Extension flexion adjustable femoral distal cutting guide system

Abstract

A femoral distal cutting guide system for guiding distal femoral bone resection includes a base for mounting to a fixation device fixed relative to a femur, wherein the fixation device is configured to establish a positional reference relative to the femur; and a pivoting portion for registering against a distal femoral surface, wherein the pivoting portion is pivotably connected to the base and configured for adjustably setting a distal femoral bone resection angle in a sagittal plane for intraoperative adjustment of sagittal alignment of the femoral distal cutting guide system prior to bone resection.

Description

EXTENSION FLEXION ADJUSTABLE FEMORAL DISTAL CUTTING GUIDE SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority benefit of U.S. Provisional Patent Application No.63 / 776,191, filed March 23, 2025, the entire contents of which is incorporated herein by reference.FIELD

[0002] This disclosure relates, generally, to knee replacement, and more specifically, to guide systems for femoral resection.BACKGROUND

[0003] In total knee arthroplasty (TKA), the appropriate placement of the femoral component is one of the most critical factors affecting postoperative clinical outcomes. The placement of the femoral component is determined by the following three spatial elements: coronal plane: varus / valgus alignment; sagittal plane: flexion / extension alignment; and axial plane: rotational alignment. The coronal plane and axial plane adjustments can be controlled using existing surgical instruments. However, adjustments in the sagittal plane may not be assisted by current instruments and, instead, may rely on a surgeon's intraoperative judgment and experience.

[0004] The installation angle of the femoral component in the Sagittal Plane is influenced by two factors: the anatomical anterior bowing of the femur (a natural forward curvature is common); and the entry point of the intramedullary (IM) rod, which acts as a reference for the surgical instrument. These elements tend to result in the femoral component being unintentionally positioned in flexion (anterior tilt). Such improper component positioning in the sagittal plane can lead to: flexion gap imbalance, resulting in limited range of motion; increased risk of supracondylar femoral fracture; and reduced long-term joint stability due to altered load transfer.

[0005] In many cases, the distal surface of the femoral component should be perpendicular to the distal one-third of the femoral shaft. With this, the anterior and posterior surfaces of thefemoral component may align more parallel with the femoral shaft, enabling more stable implant positioning. However, with conventional approaches, it is only after bone resection is completed that the appropriateness of the sagittal plane alignment becomes apparent. At that stage, correction is difficult, leading to potential postoperative malalignment.SUMMARY

[0006] Femoral distal cutting guide systems, devices, and methods described herein provide controlled adjustment of the distal femoral bone resection angle in the sagittal plane during total knee arthroplasty, enabling surgeons to set an optimal extension or flexion orientation prior to bone cutting. According to various aspects, a system generally includes a base configured to mount onto an intramedullary rod and a pivoting portion configured to engage the distal femoral surface, with the pivoting portion being movable relative to the base to adjust the sagittal alignment of the distal femoral cut. An adjustment mechanism, such as a threaded adjustment screw, allows controlled modification of the pivot angle, while features such as a visual indicator, biasing member, elongated pin holes, and interchangeable bushings facilitate precise positioning and stable fixation of the guide system. In certain embodiments, the system supports both mechanical alignment (MA) techniques with predetermined valgus angles and kinematic alignment (KA) techniques with non-fixed valgus angles using a single guide system, and may include a small-diameter intramedullary rod to reduce surgical invasiveness. By enabling surgeon-controlled sagittal alignment before bone resection, the systems and methods may improve implant positioning accuracy, reduce complications associated with excessive flexion or extension, maintain proper postoperative load balance, and enhance the reproducibility and precision of femoral component placement during knee arthroplasty procedures.

[0007] According to an aspect, a femoral distal cutting guide system for guiding distal femoral bone resection includes a base for mounting to a fixation device fixed relative to a femur, wherein the fixation device is configured to establish a positional reference relative to the femur; and a pivoting portion for registering against a distal femoral surface, wherein the pivoting portion is pivotably connected to the base and configured for adjustably setting a distal femoral bone resection angle in a sagittal plane for intraoperative adjustment of sagittal alignment of the femoral distal cutting guide system prior to bone resection.

[0008] The system may include interchangeable bushings for accommodating different fixation devices. The interchangeable bushings may include a plurality of different angle variations for positioning the base at different angles relative to the fixation device. The system may include a bushing configured for a non-fixed distal valgus angle.

[0009] The system may include an adjustment mechanism for adjustably controlling a pivot angle of the pivoting portion relative to the base in the sagittal plane while the pivoting portion is fixed relative to the femur in at least one other plane. The adjustment mechanism may include a screw mechanism, a gear mechanism, a ratchet mechanism, a linkage mechanism, or an electromechanical mechanism.

[0010] The pivoting portion may be biased toward a position in which a surface of the pivoting portion that registers against the distal femoral surface during use is perpendicular to the fixation device when the base is mounted to the fixation device. The pivoting portion may include at least one elliptical pin hole for engaging fixation pins fixed to the bone to maintain an orientation of the pivoting portion in a coronal plane while permitting the adjustable setting of the distal femoral bone resection angle in a sagittal plane without removing the fixation pins. A range of the adjustable setting of the distal femoral bone resection angle may be 40 degrees or less. A range of the adjustable setting of the distal femoral bone resection angle may be at least 5 degrees.

[0011] The system may include at least one shim for reproducing a pre-defect joint surface height associated with a kinematic alignment method. The system may include a resection checker configured for detachably connecting to the pivoting portion for checking an alignment of the pivoting portion with reference to an anterior surface of a femur. The resection checker may include a plurality of slots for receiving a resection guide. The system may include a cutting block configured for detachably connecting to the pivoting portion and for attachment to the femur for guiding a bone saw. The fixation device may include an intramedullary rod.

[0012] According to an aspect, a method for distal femoral bone resection includes mounting a guide system to a fixation device fixed to a femur; adjusting the guide system to set a distal femoral bone resection angle in a sagittal plane; and using the guide system to position a cutting block relative to the femur.

[0013] Mounting the guide system to the fixation device may include sliding a base of the guide system along the fixation device until a pivoting portion of the guide system contacts a distal surface of the femur. Adjusting the guide system may include pivoting a pivoting portion of the guide system relative to a base of the guide system about a pivot axis extending generally in a medial-lateral direction.

[0014] Adjusting the guide system may include engaging an adjustment mechanism to change an angular orientation of a pivoting portion of the guide system relative to a base of the guide system. The adjustment mechanism may include a screw mechanism, a gear mechanism, a ratchet mechanism, a linkage mechanism, or an electromechanical mechanism. The method may include engaging a tool with a tool-engagement feature of the adjustment mechanism to make an adjustment.

[0015] The method may include temporarily securing the guide system to the femur with at least one fixation pin inserted through an elongated pin hole of the guide system, wherein the guide system is adjusted to set the distal femoral bone resection angle in the sagittal plane while the guide system is secured to the femur with the at least one fixation pin. The method may include attaching a resection checker to the guide system and evaluating alignment of the guide system relative to an anterior surface of the femur. The method may include removing the resection checker prior to positioning the cutting block. Using the guide system to position the cutting block may include attaching the cutting block to the guide system and securing the cutting block to the femur with fixation pins. The method may include removing the guide system and the fixation device while leaving the cutting block secured to the femur and resecting a distal femoral bone surface using a surgical saw guided by the cutting block.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will now be described, by way of example only, with reference to the accompanying drawings.

[0017] FIGS. 1A and IB are perspective views of an extension / flexion adjustable femoral distal cutting guide system, according to various embodiments of the present disclosure.

[0018] FIG. 1C is a front view of the femoral distal cutting guide system illustrating elongated pin holes of a pivoting portion of the guide system according to various embodiments of the present disclosure.

[0019] FIG. ID is a side view of the femoral distal cutting guide system according to various embodiments of the present disclosure.

[0020] FIG. IE is an exploded view of the femoral distal cutting guide system according to various embodiments of the present disclosure.

[0021] FIGS. IF and 1G illustrate the pivoting adjusting of the femoral distal cutting guide system according to various embodiments of the present disclosure.

[0022] FIG. 1H is an exploded or partially separated view illustrating a resection checker configured for attachment to the pivoting portion of the guide system according to various embodiments of the present disclosure.

[0023] FIG. 2A-2I illustrate an exemplary method for use of the femoral distal cutting guide system according to various embodiments of the present disclosure.DETAILED DESCRIPTION

[0024] According to various aspects, femoral distal cutting guide systems, devices, and methods described herein provide for adjusting the optimal extension / flexion angle in the Sagittal Plane before distal femoral resection, provide an all-in-one system that supports both mechanical alignment (MA) with fixed valgus angle and kinematic alignment (KA) with nonfixed distal valgus angle via a single guide system, and / or provide a small-diameter intramedullary rod for KA methodology. The adjustable distal femoral cutting guide systems, devices, and methods described herein may enable optimal component placement regardless of preoperative anatomical variations (e.g., femoral bowing), deliver stable results irrespective of surgeon experience, improve knee balance and postoperative outcomes through proper Sagittal Plane adjustment, allow flexible intraoperative selection between MA and KA techniques, and / or reduce bone and intramedullary wall invasion due to smaller drill openings, potentially decreasing postoperative bleeding. As such, the systems, devices and methods described herein address challenges in conventional TKA and significantly enhance implant placement precision.

[0025] According to various aspects, femoral distal cutting guide systems, devices, and methods enable high-precision adjustment of the distal femoral osteotomy angle in the Sagittal Plane during TKA. Conventionally, surgeons have been unable to directly control the distal femoral cutting angle and had to rely on intraoperative judgment. With the femoral distal cutting guide systems, devices, and methods described herein, the desired cutting angle can be pre-adjusted and fixed, allowing for bone resection as intended. According to some embodiments, an all-in-one mechanism supports both MA and KA methodologies, offering flexibility for intraoperative selection. According to some embodiments, the use of a dedicated small-diameter intramedullary rod for KA not only reduces surgical invasiveness to the bone and intramedullary wall, but also decreases postoperative bleeding.

[0026] According to various aspects, femoral distal cutting guide systems, devices, and methods allow the distal femoral bone cutting to be adjusted under the surgeon’s control, thereby preventing excessive deviation in the extension or flexion direction. As a result, more stable component placement in the Sagittal Plane can be achieved, and a reduction in the risk of the following complications is expected: Gap (GAP) mismatch during knee flexion caused by excessive flexion, and / or formation of an anterior notch due to excessive extension, and the occurrence of associated supracondylar fractures

[0027] By enabling appropriate adjustment in the Sagittal Plane, the anterior and posterior surfaces of the femoral component can be positioned more parallel to the femoral shaft, and it is expected that an ideal alignment can be obtained. As a result, maintenance of the load transmission environment in the postoperative knee joint is expected, thereby improving the long-term stability of the artificial joint.

[0028] According to some embodiments, the femoral distal cutting guide systems, devices, and methods are compatible with the principles of the KA method, which has attracted increasing attention in recent years. In the KA method, reproduction of the second axis (2nd Axis) based on the natural shape of the femur is considered important. The systems, devices, and methods described herein may achieve appropriate extension and flexion control of the femoral component, and realization of an ideal artificial knee joint placement based on the KA method may be possible. According to various aspects, both the MA method concept and the KA method concept can be addressed intraoperatively using a single guide system. Because this can be handled through simple operation, flexibility in intraoperative method selection for the surgeon and a reduction in surgical time are expected. Further, in the KAmethod, in which the distal valgus angle in the femoral Coronal Plane is not fixed, a conventional-diameter intramedullary rod is not required. Therefore, the systems, devices, and methods described herein may include the use of a dedicated small-diameter intramedullary rod (relative to conventional intramedullary rods for the MA approach), a reduction in invasiveness to the bone and the intramedullary wall due to a smaller drill opening diameter is expected. In addition, as a result of the reduced invasiveness, a reduction in postoperative bleeding from the intramedullary canal can also be expected.

[0029] According to various aspects, an extension / flexion adjustable femoral distal cutting guide system configured for use during total knee arthroplasty includes a base configured to mount onto an intramedullary rod inserted into the femoral canal and a pivoting portion configured to engage the distal surface of the femur. The pivoting portion is movable relative to the base about a pivot axis so that the orientation of the distal cutting reference surface can be selectively adjusted in a flexion or extension direction prior to bone resection. In this manner, the guide system allows the surgeon to control sagittal alignment of the distal femoral cut rather than relying solely on the orientation dictated by conventional intramedullary rod-dependent instruments.

[0030] Angular adjustment of the pivoting portion relative to the base may be achieved using an adjustment mechanism, such as a threaded adjustment screw, that allows controlled modification of the pivot angle. Rotation of the adjustment mechanism causes the pivoting portion to pivot about the pivot axis, thereby changing the angular orientation of the distal cutting reference surface in the sagittal plane. A visual indicator may be provided to indicate the angular orientation of the pivoting portion relative to the base, and a biasing member such as a spring may bias the pivoting portion toward a neutral reference orientation corresponding to a predetermined angular position.

[0031] The guide system may include additional features to facilitate stable positioning and alignment during use. For example, elongated pin holes formed in the pivoting portion may receive fixation pins that temporarily secure the guide system relative to the femur while still allowing pivoting movement during sagittal adjustment. Interchangeable bushings may be provided (e.g., in a kit that includes other components of the guide system) for interchangeably positioning in the base to accommodate intramedullary rods of different diameters and to establish desired coronal plane orientations, including predetermined distal valgus angles associated with mechanical alignment techniques. In certain embodiments, akinematic alignment subassembly including a shim attachment and removable shims of different sizes (which may be provided as part of a kit with other components of the system) may be used to reproduce pre-defect joint surface height or compensate for bone loss.

[0032] During use, the guide system may be mounted onto the intramedullary rod and advanced until the pivoting portion contacts the distal femoral surface. The guide may then be temporarily fixed to the femur using fixation pins, and a resection checker may be attached to evaluate sagittal alignment relative to the anterior surface of the femur. If adjustment is required, the surgeon may actuate the adjustment mechanism to pivot the pivoting portion until a desired orientation is achieved. After the desired orientation has been established, a distal femoral cutting block may be attached to the pivoting portion and secured to the femur. The guide system and intramedullary rod may then be removed while leaving the cutting block in place, allowing the distal femoral bone resection to be performed with a surgical saw guided by the cutting block so that the resulting resection reproduces the selected sagittal alignment.

[0033] In the following description of the disclosure and embodiments, reference is made to the accompanying drawings in which are shown, by way of illustration, specific embodiments that can be practiced. It is to be understood that other embodiments and examples can be practiced, and changes can be made without departing from the scope of the disclosure.

[0034] In addition, it is also to be understood that the singular forms “a,” “an,” and “the” used in the following description are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is also to be understood that the term “and / or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It is further to be understood that the terms “includes, “including,” “comprises,” and / or “comprising,” when used herein, specify the presence of stated features, integers, steps, operations, elements, components, and / or units, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, units, and / or groups thereof.

[0035] FIGS. 1A-1H illustrate various aspects of an extension / flexion adjustable femoral distal cutting guide system 100. The guide system 100 is configured to assist in performing distal femoral bone resection during a total knee arthroplasty procedure while allowing controlled adjustment of the distal femoral cutting angle in the sagittal plane. The system 100is configured to provide intraoperative adjustment of sagittal alignment of the distal femoral bone resection prior to bone resection. Unlike conventional distal femoral cutting guides, system 100 does not require a fixed geometry for the sagittal plane (i.e., no adjustability in the sagittal plane) and does not require surgeon intuition. Thus, system 100 can provide a more reliable and optimal distal femoral resection relative to conventional systems.

[0036] The system 100 generally includes a base 102 configured to couple with a fixation device (see, e.g., 104 in FIG. 2B). The fixation device can be any device configured to establish a positional reference relative to the femur. The fixation device can be a navigation system, a jig mounted externally to the femur, a pin-based system, a rod inserted into a medullary canal of a femur (as in the example illustrated in FIG. 2B), any device that is fixed relative to the femur, or any other type of device that establishes a positional reference relative to the femur. The system 100 includes a pivoting portion 106 configured to engage a distal surface of a femur (see FIGS. 2C-2F). The pivoting portion 106 is movable relative to the base 102 so that the orientation of the pivoting portion relative to the femur may be adjusted before bone cutting is performed. The fixation device can be any device mounted to the femur that provides registration to the femur, including any device inserted into the medullary canal. In some examples, the fixation device is a medullary rod, such as medullary rod 104 shown in the figures (the medullary rod will be referred to below merely for simplicity and is not intended to be limiting).

[0037] The base 102 is configured to mount onto the intramedullary rod 104, which may be inserted into the intramedullary canal of the femur. A rod-receiving bore 108 extends through the base 102 and is dimensioned to receive the intramedullary rod 104. The rod-receiving bore 108 may extend so that the guide system 100 may be advanced distally along the intramedullary rod 104 until the pivoting portion 106 contacts the distal femoral surface. In some embodiments, the rod-receiving bore 108 may be defined by an interchangeable bushing 110 that is received within a receptacle 112 of the base 102.

[0038] The pivoting portion 106 includes a contact surface 114 configured to register against the distal surface of the femur. When the guide system 100 is mounted to the intramedullary rod 104 and positioned against the distal femur, the orientation of the pivoting portion 106 relative to the femur determines the orientation of the distal femoral cutting plane that will be established by the system 100. The pivoting portion 106 therefore functions as a referencestructure that establishes the spatial orientation of the cutting guide relative to the patient’s anatomy.

[0039] The pivoting portion 106 is connected to the base 102 by a pivot interface that allows the pivoting portion 106 to rotate relative to the base 102 about a pivot axis 116 (see FIG. 1G). The pivot interface may include a hinge joint, pin joint, an axle connection, or any other mechanical coupling that allows controlled angular movement between the components. The pivot axis may extend generally in a medial-lateral direction when the guide system 100 is mounted to the femur so that rotation about the pivot axis produces angular adjustment in the sagittal plane. Through this configuration, the pivoting portion 106 may be selectively moved increase and decrease an angular orientation relative to the base 102 in a flexion / extension direction (i.e., in the sagittal plane).

[0040] In some embodiments, a pivot interface may include a hinge pin that passes through aligned apertures formed in the base 102 and the pivoting portion 106. The hinge pin may be fixed relative to one component and rotatable relative to the other component so that the pivoting portion 106 may rotate about the hinge pin. In other embodiments the pivot interface may include a trunnion arrangement, a cylindrical bearing surface, or other rotational coupling that allows relative angular movement while maintaining structural stability of the guide system.

[0041] Angular adjustment of the pivoting portion 106 relative to the base 102 may be achieved using an adjustment mechanism 120 (see FIGS. IF and 1G). The adjustment mechanism 120 may include a threaded adjustment screw that is in threaded engagement with the pivoting portion 106. The adjustment mechanism 120 can be any mechanism that adjusts angular orientation, including gear-based mechanisms, ratchet-based mechanisms, electromechanical mechanisms, etc. The threaded screw may be rotatable relative to the base so that rotation of the screw causes the pivoting portion 106 to pivot relative to the base 102, thereby changing the angular orientation 118 of the pivoting portion 106 in the sagittal plane (see exemplary 14-degree angle in FIG. 1G).

[0042] The adjustment mechanism 120 may include a user interface for enabling a user to actuate the adjustment mechanism 120 to adjust the angular position of the pivoting portion 106 relative to the base 102. For example, in the illustrated embodiment, the adjustment mechanism 120 includes a tool-engagement feature 122, such as a hex socket, slot, or recess,that allows the adjustment mechanism 120 to be rotated using a driver or other type of tool (see tool 172 in FIG. 2E). The adjustment mechanism 120 may be positioned on an upper surface of the pivoting portion 106 so that the surgeon may access the adjustment mechanism 120 while the guide system 100 is positioned against the femur. However, this is merely exemplary. The adjustment mechanism 120 can be located in any suitable location, including on a top, side, bottom, or distal surface of the pivoting portion 106 and / or the base 102.Incremental rotation (or other type of adjustment) of the adjustment mechanism 120 may therefore allow the surgeon to gradually adjust the angular position of the pivoting portion 106 until the desired orientation is achieved.

[0043] In certain embodiments the adjustment mechanism 120 may allow continuous angular adjustment across a defined range of motion. In other embodiments, the adjustment mechanism 120 may include indexing features that allow discrete angular adjustments corresponding to predetermined increments. For example, the mechanism 120 may include detents or ratchet structures that provide tactile feedback to the surgeon when the pivoting portion reaches specific angular positions. Such configurations may help the surgeon achieve reproducible alignment settings during surgical procedures.

[0044] With reference to FIG. 1G, a visual indicator 124 may indicate an angular orientation of the pivoting portion 106 relative to the base 102. The visual indicator 124 may be an angular scale on the base 102. The position of a corresponding feature of the pivoting portion 106 with the visual indicator 124 may provide visual guidance to the surgeon regarding the current angular orientation of the pivoting portion 106 relative to the base 102.

[0045] A biasing member 126 may be provided between the base 102 and the pivoting portion 106 to bias the pivoting portion 106 toward or away from the base 102. The biasing member may include a spring or other type of resilient element configured to bias the pivoting portion toward a neutral orientation relative to the base. For example, the biasing member 126 may include a tension spring that biases the pivoting portion 106 and the base 102 together. In some variations, the biasing member 126 is not included. For examples, the adjustment mechanism 120 may be a non-biased screw-based locking mechanism or a ratchet-based gear locking system. The neutral orientation may correspond to a configuration in which the distal contact surface of the pivoting portion 106 is substantially perpendicular to the intramedullary rod 104 when the base 102 is mounted on the rod 104. The biasing member may therefore maintain the pivoting portion in a defined minimum referenceorientation until the surgeon intentionally adjusts the pivot angle using the adjustment mechanism 120. Optionally, the defined minimum reference orientation is indicated by the visual indicator 124, such as by a 0-degree orientation.

[0046] In some embodiments, the guide component may be configured to allow adjustment of the distal femoral bone resection angle across a defined angular range in the sagittal plane. The adjustable setting may include a range of about 40 degrees or less, such that the pivoting portion of the guide component can be positioned at different flexion or extension orientations relative to the base. In certain embodiments, the adjustable setting may include a range of at least about 5 degrees, thereby permitting meaningful adjustment of the distal femoral cutting orientation to accommodate patient- specific anatomical variation. In some implementations, the adjustable range may be approximately up to 5 degrees between a minimum angle position (e.g., 0 degrees) and a maximum angle position (e.g., 5 degrees), up to 10 degrees between a minimum angle position (e.g., 0 degrees) and a maximum angle position (e.g., 10 degrees), up to 12 degrees between a minimum angle position (e.g., 0 degrees) and a maximum angle position (e.g., 12 degrees), up to 14 degrees between a minimum angle position (e.g., 0 degrees) and a maximum angle position (e.g., 14 degrees), up to 16 degrees between a minimum angle position (e.g., 0 degrees) and a maximum angle position (e.g., 16 degrees), up to 18 degrees between a minimum angle position (e.g., 0 degrees) and a maximum angle position (e.g., 18 degrees), up to 20 degrees between a minimum angle position (e.g., 0 degrees) and a maximum angle position (e.g., 20 degrees), up to 30 degrees between a minimum angle position (e.g., 0 degrees) and a maximum angle position (e.g., 30 degrees), up to 40 degrees between a minimum angle position (e.g., 0 degrees) and a maximum angle position (e.g., 40 degrees), or greater than 40 degrees between a minimum angle position (e.g., 0 degrees) and a maximum angle position (e.g., greater than 40 degrees). In preferred embodiments, the adjustable setting may include a range of about 14 degrees (e.g., the angle can be adjusted from 0 degrees to 14 degrees), which may provide sufficient flexibility for sagittal alignment adjustments while maintaining stability of the guide system during surgical use. It will be appreciated that other ranges may also be provided depending on the design of the pivoting mechanism and adjustment components. Optionally, the angle is adjustable in fixed increments, such as 1-degree increments.

[0047] The pivoting portion 106 may include one or more elongated pin holes 128 (an example of which is shown in FIG. 1C) configured to receive fixation pins used to secure theguide system relative to the femur. The elongated geometry of the pin holes 128 allows the pivoting portion 106 to be temporarily fixed to the femur while still permitting pivoting movement of the pivoting portion 106 relative to the base in the sagittal plane. In particular, the elongated dimension of the pin holes may extend generally in a sagittal direction so that pivoting of the pivoting portion in the sagittal plane can occur without requiring removal or repositioning of the fixation pins. The pin holes 128 may be configured as elongated slots or elliptical openings extending through the pivoting portion 106. Surgical pins may be inserted through the pin holes and into the distal femur to stabilize the guide system against translational movement and rotational movement in the axial and coronal planes. Because the pin holes 128 are elongated, the pivoting portion 106 may still move relative to the pins while angular adjustments are performed using the adjustment mechanism 120.

[0048] In some embodiments the guide system 100 may include interchangeable bushing 110 configured to couple the base 102 to the intramedullary rod 104. A given system (e.g., in the form of a kit) may include a plurality of different bushings for mating to different intramedullary rods (which may be part of the same kit or may be separately obtained by the surgeon). The bushings 110 may include cylindrical bodies sized and shaped to fit within the receptacle 112 of the base 102. The bushings 110 may include internal bores 130 configured to receive the intramedullary rod 104. Each type of bushing 110 may be configured to position the base relative to the rod at a particular angular orientation in the coronal plane. For example, different bushings may correspond to different distal valgus angles that are commonly used in mechanical alignment techniques during knee arthroplasty.

[0049] The bushing 110 may be removable from the base 102 so that different bushings 110 may be installed depending on the surgical technique being used. In certain embodiments, a set of bushings may be provided that correspond to several different predetermined valgus angles. In other embodiments, a bushing may be provided that allows the base to align with the intramedullary rod without establishing a fixed valgus angle, thereby enabling use of the guide system in kinematic alignment procedures.

[0050] In some implementations, different types of bushings 110 may be configured to accommodate different types of intramedullary rods (or other types of fixation devices), such as intramedullary rods of different diameters. For example, a bushing having an internal bore that does not prescribe a specific angle may be used with a small-diameter intramedullary rod, such as a small-diameter intramedullary rod suitable for use in the KA method. The useof a smaller rod may reduce the size of the entry opening in the femur and may therefore reduce surgical trauma to the intramedullary canal.

[0051] The pivoting portion 106 may further include a kinematic alignment subassembly 142, which may include a shim attachment 144 configured to receive one or more shims 146. The shim attachment 144 may be selectively received in a main body 148 of the pivoting portion 106 or another component of the guide system so that shims may be installed between the main body 148 of the pivoting portion 106 and the distal femoral surface. When used, the shim 146 may define the contact surface 114 that registers against the distal surface of the femur. The kinematic alignment subassembly 142 may be used to reproduce a pre-defect joint surface height or to compensate for bone loss in certain surgical techniques.

[0052] The shims 146 may be provided in a variety of thicknesses so that the surgeon may select an appropriate combination to achieve a desired spacing. For example, the shims may be provided in increments of approximately 0.5 millimeters, 1.0 millimeter, 1.5 millimeters, and 2.0 millimeters. Multiple shims 146 may be stacked or combined to achieve a desired total thickness. This arrangement may allow the guide system to accommodate a wide range of patient anatomies and surgical approaches.

[0053] In some embodiments, the guide system 100 may include a resection checker 150 configured to verify alignment of the cutting guide relative to the anterior surface of the femur. The resection checkerl50 may be detachably connected to the main body 148 of the pivoting portion 106 so that it may be installed during alignment verification and removed prior to final fixation of the cutting block. With reference to FIG. 1H, the resection checker 150 may include one or more alignment pins 154 for insertion into corresponding alignment holes 156 of the main body 148 of the pivoting portion 106. The resection checker 150 may include one or more slots 152 configured to receive a resection guide. The slots 152 may be oriented according to an inclination of the intended implant. For example, the slots may have a 3-degree inclination to match the 3-degree anterior inclination of the intended implant. Slots 152 may be provided on both sides of the resection checker 150 (as illustrated) to enable the surgeon to freely check from either direction — whether it is a left or right knee, and from either the medial or lateral side.

[0054] When the resection checker 150 is attached to the guide system, a resection guide may be inserted through one of the slots 152 so that the surgeon may visually assess theorientation of the guide relative to the anterior surface of the femur. If the orientation is not optimal, the surgeon may adjust the pivoting portion 106 by rotating the adjustment mechanism 120 until the desired sagittal orientation between the resection guide and the femur is achieved.

[0055] After the desired sagittal orientation has been established, a distal femoral cutting block 158 may be detachably connected to the pivoting portion 106 so that the orientation of the cutting block 158 corresponds to the selected angular orientation of the pivoting portion 106. The cutting block 158 may be inserted into the same alignment holes 156 in the main body 148 of the pivoting portion 106 used for the resection checker 150. Once attached, the cutting block 158 may be secured to the femur using surgical pins inserted through pin holes 160 in the cutting block 158. The cutting block 158 may include one or more cutting slots 162 configured to guide a surgical saw blade during distal femoral bone resection. The cutting slot 162 may be configured so as to be parallel to the contact surface 114 of the pivoting portion 106. As such, if the guide system 100 is used to position the resection checker 150 in alignment with the anterior surface of the femur, the cutting slots 162 may be oriented to guide a resected distal femur plane having an optimal sagittal orientation. The relationship between the orientation of the cutting slot 162 and the slots 152 of the resection checker 150 may depend on the configuration of the desired femoral component implant. For example, in configurations in which the desired femoral component implant has an anterior surface oriented X-degrees relative to the distal surface of the implant, the angle of the slots 152 of the resection checker 150 may be oriented X-degrees relative to the cutting guide slot 162 to provide a distal femoral resection that corresponds to the relationship between the anterior and distal surfaces of the femoral component implant.

[0056] After the cutting block has been secured to the femur, the guide system 100 and the intramedullary rod 104 may be removed while leaving the cutting block fixed in place. With the cutting block 158 secured to the femur, the surgeon may perform the distal femoral bone resection by advancing a surgical saw through the cutting slot 162. Because the orientation of the cutting block 158 corresponds to the previously adjusted orientation of the pivoting portion 106, the resulting bone cut may reproduce the sagittal alignment selected during the adjustment step.

[0057] The guide system 100 may be constructed from materials suitable for repeated surgical use and sterilization. For example, structural components of the guide system may beformed from stainless steel, titanium alloys, cobalt-chromium alloys, or other biocompatible metals commonly used in surgical instrumentation. In some embodiments certain components may also be formed from high-strength polymer materials or composite materials capable of withstanding surgical loads and sterilization processes.

[0058] In use, a femoral distal cutting guide system, such as femoral distal cutting guide system 100, may be employed during preparation of the distal femur in a total knee arthroplasty procedure in order to establish a desired distal femoral bone resection orientation in the sagittal plane. Below is a description of an exemplary method of using a femoral distal cutting guide system, such as system 100. Aspects of the method are illustrated in FIGS. AI. The below description refers to various components of system 100, but this is merely for convenience, and it is to be understood that the method can be practiced with any suitable femoral distal cutting guide system configured in accordance with the principles described herein. The method may include a sequence of steps in which an intramedullary reference axis is established, the adjustable guide system is mounted to the intramedullary rod, the sagittal plane orientation of the guide is evaluated and adjusted, and a distal femoral cutting block is positioned for performing the distal femoral bone resection.

[0059] The method may begin with formation of an entry opening in the distal femur for receiving an intramedullary rod 104. As illustrated in FIG. ZA, a drill or other surgical instrument may be used to create an entry hole in the femoral canal at a selected location on the distal femur. The location of the entry opening may be selected according to conventional surgical practices for total knee arthroplasty procedures so that the intramedullary rod 104 will extend proximally within the intramedullary canal of the femur and provide an alignment reference for the guide system 100.

[0060] After the entry opening is created, the intramedullary rod 104 may be inserted through the entry opening and advanced into the intramedullary canal of the femur, as illustrated in FIG. ZB. The intramedullary rod 104 may extend proximally along the canal and define a reference axis corresponding generally to the axis of the femoral shaft. In certain embodiments the intramedullary rod may have a diameter associated with conventional mechanical alignment techniques. In other embodiments a smaller-diameter intramedullary rod may be used, for example when a kinematic alignment procedure is being performed or when reduced intrusion into the intramedullary canal is desired.

[0061] Prior to mounting the guide system 100 onto the intramedullary rod 104, the guide system may be prepared for use by selecting an appropriate interchangeable bushing 110 (see FIG. IE). The selected bushing may correspond to a desired distal valgus orientation in the coronal plane or may correspond to a configuration suitable for a kinematic alignment technique in which a fixed distal valgus angle is not imposed. The bushing 110 may be inserted into the receptacle 112 of the base 102 so that the internal bore 130 of the bushing defines the rod-receiving bore 108 that will receive the intramedullary rod 104. Optionally, the resection checker 150 may be coupled to the pivoting portion 106 by inserting alignment pins 154 of the resection checker 150 into corresponding alignment holes 156 of the pivoting portion 106.

[0062] In certain implementations, the guide system 100 may be prepared by installing optional components associated with the kinematic alignment subassembly 142, such as illustrated in FIG. IE. For example, a shim attachment 144 may be coupled to the main body 148 of the pivoting portion 106 and one or more shims 146 may be attached to the shim attachment. The shims 146 may be selected according to a desired joint surface height or according to a need to compensate for bone loss at the distal femur. When installed, the shims 146 may define the contact surface 114 that registers against the distal femoral surface during positioning of the guide system.

[0063] After the guide system 100 has been prepared, the base 102 of the guide system may be mounted onto the intramedullary rod 104. The rod may be inserted through the rodreceiving bore 108 defined by the interchangeable bushing 110 so that the guide system can slide along the rod toward the distal end of the femur. The guide system may be advanced distally along the rod until the contact surface 114 of the pivoting portion 106 engages the distal surface of the femur.

[0064] Once the pivoting portion 106 contacts the distal femoral surface (see FIG. 2C-1 and FIG. 2C-2), the pivoting portion 106 establishes an initial orientation relative to the distal femur, which may correspond to a neutral orientation defined by the biasing member 126 that biases the pivoting portion relative to the base. After the guide system has been positioned against the distal femur, the pivoting portion 106 may be temporarily secured relative to the bone using one or more fixation pins inserted through the elongated pin holes 128 of the pivoting portion 106 (see FIG. 1C). The fixation pins may be driven into the femur so that the guide system is stabilized against translational movement and against rotation in the axial andcoronal planes. Because the pin holes 128 are elongated in a generally sagittal direction, the pivoting portion 106 may still be capable of pivoting relative to the base 102 while the pins remain in place.

[0065] As shown in FIG. 2D, the resection checker 150 may provide one or more slots 152 configured to receive a resection guide or similar alignment instrument that is used to check the alignment in the sagittal plane. A resection guide may be inserted through one of the slots 152 of the resection checker so that the surgeon may visually assess the orientation of the guide system relative to the anterior surface of the femur. By observing the relationship between the resection guide and the anterior femoral cortex, the surgeon may determine whether the current sagittal orientation of the pivoting portion 106 is appropriate for the planned distal femoral resection.

[0066] If the observed orientation is not optimal, the surgeon may adjust the angular orientation 118 of the pivoting portion 106 relative to the base 102 by actuating the adjustment mechanism 120, as shown in FIG. 2E. In embodiments in which the adjustment mechanism includes a threaded adjustment screw, the surgeon may rotate the adjustment mechanism using a surgical driver engaged with the tool-engagement feature 122. Rotation of the adjustment mechanism may cause the pivoting portion 106 to pivot about the pivot axis 116 relative to the base 102, thereby increasing or decreasing the angular orientation 118 in the sagittal plane, as shown in FIG. 2F.

[0067] During adjustment of the pivoting portion 106, the surgeon may continue to observe the alignment relationship between the resection guide and the anterior surface of the femur. Incremental rotation of the adjustment mechanism 120 may allow the surgeon to gradually modify the sagittal orientation of the pivoting portion until a desired relationship between the resection guide and the femur is achieved. The visual indicator 124 on the base 102 may also provide guidance regarding the magnitude of the angular adjustment applied to the pivoting portion.

[0068] Once the desired sagittal orientation has been established, the resection checker 150 may then be removed by withdrawing the alignment pins 154 from the alignment holes 156 of the pivoting portion 106. After removal of the resection checker 150, a distal femoral cutting block 158 may be attached to the pivoting portion 106, as illustrated in FIG. 2G. Through this arrangement the cutting block 158 may be positioned relative to the pivotingportion 106 in a predetermined orientation corresponding to the adjusted sagittal alignment of the guide system.

[0069] Once coupled to the pivoting portion 106, the distal femoral cutting block 158 may be secured directly to the femur by inserting fixation pins 220 through pin holes 160 formed in the cutting block 158 (see FIG. 21). The fixation pins may anchor the cutting block to the bone so that the cutting block remains fixed relative to the femur when the remainder of the guide system is removed.

[0070] After the cutting block 158 has been secured to the femur, the base 102 and pivoting portion 106 may be withdrawn. Pins that were temporarily fixing the pivoting portion 106 may be removed. The bushing 110 may be pulled distally and removed. A coupling feature 170 that couples the cutting block 158 to the pivoting portion 106 is released (see FIG. 2H), such as by squeezing two levers 175 together to open a gripping interface between the coupling knob 170 and the cutting block 158 and / or the pivoting portion 106. The illustrated coupling feature 170 is merely exemplary and it should be understood that any suitable coupling feature may be used, including a clip-type or lever- actuated coupling. The base 102 and pivoting portion 106 are removed by sliding the base 102 distally along the intramedullary rod 104, as illustrated in FIG. 2H. The intramedullary rod 104 may then be removed from the femur while leaving the cutting block 158 fixed in place.

[0071] With the distal femoral cutting block 158 secured to the femur, the surgeon may verify the intended bone resection orientation by inserting a resection guide or saw blade into the cutting slot 162 of the cutting block. The cutting slot 162 may extend in a direction corresponding to the sagittal orientation previously established by the pivoting portion 106. In some embodiments, additional fixation pins may be inserted through auxiliary pin holes of the cutting block to provide additional stabilization during the cutting procedure.

[0072] The distal femoral bone resection may then be performed by advancing a surgical saw 230 blade through the cutting slot 162 of the cutting block 158 (see FIG. 21). The cutting slot may guide the saw blade so that the resulting resection plane corresponds to the sagittal orientation established during adjustment of the pivoting portion 106.

[0073] Completion of the bone resection produces a distal femoral surface oriented according to the sagittal alignment selected during the adjustment stage of the procedure. After the resection has been completed, the distal femoral cutting block 158 may be removed from thefemur by withdrawing the fixation pins securing the block to the bone. The surgical procedure may then proceed with subsequent steps of the total knee arthroplasty procedure, including preparation of the femoral component surfaces and implantation of the femoral prosthesis.

[0074] The extension / flexion adjustable femoral distal cutting guide system described herein provides a surgical instrument configured to enable controlled adjustment of a distal femoral bone resection angle in the sagittal plane during total knee arthroplasty procedures.Conventional surgical systems generally determine the sagittal orientation of the distal femoral cut indirectly through the geometry of intramedullary rod-based instruments, leaving the anterior-posterior inclination of the femoral component largely dependent on the surgeon’s intraoperative judgment. In contrast, the present guide system provides structural features that allow the sagittal orientation of the distal femoral cutting guide to be adjusted, verified, and fixed prior to performing bone resection.

[0075] Through the use of a pivoting portion that is movable relative to a base coupled to an intramedullary rod, together with an adjustment mechanism that allows controlled angular positioning, the guide system enables surgeons to establish a desired sagittal cutting orientation before bone removal occurs. By allowing sagittal orientation to be set and confirmed during the pre -resection stage, the system allows the surgeon to reproducibly achieve an intended distal femoral alignment that would otherwise be difficult to control using conventional instruments.

[0076] The guide system may provide several clinical advantages when used during femoral preparation. For example, improved control of sagittal alignment may reduce the likelihood of flexion gap imbalance that can occur when the femoral component is positioned in excessive flexion. Similarly, the ability to limit excessive extension of the distal femoral cut may reduce the likelihood of anterior notching and associated supracondylar femoral fracture. More consistent sagittal alignment may also improve postoperative load distribution and long-term joint stability by enabling more accurate placement of the femoral implant component relative to the femoral shaft.

[0077] The guide system may also be configured to support multiple surgical alignment methodologies. In particular, the system may include interchangeable bushings and associated components that allow use with both mechanical alignment techniques andkinematic alignment techniques. In embodiments used for kinematic alignment procedures, the system may further accommodate the use of smaller-diameter intramedullary rods and optional shim structures that facilitate reproduction of pre-defect joint surface geometry.

[0078] The structural arrangement of the system integrates multiple functional elements into a unified surgical instrument. These elements may include a pivoting guide structure that enables sagittal adjustment, an adjustment mechanism that allows controlled angular positioning, fixation features that maintain coronal plane stability during adjustment, and verification structures such as a resection checker that allow the surgeon to visually confirm the cutting orientation relative to the anterior surface of the femur. When combined with a detachable distal femoral cutting block, the system allows the established sagittal orientation to be transferred directly to the bone resection guide.

[0079] By integrating these features into a single guide system, the invention provides a comprehensive solution to limitations associated with conventional intramedullary roddependent instruments. The ability to independently adjust the sagittal plane orientation while maintaining stability of the guide relative to the femur allows surgeons to select a desired distal femoral cutting angle based on patient anatomy and surgical planning rather than relying solely on fixed instrument geometry.

[0080] Accordingly, the guide system described herein provides a surgical instrument that improves the reproducibility and controllability of distal femoral bone resection during total knee arthroplasty. The system allows surgeons to adjust, confirm, and secure the sagittal plane orientation of the distal femoral cut prior to bone removal, thereby providing improved alignment control compared with conventional systems in which sagittal orientation is largely predetermined by intramedullary rod positioning. Numerous modifications and alternative implementations may be employed without departing from the scope of the invention, and the invention is therefore defined by the claims that follow and their equivalents.

[0081] The following lists several examples in accordance with the principles described here. Example 1, an EFA Femoral Distal Cutting Guide for use in determining and adjusting the distal femoral bone-cutting angle in the Sagittal Plane prior to resection, as part of a bonecutting system for artificial knee joint placement, includes: a mechanism for real-time extension-flexion adjustment that can be set before actual bone cutting, thereby allowing the surgeon to obtain the intended femoral component angle in the Sagittal Plane.

[0082] Example 2: The bone-cutting system for artificial knee joint placement according to Example 1, wherein the EFA Femoral Distal Cutting Guide connects to a femoral- side fixation instrument, including an intramedullary (IM) rod, for the purpose of performing distal femoral resection, and thereby enables adjustment of extension-flexion angles in the Sagittal Plane.

[0083] Claim 3: The bone-cutting system for artificial knee joint placement according to Example 1 or 2, wherein: after determining the angle in the femoral Coronal Plane, said EFA Femoral Distal Cutting Guide fixes the Coronal Plane angle using an elliptical pinhole designated for Coronal Plane fixation, while still allowing extension-flexion angle adjustment in the Sagittal Plane.

[0084] Example 4: The bone-cutting system for artificial knee joint placement according to any of the above examples, wherein the EFA Femoral Distal Cutting Guide comprises an upper movable portion and a base portion. By means of an EFA adjustment screw, it forms a variable structure capable of adjusting the extension-flexion angle in the femoral Sagittal Plane.

[0085] Example 5: The bone-cutting system for artificial knee joint placement according to any of the above examples, wherein the EFA Femoral Distal Cutting Guide includes an EFA adjustment screw for setting the extension-flexion angle, and an angle fixing screw for locking the chosen angle.

[0086] Example 6: The bone-cutting system for artificial knee joint placement according to any of the above examples, wherein a set of angle bushings offering multiple angle variations (6°, 7°, 8°, 9°), and an additional bushing compatible with kinematic alignment (KA) methodology, are provided.

[0087] Example 7: The bone-cutting system for artificial knee joint placement according to any of the above examples, wherein a set of bone defect filling plates in multiple thicknesses (0.5mm, 1.0mm, 1.5mm, 2.0mm) is included, enabling reconstruction of the pre-defect joint surface height for KA-based procedures.

[0088] The foregoing description, for the purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Manymodifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the techniques and their practical applications. Others skilled in the art are thereby enabled to best utilize the techniques and various embodiments with various modifications as are suited to the particular use contemplated.

[0089] Although the disclosure and examples have been fully described with reference to the accompanying figures, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosure and examples as defined by the claims. Finally, the entire disclosure of the patents and publications referred to in this application are hereby incorporated herein by reference.

Claims

CLAIMS1. A femoral distal cutting guide system for guiding distal femoral bone resection comprising:a base for mounting to a fixation device fixed relative to a femur, wherein the fixation device is configured to establish a positional reference relative to the femur; anda pivoting portion for registering against a distal femoral surface, wherein the pivoting portion is pivotably connected to the base and configured for adjustably setting a distal femoral bone resection angle in a sagittal plane for intraoperative adjustment of sagittal alignment of the femoral distal cutting guide system prior to bone resection.

2. The system of claim 1, comprising interchangeable bushings for accommodating different fixation devices.

3. The system of claim 2, wherein the interchangeable bushings comprise a plurality of different angle variations for positioning the base at different angles relative to the fixation device.

4. The system of claim 1, comprising a bushing configured for a non-fixed distal valgus angle.

5. The system of claim 1, comprising an adjustment mechanism for adjustably controlling a pivot angle of the pivoting portion relative to the base in the sagittal plane while the pivoting portion is fixed relative to the femur in at least one other plane.

6. The system of claim 5, wherein the adjustment mechanism comprises a screw mechanism, a gear mechanism, a ratchet mechanism, a linkage mechanism, or an electromechanical mechanism.

7. The system of claim 1, wherein the pivoting portion is biased toward a position in which a surface of the pivoting portion that registers against the distal femoral surface during use is perpendicular to the fixation device when the base is mounted to the fixation device.

8. The system of claim 1, wherein the pivoting portion comprises at least one elliptical pin hole for engaging fixation pins fixed to the bone to maintain an orientation of the pivoting portion in a coronal plane while permitting the adjustable setting of the distal femoral bone resection angle in a sagittal plane without removing the fixation pins.

9. The system of claim 1, wherein a range of the adjustable setting of the distal femoral bone resection angle is 40 degrees or less.

10. The system of claim 1, wherein a range of the adjustable setting of the distal femoral bone resection angle is at least 5 degrees.

11. The system of claim 1, comprising at least one shim for reproducing a predefectjoint surface height associated with a kinematic alignment method.

12. The system of claim 1, comprising a resection checker configured for detachably connecting to the pivoting portion for checking an alignment of the pivoting portion with reference to an anterior surface of a femur.

13. The system of claim 12, wherein the resection checker comprises a plurality of slots for receiving a resection guide.

14. The system of claim 12, comprising a cutting block configured for detachably connecting to the pivoting portion and for attachment to the femur for guiding a bone saw.

15. The system of claim 1, wherein the fixation device comprises an intramedullary rod.

16. A method for distal femoral bone resection comprising:mounting a guide system to a fixation device fixed to a femur;adjusting the guide system to set a distal femoral bone resection angle in a sagittal plane; andusing the guide system to position a cutting block relative to the femur.

17. The method of claim 16, wherein mounting the guide system to the fixation device comprises sliding a base of the guide system along the fixation device until a pivoting portion of the guide system contacts a distal surface of the femur.

18. The method of claim 16, wherein adjusting the guide system comprises pivoting a pivoting portion of the guide system relative to a base of the guide system about a pivot axis extending generally in a medial-lateral direction.

19. The method of claim 16, wherein adjusting the guide system comprises engaging an adjustment mechanism to change an angular orientation of a pivoting portion of the guide system relative to a base of the guide system.

20. The method of claim 19, wherein the adjustment mechanism comprises a screw mechanism, a gear mechanism, a ratchet mechanism, a linkage mechanism, or an electromechanical mechanism.

21. The method of claim 19, further comprising engaging a tool with a toolengagement feature of the adjustment mechanism to make an adjustment.

22. The method of claim 16, comprising temporarily securing the guide system to the femur with at least one fixation pin inserted through an elongated pin hole of the guide system, wherein the guide system is adjusted to set the distal femoral bone resection angle in the sagittal plane while the guide system is secured to the femur with the at least one fixation pin.

23. The method of claim 16, comprising attaching a resection checker to the guide system and evaluating alignment of the guide system relative to an anterior surface of the femur.

24. The method of claim 23, comprising removing the resection checker prior to positioning the cutting block.

25. The method of claim 16, wherein using the guide system to position the cutting block comprises attaching the cutting block to the guide system and securing the cutting block to the femur with fixation pins.

26. The method of claim 25, comprising removing the guide system and the fixation device while leaving the cutting block secured to the femur and resecting a distal femoral bone surface using a surgical saw guided by the cutting block.

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