ways.

[0006] This disclosure considers that the total knee arthroplasty (TKA) knee joint often exhibits femoral condyle movement opposite to that of a normal knee, and that one or both femoral condyles may slide forward before reaching mid-flexion. The movement patterns of the TKA femoral condyles, as reflected in Figures 2 and 3, can be "jerky" or oscillating, involving abrupt changes in direction near mid-flexion, which patients may perceive as knee joint instability and experience anxiety during normal daily activities.

[0007] Unlike the total knee arthroplasty (TKA) knee joint, this disclosure considers that in full extension, the contact point of the lateral femoral condyle in a normal knee joint begins approximately 5–10 mm anterior to the anterior-posterior midline and progressively moves posteriorly until reaching full flexion, approximately 10–20 mm posterior to the anterior-posterior midline. These contact points from full extension to full flexion allow for greater flexion of the femur relative to the tibia.

[0008] This disclosure considers that numerous studies performed on TKA patients using three-dimensional in vivo fluoroscopy have demonstrated very different kinematic knee joint movement patterns compared to normal knees. These differences in joint movement patterns are presumed to be due to ACL loss in PCR TKA and loss of both cruciate ligaments in PS TKA, as well as improper balance adjustment of the collateral ligaments. Unlike in normal knees, where the lateral femoral condyle contact progressively moves posteriorly with increasing knee flexion, TKA patients often exhibit marked anterior movement during flexion (the opposite of the kinematics of a normal knee). In normal knees, the medial femoral condyle contact begins approximately 0–5 mm anterior to the anterior-posterior midline in full extension and remains very stable even with increasing knee flexion. In TKA patients, the medial femoral condyle often exhibits abnormal movement that reverses direction between full extension and intermediate flexion, resulting in instability in intermediate flexion.

[0009] This disclosure considers that, particularly near mid-flexion, these abnormal medial and lateral femoral condyle contact points often cause patients to notice this abnormal movement and become concerned about stability. During fluoroscopy, it has been observed that patients need to hold onto a handrail or receive support from another person while flexing their knee due to this sliding movement that causes them to feel unstable. In a normal knee, the femoral condyle starts from the anterior aspect of the tibia and moves progressively posteriorly, but the contact pattern in TKA knee joints varies considerably, often resulting in abrupt changes in direction that patients perceive as the femoral condyle sliding on the tibial tray. Thus, when a TKA patient flexes their knee joint, the femur slides forward without rolling back. In addition, during chair rise and step-up maneuvers, the femoral condyle slides posteriorly without rolling forward. In a normal knee, rolling may feel stable to the individual, but in a total knee arthroplasty (TKA) knee joint, abnormal sliding and changes in direction can lead the patient to feel instability during mid-flexion.

[0010] This disclosure considers that during knee replacement surgery, the knee joint is typically balanced in full extension and / or 90 degrees of flexion. Therefore, even though the range in which the patient experiences significant abnormal movement is intermediate flexion, the knee joint is typically not balanced by the surgeon at or near this degree of flexion. Consequently, the lack of balancing within the range of motion between full extension and 90 degrees of flexion may result in the ligaments not being properly balanced throughout the entire range of motion of the knee joint. In addition, this improper balancing may result in improper femoral and tibial transection, or conversely, improper or incorrect bone transection may result in insufficient knee balance. This disclosure considers that if balancing had been performed in the intermediate flexion range, the knee would have felt more stable between full extension and 90 degrees of flexion, because, for example, the amount of transition to full extension or 90 degrees of flexion would be only about 45 degrees. Understanding ligament balancing near intermediate flexion may provide knowledge about ligament length, strain, and force for improving joint balancing in knee arthroplasty. Unfortunately, knee balancing in full extension and / or 90 degrees of flexion is often done passively, by sensation. Therefore, no load is applied to the bearing surface, and the ligaments are not strained. This form of knee balancing can be the cause of knee instability and the patient's feeling that something is slipping in their knee.

[0011] Therefore, in the art, it is necessary to perform ligament balancing of the knee joint in knee arthroplasty, including balancing at least near intermediate flexion of the joint. In some embodiments of at least some aspects of this disclosure, intermediate flexion may include angles such as approximately 30 to 70 degrees, but instability in intermediate flexion also appears at other flexion angles between full extension (0 degrees) and 90 degrees away from full extension. In this manner, the knee joint in knee arthroplasty is balanced at angles near where many of the abnormal movements of the orthopedic knee joint may exist when knee arthroplasty is not balanced between full extension and 90 degrees away from full extension.

[0012] In this technical field, there is also a need for surgical instruments and devices specifically designed to facilitate the adjustment of ligamental balance in knee arthroplasty at angles encompassing full extension and intermediate flexion angles between full extension and 90 degrees, specifically angles ranging from approximately 30 to 70 degrees from full extension. [Overview of the Initiative] [Means for solving the problem]

[0013] Aspects of the present disclosure provide a knee balance adjustment fixture for an arthroplasty procedure, the knee balance adjustment fixture comprising: a tibial positioning guide configured to be mounted on a tibial reference in a generally medial-lateral orientation at a generally anterior position to the knee, including the femur and tibia; and / or at least one balance adjustment assembly. The at least one balance adjustment assembly comprises: a vertical guide configured to be releasably mounted on the tibial positioning guide in a generally downward-upward orientation; at least one posteriorly extending paddle selectively movable vertically along the vertical guide, the at least one paddle configured to selectively engage with at least one of the distal femur and the proximal tibia; and / or at least one pin guide selectively movable vertically along the vertical guide, the at least one pin guide comprising at least one opening configured to receive at least one of a drill bit and a bone pin.

[0014] In a detailed embodiment, at least one balance adjustment assembly may include at least two balance adjustment assemblies, the at least two of which include a medial balance adjustment assembly configured to be releasably mounted medially to the tibial positioning guide; and / or a lateral balance adjustment assembly configured to be releasably mounted laterally to the tibial positioning guide.

[0015] In a detailed embodiment, at least one paddle of the medial balance adjustment assembly may be configured to selectively engage with at least one of the medial condyle of the distal femur and the medial condyle of the proximal tibia; and / or at least one paddle of the lateral balance adjustment assembly may be configured to selectively engage with at least one of the lateral condyle of the distal femur and the lateral condyle of the proximal tibia.

[0016] In a detailed embodiment, at least one paddle may include two paddles, including an upper paddle and a lower paddle. The upper paddle may be configured to selectively engage with the distal femur. The lower paddle may be configured to engage with the proximal tibia.

[0017] In a detailed embodiment, at least one pin guide may include two pin guides, including a femoral pin guide and a tibial pin guide. The femoral pin guide may be configured for use related to positioning a femoral pin within the femur. The tibial pin guide may be configured for use related to positioning a tibial pin within the tibia.

[0018] In a detailed embodiment, the knee balance adjustment jig may include a tibial reference. In a detailed embodiment, the tibial reference may include a tibial extramedullary rod.

[0019] In a detailed embodiment, the knee balance adjustment jig may include a femoral positioning guide configured for attachment to a tibial reference. The femoral positioning guide may include a receiving device configured to engage with the femoral reference. In a detailed embodiment, the femoral positioning guide may be configured to engage with the femoral reference at a fixed angle associated with an intermediate flexion position of the knee. The intermediate flexion position of the knee may substantially correspond to the posterior chamfer cut angle of the femoral implant associated with the joint replacement procedure.

[0020] In a detailed embodiment, the intermediate knee flexion position may be between approximately 30 degrees of flexion and approximately 70 degrees of flexion. In a detailed embodiment, the intermediate knee flexion position may be between approximately 30 degrees of flexion and approximately 60 degrees of flexion. In a detailed embodiment, the intermediate knee flexion position may be approximately 45 degrees of flexion.

[0021] In a detailed embodiment, the femoral positioning guide may be configured to engage with a femoral reference at an adjustable angle related to the intermediate flexion position of the knee.

[0022] In a detailed embodiment, the knee balance adjuster may include a femur reference. The femur reference may include an intramedullary rod of the femur. The femur reference may include an external femoral component.

[0023] In a detailed embodiment, the knee balance adjuster may include at least one cutting guide. The at least one cutting guide may be configured to guide a cutting device in relation to resection of at least one of the femur and the tibia. The at least one cutting guide may be configured to be attached to at least one of the femur and the tibia using a bone pin associated with an opening of at least one pin guide of at least one balance adjustment assembly.

[0024] In a detailed embodiment, the at least one cutting guide may include two cutting guides including a femur cutting guide and a tibia cutting guide. The femur cutting guide may be configured to guide a cutting device in relation to resection of the femur. The tibia cutting guide may be configured to guide a cutting device in relation to resection of the tibia.

[0025] In a detailed embodiment, the femur cutting guide may include two femur cutting guides including a posterior cutting guide and a femur extension cutting guide. The posterior cutting guide may be configured to guide a cutting device in relation to posterior cutting of the femur. The femur extension cutting guide may be configured to guide a cutting device in relation to femur extension cutting of the femur.

[0026] In a detailed embodiment, at least one paddle extending rearwardly may include at least one adjustable engagement feature. The adjustable engagement feature may be repositionable in a front - rear direction.

[0027] Aspects of the present disclosure provide a method of preparing the knee to receive a knee implant, the method comprising positioning the knee, including the distal femur and proximal tibia, at an intermediate flexion angle; performing soft tissue balance adjustment of the knee at the intermediate flexion angle; determining the position of a posterior cut of the distal femur configured to engage the posterior surface angle of the femoral component of the knee implant based at least in part on the soft tissue balance adjustment of the knee at the intermediate flexion angle; and excising the distal femur to create the posterior cut.

[0028] In a detailed embodiment, the intermediate flexion angle may substantially correspond to the posterior surface angle of the femoral component of the knee implant. In a detailed embodiment, the intermediate flexion angle may be between about 30 degrees of flexion and about 70 degrees of flexion. In a detailed embodiment, the intermediate flexion angle may be between about 30 degrees of flexion and about 60 degrees of flexion. In a detailed embodiment, the intermediate flexion angle may be about 45 degrees of flexion.

[0029] In a detailed embodiment, the method may include performing soft tissue balance adjustment of the knee with respect to the posterior cut; determining the position of a tibial plateau cut configured to engage the tibial component of the knee implant based at least in part on the soft tissue balance adjustment of the knee with respect to the posterior cut; and / or excising the proximal tibia to create the tibial plateau cut.

[0030] In a detailed embodiment, the method may include positioning the knee at full extension; performing soft tissue balance adjustment of the knee with respect to the tibial plateau cut; determining the position of a femoral extension cut configured to engage the femoral component of the knee implant based at least in part on the soft tissue balance adjustment of the knee with respect to the tibial plateau cut; and / or excising the distal femur to create the femoral extension cut.

[0031] In a detailed embodiment, the method may include positioning the knee at approximately 90 degrees of flexion; balancing the soft tissues of the knee for a tibial plateau transection; determining the position of a femoral flexion transection configured to engage with the femoral components of a knee implant, at least partially based on balancing the soft tissues of the knee for a tibial plateau transection; and / or resecting the distal femur to create a femoral flexion transection.

[0032] In a detailed embodiment, the method may include determining the location of a femoral flexion cut that is configured to engage with a femoral component of a knee implant, at least partially based on the size of the femoral component determined using an anterior reference guide; and / or resecting the distal femur to make the femoral flexion cut.

[0033] In a detailed embodiment, the use of an anterior reference guide may include positioning the movable stylus of the anterior reference guide on the anterior surface of the distal femur; and / or using the movable stylus to translate the posterior indicator of the anterior reference guide.

[0034] In detailed embodiments, the forward reference guide may include a rear face cutting contact surface; and / or the use of the forward reference guide may include positioning the rear face cutting contact surface over the rear face cutting.

[0035] In a detailed embodiment, adjusting the soft tissue balance of the knee at an intermediate flexion angle may include adjusting the soft tissue balance of the knee at an intermediate flexion angle relative to the tibial plateau transection of the proximal tibia.

[0036] In a detailed embodiment, this method may include resecting the proximal tibia to create a tibial plateau transection before adjusting the soft tissue balance of the knee at an intermediate flexion angle relative to the tibial plateau transection of the proximal tibia.

[0037] In a detailed embodiment, adjusting the soft tissue balance of the knee at an intermediate flexion angle may include applying a linear separation force to the bones, including the knee, using a gap tensioner.

[0038] In a detailed embodiment, applying a linear separation force to the knee bones using a gap tensioner may include inserting a first paddle and a second paddle into the gap between the knee bones; and / or applying a linear separation force to the knee bones using the first paddle and the second paddle.

[0039] In a detailed embodiment, applying a linear separation force to the knee bone using the first and second paddles may also include applying a torsional force to a gap tensioner, which converts the torsional force into a linear separation force.

[0040] In a detailed embodiment, applying a torsional force to the gap tensioner may include applying a torsional force to the actuating shaft of the gap tensioner using a torque wrench.

[0041] Aspects of the present disclosure provide an intramedullary rod comprising a straight shaft having a predetermined length, the straight shaft comprising a surgical-grade material, and the straight shaft comprising a collar that distinguishes the proximal portion of the straight shaft for insertion into a bone canal from the distal portion of the straight shaft extending outward from the bone canal.

[0042] Aspects of the present disclosure provide a set of guides for knee arthroplasty, the set of guides including a femoral guide configured to be fitted to the distal femur; and / or a tibial guide configured to be fitted to the proximal tibia. The femoral guide and / or tibial guide may be configured to engage with each other and lock at an angle of 30 to 70 degrees between the longitudinal axis of the distal femur and the longitudinal axis of the proximal tibia.

[0043] In a detailed embodiment, the set of guides may include a medial condyle insert configured to measure the gap between the medial condyle of the distal femur and the medial condyle receiver of the proximal tibia; and / or a lateral condyle insert configured to measure the gap between the lateral condyle of the distal femur and the lateral condyle receiver of the proximal tibia. The medial condyle insert and / or the lateral condyle insert may be configured to be repositionably mounted on at least one of the femoral guide and the tibial guide.

[0044] In a detailed embodiment, the medial condylar insert and / or the lateral condylar insert may be configured to be repositionably mounted on a tibial guide; the medial condylar insert may include at least two paddles that vary the distance between them by being repositionable relative to each other; and / or the lateral condylar insert may include at least two paddles that vary the distance between them by being repositionable relative to each other.

[0045] In a detailed embodiment, at least two paddles of the medial condyle insertion portion may be configured to engage with the medial guide of the tibial guide, and the medial guide and at least one of the at least two paddles include an indicia for determining the distance between the opposing surfaces of the at least two paddles from each other; and / or at least two paddles of the lateral condyle insertion portion may be configured to engage with the lateral guide of the tibial guide, and the lateral guide and at least one of the at least two paddles include an indicia for determining the distance between the opposing surfaces of the at least two paddles from each other.

[0046] In a detailed embodiment, the set of guides may include a medial condyle drill guide and / or a lateral condyle drill guide. The medial condyle drill guide and / or lateral condyle drill guide may be configured to be repositionably mounted on at least one of the femoral guide and the tibial guide.

[0047] In a detailed embodiment, the medial condyle drill guide and / or the lateral condyle drill guide may be configured to be repositionably mounted on the tibial guide. In a detailed embodiment, the medial condyle drill guide may be configured to engage with the medial guide of the tibial guide, and at least one of the medial guide and the medial condyle drill guide includes a mark for determining the distance between a reference point and the medial condyle drill guide; and / or the lateral condyle drill guide may be configured to engage with the lateral guide of the tibial guide, and at least one of the lateral guide and the lateral condyle drill guide includes a mark for determining the distance between a reference point and the lateral condyle drill guide.

[0048] In a detailed embodiment, the set of guides may include a medial condyle receiving drill guide and / or a lateral condyle receiving drill guide. The medial condyle receiving drill guide and / or the lateral condyle receiving drill guide may be configured to be repositionably mounted on at least one of the femoral guide and the tibial guide.

[0049] In a detailed embodiment, the medial condyle receiving drill guide and the lateral condyle receiving drill guide may be configured to be repositionably mounted on the tibial guide.

[0050] In a detailed embodiment, the medial condyle receiving drill guide may be configured to engage with the medial guide of the tibial guide, and at least one of the medial guide and the medial condyle receiving drill guide includes a mark for determining the distance between a reference point and the medial condyle receiving drill guide; and / or the lateral condyle receiving drill guide may be configured to engage with the lateral guide of the tibial guide, and at least one of the lateral guide and the lateral condyle receiving drill guide includes a mark for determining the distance between a reference point and the lateral condyle receiving drill guide.

[0051] In a detailed embodiment, the set of guides may include a cutting guide for a posterior cross section. The posterior cross section guide may be configured to engage with artificial features on the distal femur for aligning the cutting guide for the posterior cross section with respect to the distal femur in order to perform a posterior cross section.

[0052] In a detailed embodiment, the set of guides may include a tibial cutting guide. The tibial cutting guide may be configured to engage with an artificial mechanism on the proximal tibia for aligning the tibial cutting guide with respect to the proximal tibia in order to perform a tibial plateau cut.

[0053] In a detailed embodiment, the set of guides may include a femoral extension amputation guide. The femoral extension amputation guide may be configured to engage with an artificial mechanism on the distal femur for aligning the femoral extension amputation guide with respect to the distal femur in order to perform a femoral extension amputation.

[0054] In a detailed embodiment, the set of guides may include anterior cross-section cutting guides. The anterior cross-section cutting guides may be configured to engage with an artificial mechanism on the distal femur for aligning the anterior cross-section cutting guides with respect to the distal femur in order to perform an anterior cross-section.

[0055] In a detailed embodiment, the tibial guide may include an extramedullary rod configured to extend longitudinally along the tibia; the tibial guide may include a crossbeam operably coupled to the extramedullary rod; the tibial guide may include a first guide configured to traverse along the crossbeam; and / or the tibial guide may include a second guide configured to traverse along the crossbeam.

[0056] In a detailed embodiment, the set of guides may include a medial condylar insertion configured to traverse a first guide, wherein the medial condylar insertion is configured to measure the gap between the medial condyle of the distal femur and the medial condylar socket of the proximal tibia; and / or a lateral condylar insertion configured to traverse a second guide, wherein the lateral condylar insertion is configured to measure the gap between the lateral condyle of the distal femur and the lateral condylar socket of the proximal tibia.

[0057] In a detailed embodiment, the set of guides may include an inner condyle drill guide configured to traverse a first guide; and / or an outer condyle drill guide configured to traverse a second guide.

[0058] In a detailed embodiment, the set of guides may include an inner condyle receiving drill guide configured to traverse a first guide; and / or an outer condyle receiving drill guide configured to traverse a second guide.

[0059] Aspects of the present disclosure provide a method for performing knee arthroplasty, the method comprising: attaching a femoral guide to the distal femur; aligning and engaging a tibial guide with the femoral guide, such that the angle between the femoral guide and the tibial guide is 30 to 70 degrees; attaching a tibial guide to the proximal tibia; using the tibial guide to establish the position and orientation of at least one of the cutting guides for a posterior femoral resection; using the posterior femoral resection guide to perform a posterior resection at at least one condyle of the distal femur; resecting the proximal tibia to remove at least a portion of the bone that was previously underlying at least one condylar socket; and / or resecting at least one condyle of the distal femur, the resection being angled 30 to 70 degrees with respect to the posterior resection.

[0060] Aspects of the present disclosure provide a method for performing knee arthroplasty, the method comprising: fixing the orientation of the distal femur relative to the proximal tibia such that the longitudinal axis of the distal femur is angled 30 to 70 degrees with respect to the longitudinal axis of the proximal tibia; while the longitudinal axis of the distal femur is angled 30 to 70 degrees with respect to the longitudinal axis of the proximal tibia, balancing at least one of (i) the medial portion of the knee joint including the distal femur and the proximal tibia, and (ii) the lateral portion of the knee joint including the distal femur and the proximal tibia; determining the spacing between at least one of (i) the medial condyle of the distal femur and the medial condylar socket of the proximal tibia, and (ii) the lateral condyle of the distal femur and the lateral condylar socket of the proximal tibia, once the balancing is complete; and / or using a posterior femoral resection guide to perform a posterior resection at at least one condyle of the distal femur before performing an anterior or distal resection.

[0061] Aspects of the present disclosure provide a method for performing knee arthroplasty, the method comprising: fixing the orientation of the distal femur relative to the proximal tibia such that the longitudinal axis of the distal femur is angled 30 to 70 degrees with respect to the longitudinal axis of the proximal tibia; while the longitudinal axis of the distal femur is angled 30 to 70 degrees with respect to the longitudinal axis of the proximal tibia, balancing at least one of (i) the medial portion of the knee joint including the distal femur and the proximal tibia, and (ii) the lateral portion of the knee joint including the distal femur and the proximal tibia; determining the spacing between at least one of (i) the medial condyle of the distal femur and the medial condylar socket of the proximal tibia, and (ii) the lateral condyle of the distal femur and the lateral condylar socket of the proximal tibia, once the balancing is complete; and / or using a tibial resection guide to perform a tibial plateau resection at at least one condyle of the proximal tibia before performing an anterior femoral resection or a distal femoral resection.

[0062] Aspects of the present disclosure provide a gap tensioner for a balance adjustment fixture for a joint replacement procedure, the gap tensioner comprising: a first engaging element configured to operably couple with a first paddle of a balance adjustment assembly; a second engaging element configured to operably couple with a second paddle of a balance adjustment assembly; and an operating mechanism configured to change the distance between the first engaging element and the second engaging element; the balance adjustment fixture comprising a first paddle and a second paddle positioned on a guide, the first and second paddles configured to be positioned between the bones of a joint; and / or the balance adjustment assembly configured such that at least one of the first and second paddles is movable along the guide to widen the gap between the bones of a joint.

[0063] In detailed embodiments, the gap tensioner may include a housing; the first engaging element may be linearly slidable relative to the housing; and / or the second engaging element may be rigidly positioned relative to the housing.

[0064] In detailed embodiments, the operating mechanism may include a rack and pinion mechanism. The rack and pinion mechanism may include a pinion rotatably mounted on a housing and / or a rack fixedly mounted to a first engaging element.

[0065] In a detailed embodiment, the gap tensioner may include an operating shaft operably coupled to a pinion, the operating shaft configured to receive an input torsional force.

[0066] One aspect of this disclosure is to provide an apparatus including the gap tensioner and / or balancing assembly described above.

[0067] Aspects of the present disclosure provide a device for balancing a knee joint as part of a knee joint replacement procedure, the device comprising: (i) a first paddle operably coupled to a second paddle, the first and second paddles configured to be positioned between the femur and tibia of a knee joint, and at least one of the first and second paddles being repositionable relative to each other to change the linear distance between them; and (ii) a gap tensioner including a clutch configured to reposition at least one of the first paddles relative to the second paddle, the gap tensioner being operable to convert an applied force into the movement of at least one of the first and second paddles to increase the linear distance between the first and second paddles when it is not overcome by a resistive force arising from resistance to an increase in the gap between the femur and tibia of a knee joint resulting from ligament tension from ligaments extending over the femur and tibia.

[0068] Aspects of the present disclosure provide a device for adjusting the balance of a knee joint as part of a knee joint replacement procedure, in a more detailed embodiment, a first paddle is coupled to a first engagement element, a second paddle is coupled to a second engagement element, and at least one of the first and second engagement elements is repositionable along a common rail.

[0069] Aspects of the present disclosure provide a device for balancing a knee joint as part of a knee joint replacement procedure, in a more detailed embodiment the gap tensioner includes a rack engaged by a pinion, at least one of the rack and pinion being repositionable perpendicular to each other, and the rack and pinion are alternatively operably coupled with first and second paddles.

[0070] Aspects of the present disclosure provide a device for balancing a knee joint as part of a knee joint replacement procedure, in a more detailed embodiment, a pinion is operably coupled to an operating shaft configured to rotate the pinion by being rotated, and a clutch is sandwiched between the pinion and the operating shaft.

[0071] Aspects of the present disclosure provide a device for balancing a knee joint as part of a knee joint replacement procedure, in a more detailed embodiment the device includes a tibial positioning guide configured to be detachably coupled to the tibia, the tibial positioning guide includes a horizontal rail, the device is repositionable along the horizontal rail, first and second paddles are operably coupled to a vertical rail perpendicular to the horizontal rail, and at least one of the first and second paddles is repositionable perpendicular to the vertical rail. [Brief explanation of the drawing]

[0072] [Figure 1] This figure shows a plot of movement patterns relative to a normal knee joint, illustrating the anterior-posterior positions of the medial and lateral condyles at various degrees of flexion. [Figure 2] This figure shows a plot of the anterior-posterior position of the lateral condyle as a function of flexion angle for five subjects who underwent implantation in total knee arthroplasty with posterior cruciate ligament preservation. [Figure 3] This figure shows a plot of the anterior-posterior position of the medial condyle as a function of flexion angle for five subjects who underwent total knee arthroplasty with posterior cruciate ligament preservation. [Figure 4] This figure shows a plot of force as a function of flexion for the medial and lateral condyles of a normal knee. [Figure 5] This figure shows a bar graph illustrating the percentage of total force applied to the medial and lateral condyles at various bending angles. [Figure 6]This figure plots quadriceps force as a function of flexion angle for a normal knee and a knee with an implant. [Figure 7A] This figure shows one of the sequential, simplified lateral cross-sectional views of a knee joint undergoing femoral and tibial resection in connection with a total knee replacement procedure. [Figure 7B] This figure shows one of the sequential, simplified lateral cross-sectional views of a knee joint undergoing femoral and tibial resection in connection with a total knee replacement procedure. [Figure 7C] This figure shows one of the sequential, simplified lateral cross-sectional views of a knee joint undergoing femoral and tibial resection in connection with a total knee replacement procedure. [Figure 7D] This figure shows one of the sequential, simplified lateral cross-sectional views of a knee joint undergoing femoral and tibial resection in connection with a total knee replacement procedure. [Figure 7E] This figure shows one of the sequential, simplified lateral cross-sectional views of a knee joint undergoing femoral and tibial resection in connection with a total knee replacement procedure. [Figure 7F] This figure shows one of the sequential, simplified lateral cross-sectional views of a knee joint undergoing femoral and tibial resection in connection with a total knee replacement procedure. [Figure 7G] This figure shows one of the sequential, simplified lateral cross-sectional views of a knee joint undergoing femoral and tibial resection in connection with a total knee replacement procedure. [Figure 7H] This figure shows one of the sequential, simplified lateral cross-sectional views of a knee joint undergoing femoral and tibial resection in connection with a total knee replacement procedure. [Figure 8] This is a perspective view showing a connected (mated) intramedullary femoral rod of an example knee balance adjustment jig. [Figure 9] This is a side view showing the intramedullary femoral rod connected to the receiving device of the knee balance adjustment jig. [Figure 9A] This is a perspective view showing an alternative receiving device 140A configured for bending at approximately 90 degrees. [Figure 9B]This is a perspective view showing an alternative receiving device 140B configured for bending at approximately 60 degrees. [Figure 9C] This is a perspective view showing an alternative receiving device 140C configured for bending at approximately 30 degrees. [Figure 10A] This is a perspective view showing an example of a knee balance adjustment jig when a balance adjustment assembly is installed and used on the knee joint. [Figure 10B] This is an exploded perspective view showing an example of a balance adjustment assembly. [Figure 10C] This is a perspective view showing an example of a knee balance adjustment jig with the receiving device and balance adjustment assembly installed. [Figure 10D] This is a side elevation view showing an example of an alternative balance adjustment assembly that includes a posteriorly adjustable tibial element. [Figure 10E] Figure 10D is a side elevation view showing a balance adjustment assembly with an anteriorly adjustable tibial element. [Figure 10F] Figures 10D and 10E show perspective views illustrating examples of balance adjustment assemblies. [Figure 11] This is a perspective view showing a balance adjustment jig used when a spacer establishes the position of the femoral pin. [Figure 12] This is a perspective view showing the knee after a femoral pin has been implanted. [Figure 13] This is an anterior view showing the femur with a posterior cross-section guide in place. [Figure 14A] This is an anterior view showing a posterior cross-section of the femur. [Figure 14B] This is a lateral view showing the femur in a posterior cross-section. [Figure 15] This is a perspective view showing a balance adjustment jig used in the knee after posterior transection. [Figure 15AB] Figure 15A is a perspective view showing an alternative balance adjustment jig used in the knee after posterior amputation, and 15B is a perspective view showing the alternative balance adjustment jig of Figure 15A used in the knee after posterior amputation. [Figure 16A]This is a detailed perspective view showing an example of a balance adjustment assembly including a pin-to-pin spacer for establishing the desired vertical separation between the femoral and tibial pins. [Figure 16B] This is a perspective view showing a knee balance adjustment jig when an inversion-valgus alignment device is installed. [Figure 17] This is a perspective view showing the knee with a tibial pin in place. [Figure 18] This is a perspective view showing the knee when a tibial amputation guide is in place. [Figure 19] This is an anterior view of the tibia showing a tibial plateau section. [Figure 20] This is a lateral view of the knee showing a tibial plateau section and a posterior section. [Figure 21] This is a front view showing an example of an alternative tibial plateau section guide. [Figure 22] This is a side view showing an example of an alternative tibial plateau section guide. [Figure 23] This is a perspective view showing a knee balance adjustment jig used in the knee after tibial plateau amputation. [Figure 24] This is a side view showing the knee rotated to the fully extended position. [Figure 25] This is a perspective view showing a knee balance adjustment jig used in preparation for femoral extension amputation. [Figure 26] This is a frontal view of the knee when a femoral extension amputation guide is in place. [Figure 27] This is a lateral view of the knee showing femoral extension transection, tibial plateau transection, and posterior transection. [Figure 28] This is a perspective view showing a knee balance adjustment jig used in the knee for posterior referencing. [Figure 29] This is a perspective view showing a knee balance adjustment jig used in the knee after femoral flexion amputation. [Figure 30] This is a side view of the distal femur showing various cuts in preparation for the placement of a femoral implant. [Figure 31A]This is a perspective view showing an example of a forward reference guide. [Figure 31B] Figure 31A is a side view showing the forward reference guide. [Figure 32] This is a distal view showing the anterior reference guide used in the femur. [Figure 33] This is a perspective view showing the anterior reference guide used in the femur. [Figure 34A] This is a terminal diagram showing an anterior reference guide, including an alternative anterior stylus used in the femur. [Figure 34B] This is a perspective view showing an anterior reference guide, including an alternative anterior stylus used in the femur. [Figure 35A] This is a perspective view showing the unicompartmental use of the knee balance adjustment jig. [Figure 35B] This is a perspective view showing the single-compartment use of the knee balance adjustment jig. [Figure 36A] This is a perspective view showing an example of a gap tensioner positioned on a balance adjustment assembly. [Figure 36B] This is a perspective view showing an example of a gap tensioner positioned on a balance adjustment assembly. [Modes for carrying out the invention]

[0073] Exemplary embodiments of this disclosure are described below to encompass surgical instruments and related methods for performing knee joint replacement procedures. While the following discussion may refer to total knee arthroplasty (TKA), it should be understood that for the purposes of this specification, TKA is intended to also encompass partial knee arthroplasty (PKA), unicompartmental knee arthroplasty (UKA), and revision knee arthroplasty (RKA). Wherever any surgical instrument and technique described herein is specific to PKA, UKA, or RKA, the relevant discussion will be included. Otherwise, any reference to TKA is intended to encompass PKA, UKA, and RKA. In addition, any reference to “patient” herein includes living and deceased humans, as well as any living or deceased non-human mammals. Of course, it will be apparent to those skilled in the art that the embodiments discussed below are illustrative and may be reconfigured without departing from the scope and spirit of the invention. However, for clarity and accuracy, the exemplary embodiments discussed below may include optional steps, methods, and features that those skilled in the art should recognize are not essential to the scope of the invention.

[0074] This disclosure considers that there are two main methods for performing knee replacement to achieve the alignment and position of the femoral and tibial components as part of the TKA procedure. In the first method, commonly known as the “Gap Balanced” technique, the patient’s knee joint is first distracted in extension or 90 degrees of flexion, meaning that the tension of the collateral ligaments is “balanced,” and then the femur and proximal tibia are resected. The conventional concept of bone distance removal of 9 mm from the non-defective distal femoral condyle and 4 mm from the defective tibial condyle may be used, and the resection is performed in varus and valgus in both the femur and tibia to achieve a neutral functional axis (i.e., the leg is “straight” when the ends of the bones are aligned together). Depending on whether the proximal tibia or the distal femur is resected first, there are implications for the subsequent ligament balance that is achieved. The gap balance adjustment technique is expected to result in a rectangular or near-rectangular shape between the ends of the bones, with a known distance, where this rectangle contains the same dominant distance in full extension and 90 degrees of flexion.

[0075] In contrast, the disclosure considers that a second most common method, known as “measured resection” technique, requires a surgeon to take measured amounts of bone from the distal femur and proximal tibia (similar to gap-balancing technique) and then make releases as needed to create a rectangle of known distance. It is assumed that a rectangle of known (and equal) distance is created by removing equal amounts of bone from the posterior and distal femur and making any releases. The disclosure considers that this assumption that a rectangle is desirable in either method, and where this rectangle should be placed, may be flawed in some situations.

[0076] The disclosure acknowledges that it is desirable for the rectangle to be rectangular and that the position of the rectangle may be based on at least four inherent, poorly defined assumptions: 1) the assumption that a rectangle of constant distance is created in extension and flexion; 2) the assumption that the width of the rectangle does not change over a 90-degree arc motion (from extension to 90-degree flexion); 3) the assumption that the balanced ligaments are equidistant in the positions of extension and flexion; and 4) the assumption that the rectangular arrangement in three planes can be determined by making cuts at two different angles (distal femur and proximal tibia) without knowing the precision of the planes brought to the femur and tibia.

[0077] This disclosure considers that in a computer-navigated study of TKA knees, it was found that after first creating a “mechanically neutral” proximal tibial and distal femoral resection, followed by an anterior-posterior (AP) femoral resection, an average of two “releases” were required for the placement of trial components to achieve a balanced knee (balance is defined as equal “force” being obtained medially and laterally via tibial sensors when a “heel push test” is performed throughout the full range of motion). Interestingly, it was suggested that the bone resections were performed separately and the total force applied was only (120–145 Newtons per manuscript). Notably, there was a tendency for increasing the thickness of the tibial insertion by 2 millimeters to increase the total force by approximately 70%, indicating that stability could be achieved. In most manufacturing processes for orthopedic implant components, this level of inaccuracy would result in a process redesign. In total knee arthroplasty (TKA), such inaccuracies can lead to intermediate flexion and flexion relaxation, as well as patient dissatisfaction. This disclosure acknowledges that inherent inaccuracies can occur regardless of whether gap-balancing or measurement-resection techniques are used.

[0078] This disclosure considers that the fundamental issue in ligament balancing is not only achieving some kind of relationship between the medial and lateral collateral ligaments, but also agreeing on where this relationship should occur. In studies performed on the medial and lateral collateral ligaments, these ligaments were divided into three parts (anterior, intermediate, and posterior) and in vivo changes in ligament length during flexion were investigated. Generally, over the range of motion from full extension to at least 90 degrees of flexion, the length of the anterior fibers increased, the intermediate fibers remained unchanged, and the length of the posterior fibers decreased. Applying these observations to gap balancing techniques reveals the mechanical conflict in ligament balancing caused by the technique itself. Understanding the length of the ligaments, particularly the medial collateral ligament (MCL), and the range of length changes observed from extension to 90 degrees of flexion, suggests that balancing in flexion and extension results in a relaxed MCL in intermediate flexion.

[0079] This disclosure considers that, after a proximal tibial resection has been performed, when the knee is held in flexion, the ligaments are balanced, and the posterior resection is marked, gap balancing can be reduced to a simple imposition of a predetermined distance between the ends of the two bones (one of which must be cut first). However, a resection performed without reference to the previous cut (except anteriorly) may result in a larger or smaller gap posteriorly. The same problem arises when performing a distal femoral resection in extension. The amount of anterior bone to be resected is planned based on the distance identified in flexion, but its execution often fails to maintain a constant flexion-extension axis. Thus, resections / cuts that are not linked in plane differ from anterior to posterior. Therefore, a gap-balanced knee may maintain a constant anterior distance between the anterior aspect of the femoral resection(s) and the proximal tibial resection, but not a constant posterior distance. Empirical evidence suggests that when using gap balance adjustment techniques, the creation of a consistent rectangle is almost never achieved, which is one of the factors contributing to flexion laxity. In addition, the lengths of the MCL and lateral collateral ligament (LCL) vary between full extension and flexion beyond 90 degrees. Therefore, when gap balance adjustment techniques are initially based on flexion balance adjustment, the "gap" identified in flexion leads to excessive resection of the distal femur, and again to laxity in intermediate flexion. Furthermore, when the distal femur is resected after the proximal tibia, followed by posterior femoral resection, this often results in excessive resection of the posterior femur. These same problems occur even when using measurement resection techniques.

[0080] This disclosure considers that despite the technical appearance of a successful TKA (full range of motion, varus / valgus and anterior-posterior stability, and radiographic confirmation of proper placement of components), at least 25% of patients report dissatisfaction with their reconstructed knee joint. Typical problems include, but are not limited to, persistent pain, instability, quadriceps pain, and swelling. Essentially, what is happening is anterior translation of the tibial components relative to the femoral components, which is equivalent to the knee with an anterior cruciate defect. The clinical diagnosis of what this factor is can be divided into two possibilities (or both) based on where the knee exhibits laxity to stress: (a) intermediate flexion, defined as increased varus / valgus opening to stress at 30–60 degrees of flexion; or (b) flexion, defined as increased anterior laxity at 90 degrees of flexion. Generally, because these conditions are present, the knee is stable in full extension (i.e., no opening to varus / valgus reaction forces).

[0081] This disclosure considers that flexion laxity at 90 degrees of flexion is often easier to diagnose than intermediate flexion laxity. The clinical finding of flexion laxity is generally recognized as anterior-posterior (AP) laxity greater than 5 mm at 90 degrees of flexion, although some supplementary explanations may be given. With respect to an arbitrary midpoint sagittal axis defined by the femoral components, the tibial components are either directly below (neutral), anterior, or posterior to this axis. The knee should be pushed posteriorly to the maximum position defined by the post of the posteriorly stabilized component that strikes the femoral cam, or where the posterior translation is stopped by the posterior cruciate ligament. From this position, the leg is suspended (note that performing this test with the patient lying down may affect the findings due to the weight of the thigh and the fit of the tibial liner) and the knee is pulled forward, and the laxity is graded as less than 5 mm, 5-10 mm, or greater than 10 mm. The laxity can also be evaluated by applying pressure to the varus and valgus of the knee and noting where the initiation of femoral rotation occurs. A sign called "hanging clunk" is defined, which represents a reduction of the tibia relative to the posterior femur. This clunk can be identified by testing deep tendon reflexes or by having the patient quickly straighten their knee from 90 degrees of flexion and observing the superior parallel movement of the tibia before leg extension. Intermediate flexion laxity is also considered to be present at this level of laxity.

[0082] This disclosure acknowledges that diagnosing laxity in intermediate flexion is more difficult. Testing of varus / valgus stability at 30 degrees of flexion may suggest laxity of one or both collateral ligaments.

[0083] This disclosure considers that the current state of preparation and procedures for performing TKA does not address or assess the laxity observed when femoral and tibial transsections are performed without planar reference (relationship) to each other, nor does it suggest where orthopedic implants should be placed within the soft tissue envelope. Briefly, the precise assignment of a constant rectangle of known width from extension to 90 degrees of flexion is not achieved. From a biomechanical standpoint, if the distance of the rectangle is not constant when the knee begins to flex, the increasing distance results in anterior translation of the tibia. This may be counteracted by the contraction of the quadriceps. Over the first 90 degrees of movement, the tibial components do not maintain a constant distance relationship with respect to the femoral components, but rather oscillate forward, then downward due to the force of the quadriceps, then oscillate again, resulting in a sinusoidal curve over the first 90 degrees of flexion.

[0084] This disclosure considers that a major concern regarding gap balance adjustment is the inaccuracy of determining the tension or spacing on each side. When a surgeon attempts gap balance adjustment and hopes to achieve 50% tension on the lateral ligament and 50% tension on the medial ligament or 50% compression on each condyle, but does not do so accurately, the patient may have 60-80% tension or compression on one side and 20-40% on the other. This can result in an imbalance and the abnormal kinetics discussed previously. Having greater tension on one side or greater compression on one slide can lead to excessive abnormal sliding of one condyle, resulting in abnormal or opposite axial rotation.

[0085] Figure 4 is a plot of forces as a function of flexion for the medial and lateral condyles of a normal knee, and Figure 5 is a bar graph showing the percentage of total force given to each of the medial and lateral condyles at various flexion angles. Referring to Figures 4 and 5, this disclosure considers that in a normal knee joint, the femorotibial forces interacting at the medial femoral condyle are higher than those interacting at the lateral femoral condyle. The femorotibial forces passing through the medial femoral condyle are always about 60–70% of the total force, while the lateral femoral condyle accounts for 30–40% of the total knee force. In extreme cases, the femorotibial forces passing through the medial femoral condyle can be more than 2.5X of the forces passing through the lateral femoral condyle.

[0086] This disclosure considers that while forces in a normal knee are not symmetrical, surgeons may attempt to balance the knee gap in the hope of having equal forces on the medial and lateral condyles. Unfortunately, this can sometimes be done under passive conditions and without reliable instruments to ensure that the goal is equal to the result. Furthermore, despite asymmetrical loading before surgery, TKA surgery may be intentionally performed to obtain symmetrical loading. This may be the reason why the axial rotation of an implanted knee is considerably less than that of a normal knee.

[0087] This disclosure considers that in a normal knee joint, the lateral femoral condyle experiences more rollback during knee flexion, allowing the axial rotation of the lateral femoral condyle relative to the medial femoral condyle to remain more central, and the lateral femoral condyle, with less force, to rotate around the medial femoral condyle. In addition, in a normal knee, the shape of the femoral condyles is asymmetrical, as are the ligamentary balance adjustments and soft tissue forces. When a surgeon attempts to adjust the gap balance in a TKA, the surgeon is altering the balance of the knee, which can result in a hinge-like movement pattern in which both condyles move symmetrically and exhibit significantly less axial rotation. In a normal knee, the knee experiences approximately 27 degrees of axial rotation on average, whereas in the average TKA joint, an abnormal axial rotation pattern is observed with substantially less axial rotation (on the order of less than 3 degrees). When surgeons attempt to balance the knee with equal gap and tension, the result is often that the TKA knee experiences minimal axial rotation, no axial rotation at all, or even the opposite axial rotation.

[0088] Figure 6 plots quadriceps force as a function of flexion angle for a normal knee and an implanted knee. Referring to Figure 6, this disclosure considers that when the TKA joint is improperly balanced (e.g., unbalanced in intermediate flexion), the sliding of the femoral components can trigger a quadriceps response that can be considerably greater than necessary. Because the quadriceps force fires considerably earlier for a TKA than for a normal knee, higher quadriceps forces can be achieved at deeper flexions. The force that the quadriceps can exert to drive knee movement is limited, and when the maximum is used, the implanted knee can no longer flex further. Movement in an implanted knee has been shown to be statistically less than in a normal knee. This sliding of the femoral components induces the quadriceps to exert greater force in an attempt to stabilize the knee joint. Unfortunately, the quadriceps can only provide maximum force, and since this force is necessary to stabilize the TKA joint in initial flexion, some patients may reach their flexion limit at approximately 70–90 degrees of flexion due to the fact that their quadriceps become too tight and exceed their maximum allowable force too early. Figure 6 reflects data obtained during an in vivo study measuring the applied quadriceps force as a function of flexion angle for normal and TKA joints during weight-loading activity. In a normal knee joint, quadriceps force increases from full extension, on the order of a 3X increase when 90 degrees of flexion is reached. In contrast, quadriceps force for a TKA joint increases quite dramatically from full extension, on the order of a 6.5X increase when 90 degrees of flexion is reached. These higher quadriceps forces result in abnormal knee mechanism and less weight-loaded flexion than desired in the TKA joint.

[0089] According to this disclosure, it has been found that balancing the TKA joint in or near intermediate flexion prevents most, if not all, of the aforementioned problems that occur when balancing the TKA joint in other positions such as full extension (0-degree flexion) or flexion beyond 90 degrees. Specifically, balancing the TKA joint in intermediate flexion may allow for less muscle force (e.g., quadriceps) by keeping the knee joint more stable during weight-bearing activities, and may enable a larger range of motion during weight-bearing knee flexion.

[0090] The Disclosure considers that ligament balancing may result in the provision of rectangles on the surfaces of two bones (distal femur, proximal tibia), where the rectangles should be positioned, using conventional concepts of requirements for measuring resection (as described above; requiring the removal of some bone, the removal of which cannot impair the origin (one or more) or insertion (one or more) of the collateral ligaments) and / or gap balancing. Some exemplary techniques of the Disclosure may differ from others by providing a rectangle for symmetrical balancing or a trapezoid for asymmetrical balancing with six degrees of freedom, where each cutting plane (varus-valgus, anterior-posterior, and rotation) in the femur and tibia is closely related to and parallel to the corresponding cutting plane (e.g., varus-valgus isosceles ligament balancing of tibial cutting followed by varus-valgus femoral cutting, with the level of resection based on the known TKA principle).

[0091] This disclosure considers that when a surgeon balances the knee in full extension and / or 90 degrees of knee flexion under passive conditions, the ligaments are not subjected to load, and as the knee flexes or extends away from the balance point, the ligaments may not remain balanced at different degrees of flexion and / or extension. This disclosure considers that instances of maximum instability or laxity in the knee may occur during intermediate flexion, which may result in abnormal knee kinetics and excessive sliding. Patients may experience this sliding sensation, leading to a lack of confidence due to the knee not feeling stable.

[0092] Generally, some method examples according to at least some aspects of this disclosure include measuring ligament tension and compartment gaps of the knee at an angle corresponding to (or near) the femoral plane angle. When the knee is positioned at that angle, ligament and compartment information is obtained and recorded. The first cut is a femoral plane cut. Then, a tibial cut is made relative to the femoral plane cut. Alternatively, the first cut may be a tibial cut, and then a femoral plane cut may be made relative to the tibial cut. The knee is measured again in this orientation so that ligament length and tension and the distance between cuts are maintained and recorded. The knee is then reoriented to full extension so that ligament length and tension and compartment gaps are appropriately positioned and referenced with respect to the information obtained and recorded at the knee plane angle. Then, a femoral extension cut is made. Thus, the femoral component plane cut is at the same distance from the tibial cut, and the femoral extension cut is also at the same distance from the tibial cut. In addition, the ligament tension and length measured between a tibial transection and a surface transection are the same as those measured between an extension transection and a tibial transection.

[0093] Figures 7A–7H are sequential simplified side cross-sectional views of a knee joint undergoing femoral and tibial resection in connection with an example of a total knee arthroplasty (TKA) procedure, all according to at least some aspects of this disclosure. The following description with reference to Figures 7A–7H is intended to provide an overview and context of the methods and apparatus described in detail below.

[0094] Referring to Figure 7A, the knee joint 108 is positioned at a desired degree of flexion. For example, the knee joint 108 is positioned such that the flexion angle 108A between the femur 110 (e.g., femoral canal axis 124) and the tibia 112 (e.g., tibia longitudinal axis 174) is a desired intermediate flexion angle, such as about 45 degrees. In some embodiments, the balancing of the TKA joint according to this disclosure is performed at or near the intermediate flexion of the femur 110 relative to the tibia 112. In exemplary embodiments, the posterior angle 122A of the TKA may coincide with the intermediate flexion angle of the knee joint 108 (e.g., about 45 degrees between the femur 110 and tibia 112). For example, the posterior section 122 may be angled about 45 degrees with the femoral canal axis 124. By determining the posterior angle 122A with respect to the fixed axis (e.g., the femoral canal axis 124, also known as the intramedullary femoral canal), the surgeon can determine the angle at which the distal femur 110 should be oriented relative to the proximal tibia 112 so that the posterior resection 122 can be performed first. For example, when the posterior angle is 45 degrees, the distal femur 110 may be repositioned by the surgeon so that it is angled approximately 45 degrees relative to the proximal tibia 112. In this manner, some TKA procedures according to at least some aspects of the present disclosure may involve performing a posterior resection 122 as the first resection of the distal femur 110.

[0095] Referring to Figure 7B, the posterior cross section 122 is performed with the knee 108 balanced at a desired intermediate flexion angle. Referring to Figure 7C, the position and orientation of the tibial plateau cross section 278 are determined, for example, by balancing the knee 108 with reference to the posterior cross section 122. Referring to Figure 7D, the tibial plateau cross section 278 is performed. Referring to Figure 7E, the distance between the posterior cross section 122 and the tibial plateau cross section 278 is determined.

[0096] In some alternative methods, a tibial plateau section 278 may be performed first. Then, a posterior section 122 may be performed, for example, by balancing the knee 108 with reference to the tibial plateau section 278. In some such methods, the posterior section 122 may be performed after the tibial plateau section 278, but the posterior section 122 may be the first section at the femur 110.

[0097] Referring to Figure 7F, the knee 108 is positioned in full extension. The position and orientation of the femoral extension cut 296 are determined. Referring to Figure 7G, the distance between the tibial plateau cut 278 and the femoral extension cut 296 may be matched to the distance between the posterior cut 122 and the tibial plateau cut 278 (Figure 7E), for example, by selecting the position of the femoral extension cut 296 along the femoral canal axis 124 to yield the desired shape. Referring to Figure 7H, the femoral extension cut 296 is made. In various method examples, additional measurements, balancing, and / or cuts may be performed to prepare the knee 108 for implant trials and to receive orthopedic implants.

[0098] Figure 8 is a perspective view of a femoral intramedullary rod connected to a receiving device of an example knee balance adjustment jig, and Figure 9 is a side view of a femoral intramedullary rod connected to a receiving device of a knee balance adjustment jig, all of which are according to at least some aspects of the present disclosure. Referring to Figures 7A, 7B, 8, and 9, a posterior section 122 can be achieved in several ways. For example, an opening 130 is drilled in the distal femur 110 just above the apex of the intercondylar notch 132 such that a drill bit (not shown) for bone removal to create the opening is coaxial with the femoral canal axis 124 in both the coronal (anterior) and sagittal (lateral) planes. After the opening 130 is drilled, an intramedullary rod 134 is inserted into the opening 130 and positioned to be fixed within the opening, with a portion of the intramedullary rod 134 extending distally from the femur 110. In the exemplary embodiment, the intramedullary rod 134 includes a straight shape in the longitudinal direction and has a circular cross-section perpendicular to that straight shape.

[0099] In various embodiments, the intramedullary rod 134 may have a circular, elliptical, square, rectangular, or any other cross-section suitable for connection with other components described below. The intramedullary rod 134 may include a stop device that is coplanar with the femur on the outer surface of the intramedullary canal so that the entire rod 134 does not sink into the intramedullary canal. Thus, when this stop device is coplanar with the bone, a portion of the intramedullary rod protrudes outward. In some alternative embodiments, an extramedullary rod may be replaced with the intramedullary rod 134.

[0100] The femoral placement guide 140 engages with the intramedullary rod 134 and is used to properly locate various components throughout the rest of the TKA procedure. In exemplary embodiments, the placement guide 140 may include a receiving device including a cylindrical collar 144, which may be in the form of a hinged catcher's mitt-like receiving section or any shape capable of receiving the intramedullary rod 134 at a specified flexion angle. The collar 144 includes a cylindrical through-hole, which is sized to accommodate the throughput of at least a portion of the intramedullary rod 134 extending distally from the femur 110 and is positioned to receive the rod 134 at a specified angle. In further examples, the through-hole is dimensioned with a relatively tight inner circumference tolerance relative to the outer circumference of the intramedullary rod 134 so that the rod slides freely against the collar 144, but there is not enough play for the collar to move along an axis angled greater than 5 degrees with respect to the longitudinal axis of the intramedullary rod. In exemplary embodiments, the collar 144 may include a set screw 146 or other retaining device for fixing the longitudinal movement of the collar relative to the intramedullary rod 134 when it reaches a desired position. In alternative embodiments, the receiving device or catcher's mitt may have any preferred shape for connecting to the intramedullary rod. The receiving device 144 may have the same diameter or dimensions as the intramedullary rod 134, or it may be larger to allow any relative movement if necessary. For illustrative purposes, the movement of the collar 144 relative to the intramedullary rod 134 will be described as angular motion along two axes: the Z-axis and the Y-axis perpendicular to the Z-axis.

[0101] In some alternative embodiments, one or more external femoral components may be used instead of, or in addition to, the intramedullary rod 134. For example, an extramedullary rod and / or an external clamp or positioning component may be used as an external femoral component.

[0102] A molded shaft 148 extends from the collar 144. In this exemplary embodiment, the molded shaft 148 may be repositionably or fixedly mounted on the outer circumference of the collar 144 and may be angled to incorporate a predetermined angle relative to the collar. When not fixed, the shaft 148 may be rotatable in one or three directions and / or translatable in one or three directions. In the shown embodiment, the predetermined angle may be, for example, 35 to 55 degrees (e.g., about 45 degrees), and this also depends on the implant and implant surface angle. Other similar embodiments may relate to other predetermined angles described elsewhere in this specification, such as intermediate bend angles which are bends of approximately 30 to 70 degrees. In any case, the molded shaft 148 is generally straight and incorporates a shape that allows the follower 150 to traverse along the molded shaft in a linear manner. In the exemplary embodiment, the molded shaft 148 may include a constant rectangular cross-section or other constant cross-sectional shapes that facilitate motion along a single axis.

[0103] For example, the follower 150 may include a first molding opening sized to accommodate the throughput of at least a portion of the molding shaft 148. In a further example, the opening is dimensioned by a relatively tight internal tolerance relative to the outside tolerance of the molding shaft 148 so that the follower 150 slides freely relative to the molding shaft, but does not have enough play for movement of the follower along an axis angled greater than 5 degrees with respect to the longitudinal axis of the molding shaft. In this way, the interaction between the molding shaft 148 and the follower 150 provides adjustment in only one of the three axes. For explanatory purposes, the vertical motion of the follower 150 relative to the molding shaft 148 will be described as motion along the Y-axis. If the cross-section of the molding shaft 148 is rectangular, the cross-section of the first molding opening may be a corresponding rectangle, or it may be coupled around it in a different way to restrict the motion of the molding shaft to occur along only a single axis. In some embodiments, these components may also be able to rotate around one or more axes and then be locked to achieve a suitable angle when correctly positioned.

[0104] In an exemplary embodiment, the follower 150 may include a set screw 156 or other retaining device for fixing the vertical movement of the follower relative to the molding shaft 148 when it reaches a desired vertical position and / or orientation. As will be discussed in more detail thereafter, after balancing of the knee joint in or near intermediate flexion is achieved, the relative positions of the femoral positioning guide 140, the follower 150, and the tibial positioning guide 160 are fixed relative to each other.

[0105] In this exemplary embodiment, the follower 150 also includes a second forming opening 162 sized to accommodate the throughput of at least a portion of the beam 166 of the tibial placement guide 160. As a further example, the opening 162 is dimensioned by a relatively tight internal tolerance relative to the external tolerance of the beam 166 so that the follower 150 slides freely relative to the beam, but does not have enough play for movement of the follower along an axis angled greater than 5 degrees with respect to the longitudinal axis of the beam. In this way, the interaction between the beam 166 and the follower 150 provides adjustment in only one of the three axes. For explanatory purposes, the horizontal movement of the follower 150 relative to the beam 166 will be described as movement along the X-axis, where the X-axis is perpendicular to both the Y-axis and the Z-axis. In other words, the movement of the follower 150 along the beam 166 occurs along an axis perpendicular to the axis along which the follower 150 traverses the forming shaft 148. If the cross-section of the beam 166 is rectangular, the cross-section of the second forming opening 162 may be a corresponding rectangle, or it may be coupled around the periphery in a different way to restrain the beam's motion so that it occurs only along a single axis, i.e., the X-axis.

[0106] In exemplary embodiments, in addition to the beam 166, a tibial placement guide 160 may be positioned on a tibial reference such as a cylindrical rod 170, the cylindrical rod 170 may include an extramedullary tibial rod extending perpendicularly from the beam. In the shown embodiment, the tibial placement guide 160 is mounted to the rod 170 generally anterior to the knee 108, so that the beam 166 is oriented generally in a medial-lateral direction. When the tibial placement guide 160 is properly aligned, the cylindrical rod 170 may extend substantially parallel to the longitudinal axis of the tibia 174 and / or be fixed to the patient's lower leg.

[0107] The adjustment of the receiving device 144 relative to the tibial rod 170 may allow for translation and orientation changes, thereby enabling the retrieving device to be properly connected to the femoral rod 134. As shown in the drawings, various components may be placed on and removed from the tibial placement guide 160 as needed throughout the TKA procedure example. In addition, for clarity and ease of viewing, it should be understood that some drawings in this specification may not include components that remain in place step by step in some procedure examples.

[0108] In practice, an opening 130 is drilled into the distal femur 110, and an intramedullary rod 134 is inserted therein, after which a portion of the intramedullary rod extends distally from the femur. The collar 144 is then positioned along the intramedullary rod 134 by repositioning the femoral placement guide 140. After positioning the collar 144 around the intramedullary rod 134, or during or before this, the follower 150 is positioned to traverse along the molding shaft 148, in addition to the follower engaging with and traversing along the beam 166. In exemplary embodiments, the component parts of the femoral placement guide 140 and the tibial placement guide 160 allow the component parts to be repositioned so that the cylindrical rod 170 is positioned adjacent to the tibial tuberosity and parallel to the longitudinal axis of the tibia 174, while the collar 144 circumscribes the intramedullary rod 134. Once this configuration is reached, the component parts are fixed to each other, so that the collar 144 is fixed in place relative to the intramedullary rod 134 (for example, by tightening a set screw 146), and the follower 150 is fixed in place relative to the molding shaft 148 (for example, by tightening a set screw 156). By fixing the femoral position guide 140 in a fixed position relative to the intramedullary rod 134, the movement of the femoral position guide 140 along the Z axis is suppressed. Similarly, by fixing the femoral position guide 140 in a fixed position relative to the follower 150, the movement of the follower along the Y axis is suppressed. The follower 150 is fixed to the beam 166 using, for example, one or more set screws 168.

[0109] Figure 10A is a perspective view of example knee balance adjustment fixture 188 when the balance adjustment assembly 190 is installed and in use on the knee joint 108; Figure 10B is an exploded perspective view of example balance adjustment assembly 190; and Figure 10C is a perspective view of example knee balance adjustment fixture with the receiving device and balance adjustment assembly installed, all of which are in accordance with at least some aspects of the present disclosure. The knee balance adjustment fixture 188 may be configured and / or used for any flexion angle, but its use is described below in relation to an example of an intermediate flexion balance adjustment approach.

[0110] In an exemplary embodiment, the knee balance adjustment jig 188 is initially used in connection with making a posterior plane cut 122 in the femur 110. With the knee 108 fixed at a desired initial flexion angle, for example using a receiving device 140 and an intramedullary rod 134 and / or an external fixation, the balance adjustment jig 188 is used to balance the ligament. In the shown embodiment, the knee is held in an intermediate flexion of approximately 45 degrees, this flexion corresponding to an appropriate plane angle for the intended implant. In other embodiments, the intermediate flexion position may be, for example, knee flexion from approximately 30 degrees to approximately 75 degrees. Since alternative femoral component designs may have different plane angles, in some embodiments the receiving device 140 may be adjustable to rotate to an appropriate angle corresponding to the plane angle of the femoral component.

[0111] In some embodiments, the receiving device 140 may be modular and / or removable / replaceable in a balancing fixture 188, and multiple receiving devices 140 corresponding to different face angles may be provided. Figure 9A is a perspective view of an alternative receiving device 140A configured for a bend of about 90 degrees, Figure 9B is a perspective view of an alternative receiving device 140B configured for a bend of about 60 degrees, and Figure 9C is a perspective view of an alternative receiving device 140C configured for a bend of about 30 degrees, all of which are according to at least some aspects of the present disclosure. Generally, when the face angle is 45 degrees, the receiving device 140 used by the surgeon may be angled at a fixed angle of 45 degrees. Alternatively, appropriate receiving devices 140A, 140B, and 140C may be selected and used for other face angles. Furthermore, other positioning devices, such as external fasteners or external positioners, may also be used.

[0112] In some procedure examples, the intramedullary rod 134 may be removed from the femur 110 and from the collar 144. In addition, the femoral positioning guide 140 and follower 150 may be removed from the tibial positioning guide 160, leaving the tibial positioning guide 160 attached to the tibia and held in place via the tibial extramedullary rod 170. The knee position may be maintained using, for example, an external fixation device. In other procedure examples, the intramedullary rod 134 and receiving device 140 may remain in place and / or be used to maintain the knee position.

[0113] Referring to Figures 10A-10C, the example knee balance adjustment jig 188 may include a pair of balance adjustment assemblies 190 mounted on a beam 166, one of which is positioned generally medially (e.g., for use in the medial condyle) and the other balance adjustment assembly is positioned generally laterally (e.g., for use in the lateral condyle). In the exemplary embodiment, the balance adjustment assembly 190 may include a vertical guide 192 having a rectangular cross-section. The cross-section of the vertical guide 192 may differ from a rectangular cross-section and may include any other shape (e.g., triangle, circle, quadrilateral or more) that is repeatedly reproduced vertically to maintain a constant or near-constant horizontal cross-section. In this exemplary embodiment, the vertical guide 192 is configured to be releasably mounted on the tibial positioning guide 160 in a generally downward-upward orientation. For example, in the shown embodiment, the vertical guide 192 includes an adapter 194 configured to engage with the beam 166 to hold the three-dimensional position of the vertical guide relative to the beam. In the shown embodiment, the adapter is removably secured to the beam 166 using set screws. Both sides are open to allow inward / outward sliding.

[0114] One exemplary component of the balance adjustment assembly 190 may include a paddle 200, which may extend generally posteriorly relative to the vertical guide 192. For example, the balance adjustment assembly 190 may include one or more paddles 200, such as an upper paddle and a lower paddle. One or more paddles 200 may be used to measure the distance between the tibia 112 and the femur 110, as will be discussed in more detail later. In an exemplary embodiment, the paddle 200 may include a connector 202 configured to engage with the vertical guide 192 to allow selective vertical repositioning of the paddle relative to the vertical guide. For example, the connector 202 may include an opening or cavity 206 that is similar in cross-section to the vertical guide 192 but slightly larger to accommodate the throughput of the vertical guide. The connector 202 may also include a set screw 208 or a spring-loaded projection that extends into the cavity 206 and is used to selectively secure the paddle 200 to the vertical guide 192. A blade 210 extends from the connector 202, and in an exemplary embodiment, the blade 210 has its main longitudinal dimension extending from the connector and has a rectangular profile in both the horizontal and vertical directions. As an example, the blade 210 may embody a cuboid shape. Other shapes may also be used, such as a spoon or a shape that mimics the shape of each condyle obtained preoperatively. This may be achieved by preoperative imaging. Another shape may be a rectangular shape. In some embodiments, the blade 210 may be fairly thin while being sufficiently rigid to perform the balancing function described herein. This shape may also be patient-specific, based on the shape of the patient's condyles.

[0115] Although not required, the vertical dimension (i.e., thickness) of the paddle 200 may be constant along its longitudinal length. Furthermore, although not required, the horizontal width dimension across the entire paddle 200 may be constant. Furthermore, although not required, the horizontal length across the paddle 200 may be constant. Furthermore, although not required, the uppermost and lowermost surfaces of the blade 210 and the connector 202 may be coplanar with each other. In this manner, measurements involving the uppermost or lowermost surface of the blade 210 can be easily used.

[0116] Another exemplary component of the balancing assembly 190 may be one or more pin guides 220. For example, the pin guide 220 may include a coupler 222 configured to engage with a vertical guide 192 to allow selective vertical repositioning of the pin guide relative to the vertical guide. For example, the coupler 222 may include an opening or cavity 226 that is similar in cross-section to the vertical guide 192 but slightly larger to accommodate the throughput of the vertical guide. The coupler 222 may also include a set screw 227 or a spring-loaded projection that extends into the cavity 226 and is used to selectively secure the pin guide 220 to the vertical guide 192. A pin flange 230 extends from the coupler 222, and in an exemplary embodiment, this pin flange 230 includes an opening 232 configured to receive the throughput of at least one of a drill bit and a bone pin, as described below.

[0117] Although not a requirement, the vertical dimension (i.e., thickness) of the pin guide 220 may be constant. In this configuration, measurements can be easily taken at the top or bottom surface of the pin flange 230.

[0118] Specifically, referring to Figure 10A, before the vertical guides 192 are mounted on the beam 166 during use, each vertical guide may be fitted with a pair of paddles 200 and pin guides 220. In an exemplary embodiment, the paddles 200 mounted on each vertical guide 192 are oriented so that they overlap each other, so that the paddles of the medial vertical guide 192 are positioned to be sandwiched between the articular surface of the medial femoral condyle and the articular surface of the medial tibial condyle. Similarly, the paddles of the lateral vertical guide 192 are oriented to be sandwiched between the articular surface of the lateral femoral condyle and the articular surface of the lateral tibial condyle.

[0119] While the knee joint 108 is bent to approximately 45 degrees or another desired intermediate flexion angle (e.g., the same angle as the posterior cross-section angle) and held in place (e.g., using an external fastener not shown), the surgeon performs soft tissue balancing on the medial and lateral sides of the knee. As part of this soft tissue balancing, the surgeon manipulates the spacing of the overlapping paddles 200 on both the medial and lateral sides until the desired balance is achieved. After the desired balance is achieved on both the medial and lateral sides, the surgeon records the spacing of the paddles on both sides (medial and lateral), for example, by using the position of the paddles 200 relative to the vertical guide 192. If the vertical guide 192 includes measurement markings, the spacing of the paddles 200 may be recorded using these markings, or simply by using the position of the connector 202 relative to the vertical guide.

[0120] In some embodiments, components connected to bone may be adjustable to accommodate different bone sizes. For example, a portion of a balance assembly connected to the tibia may be adjustable (e.g., in anterior-posterior directions) for use with tibias of different sizes. Figure 10D is a side elevation view of an alternative balance assembly example 190A including a tibial element adjustable to a posterior position; Figure 10E is a side elevation view of the balance assembly 190A of Figure 10D having a tibial element adjustable to an anterior position; and Figure 10F is a perspective view of the balance assembly examples 190A of Figures 10D and 10E, all of which are according to at least some aspects of this disclosure. Various elements of the balance assembly 190A are similar in structure and operation to corresponding components in other embodiments described herein, and for brevity, repetitions of description have been omitted. Furthermore, features described in relation to the balance assembly 190A may be used in relation to any other embodiments described herein. For example, in some embodiments, a generally similar adjustable femoral element may be used.

[0121] In the balance adjustment assembly 190A, one of the paddles 200A includes an adjustable engagement mechanism 201A. In the shown embodiment, the engagement mechanism 201A is repositionable linearly in a generally forward-backward direction, for example, between a rearward position shown in Figure 10D and an anterior position shown in Figure 10E. Thus, the tibial element may be adjusted to better fit a particular tibia. In the shown embodiment, the adjustable engagement mechanism 201A may be movable by the operation of an actuator 203A which may be located on the coupling 202A. For example, by sliding and / or rotating the actuator 203A, the engagement mechanism 201A may traverse forward and / or backward along a track formed on the distal side of the paddle 200A.

[0122] Figure 11 is a perspective view of the balance adjustment jig 188 when the spacer 236 establishes the position of the femoral pin, and Figure 12 is a perspective view of the knee when the femoral pin is in place, all of which are according to at least some aspects of the present disclosure. After the desired balance is achieved, the position of one or more femoral pins 234 is determined. In the shown embodiment, the spacer 236 is positioned on the vertical guide 192 on the paddle 200 associated with one of the femoral condyles. Then each pin guide 220 is positioned on the spacer 236 on the spacer 236. Thus, the spacer 236 having known vertical dimensions positions the pin guide 220 at a known position on the paddle 200. A similar procedure is performed for the paddle 200 associated with the other femoral condyle. These steps of paddle extension of the joint then allow for the placement of pins in both the femur and tibia, based on ligament balance and assuming a standard TKA resection level, with a rectangular relationship for symmetrical balance adjustment or a trapezoidal relationship for asymmetrical spacing.

[0123] After the position of each pin guide 220 is finalized, a bone drill bit (not shown) is inserted into the opening 232, with the delineating flange 230 wall acting as a guide for the drill bit. Two holes aligned with each opening 232 are drilled into the distal femur. A pair of bone pins 234 are then inserted into each opening 232 of the pin guide 220 and fixed within the drilled femoral cavity. After the placement of the bone pins 234, the remaining components (pin guide 220, paddle 200, vertical guide 192, tibial placement guide 160) may be removed, resulting in the configuration shown in Figure 12. The tibial guide and / or EM rod may be removed for bone cutting or leg repositioning. The guides and / or rod may be replaced to later reconstruct the previously defined fixed relationship between the femur and tibia (e.g., knee angle in plane cutting).

[0124] The desired ligament tension at the intermediate flexion position may be promoted by first balancing the ligaments near the intermediate flexion plane angle. In some embodiments, the knee balancing jig 188 may include one or more reading devices configured to indicate the gap distance between the medial condyle and the lateral condyle and the lateral condyle and the lateral tibial plateau, and / or the tension in one or more ligaments. Generally, when a surgeon performs gap balancing, the goal is to make these distance measurements equal or approximately equal. When a surgeon attempts anatomical balancing or uses a form of kinematic balancing, the gap distances to the medial and lateral condyles (and subsequently the medial and lateral collateral ligaments) may differ. In any case, these values ​​may be saved and / or recorded for use, for example, as future target values ​​for gaps and tensions at other flexion angles (or in calculating future target values). In some procedure examples, the intermediate flexion readings may be used as a baseline and as the desired gaps and tensions for the individual's knee. As discussed above, intermediate flexion may be an important range of flexion for balance adjustment, and / or it may be easier for the surgeon to maintain this balance in full extension and 90 degrees of knee flexion.

[0125] Figure 36A is a perspective view of an example gap tensioner 500 positioned on a balance adjustment assembly 190, and Figure 36B is a perspective view of the gap tensioner 500, both of which are in accordance with at least some aspects of the present disclosure. Generally, the gap tensioner 500 includes a linear motion mechanism operably coupled between a lower (first) paddle 200A and an upper (second) paddle 200B, thereby changing the vertical distance between the paddles 200A and 200B by operating the mechanism.

[0126] In the shown embodiment, the gap tensioner 500 includes a lower (first) engaging element 502 configured to engage with a coupler 202 associated with a lower paddle 200A, and an upper (second) engaging element 504 configured to engage with a coupler 222 associated with an upper paddle 200B. In the shown embodiment, the lower engaging element 502 is fixedly mounted to the gap tensioner housing 506, and the upper engaging element 504 is slidably positioned vertically relative to the housing 506. The operating shaft 508 is rotatably positioned relative to the housing 506 and is configured to selectively engage with a rotating instrument, such as a torque wrench (not shown).

[0127] The linear motion mechanism may be operably sandwiched between the operating shaft 508 and a movable upper engaging element 504. In the shown embodiment, the linear motion mechanism is generally in the form of a rack and pinion mechanism. A pinion 510 (e.g., a circular gear) is mounted to rotate with the operating shaft 508. A rack 512 (e.g., a linear gear) is mounted to move linearly with the upper engaging element 504, so that the teeth of the rack 512 and the teeth of the pinion 510 mesh with each other. In the shown embodiment, rotation of the shaft 508 in a clockwise direction moves the rack 512 and pinion 510 mechanism toward the upper and lower paddles 200A, 200B toward each other. Rotation of the shaft 508 in a counterclockwise direction moves the rack 512 and pinion 510 mechanism toward the upper and lower paddles 200A, 200B toward each other. In an alternative embodiment, this arrangement may be reversed so that the mechanism moves the lower engaging element 502 relative to the housing 506.

[0128] As described elsewhere in this specification, during operation, the gap tensioner 500 may be used to apply separating forces to the femur and tibia. In the shown embodiment, the torsional force applied to the shaft 508 results in a linear force provided by the paddles 200A, 200B. In the shown embodiment, those skilled in the art will recognize that the linear separating force provided by the paddles 200A, 200B is directly related to the torsional force applied to the shaft 508. Thus, by applying a measured or mechanically limited torsional force to the shaft 508, a desired linear separating force may be applied to the femur and tibia via the paddles 200A, 200B to provide, for example, desired ligament or other soft tissue tension related to a joint replacement procedure. For example, a torque wrench having a clutch mechanism may be set to a specific torque value related to the desired gap tension. The torque wrench may be used to apply torsion to the shaft 508 up to the preset torque value. Alternatively, a torque wrench with a torque readout may be used to apply the desired torque and / or measure the applied torque, which may indicate, for example, ligament tension at a specific gap distance.

[0129] The gap tensioner 500 is shown and described as including a manually operated rack-and-pinion type linear motion mechanism, but the use of any preferred motion mechanism is within the scope of this disclosure. For example, in alternative embodiments, any other mechanical or electromechanical mechanism capable of applying controlled separation forces to the femur and tibia via paddles 200A, 200B may be used.

[0130] In the embodiments shown, the gap tensioner 500 is provided with pin guides 514, 516, which may be substantially similar to other pin guides 220 described herein. In the embodiments shown, the lower pin guide 514 is fixedly positioned relative to the housing 506 of the gap tensioner 500. Thus, the position of one or more openings 518 is fixed relative to the housing 506. As described elsewhere herein, the openings 518 of the lower pin guide 514 may be used to position pins related to tibial transsection guides.

[0131] In the embodiments shown, the upper pin guide 516 may be movably positioned relative to the housing 506 of the gap tensioner 500. For example, the upper pin guide 516 may be slidably positioned vertically on the housing 506. Thus, the vertical position of one or more openings 520 may be adjustable relative to the housing 506. In some embodiments, the upper pin guide 516 may be incrementally adjustable in increments, for example, about 2 mm. In some embodiments, the locking mechanism 522 may be operable to releasably lock the upper pin guide 516 relative to the housing 506. As described elsewhere in this specification, the opening 520 of the upper pin guide 516 may be used to position a pin associated with a femoral cutting guide.

[0132] Figure 13 is an anterior view of the femur with the posterior cross section guide in place, Figure 14A is an anterior view of the femur showing the posterior cross section, and Figure 14B is a lateral view of the femur showing the posterior cross section, all of which are in accordance with at least some aspects of the present disclosure. Referring to Figures 13, 14A, and 14B, the posterior cross section guide 250 is fitted to the distal femur 110 using bone pins 234 for use when performing an excision to create a posterior cross section 122. Specifically, the posterior cross section guide 250 may include a pair of through-holes 252 sized to receive each bone pin 234. In the shown embodiment, one through-hole 252 is substantially circular to fit the shape of each bone pin 234, and the other through-hole 252 is generally elongated horizontally. As a result, the posterior cross section guide 250 may be adapted to small horizontal variations in the positioning of the bone pins 234 while maintaining the desired vertical positioning of the posterior cross section guide 250, i.e., the position and orientation of the cutting plane. The specific shape of the rear face cutting guide 250 is freely assignable, as long as the guide includes a suitable guide surface, such as a flat surface 254, or a cutting slit 256, adapted for guiding a surgical saw blade (not shown) or deburring device for making a rear face cut. In this exemplary embodiment, the rear face cutting guide 250 includes both a flat bottom surface 254 and a cutting slit 256 adapted for guiding a surgical saw blade when performing a rear face cut 122. However, it should be understood that the rear face cutting guide 250 may omit the slit 256 or the flat surface 254. Furthermore, it should be understood that the rear face cutting guide 250 may include multiple slits 256. In any case, the rear face cutting guide 250 is used by a surgeon to guide a surgical saw blade to make a planar rear face cut 122. After the posterior segmentation is complete, the posterior segmentation guide 250 and bone pin 234 may be removed from the femur 110, resulting in the femur shown in Figures 14A and 14B, where the posterior segmentation 122 is the first segment of the femur to be completed.In some alternative procedures, the bone pin 234 may remain in the femur 110 for subsequent use, such as in the positioning of the tibial plateau section described below.

[0133] This disclosure acknowledges that some conventional TKA procedures may not include a reference to a tibial resection in relation to a femoral resection, or vice versa. That is, in some conventional surgeries, the femoral and tibial resections are performed independently. In contrast, in some embodiments of at least some aspects of this disclosure, knee balancing and bone resections are performed by devices and fixtures that reference each other. For example, the tibial resection may be performed in relation to the femoral plane resection, by first performing a femoral plane resection, and then determining ligament balancing at an intermediate flexion or specified flexion angle, and thus the tibial resection is performed in relation to the plane resection, and the ligaments are appropriately balanced to ensure the desired relationship of the femur to the tibia. In contrast, some conventional TKA procedures do not spatially associate one bone resection with another.

[0134] Figure 15 is a perspective view of a balance adjustment jig used in the knee after a posterior transsection, according to at least some aspects of the present disclosure. Referring to Figure 15, a tibial positioning guide 160 may be attached to the tibia 112 after a posterior transsection 122. A vertical guide 192 may also be attached to the tibial positioning guide 160, specifically attached to a beam 166. When attached to the beam 166, each vertical guide 192 may include one or more pin guides 220 and one or more paddles 200. In an exemplary embodiment, each vertical guide 192 may be attached to a pair of paddles 200 and pin guides 220, with the pin guides being closer to the adapter 194 than to the paddles. In an exemplary embodiment, the paddles 200 attached to each vertical guide 192 are oriented to overlap each other, so that the paddle of the medial vertical guide 192 is oriented to be sandwiched between the medial lateral transsection surface of the femur and the articular surface of the medial tibial condyle socket. Similarly, the paddles of the lateral vertical guide 192 are oriented to be sandwiched between the lateral surface of the femur and the articular surface of the lateral tibial condyle socket.

[0135] While the knee joint is flexed to approximately 45 degrees or intermediate flexion (the same angle as the posterior cross-section angle) and held in place (for example, using an external fastener not shown or an intramedullary rod connected to the receiver of a tibial fixture), the surgeon performs soft tissue balancing on the medial and lateral sides of the knee. As part of this soft tissue balancing, the surgeon manipulates the spacing of the overlapping paddles 200 on both the medial and lateral sides until the desired balance is achieved. For example, ligament length and / or tension and / or condylar separation from the tibial plateau are recorded and set as targets for balancing at other degrees of flexion, such as full extension and 90 degrees of flexion. After achieving balance on the medial and lateral sides, the surgeon records the spacing of the paddles on both sides (medial and lateral) using the position of the paddles 200 relative to the vertical guide 192, as described above. If the vertical guide 192 includes markings, the spacing of the paddles 200 may be recorded using these markings, or simply by using the position of the connector 202 relative to the vertical guide.

[0136] After the desired balance is achieved, the position of one or more tibial pins 264 is determined. In some embodiments, spacers may be used in a manner generally similar to the use of spacers 236 described above, except that the spacers may be positioned under and relative to each paddle 200, and the pin guides 220 may be positioned under and relative to each spacer.

[0137] Figure 15A in Figure 15AB is a perspective view of an alternative balance adjustment jig 188A used in knee 108 before posterior sectional section, and Figure 15B is a perspective view of an alternative balance adjustment jig 188A used in knee 108 before posterior sectional section, all of which are in accordance with at least some aspects of the present disclosure. The configuration and operation of the alternative balance adjustment jig 188A are generally similar to those of the balance adjustment jig 188 described elsewhere in this specification, and for the sake of brevity, repetition of the description is omitted. The alternative balance adjustment jig 188A may be useful, for example, when the gap between the condyle and the tibial plateau is too tight to use the paddle 200. In the shown embodiments, a balance adjustment pin 236A may be used instead of the spacer 236. When the fixture 188A is fixed to the femur and tibia, a gap is created between the condyle and the plateau, which can be measured in a manner similar to that of the fixture 188, and a balance adjustment gap can be generated using the balance adjustment pin 236A.

[0138] Figure 16A is a detailed perspective view of an example of a balancing assembly including a pin-pin spacer for establishing a desired vertical separation between a femoral pin and a tibial pin, according to at least some aspects of the present disclosure. Referring to Figure 16A, in some alternative embodiments, a pin-pin spacer 237 may be used to establish a desired vertical separation between a femoral pin 234 and a tibial pin 264. Soft tissue balancing is performed by applying a balancing jig 188, thereby positioning the pins for posterior and proximal tibial sections. In the shown embodiment, the pin-pin spacer 237 includes a femoral component 239, a tibial component 241, and a spacing portion 243 sandwiched between the femoral component 239 and the tibial component 241. The femoral component 239 is configured to engage with a pin guide 220 for one femoral pin 234. The tibial component 241 is configured to engage with a pin guide 220 for one tibial pin 264. The spacing portion 243 is configured to define the distance between the femoral component 239 and the tibial component 241. In some embodiments, the spacing portion 243 may provide a fixed distance between the femoral component 239 and the tibial component 241. In the shown embodiments, the spacing portion 243 has an adjustable length so that the distance between the femoral component 239 and the tibial component 241 is adjustable.

[0139] Figure 16B is a perspective view of a knee balance adjustment fixture with a varus-valgus alignment device installed, according to at least some aspects of the present disclosure. Referring to Figure 16B, in some alternative embodiments, the varus-valgus alignment device 245 may be used, for example, to determine and / or establish a varus-valgus angle for tibial plateau cutting. In the shown embodiment, the varus-valgus alignment device 245 includes a connecting bar 247 that is rotatably coupled to one tibial pin guide 220 and rotatably and slidably coupled to the other tibial pin guide 220. The varus-valgus angle may be measured by determining the angle of the connecting bar 247 relative to other components of the balance adjustment fixture 188. Similarly, when it is desired to establish a specific varus-valgus angle, the connecting bar 247 may be positioned relative to other components of the balance adjustment fixture 188 at that desired angle.

[0140] In some embodiments, the balancing jig 188 may serve as a ligament balancing device and / or a bone resection guide, allowing forces to be applied to two paddles positioned against the medial distal femur (superior medial paddle) and medial proximal tibia (inferior medial paddle), respectively, and to two paddles positioned against the lateral distal femur (superior lateral paddle) and lateral proximal tibia (inferior lateral paddle), respectively, based on the generally accepted principles of TKA; and / or it may also serve as one or both of these functions. Viewed from a lateral perspective, the TKA may be described as the thickness of a composite with three heights, including the height of the metal in the femoral component, the expected height of the polyethylene insert, and the height of the metal in the tibia component. Using the balancing jig 188, the height of the composite can be applied to the distal femur and proximal tibia at many positions. For compliance with generally accepted TKA techniques, the pins accompanying the medial distal paddle may generally be located about 2–4 millimeters below the surface of the natural medial tibia. The pins associated with the lateral-medial paddle may generally be located about 8–10 millimeters below the surface of the natural lateral tibia. These pins may then represent a 6-degree-of-freedom tibial cross-sectional plane, which may be referenced off of and geometrically related to the posterior cross-sectional plane. This geometric relationship may be rectangular, for example, when a 45-degree angle is added to the tibial cross-sectional plane.

[0141] Figure 17 is a perspective view of the knee when the tibial pins are in place, according to at least some aspects of the present disclosure. Referring to Figures 15 and 17, similar to the procedure described above for the femur, after the position of each pin guide 220 for the tibial pins 264 is finalized, a bone drill bit (not shown) is inserted into the opening 232, with the wall of the flange 230 defining the opening acting as a guide for the drill bit. Two holes aligned with each opening 232 are drilled into the proximal tibia 112. A pair of bone pins 264 are then inserted into the respective openings 232 of the pin guides 220 and fixed within the drilled tibial cavities. After the placement of the bone pins 264, the remaining components may be removed (pin guides 220, paddles 200, vertical guides 192, tibial placement guides 160), resulting in the configuration shown in Figure 17.

[0142] Figure 18 is a perspective view of the knee with an example of a tibial cutting guide in place, Figure 19 is an anterior view of the tibia showing a tibial plateau cut, and Figure 20 is a lateral view of the knee showing a tibial plateau cut and a posterior view, all of which are in accordance with at least some aspects of the present disclosure. Referring to Figures 18-20, a tibial cutting guide 270 is fitted to the proximal tibia using bone pins 264. Specifically, the tibial cutting guide 270 may include a pair of through-holes 272 sized to receive each bone pin 264. The particular shape of the tibial cutting guide 270 is freely assignable, as long as the guide includes a suitable guide surface, such as a flat surface 274 or a cutting slit 276 adapted for guiding a surgical saw blade or deburring device (not shown) for making a tibial plateau cut. In this exemplary embodiment, the tibial cutting guide 270 includes both a flat top surface 274 and a cutting slit 276 adapted for guiding the surgical saw blade when performing a tibial plateau cut 278. However, it should be understood that the tibial cutting guide 270 may omit the slit 276 or the flat surface 274. Furthermore, it should be understood that the tibial cutting guide 270 may include multiple slits 276. In any case, the tibial cutting guide 270 is used by the surgeon to guide the surgical saw blade to perform a planar tibial plateau cut 278. After the tibial plateau cut 278 is completed, the tibial cutting guide 270 and the remaining bone pins 234, 264 may be removed to obtain the tibia shown in Figure 20, where the tibial plateau cut is the first bone cut completed in the tibia and the second bone cut completed in the entire procedure.

[0143] In some alternative procedures, the tibial plateau cut 278 may be performed before the posterior femoral cut 122 using actions generally similar to those described above. For example, the position of the tibial plateau cut 278 may be determined first, and the tibial pin 264 may be placed. A tibial cut guide 270 may be set up, and the tibial plateau cut 278 may be performed. Then, the knee 108 may be balanced relative to the tibial plateau cut 278 using a balancing jig 188, and the position of the femoral pin 234 may be established. A posterior cut guide 250 may be set up, and the posterior cut 122 may be performed.

[0144] Figure 21 is a front view of an example of an alternative tibial plateau cutting guide, and Figure 22 is a side view of an example of an alternative tibial plateau cutting guide, both of which are in accordance with at least some aspects of the present disclosure. Referring to Figures 21 and 22, an alternative exemplary tibial plateau cutting guide 300 may be used to perform a tibial plateau cutting 278. The plateau cutting guide 300 may be adjustable before or after placement and may serve to fixate the femur 110 to the desired tibial cutting.

[0145] For example, after the posterior cut 122 is completed, the posterior cut guide 250 and bone pin 234 are removed from the femur 110. The cut guide 300 is attached to the posterior cut 122 of the femur by the cut reference mounting plate 302. The tibial cut guide slot 304 may be moved upward or downward through the extension mechanism 306, thereby allowing adjustment of the vertical distance between the posterior cut 122 and the tibial plateau cut 278. In addition, the varus / valgus or slope angle of the tibial cut can be adjusted at the surgeon's discretion using a pivot coupling mechanism integrated into the extension mechanism 306. The required distance and angle can be read in the extension mechanism 306, and once the desired tibial position is determined, the system is locked in place and the tibial plateau cut 278 is performed through the tibial cut guide slot 304.

[0146] Figure 23 is a perspective view of a knee balance adjustment jig used in a knee after a tibial plateau cut, according to at least some aspects of the present disclosure. Referring to Figures 10A-10C and Figure 23, a tibial positioning guide 160 may be mounted on the tibia 112 after the posterior cut 122 and the tibial plateau cut 278 are completed. The vertical guides 192 of the balance adjustment assembly 190 may also be mounted on the tibial positioning guide 160, specifically mounted on a beam 166. When mounted on the beam 166, each vertical guide 192 may include one or more pin guides 220. In an exemplary embodiment, a pair of paddles 200 may be mounted on each vertical guide 192 and oriented to overlap each other, so that the paddles of the medial vertical guide 192 are oriented to be sandwiched between the medial femoral cut surface 122 and the tibial plateau cut surface 278. Similarly, the paddles of the lateral vertical guide 192 are oriented to be sandwiched between the lateral femoral surface cutting surface 122 and the tibial plateau cutting surface 278. The fixture is configured for measuring the cutting distance. Specifically, the distance between the posterior surface cutting surface 122 and the tibial slope cutting surface 278 (D_PCC_TSC) is measured.

[0147] Figure 24 is a lateral view of the knee rotated to a fully extended position, according to at least some aspects of the present disclosure. Referring to Figure 24, the surgeon may rotate the tibia 112 relative to the femur 110 to reach a fully extended position. While the knee joint 108 is held in full extension (e.g., using an external fastener not shown), the surgeon adjusts the soft tissue balance to the medial and lateral sides of the knee, and then adjusts the knee again with the information obtained for the intermediate flexion balance adjustment to perform a femoral plane cut. The same distance and soft tissue tension obtained for the plane cut relative to the tibial cut may be maintained for the femoral extension cut.

[0148] Figure 25 is a perspective view of a knee balancing jig used in the knee in preparation for femoral extension amputation, according to at least some aspects of the present disclosure. Referring to Figures 10A–10C and Figure 25, as part of this soft tissue balancing, the surgeon manipulates the spacing of the overlapping paddles 200 of the balancing assembly 190 both medially and laterally until the desired balance is achieved. The determined distance (width) between the posterior resection and the proximal tibial resection is maintained here by defining the distal femoral resection plane by giving the same distance to the distal femur based on the proximal tibial resection. After balance is achieved medially and laterally, the surgeon records the spacing of the paddles on both sides (medially and laterally) using the position of the paddles 200 relative to the vertical guide 192. If the vertical guide 192 includes markings, the spacing of the paddles 200 may be recorded using these markings, or simply by using the position of the connector 202 relative to the vertical guide.

[0149] After adjusting the soft tissue balance in full extension, the position of the pin guides 220 attached to the vertical guide 192 is determined and fixed in place using the same method as described above. After the position of each pin guide 220 is finalized, a bone drill bit (not shown) is inserted into the opening 232 of the pin guide, with the wall of the flange 230 defining the opening acting as a guide for the drill bit. Two holes aligned with each opening 232 are drilled into the distal femur.

[0150] Figure 26 is an anterior view of the knee with an example of a femoral extension amputation guide in place, according to at least some aspects of the present disclosure. Referring to Figures 25 and 26, a pair of bone pins 294 are inserted into their respective openings 232 in the pin guide 220 and fixed within a drilled femoral cavity. After the placement of the bone pins 294, the remaining components may be removed (pin guide 220, paddle 200, vertical guide 192, tibial placement guide 160). Referring to Figure 26, the femoral extension amputation guide 302 is placed on the bone pins 294 in a manner similar to that described above.

[0151] Figure 27 is a lateral view of the knee showing a femoral extension section, a tibial plateau section, and a posterior section according to at least some aspects of the present disclosure. The bone structure shown in Figure 27 is obtained as a result of the femoral extension section 304. As shown in this lateral view, the distal femoral section 304 and the proximal tibial section 278 may be substantially parallel and known to separate, which may be done by using the balancing jig 188 as described. In a similar manner, the posterior section 122 and the proximal tibial section 278 have a substantially similar relationship. At this point, the surgeon sizing of the femoral components may be done by anterior reference, posterior reference, or a combination of both.

[0152] Figure 28 is a perspective view of a knee balancing jig used in the knee for posterior reference, according to at least some aspects of the present disclosure. Referring to Figure 28, when posterior reference is selected, the knee is positioned, for example, in knee flexion at approximately 90 degrees. The knee is then balanced as desired, using, for example, values ​​obtained between the plane section and the tibial section, and maintained for femoral extension and tibial sections. Thus, the same ligament length and tension, as well as the femorotibial space, may be maintained throughout the entire range of knee flexion. The position of the femoral flexion section is determined, and the section is performed using a femoral section guide attached to a bone pin in the same manner as described above.

[0153] Figure 29 is a perspective view of a knee balance adjustment jig used in a knee after femoral flexion amputation according to at least some aspects of the present disclosure. Referring to Figure 29, the balance of the knee can be checked using the balance adjustment jig 188 in the same manner as described above, when desired. Here, the femoral components are sized and appropriate balance adjustment is obtained and maintained.

[0154] Figure 30 is a side view of the distal femur showing various cuts in preparation for implantation of a femoral implant, according to at least some aspects of the present disclosure. Referring to Figure 30, the remaining anterior and anterior plane cuts may be made, for example, to accommodate the size and / or configuration of the required implant. In some embodiments, a selected manufacturer's femoral sizing guide may be positioned relative to the posterior femoral and posterior chamber cuts, and the size of the femoral components may be selected so as notching of the distal femur. The manufacturer's cutting guide may be positioned to be planar relative to the posterior femoral and distal femoral resections, and the anterior and anterior plane cuts may be made.

[0155] Figure 31A is a perspective view of an example of an anterior reference guide, Figure 31B is a side view of an anterior reference guide, Figure 32 is a terminal view of an anterior reference guide used in the femur, and Figure 33 is a perspective view of an anterior reference guide used in the femur, all of which are in accordance with at least some aspects of the present disclosure. Referring to Figures 31A-33, when a surgeon chooses to use an anterior reference, for example by a knee positioned at 90 degrees of flexion, the following procedure may be used: For anterior reference, an anterior reference guide 400 having a posterior cutting plane indicator 402 is used. A femoral extension cutting contact surface 403 is positioned relative to a femoral extension cutting 304. Some embodiments may also include a posterior cutting contact surface 405, which may be positioned relative to a posterior cutting 122. The anterior stylus 404 is associated with the posterior cutting plane indicator 402 in the anterior / posterior direction. As the anterior stylus 404 performs translation and sweep to find the correct component sizes, the posterior indicator 402 also translates accordingly. For example, the guide 400 may include a mechanism 406 having opposing racks operably connected by a rotatable pinon gear. Translation of one rack (e.g., coupled to the anterior stylus 404) may cause rotation of the pinon, which may cause translation of the other rack in the opposite direction (e.g., coupled to the posterior cutting plan indicator 402). The posterior indicator 402 indicates the position of the posterior cutting plane. Once the guide 400 is properly positioned and the femoral components are sized, a posterior femoral cutting may be performed (e.g., at 90 degrees).

[0156] Figure 34A is a terminal view of an anterior reference guide including an alternative anterior stylus used in the femur, and Figure 34B is a perspective view of an anterior reference guide including an alternative anterior stylus used in the femur, both of which are in accordance with at least some aspects of the present disclosure. Referring to Figures 34A and 34B, an alternative anterior stylus may be attached for the alternative anterior referencing method. In the embodiments shown, the alternative stylus 408 may be shaped, for example, a trough, spoon, or saucer, and may be positioned within the trochlear groove. In some method examples, the shape of the trochlear groove may be obtained using preoperative planning (e.g., preoperative imaging), and a patient-specific fixture, which may be disposable, may be fabricated to this shape. The patient-specific fabricated fixture may fit tightly into the trochlear groove and / or minimize errors that may be introduced by the use of a pointed stylus that can contact the trochlear groove at multiple positions. When it is undesirable to use preoperative imaging to create a patient-specific trough-shaped stylus, styluses of multiple sizes and / or shapes may be provided, and these styluses may be disposable or reusable after sterilization.

[0157] Figures 35A and 35B are perspective views showing the unicompartmental use of the knee balance adjustment jig 188. Generally, the balance adjustment jig 188 may be used for TKA in the manner described above. However, in some situations, only one balance adjustment assembly 190 may be used in relation to the affected area of ​​the knee.

[0158] In some embodiments of at least some aspects of the present disclosure, the order in which bone cuttings are performed may include, without limitation, any of the following exemplary cutting orders: (1) posterior cutting, tibial cutting, distal femoral cutting, anterior cutting and other cuttings; (2) posterior cutting, tibial cutting, posterior femoral cutting, anterior cutting and other cuttings; (3) tibial cutting, posterior cutting, distal femoral cutting, anterior cutting and other cuttings; or (4) tibial cutting, posterior cutting, posterior femoral cutting, anterior cutting and other cuttings.

[0159] From the above description, the methods and apparatus described herein constitute exemplary embodiments of the present invention, but it should be apparent to those skilled in the art that the invention described herein is not limited to any exact embodiment, and that modifications to such embodiments may be made without departing from the scope of the invention as defined by the claims. In addition, it should be understood that the invention is defined by the claims, and any limitations or components describing the exemplary embodiments shown herein are not intended to be incorporated into the interpretation of any claim component unless such limitations or components are explicitly stated herein. Similarly, the invention is defined by the claims, and there may be inherent and / or unexpected advantages of the invention even if not explicitly considered herein, so it should be understood that it is not necessary to satisfy any or all of the identified advantages or objectives of the invention disclosed herein in order to fall within the scope of any claim.

Claims

1. A knee balance adjustment jig for joint replacement procedures, A tibial positioning guide configured to be attached to the tibial reference in a generally medial-lateral orientation at a generally anterior position to the knee, including the femur and tibia; Includes at least one balancing assembly; The at least one balance adjustment assembly is A vertical guide configured to be releasably attached to the tibial positioning guide in a generally downward-upward orientation, At least one posteriorly extending paddle that is selectively movable vertically along the vertical guide, wherein the at least one paddle is configured to selectively engage with at least one of the distal femur and the proximal tibia; A knee balance adjustment fixture comprising at least one pin guide that is selectively movable vertically along the vertical guide, wherein the at least one pin guide includes at least one opening configured to receive at least one of a drill bit and a bone pin.

2. The at least one balancing assembly comprises at least two of the balancing assemblies, A medial balance adjustment assembly configured to be releasably fitted to the medial side of the tibial positioning guide; The knee balance adjustment jig according to claim 1, comprising an outer balance adjustment assembly configured to be releasably attached to the outside of the tibial positioning guide.

3. The at least one paddle of the medial balance adjustment assembly is configured to selectively engage with at least one of the medial condyle of the distal femur and the medial condyle of the proximal tibia; The knee balance adjustment jig according to claim 2, wherein the at least one paddle of the lateral balance adjustment assembly is configured to selectively engage with at least one of the lateral condyle of the distal femur and the lateral condyle of the proximal tibia.

4. The at least one paddle includes two paddles, an upper paddle and a lower paddle; The upper paddle is configured to selectively engage with the distal femur; The knee balance adjustment jig according to claim 1, wherein the lower paddle is configured to engage with the proximal tibia.

5. The at least one pin guide includes two pin guides, including a femoral pin guide and a tibial pin guide; The femoral pin guide is configured for use in relation to positioning a femoral pin within the femur, The knee balance adjustment jig according to claim 1, wherein the tibial pin guide is configured for use related to positioning a tibial pin within the tibia.

6. The knee balance adjustment jig according to claim 1, further comprising the tibial reference.

7. The knee balance adjustment jig according to claim 1, wherein the tibial reference includes an extramedullary rod of the tibia.

8. The present invention further includes a femoral positioning guide configured for attachment to the aforementioned tibial reference; The knee balance adjustment jig according to claim 1, wherein the femoral positioning guide includes a receiving device configured to engage with a femoral reference.

9. The knee balance adjustment jig according to claim 8, wherein the femoral positioning guide is configured to engage with the femoral reference at a fixed angle related to the intermediate flexion position of the knee.

10. The knee balance adjustment jig according to claim 9, wherein the intermediate flexion position of the knee substantially corresponds to the posterior cross-sectional angle of the femoral implant related to the joint replacement procedure.

11. The knee balance adjustment jig according to claim 9, wherein the intermediate flexion position of the knee is between approximately 30 degrees of flexion and approximately 70 degrees of flexion.

12. The knee balance adjustment jig according to claim 9, wherein the intermediate flexion position of the knee is between approximately 30 degrees of flexion and approximately 60 degrees of flexion.

13. The knee balance adjustment jig according to claim 9, wherein the intermediate flexion position of the knee is flexed at approximately 45 degrees.

14. The knee balance adjustment jig according to claim 8, wherein the femoral positioning guide is configured to engage with the femoral reference at an adjustable angle related to the intermediate flexion position of the knee.

15. The knee balance adjustment jig according to claim 8, further comprising the aforementioned femoral reference.

16. The knee balance adjustment jig according to claim 15, wherein the femoral reference includes a femoral intramedullary rod.

17. The knee balance adjustment jig according to claim 15, wherein the femoral reference includes external femoral components.

18. Further including at least one cutting guide; The at least one cutting guide is configured to guide the cutting device in relation to the resection of at least one of the femur and the tibia; The knee balance adjustment jig according to claim 1, wherein the at least one cutting guide is configured to be attached to at least one of the femur and the tibia using the bone pine associated with the opening of the at least one pin guide of the at least one balance adjustment assembly.

19. The at least one cutting guide includes two cutting guides, including a femoral cutting guide and a tibial cutting guide; The femoral cutting guide is configured to guide the cutting device in relation to the resection of the femur; The knee balance adjustment jig according to claim 18, wherein the tibial cutting guide is configured to guide the cutting device in relation to the resection of the tibia.

20. The femoral cutting guide includes two femoral cutting guides, one of which is a posterior cutting guide and the other is a femoral extension cutting guide; The posterior cutting guide is configured to guide the cutting device in relation to the posterior cutting of the femur; The knee balance adjustment jig according to claim 19, wherein the femoral extension cutting guide is configured to guide the cutting device in relation to the femoral extension cutting of the femur.

21. The knee balance adjustment jig according to claim 1, wherein the at least one rearward-extending paddle includes at least one adjustable engagement mechanism.

22. The knee balance adjustment jig according to claim 21, wherein the adjustable engagement mechanism is repositionable in the forward-backward direction.

23. A method for preparing a knee to receive a knee implant, wherein the method is Positioning the knee, including the distal femur and proximal tibia, at an intermediate flexion angle; To adjust the balance of the soft tissues of the knee at the aforementioned intermediate flexion angle; Determining the position of the posterior cross section of the distal femur configured to engage with the posterior angle of the femoral component of the knee implant, at least in part, based on adjusting the soft tissue balance of the knee at the intermediate flexion angle; A method comprising resecting the distal femur in order to produce the posterior cross section.

24. The method according to claim 23, wherein the intermediate flexion angle substantially corresponds to the posterior angle of the femoral component of the knee implant.

25. The method according to claim 23, wherein the intermediate bending angle is between approximately 30 degrees of bending and approximately 70 degrees of bending.

26. The method according to claim 23, wherein the intermediate bending angle is between approximately 30 degrees of bending and approximately 60 degrees of bending.

27. The method according to claim 23, wherein the intermediate bending angle is a bend of about 45 degrees.

28. To adjust the balance of the soft tissues of the knee relative to the posterior cross-section; To determine the position of a tibial plateau section configured to engage with the tibial component of the knee implant, at least partially based on adjusting the soft tissue balance of the knee relative to the posterior section; The method according to claim 23, further comprising excising the proximal tibia in order to produce the tibial plateau section.

29. To position the knee in full extension; To adjust the balance of the knee's soft tissues in relation to the tibial plateau transection; Determining the position of a femoral extension amputation configured to engage with the femoral component of the knee implant, at least in part, based on adjusting the soft tissue balance of the knee with respect to the tibial plateau amputation; The method according to claim 28, further comprising excising the distal femur in order to produce the aforementioned femoral extension transsection.

30. Positioning the knee at approximately 90 degrees of flexion; To adjust the balance of the knee's soft tissues in relation to the tibial plateau transection; Determining the position of a femoral flexion transection configured to engage with the femoral component of the knee implant, at least in part, based on adjusting the soft tissue balance of the knee relative to the tibial plateau transection; The method according to claim 29, further comprising excising the distal femur in order to produce the aforementioned flexed femoral transsection.

31. Determining the position of the femoral flexion transection configured to engage with the femoral component of the knee implant, at least partially based on the size of the femoral component determined using an anterior reference guide; The method according to claim 30, further comprising excising the distal femur in order to produce the aforementioned flexed femoral transsection.

32. Using the aforementioned forward reference guide, The movable stylus of the anterior reference guide is positioned on the anterior surface of the distal femur; The method according to claim 31, further comprising using the movable stylus to move the rear indicator of the forward reference guide in a parallel manner.

33. The forward reference guide includes a rear surface cutting contact surface; The method according to claim 31, wherein using the forward reference guide includes positioning the rear surface cutting contact surface on the rear surface cutting.

34. The method according to claim 23, wherein adjusting the balance of the soft tissues of the knee at the intermediate flexion angle includes adjusting the balance of the soft tissues of the knee at the intermediate flexion angle relative to the tibial plateau transection of the proximal tibia.

35. The method according to claim 34, further comprising excising the proximal tibia to create the tibial plateau before adjusting the soft tissue balance of the knee at the intermediate flexion angle of the proximal tibia relative to the tibial plateau transection.

36. The method according to claim 23, wherein adjusting the balance of the soft tissues of the knee at the intermediate flexion angle includes applying a linear separation force to the bones including the knee using a gap tensioner.

37. Applying the linear separation force to the knee bone using the gap tensioner is Inserting the first paddle and the second paddle into the space between the bones of the knee; The method according to claim 36, comprising applying the linear separation force to the bone of the knee using the first paddle and the second paddle.

38. The method according to claim 37, wherein applying the linear separation force to the bone of the knee using the first paddle and the second paddle includes applying a torsional force to the gap tensioner, the gap tensioner converting the torsional force into the linear separation force.

39. The method according to claim 38, wherein applying the torsional force to the gap tensioner includes applying a torsional force to the operating shaft of the gap tensioner using a torque wrench.

40. An intramedullary rod comprising a straight shaft having a predetermined length, wherein the straight shaft comprises a surgical-grade material, and the straight shaft comprises a collar that distinguishes the proximal portion of the straight shaft for insertion into a bone canal from the distal portion of the straight shaft extending outward from the bone canal.

41. This is a set of guides for knee joint replacement surgery. A femoral guide configured to be attached to the distal femur; Includes a tibial guide configured to be attached to the proximal tibia; A set of guides for knee joint replacement surgery, wherein the femoral guide and the tibial guide are configured to engage with each other and lock at an angle of 30 to 70 degrees between the longitudinal axis of the distal femur and the longitudinal axis of the proximal tibia.

42. A medial condyle insertion portion configured to measure the gap between the medial condyle of the distal femur and the medial condyle receiving portion of the proximal tibia; The present invention further includes a lateral condyle insertion portion configured to measure the gap between the lateral condyle of the distal femur and the lateral condyle receiving portion of the proximal tibia; The set of guides for knee joint replacement surgery according to claim 41, wherein the medial condylar insertion portion and the lateral condylar insertion portion are configured to be repositionably attached to at least one of the femoral guide and the tibial guide.

43. The medial condyle insertion portion and the lateral condyle insertion portion are configured to be repositionably attached to the tibial guide; The inner condyle insertion portion includes at least two paddles that are repositionable relative to each other, thereby varying the distance between them; A set of knee joint replacement guides according to claim 41, wherein the lateral condylar insertion portion includes at least two paddles that vary the distance between them by being repositionable relative to each other.

44. The at least two paddles of the medial condylar insertion portion are configured to engage with the medial guide of the tibial guide, and the medial guide and at least one of the at least two paddles include markings for determining the distance between the opposing surfaces of the at least two paddles from each other; A set of guides for knee joint replacement according to claim 43, wherein the at least two paddles of the lateral condylar insertion portion are configured to engage with the lateral guide of the tibial guide, and the lateral guide and at least one of the at least two paddles include markings for determining the distance between the opposing surfaces of the at least two paddles from each other.

45. With the internal condyle drill guide; Further including an outer condyle drill guide; The set of guides for knee joint replacement according to claim 41, wherein the medial condyle drill guide and the lateral condyle drill guide are configured to be repositionably mounted on at least one of the femoral guide and the tibial guide.

46. The set of guides for knee joint replacement surgery according to claim 45, wherein the medial condyle drill guide and the lateral condyle drill guide are configured to be repositionably mounted on the tibial guide.

47. The medial condyle drill guide is configured to engage with the medial guide of the tibial guide, and at least one of the medial guide and the medial condyle drill guide includes a mark for determining the distance between a reference point and the medial condyle drill guide; The set of guides for knee joint replacement according to claim 46, wherein the lateral condyle drill guide is configured to engage with the lateral guide of the tibial guide, and at least one of the lateral guide and the lateral condyle drill guide includes a mark for determining the distance between a reference point and the lateral condyle drill guide.

48. With the internal condyle receiving section drill guide; Further including an outer condyle receiving portion drill guide; The set of guides for knee joint replacement surgery according to claim 41, wherein the medial condyle receiving drill guide and the lateral condyle receiving drill guide are configured to be repositionably mounted on at least one of the femoral guide and the tibial guide.

49. The set of guides for knee joint replacement surgery according to claim 48, wherein the medial condyle receiving drill guide and the lateral condyle receiving drill guide are configured to be repositionably mounted on the tibial guide.

50. The medial condyle receiving drill guide is configured to engage with the medial guide of the tibial guide, and at least one of the medial guide and the medial condyle receiving drill guide includes a mark for determining the distance between a reference point and the medial condyle receiving drill guide; The set of guides for knee joint replacement according to claim 49, wherein the lateral condyle socket drill guide is configured to engage with the lateral guide of the tibial guide, and at least one of the lateral guide and the lateral condyle socket drill guide includes a mark for determining the distance between a reference point and the lateral condyle socket drill guide.

51. Further includes a cutting guide for rear face cutting; The set of guides for knee joint replacement according to claim 41, wherein the posterior cutting guide is configured to engage with an artificial mechanism on the distal femur for aligning the cutting guide for the posterior cutting with respect to the distal femur in order to perform a posterior cutting.

52. Further includes a tibial section guide; The set of knee joint replacement guides according to claim 41, wherein the tibial cutting guide is configured to engage with an artificial mechanism on the proximal tibia for aligning the tibial cutting guide with respect to the proximal tibia in order to perform a tibial plateau cut.

53. Further includes a femoral extension amputation guide; The set of knee joint replacement guides according to claim 41, wherein the femoral extension amputation guide is configured to engage with an artificial mechanism on the distal femur for aligning the femoral extension amputation guide with respect to the distal femur in order to perform a femoral extension amputation.

54. Further includes a cutting guide for the front face section; The knee joint replacement guide set according to claim 41, wherein the anterior cutting guide is configured to engage with an artificial mechanism on the distal femur for aligning the cutting guide for the anterior cutting with respect to the distal femur in order to perform an anterior cutting.

55. The tibial guide includes an extramedullary rod configured to extend longitudinally along the tibia; The tibial guide includes a crossbeam operably coupled to the extramedullary rod; The tibial guide includes a first guide configured to traverse along the crossbeam; A set of guides for knee joint replacement according to claim 41, wherein the tibial guide includes a second guide configured to traverse along the crossbeam.

56. A medial condyle insertion portion configured to traverse the first guide, wherein the medial condyle insertion portion is configured to measure the gap between the medial condyle of the distal femur and the medial condyle receiving portion of the proximal tibia; A set of guides for knee joint replacement according to claim 55, further comprising a lateral condyle insertion portion configured to traverse the second guide, wherein the lateral condyle insertion portion is configured to measure the gap between the lateral condyle of the distal femur and the lateral condyle receiving portion of the proximal tibia.

57. An inner condyle drill guide configured to traverse the first guide; The set of guides for knee joint replacement according to claim 55, further comprising a lateral condyle drill guide configured to traverse the second guide.

58. An inner cone receiving drill guide configured to traverse the first guide; The set of guides for knee joint replacement according to claim 55, further comprising a lateral condyle receiving drill guide configured to traverse the second guide.

59. A method for performing knee joint replacement surgery, wherein the method is The procedure involves attaching a femoral guide to the distal femur; Aligning and engaging the tibial guide and the femoral guide, wherein the angle between the femoral guide and the tibial guide is 30 to 70 degrees; Attaching the tibial guide to the proximal tibia; Using the tibial guide, establish at least one of the position and orientation of the cutting guide for the posterior femoral cross-section; Using the aforementioned posterior femoral cross-section guide, a posterior cross-section is performed at at least one condyle of the distal femur; Resecting the proximal tibia to remove at least a portion of the bone previously present beneath at least one condylar socket; A method comprising resecting at least one condyle of the distal femur, wherein the resection is angled 30 to 70 degrees with respect to the posterior cross-section.

60. A method for performing knee joint replacement surgery, wherein the method is The orientation of the distal femur relative to the proximal tibia is fixed such that the longitudinal axis of the distal femur is at an angle of 30 to 70 degrees with respect to the longitudinal axis of the proximal tibia; While the longitudinal axis of the distal femur is angled 30 to 70 degrees with respect to the longitudinal axis of the proximal tibia, the balance adjustment is performed on at least one of the medial portion of the knee joint including the distal femur and proximal tibia, and (ii) the lateral portion of the knee joint including the distal femur and proximal tibia; When the balance adjustment is completed, (i) the distance between the medial condyle of the distal femur and the medial condyle receiving portion of the proximal tibia, and (ii) the distance between the lateral condyle of the distal femur and the lateral condyle receiving portion of the proximal tibia, at least one of these; A method comprising using a posterior femoral resection guide to perform a posterior resection at at least one condyle of the distal femur before performing an anterior or distal resection.

61. A method for performing knee joint replacement surgery, wherein the method is The orientation of the distal femur relative to the proximal tibia is fixed such that the longitudinal axis of the distal femur is at an angle of 30 to 70 degrees with respect to the longitudinal axis of the proximal tibia; While the longitudinal axis of the distal femur is angled 30 to 70 degrees with respect to the longitudinal axis of the proximal tibia, the balance adjustment is performed on at least one of the medial portion of the knee joint including the distal femur and proximal tibia, and (ii) the lateral portion of the knee joint including the distal femur and proximal tibia; When the balance adjustment is completed, (i) the distance between the medial condyle of the distal femur and the medial condyle receiving portion of the proximal tibia, and (ii) the distance between the lateral condyle of the distal femur and the lateral condyle receiving portion of the proximal tibia, at least one of these; A method comprising using a tibial resection guide to perform a tibial plateau resection at at least one condyle of the proximal tibia before performing an anterior femoral resection or a distal femoral resection.

62. A gap tensioner for a balance adjustment jig for a joint replacement procedure, wherein the gap tensioner is A first engaging element configured to be operably coupled to a first paddle of the balance adjustment assembly; A second engaging element configured to be operably coupled to the second paddle of the balance adjustment assembly; The system includes an operating mechanism configured to change the distance between the first engaging element and the second engaging element; The balance adjustment jig includes the first paddle and the second paddle positioned on a guide, the first paddle and the second paddle being configured to be positioned between the bones of a joint; A gap tensioner, wherein the balance adjustment assembly is configured such that at least one of the first paddle and the second paddle is movable along the guide to widen the gap between the bones of the joint.

63. The gap tensioner includes a housing; The first engaging element is linearly slidable relative to the housing; The gap tensioner according to claim 62, wherein the second engaging element is fixedly disposed with respect to the housing.

64. The gap tensioner according to claim 63, wherein the operating mechanism includes a rack and pinion mechanism.

65. The rack and pinion mechanism described above, A pinion rotatably disposed on the housing, The gap tensioner according to claim 64, further comprising a rack fixedly disposed with respect to the first engaging element.

66. The gap tensioner according to claim 65, further comprising an operating shaft operably coupled to the pinion, wherein the operating shaft is configured to receive an input torsional force.

67. The gap tensioner according to claim 62; Apparatus including the aforementioned balance adjustment assembly.

68. A device for adjusting the balance of the knee joint as part of a knee joint replacement procedure, wherein the device is A first paddle operably coupled to a second paddle, wherein the first and second paddles are configured to be positioned between the femur and tibia of the knee joint, and at least one of the first and second paddles is repositionable relative to each other to change the straight-line distance between them; A device comprising a gap tensioner including a clutch configured to reposition at least one of the first paddles relative to the second paddle, wherein the gap tensioner is operable to convert an applied force into the movement of at least one of the first and second paddles in order to increase the straight-line distance between the first and second paddles when the resistance force arising from the resistance to the increase in the gap between the femur and the tibia of the knee joint, which is brought about by ligament tension from ligaments extending over the femur and the tibia, is not overcome.

69. The first paddle is coupled to the first engagement element; The second paddle is coupled to the second engagement element; The device according to claim 68, wherein at least one of the first engaging element and the second engaging element is repositionable along a common rail.

70. The device according to claim 68, wherein the gap tensioner includes a rack engaged by a pinion, at least one of the rack and the pinion is repositionable perpendicularly to each other, and the rack and the pinion are operably coupled to the first and second paddles.

71. The pinion is operably coupled to an operating shaft configured to rotate the pinion when the shaft is rotated; The device according to claim 70, wherein the clutch is sandwiched between the pinion and the operating shaft.

72. The device according to claim 68, further comprising a tibial positioning guide configured to be detachably coupled to the tibia, wherein the tibial positioning guide includes a horizontal rail, the device is repositionable along the horizontal rail, the first and second paddles are operably coupled to a vertical rail perpendicular to the horizontal rail, and at least one of the first and second paddles is repositionable perpendicular to the vertical rail.

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