Expandable tibial tray insert trial

Abstract

To provide knee arthroplasty trials, systems, and related methods.SOLUTION: A knee arthroplasty trial system may include an expandable tibial tray trial having top and bottom plates, an actuation screw retained in the bottom plate, and an expansion ramp configured to slide along the bottom plate and lift the top plate as the ramp translates forward. The actuation screw may define a helical cut with step portions, and the expansion ramp may include a pin configured to engage the helical cut of the actuation screw. When the actuation screw is rotated, the pin rides along the helical cut and is configured to rest within one of the step portions, thereby ensuring that the expandable tibial tray trial expands only to discrete thicknesses.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 482,889, filed February 2, 2023, and U.S. Provisional Patent Application No. 63 / 517,382, filed August 3, 2023, which are hereby incorporated by reference in their entireties for all purposes.

[0002] FIELD OF THE INVENTION This application relates generally to knee arthroplasty, and more particularly to knee arthroplasty trials and related methods for assessing the fit of permanent implants. [Background technology]

[0003] Knee arthroplasty, often referred to as knee replacement, is a surgical procedure used to reconstruct and resurface a knee damaged by, for example, arthritis. Total knee arthroplasty (TKA) devices can replace both the tibiofemoral joint and the patellofemoral joint. The tibiofemoral joint is where the tibia and femur articulate. The patellofemoral joint is where the patella and femur articulate. To replace the tibiofemoral joint, knee arthroplasty can include a femoral implant secured to the distal end of the femur (or thighbone), a tibial tray implant secured to the proximal end of the tibia (or shinbone), and an insert positioned therebetween. The femoral and tibial implants cover the ends of the femur and tibia, respectively, which form the knee joint, thereby reconstructing the knee. To replace the patellofemoral joint, knee arthroplasty may include a patellar prosthesis to replace the back of the patella and create a replacement articular surface that interfaces with a femoral implant. Summary of the Invention [Problem to be solved by the invention]

[0004] To properly determine implant size, one or more trials may be used by the surgeon during the surgical procedure. Trials are temporary components that match the shape of the final implant to a corresponding size so that the surgeon can evaluate the fit of a given size before permanently implanting the final component. The sizing of each of these components must match the native anatomy as closely as possible. Femoral and tibial trial components may vary in size in the anterior-posterior (AP) and medial-lateral (ML) directions, and inserts may also be available in many different thicknesses. This requires many trials to cover all tibial / femoral sizes and insert thicknesses. The trialing process can be time-consuming, and multiple trials may be required to find the proper fit. Discrete fixed-height trials can be difficult to insert and remove from the joint space because the optimal fit may be very snug. This can be time-consuming and frustrating if the surgeon needs to try multiple thicknesses before being confident that the correct thickness has been selected. Shim systems may include sets of shims that can be inserted to increase stack height, but these too require many components and can be time consuming and complicated to assemble. Thus, there is a need for improved trial devices that reduce the total number of instruments and increase efficiency during the trial reduction process. [Means for solving the problem]

[0005] To meet this and other needs, knee arthroplasty trials, systems, and methods are provided. In particular, the knee arthroplasty trials may include an expandable tibial trial with a screw-driven ramp mechanism for forming a separation between the top and bottom plates. The screws may include step increments, allowing the trial to be set at discrete heights corresponding to available tibial insert sizes. The expandable tibial trial may include, for example, an articular insert that slides or snaps onto the expandable trial. A complete knee arthroplasty trial system may include an expandable tibial trial with an attached articular insert and a femoral trial configured to mate with the articular insert, thereby mimicking the proper function of a knee.

[0006] According to one embodiment, a knee arthroplasty trial system includes an expandable tibial tray trial having a top plate and a bottom plate, an actuation screw retained in the bottom plate, and an expansion ramp configured to slide along the bottom plate and lift the top plate as the ramp translates anteriorly. The actuation screw defines a spiral cut having stepped portions, and the expansion ramp includes a pin configured to engage the spiral cut of the actuation screw. As the actuation screw rotates, the pin advances along the spiral cut and is configured to fit into one of the stepped portions, thereby ensuring that the expandable tibial tray trial only expands to a discrete thickness.

[0007] The knee arthroplasty trial system may include one or more of the following features. The expansion ramp may include a ramp having a pair of vertical support walls defining a channel therebetween for receiving the actuation screw. The pin may be a cross pin extending across the channel between the pair of vertical support walls. The ramp may define an upper ramped surface providing a ramped surface configured to mate with a corresponding surface on the top plate. The ramp may include a pair of rails extending from a bottom surface of the ramp, the rails being configured to mate with corresponding grooves in the bottom plate. The actuation screw may include a head having a drive recess and a shaft defining a helical cut. The helical cut may include a spiral cut extending completely through the shaft to form a fully open channel. The trial system may also include an articular insert trial attached to the top plate of the expandable tibial tray trial. The articular insert trial may include a piston having an annular groove configured to mate with a corresponding opening in the top plate such that a spring in the top plate snaps into the groove in the piston, thereby securing the articular insert trial to the expandable tibial tray trial. The system may also include a femoral trial having an anterior flange, a pair of posterior condylar flanges, and a distal portion therebetween. The femoral trial may have an outer articular surface with a smooth, rounded shape that contacts the articular insert trial, and a medial surface shaped to match the resected femur with five resection cuts.

[0008] According to one embodiment, an expandable tibial tray trial includes top and bottom plates configured to nest within one another in a collapsed position, an actuation screw configured to rotate about an actuation axis, the actuation screw having a head and a shaft defining a helical cut, the head defining a plurality of indicators around its circumference, a ramp having a pair of vertical support walls defining a channel therebetween for receiving the actuation screw, and an expansion ramp having a cross pin extending across the channel and configured to pass through the helical cut of the actuation screw. As the actuation screw rotates, the ramp translates along the actuation axis, expanding the top plate, thereby moving the top plate to an expanded position such that one of the indicators corresponds to a discrete height on the expansion trial.

[0009] The expandable tibial tray trial may include one or more of the following features: The indicator may include a series of numbers laser marked on the head of the actuation screw; The spiral cut may include stepped portions, and when the cross pin is seated in one of the stepped portions, the visible indicator corresponds to one of the discrete heights; The bottom plate may have a central block portion defining a cylindrical through-opening, and the actuation screw may be retained in the cylindrical through-opening in the central block portion of the bottom plate; The block portion may define a gap in its top surface such that when one of the indicators is aligned with the gap, the indicator readout corresponds to a discrete height of the expansion trial; The head may define a lateral opening that, when aligned with the gap, indicates an initial start position of the expandable trial.

[0010] According to one embodiment, the expandable tibial tray trial includes top and bottom plates configured to nest within one another in a collapsed position, an actuation screw configured to rotate about an actuation axis, the actuation screw having a head and a shaft defining a helical cut with stepped portions, and an expansion ramp having a ramp with a pair of pins with free ends configured to engage the helical cuts of the actuation screw. As the actuation screw rotates, the pins travel along the helical cuts and are configured to fit into one of the stepped portions, thereby ensuring that the expandable tibial tray trial only expands to a discrete thickness.

[0011] The expandable tibial tray trial may include one or more of the following features: The ramp may include a base having an obturator bore sized and dimensioned to receive the actuation screw; The free end of the pin may protrude into the bore to follow the helical cut when the screw is rotated; The pins may be off-axis and offset from one another; The helical cut of the actuation screw may be defined on the surface of the shaft without penetrating the core of the screw; The ramp may define a plurality of male ramp faces having ramped surfaces configured to engage corresponding female ramp faces on the top plate.

[0012] According to one embodiment, a method for trialing an implant may include one or more of the following steps in any suitable order: (1) attaching a modular joint insert trial to an expandable trial, for example, via a snap-fit or sliding attachment joint; (2) placing the expandable trial at the surgical site, the expandable trial having top and bottom plates, an actuation screw having a spiral cut with steps separated by a thread riser, and an expansion ramp having a pin configured to follow the spiral cut; and (3) rotating the actuation screw to slide the expansion ramp along the bottom plate and lift the top plate as the ramp translates forward, such that when the pin rests on one step, the expandable trial is expanded to a discrete thickness. If the pin is on the thread riser, the expandable trial cannot maintain its height under compression unless it reaches the step. When the step is reached during expansion, the pin retracts into the step, thereby providing tactile feedback to the user. The actuation screw may have one or more visual indicators to designate a given trial thickness, thereby providing visual feedback to the user.

[0013] Also provided are kits that include various types and sizes of implants, including femoral implants, tibial trays, and inserts with different anterior-posterior (AP) and / or medial-lateral (ML) aspects, trials, including expandable tibial trials, articular trial inserts, and femoral trials, various types and configurations of instruments, including inserter instruments, and other components for performing the procedure. [Brief explanation of the drawings]

[0014] A more complete understanding of the present invention and its attendant advantages and features will be more readily appreciated by reference to the following detailed description when considered in conjunction with the accompanying drawings. [Figure 1]1 illustrates an exploded view of a total knee arthroplasty trial including a femoral trial, a static tibial trial, and an articular insert trial, according to one embodiment. [Figure 2A] 10A-10C illustrate an expandable tibial trial assembly in a fully collapsed position and a fully extended position, respectively, according to one embodiment. [Figure 2B] 10A-10C illustrate an expandable tibial trial assembly in a fully collapsed position and a fully extended position, respectively, according to one embodiment. [Figure 3] 13 illustrates a helical stepped screw having steps and thread risers for engaging an extension ramp, according to one embodiment. [Figure 4A] 1A-1C show a perspective view, a front cross-sectional view, and a side cross-sectional view, respectively, of an expansion ramp having a cross pin configured to mate with the shoulder threads of an actuation screw, according to one embodiment. [Figure 4B] 1A-1C show a perspective view, a front cross-sectional view, and a side cross-sectional view, respectively, of an expansion ramp having a cross pin configured to mate with the shoulder threads of an actuation screw, according to one embodiment. [Figure 4C] 1A-1C show a perspective view, a front cross-sectional view, and a side cross-sectional view, respectively, of an expansion ramp having a cross pin configured to mate with the shoulder threads of an actuation screw, according to one embodiment. [Figure 5A] 10 shows the actuation screw mating with the expansion ramp in the collapsed and expanded positions, respectively. [Figure 5B] 10 shows the actuation screw mating with the expansion ramp in the collapsed and expanded positions, respectively. [Figure 6A] 10A-10C show the thread ramp joint of the cross pin in the collapsed and expanded positions, respectively. [Figure 6B] 10A-10C show the thread ramp joint of the cross pin in the collapsed and expanded positions, respectively. [Figure 7A] 10A-10C show the tibial trial assembly in a collapsed position and an extended position, respectively. [Figure 7B] 10A-10C show the tibial trial assembly in a collapsed position and an extended position, respectively. [Figure 8A]10 illustrates a cruciate retaining (CR) snap-on insert that can be attached to an expandable tibial trial, according to one embodiment. [Figure 8B] 10 illustrates a cruciate retaining (CR) snap-on insert that can be attached to an expandable tibial trial, according to one embodiment. [Figure 8C] 10 illustrates a cruciate retaining (CR) snap-on insert that can be attached to an expandable tibial trial, according to one embodiment. [Figure 9A] 10 illustrates a posterior stabilized (PS) snap-on insert that is attachable to an expandable tibial trial, according to one embodiment. [Figure 9B] 10 illustrates a posterior stabilized (PS) snap-on insert that is attachable to an expandable tibial trial, according to one embodiment. [Figure 10] 13 illustrates a laser marking indicator on the actuation screw for determining insert thickness, according to one embodiment. [Figure 11A] 10A-10C illustrate an expandable tibial trial assembly in a fully collapsed position and a fully extended position, respectively, according to one embodiment. [Figure 11B] 10A-10C illustrate an expandable tibial trial assembly in a fully collapsed position and a fully extended position, respectively, according to one embodiment. [Figure 12A] 1A and 1B show a perspective view and a bottom view of a top plate with an extended lamp assembly according to one embodiment. [Figure 12B] 1A and 1B show a perspective view and a bottom view of a top plate with an extended lamp assembly according to one embodiment. [Figure 13A] 1A and 1B show a perspective view and a top view of a bottom plate with an extended lamp assembly according to one embodiment. [Figure 13B] 1A and 1B show a perspective view and a top view of a bottom plate with an extended lamp assembly according to one embodiment. [Figure 14] 1 illustrates a shoulder screw having a step and a thread riser according to one embodiment. [Figure 15A]10 shows a cross-sectional view of an extension ramp having a protruding pin configured to mate with a shoulder thread of an actuation screw, according to one embodiment. [Figure 15B] 10 shows a cross-sectional view of an extension ramp having a protruding pin configured to mate with a shoulder thread of an actuation screw, according to one embodiment. [Figure 16A] 10 shows the actuation screw mating with the expansion ramp in the collapsed and expanded positions, respectively. [Figure 16B] 10 shows the actuation screw mating with the expansion ramp in the collapsed and expanded positions, respectively. [Figure 17A] 10A-10C show the tibial trial assembly in a collapsed position and an extended position, respectively. [Figure 17B] 10A-10C show the tibial trial assembly in a collapsed position and an extended position, respectively. [Figure 18A] 10A-10C show top and bottom views, respectively, of an articular insert trial, top and bottom plates, and an expansion assembly of an expandable tibial trial, according to one embodiment; [Figure 18B] 10A-10C show top and bottom views, respectively, of an articular insert trial, top and bottom plates, and an expansion assembly of an expandable tibial trial, according to one embodiment; [Figure 19] 10 illustrates a slide-on joint insert trial attached to an expandable tibial trial, according to one embodiment. [Figure 20A] 1 illustrates an articular insert trial and expandable tibial trial assembly having a locking pin for attaching a modular posterior stabilization (PS) post, according to one embodiment. [Figure 20B] 1 illustrates an articular insert trial and expandable tibial trial assembly having a locking pin for attaching a modular posterior stabilization (PS) post, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Embodiments of the present disclosure generally relate to trials, systems, and methods for knee replacement surgery. In particular, a knee arthroplasty trial may include an expandable tibial trial with a screw-driven ramp mechanism configured to create a separation between a top plate and a bottom plate. The actuation screw may include step increments, allowing the trial to be set to discrete heights corresponding to available tibial insert sizes. The expandable tibial trial may include, for example, an articular insert trial that slides or snaps onto the expandable trial. In this manner, utilizing expandable tibial trials representing multiple insert thicknesses may reduce the total number of trials, improving the efficiency of the trial reduction process.

[0016] Although generally described with reference to knee arthroplasty, it will be understood that the trials and stems described herein may be applied to other orthopedic locations and applications, such as the spine, including between vertebrae, long bones such as the femur, tibia, humerus, clavicle, fibula, ulna, radius, etc., bones of the foot, bones of the hand, or other suitable bones or joints. It will further be understood that although generally described with reference to temporary trials, similar features may also be applied to permanent implants.

[0017] Additional aspects, advantages, and / or other features of exemplary embodiments of the present invention will become apparent in view of the following detailed description. It will be apparent to those skilled in the art that the described embodiments provided herein are merely exemplary and illustrative, and not limiting. Numerous embodiments and modifications thereof are contemplated as falling within the scope of the present disclosure and equivalents thereto.

[0018] Referring now to the drawings, wherein like reference numerals may refer to like elements, FIG. 1 illustrates a total knee implant trial system 10 according to one embodiment. The total knee implant trial system 10 may include a trial femur or femoral trial 12, a trial tibia or tibial trial 14, and a trial insert or articular insert trial 16. The femoral trial 12 may be used to approximate a permanent femoral implant to replace the end of the femur or thigh bone, for example, after resection. The tibial trial 14 may be used to approximate a permanent tibial tray implant to replace the end of the tibia or shin bone, for example, after resection. In this embodiment, the tibial trial 14 is shown as a static component, but it will be understood that the tibial trial 14 may be replaced with any of the expandable trials 100, 200 described in more detail herein. The articular insert trial 16 is attachable to the tibial trial 14 and configured to interface with the femoral trial 12 to mimic proper knee function. Each of the trials 12, 14, 16 is a temporary component that matches the shape of the final implant to a corresponding size so that the surgeon can evaluate the fit of a given size before permanently implanting the final component in the patient.

[0019] The femoral trial 12 mimics a femoral implant, which curves from front to back across the distal femur to replicate the natural shape of the natural femur for proper knee function. The femoral trial 12 may include an anterior flange 20, a pair of posterior condylar flanges 22, 24, and a distal portion 26 therebetween. The pair of posterior condylar flanges 22, 24 include a medial condylar portion 22 and a lateral condylar portion 24 configured to mimic the condyles of a natural femur. The exterior or lateral articular surface 28 of the femoral trial 12 may form a rounded C-shape or other suitable shape corresponding to the natural distal femoral surface of a human knee. The femoral trial 12 may be positioned relative to the resected femur. For example, the femoral trial 12 may have a medial or inner surface 30 shaped to match the resection cuts in the distal femur. In the illustrated embodiment, the inner surface 30 includes a five-cut bone-interfacing surface that mates with five corresponding resection cuts to ensure an optimal fit. It will be appreciated that any mating surface suitable for resection may be used for the femoral trial 12 and corresponding femoral implant.

[0020] The tibial trial 14 mimics a tibial tray implant and replaces the proximal end of the tibia or shin bone, e.g., after resection. The tibial tray 14 may be provided in multiple sizes that vary in anterior-posterior (AP) and medial-lateral (ML) orientation to fit the patient's anatomy. In this embodiment, the tibial trial 14 includes a plate 40 having opposing proximal and distal surfaces 42 and 44. The distal surface 44 of the plate 40 is configured to engage the resected surface of the tibia. The proximal surface 42 is sized and shaped to receive or attach the insert 16, e.g., using one or more pegs or other fixation mechanisms.

[0021] The insert trial 16 is positioned between the tibial trial 14 and the femoral trial 12 to mimic natural knee motion and provide support during knee flexion and extension. The insert trial 16 includes a body having an upper articular surface 52 configured to mate with the tibial tray 14 and an opposing lower surface 54. The upper articular surface 52 may be concavely contoured to articulate with the outer articular surface 28 of the femoral trial 12. The outer wall 56 of the insert 16 may have a general shape, such as a long oval with a concave side, e.g., a kidney bean shape, that generally corresponds to the outer shape of the tibial trial 14. The insert 16 may be available in various thicknesses, e.g., ranging from 10 mm to 30 mm. The insert 16 balances the joint space and provides the articular surface 52 as the knee moves through its physiological range of motion.

[0022] 2A-2B, an expandable tibial trial assembly 100 is shown in accordance with one embodiment. The expandable trial assembly 100 includes top and bottom platforms or plates 102, 104, which are configured to expand via an expansion assembly including an actuation screw 106 and an expansion ramp 108. In FIG. 2A, the expandable tibial trial assembly 100 is shown in a fully collapsed position. As the screw 106 rotates, the expansion ramp 108 is pushed forward between the two plates 102, 104, thereby creating expansion between them. The ramp 108 slides along the bottom plate 104, lifting the top plate 102 as it translates anteriorly. In FIG. 2B, the expandable tibial trial assembly 100 is shown in a fully extended position. The actuation screw 106 may be operated using a separate instrument, such as a driver 400, located far anteriorly of the device 100. This anterior access allows the surgeon to expand the trial intraoperatively without removing the trial from the joint space. In one embodiment, the plates 102, 104 can be expanded in discrete increments that correspond to a thickness that corresponds only to the thickness of the available tibial insert. The expandable tibial trial 100 can be expanded to the available discrete thicknesses, allowing the surgeon to determine the optimal sizing and fit for the permanent insert and tibial tray implant.

[0023] The top plate 102 and the bottom plate 104 can be configured to nest within each other in a collapsed position, as best seen in FIG. 2A . Each of the top plate 102 and the bottom plate 104 includes an upper surface 110 and an opposing lower surface 112. When in the collapsed position, the bottom surface 112 of the top plate 102 can contact the top surface 110 of the bottom plate 104. Each of the plates 102 includes an anterior side 114 configured for user access and an opposing posterior side 116 that can be initially positioned within the surgical site. The outer shape of the plates 102, 104 can be rounded or curved, similar to a tibial tray implant. For example, the plates 102, 104 can have a general shape of a long oval with a concave side, such as a kidney bean shape. The anterior side 114 can form an outer convex side as one long side, and the posterior side 116 can include an inner concave side separating two lobes or wings.

[0024] The top plate 104 may include a compound recess 118 sized and dimensioned to receive at least a portion of the expansion ramp 108. The recess 118 may define an angled or inclined surface 119 that corresponds to the inclined surface 160 of the expansion ramp 108. As the expansion ramp 108 translates forward, the corresponding inclined surfaces 119, 160 slide against each other. The upward inclination of the inclined plate 160 translates the horizontal movement of the ramp 108 into vertical movement of the top plate 104, thereby lifting the top plate 104 vertically relative to the bottom plate 102. The top plate 104 may define one or more through openings 120 configured to connect the trial inserts 180A, 180B to the expandable trial 100. The openings 120 may include, for example, cylindrical openings configured to receive corresponding posts 190 from the snap-on insert trials 180A, 180B, as described in more detail with respect to FIGS. 8A-8C .

[0025] The bottom plate 104 may include a central block portion 122 configured to hold the actuation screw 106. The block portion 122 may be centrally located along the forward side 114 of the bottom plate 104. The block portion 122 defines a cylindrical through opening sized and dimensioned to hold the actuation screw 106 therein. The sides of the block 122 may define angled or sloped surfaces 124 configured to mate with protrusions 126 having corresponding mating surfaces along the top plate 102, thereby maintaining uniform vertical movement of the top plate 102 relative to the bottom plate 104. The protrusions 126 may extend forward to mate with the block surfaces 124. The protrusions 126 may be angled or sloped inward toward each other from the rearward side 116 to the forward side 114 of the plate 102. The bottom plate 104 may define one or more through openings 127 that align with the post openings 120 in the top plate 102.

[0026] The actuation screw 106 is configured to rotate about an actuation axis 128 between the forward end 114 and the rearward end 116 of the bottom plate 104. As best seen in FIG. 3 , the actuation screw 106 includes a head 130 and a shaft 132. The proximal end of the head 130 may define a drive recess 134 configured to receive an instrument, such as a driver 400, to rotate or actuate the actuation screw 106. The drive recess 134 may include a trilobe, hexagonal, star, or other suitable recess configured to engage with a driver instrument and apply torque to the actuation screw 106. A lateral opening 136, such as a circular or oval opening, may be provided in the head 130 and in fluid communication with the drive recess 134. As will be described in more detail with respect to FIG. 10 , the lateral opening 136 may function as a zero indicator or starting position for the available expansion height. The head 130 also defines a number of indicators 137, such as etchings and / or laser markings, around its circumference, which may provide the user with a visual indication of the height accrued as the screw 106 is rotated.

[0027] The actuation screw 106 may be retained within the bottom plate 104 by, for example, one or more pins 140. The actuation screw 106 may define an annular groove 138 between the head 130 and the shaft 132. The annular groove 138 may include a semicircular recess configured to receive a portion of the pin 140. For example, a pair of cylindrical pins 140 may extend vertically through the block 122 to retain the actuation screw 106 within the block 122 of the bottom plate 104 while still allowing the screw 106 to rotate. It will be understood that the screw 106 may be constrained in any suitable manner in the block portion 122 of the bottom plate 104.

[0028] In one embodiment, the actuation screw 106 is a stepped helical thread, which ensures that the trial device 100 only expands to a discrete thickness corresponding to the available tibial insert thickness. The shaft 132 of the actuation screw 106 defines a helical cut 142, which includes a spiral or helical-shaped channel cut along the length of the screw body. The helical cut 142 extends completely through the shaft 132, forming a fully open channel from the surface to the core of the shaft 132. The helical cut 142 is configured to receive and guide the cross pin 152 of the expansion ramp 108. The helical cut 142 may include one or more thread risers 144 and one or more step portions 146. Each thread riser 144 connects the step portions 146. The thread risers 144 may include a curved or angled relief, for example, having a larger radius than the step portions 146. As the screw 106 rotates, the thread rise 144 correlates with the vertical distance the spiral cut 142 advances axially. Because the thread rise 144 is steep, the trial 100 cannot maintain its height under compression until it reaches the step 146. This prevents the user from setting the trial 100 to an intermediate height where a corresponding tibial insert is not available. The step 146 may include a curved or angled notch or cutout configured to hold the cross pin 152 and accommodate the thickness of the available tibial insert. The step 146 may transition to the thread rise 144 via a pronounced ridge or crest. The thread rise 144 and step 146 may extend along one side 148 of the spiral cut 142. The opposite side 149 of the spiral cut may define a continuous helical or spiral curve. These sides 148, 149 may be inverted or configured for a stepped feature.

[0029] 4A-4C, an extension ramp 108 is shown according to one embodiment. The extension ramp 108 includes a ramp 150 and a cross pin 152 configured to engage the stepped helical screw 106. The ramp 150 includes a base 154 and a pair of vertical support walls 156 defining an open channel 158 therebetween for receiving the body of the screw 106. The channel 158 includes a curved or semicircular recess sized and dimensioned to provide clearance for the screw 106 therethrough. The central bore axis of the channel 158 is coaxial with the actuation axis 128. The ramp 150 defines a ramp or upper inclined surface 160 that provides a sloped or inclined surface configured to guide or encourage movement of the top plate 102. The sloped surface 160 includes an upward slope from a bottom surface 162 to a top surface 164 of the ramp 150, and may translate horizontal movement of the extension ramp 108 into vertical movement of the top plate 102. The tilter 150 may include a pair of lower wings 166 extending outwardly away from each other along the bottom 162 of the tilter 150. The wings 166 may provide the upper ramp surface 160 with two distinct L-shaped portions on either side of the screw-receiving channel 158. A pair of rails 168 may extend from the bottom 162 of the tilter 150. The rails 168 may have an L-shaped cross-section with free ends extending outwardly away from each other. The rails 168 are configured to fit into corresponding grooves in the bottom plate 104. In this manner, the rails 168 are configured to slide along the bottom plate 104 and provide linear movement of the tilter 150 as the actuation screw 106 is rotated.

[0030] The expandable trial 100 may initially start with a first thickness equivalent to, for example, a 10 mm tibial insert trial. Using an instrument such as the driver 400, the actuation screw 106 may be rotated to expand the trial 100 to represent discrete thicknesses corresponding to, for example, 11 mm, 12 mm, 13 mm, 15 mm, and 17 mm tibial insert trials. As the shoulder screw 106 rotates, it pushes the cross pin 152 forward through the helical cut 142. The first step 146 may be encountered after the screw 106 moves the cross pin 152, and thus the attached ramp 108, forward a given distance, such as a 1 mm increment. The sloped surface 160 of the ramp 108 may be sloped at a 45-degree angle to ensure that the rise of the top plate 102 is equal to the travel of the ramp 108 along the bottom plate 104. When expanding from 11 mm to 12 mm and from 12 mm to 13 mm, similar increments, such as 1 mm increments, may occur. When expanding from 13 mm to 15 mm, the step 146 of the screw 106 occurs after the cross pin 152 is pushed 2 mm by the screw 106. When expanding from 15 mm to 17 mm, the same 2 mm step may be used. In other words, the amount of expansion is controlled by the location and number of the step 146 of the screw 106, which allows expansion to a predetermined trial thickness.

[0031] The shoulder screw 106 ensures that the trial 100 expands only to a discrete thickness corresponding to the available tibial insert thickness. Because the thread riser 144 is steep, the trial 100 cannot maintain its height under compression until it reaches the next step 146. This prevents the user from setting the trial to an intermediate height for which a corresponding tibial insert is not available. For example, the steps 146 may not be present in 14 mm or 16 mm increments because these implant sizes are not offered. The steps 146 may incorporate a 3-degree back angle to lock expansion while the surgeon performs range-of-motion testing. Upon reaching a given step 146 during expansion, the cross pin 152 drops into the backcut step 146, providing tactile feedback to the user. This allows the surgeon to feel when the expansion has reached the available implant size. Additionally, a laser marking or indicator 137 around the head 130 of the screw 106 provides visual feedback of the represented insert trial height.

[0032] 5A-5B and 6A-6B, the movement of the extension ramp 108 due to rotation of the actuation screw 106 is shown in more detail. In FIGS. 5A and 6A, the screw 106 and ramp 108 are shown in a collapsed position with the extension ramp 108 retracted to its forward-most position. The cross pin 152 extends through the spiral cut 142 of the screw 106 and is in an initial start position. In FIGS. 5B and 6B, the screw 106 and ramp 108 are shown in an extended position with the extension ramp 108 extended to its rearmost position. As the screw 106 rotates, the cross pin 152 moves along the spiral cut 142 of the screw 106 until it reaches the final step 146. This, in turn, causes the ramp 150 to slide along the bottom plate 104 by the rail 168 and press the ramp surface 160 against the corresponding ramp surface 119 of the top plate 102, thereby expanding the top plate 102 upward. 7A-7B show the expandable tibial trial 100 in a fully collapsed position and a fully extended position, respectively.

[0033] The expansion ramp 108 is captured by the bottom plate 104, limiting its movement to a single direction. This prevents the ramp 108 from tilting when the trial 100 is subjected to an uneven load. The expansion ramp 108 slides along the bottom plate 104, elevating the top plate 102 as the ramp 108 moves anteriorly. The top plate 102 is captured by the ramp 108, allowing expansion only when driven by the expansion ramp 108. This ensures that the trial 100 always remains at the height indicated by the laser marking 137 on the screw head 130. The ramp 108 capturing the top plate 102 also prevents the top plate 102 from tilting when the trial 100 is subjected to a unilateral load. This extension trialing mechanism allows a single expansion mechanism to represent multiple different tibial insert thicknesses, e.g., six different thicknesses, thereby simplifying the trialing process.

[0034] 8A-8C and 9A-9B, examples of modular articular insert trials 180A, 180B are shown. To minimize the number of components and increase user convenience, the expandable tibial trial 100 may incorporate quick-connect articular insert trials 180A, 180B, for example, featuring a snap-on mounting interface. FIGS. 8A-8B show an articular insert trial 180A configured for trialing a cruciate-retaining (CR) implant. In a cruciate-retaining (CR) procedure, the posterior cruciate ligament (PCL) and femoral intercondyle are preserved, which may result in better proprioception, balance, and kinematics. FIGS. 9A-9B show an articular insert trial 180B configured for trialing a posterior-stabilized (PS) implant. In a posterior-stabilized (PS) procedure, the posterior cruciate ligament (PCL) and femoral intercondyle are resected. The posterior-stabilized (PS) implant includes a raised surface or post 188 configured to mate with the femoral implant. The post 188 has an articular surface 189 configured to interface with the femoral implant, which may result in better knee flexion and a more reliable restoration of knee kinematics.

[0035] The insert trials 180A, 180B may be similar to the insert trial 16. In either case, the modular insert trials 180A, 180B include a body having an upper articular surface 182 and an opposing lower surface 184 configured to attach to the expandable tibial trial 100. The upper articular surface 182 may be concavely contoured to articulate with a corresponding femoral trial. The outer wall 186 of the inserts 180A, 180B may have a general profile similar to that of the expandable tibial trial 100. As shown in FIGS. 9A-9B , the posterior stabilized (PS) insert 180B may further include a raised post 188 extending from the upper articular surface 182. The raised post 188 may be configured to fit into a corresponding box or notch in the center of the femoral component. The insert trials 180A, 180B may have a known thickness such that the corresponding insert thickness can be determined from the reading of the actuation screw indicator 137.

[0036] As best seen in FIG. 8C , one or more pegs or pistons 190 may extend from the insert trials 180A, 180B to couple the modular insert trials 180A, 180B to the expandable trial 100. The pistons 190 may include cylindrical posts having circular cross-sections extending downwardly from the lower surface 184 of the insert 180. The pistons 190 are configured to fit within corresponding cylindrical openings 120 in the top plate 102 of the expandable trial 100. Each piston 190 may define an annular groove 192 configured to retain the piston 190 in the opening 120 via, for example, a spring 198. Each opening 120 may include a downward extension or housing 194 sized and dimensioned to be received in a corresponding cylindrical opening 127 in the bottom plate 104 when the trial 100 is fully collapsed. The housing 194 defines an internal groove 196 configured to retain a spring 198 therein. The spring 198 may include a seal spring, a canted coil spring, a snap ring, a retaining ring, or other suitable fastening mechanism.

[0037] When the piston 190 is fully seated in the opening 120, a spring 198 engages an outer groove 192 on the piston 190, thereby retaining the piston 190 in the top plate 102. The spring 198 may snap into the groove 192 and apply a radial force to the piston 190, thereby securing the modular insert trial 180A, 180B to the expandable trial 100. In one embodiment, each insert trial 180A, 180B may include a pair of pistons 190 that align with the springs 198 housed in the top plate 102 of the expandable trial 100. The pistons 190 allow the insert trial 180A, 180B to be securely attached to the expandable trial 100 while facilitating easy connection and disconnection. With these modular articular insert trials 180A, 180B, a single expansion trial 100 may be used to trial both cruciate-retaining (CR) and posterior-stabilized (PS) insert styles. Employing one expansion trial 100 with two modular joint inserts 180A, 180B allows for the replacement of multiple static tibial insert trials.

[0038] Referring now to FIG. 10 , the actuation screw 106 is shown in a series of rotational positions, indicating the trial thickness to the user. The expandable trial 100 functions to allow the surgeon to see what thickness is currently being trialed during the procedure. As the thickness of the trial 100 changes as it expands, the thickness reading also changes, indicating the achieved thickness. In one embodiment, the expandable trial 100 reads the achieved thickness using the method shown in FIG. 10 . The top surface of the block portion 122 of the bottom plate 104 is laser marked with the number “1” that is the same for all sizes (e.g., 10, 11, 12, 13, 15, 17). A second number 137 may be engraved or laser marked on the head 130 of the shoulder screw 106, allowing the indicator number 137 to change as the screw 106 is rotated. The indicator 137 directly ties the expansion of the trial 100 to the indicated thickness, so the surgeon always knows what thickness the trial 100 is currently representing.

[0039] In the example shown in FIG. 10 , at position (a), the opening 136 represents an initial starting position or implant size "10." As the screw 106 rotates to position (b), the indicator 137 aligns with a gap in the top surface of the block 122 of the bottom plate 104, representing an implant size "11." Similarly, as the screw 106 rotates further, position (c) represents an implant size "12," position (d) represents an implant size "13," position (e) represents an implant size "15," and position (f) represents an implant size "17." It will be appreciated that any appropriate trial and implant size may be represented on the trial 100 based on a given expansion. The incremental increments of the actuation screw 106 allow the surgeon to intraoperatively expand the trial 100 and set it to discrete heights corresponding to available tibial insert sizes.

[0040] 11A-11B, another embodiment of an expandable tibial trial assembly 200 is shown. The expandable trial assembly 200 is similar to the expandable trial assembly 100 and includes top and bottom platforms or plates 202, 204 that are configured to expand via an expansion assembly that includes an actuation screw 206 and an expansion ramp 208. In this embodiment, the expansion assembly is modified with a shoulder actuation screw 206 that mates with a protruding pin 252 on the expansion ramp 208 to expand the top plate 202.

[0041] In FIG. 11A , the expandable tibial trial assembly 200 is shown in a fully collapsed position. As the actuation screw 206 rotates, the expansion ramp 208 is pushed forward between the two plates 202, 204, thereby creating expansion between them. The expansion ramp 208 slides along the bottom plate 204, lifting the top plate 202 as the ramp 208 translates anteriorly. In FIG. 11B , the expandable tibial trial assembly 200 is shown in a fully extended position. In one embodiment, the plates 202, 204 can be expanded in discrete increments corresponding to thicknesses corresponding to available tibial inserts. In an alternative embodiment, the expandable tibial trial 200 can be adjusted to any height between the fully collapsed and fully extended positions.

[0042] The top plate 202 and the bottom plate 204 can be configured to nest within each other in a collapsed position, as best seen in FIG. 11A . The top plate 202 and the bottom plate 204 each include an upper surface 210 and an opposing lower surface 212. When in the collapsed position, the bottom surface 212 of the top plate 202 can contact the top surface 210 of the bottom plate 204. The plates 202 each include an anterior side 214 configured to be accessible to the user and an opposing posterior side 216 that can be initially placed within the surgical site. The outer shape of the plates 202, 204 can be somewhat rounded or curved, similar to a tibial tray implant. For example, the tibial tray 202, 204 can have the general shape of a long oval with a concave side, such as a kidney bean shape. The anterior side 214 may form an outer convex side as one long side, and the posterior side 216 may include an inner concave side separating two lobes or wings.

[0043] 12A-12B, the top plate 202 can include a compound recess 218 sized and dimensioned to receive at least a portion of the extension ramp 208. The recess 218 can define a plurality of angled or inclined surfaces 219 that correspond to the inclined surfaces 260 of the extension ramp 208. As the extension ramp 208 translates forward, the corresponding inclined surfaces 219, 260 slide against one another. The upward slope of the inclined surfaces 260 translates the horizontal movement of the ramp 208 into vertical movement of the top plate 202, thereby lifting the top plate 202 vertically relative to the bottom plate 204.

[0044] The top plate 202 may define one or more clips 221 and through slots 223 configured to connect the trial insert 280 to the expandable trial 200. The clips 221 may include a pair of L-shaped extensions on the anterior side 214 of the top plate 202. The L-shaped clips 221 may extend upward from the top plate 202 and bend toward the posterior side 216 of the plate 202. The slots 223 may include a pair of elongated slots, which may be aligned substantially parallel to the actuation axis 228. The slots 223 may extend from the posterior side 216 of the top plate 202 and terminate in a closed end defining, for example, a semicircular recess. As shown in FIG. 19 , when the insert 280 is slid into the slots 223, the clips 221 secure the insert 280 to the top plate 202. It will be appreciated that a sliding, snap-fit, or any other suitable attachment joint may be employed to temporarily attach the insert 280 to the top plate 202. The top plate 202 may also include holes 217 configured to align with the holes 292 in the articular insert 280. The holes 217 may include a pair of vertical cylindrical holes 217 centrally located near the anterior side 216 of the top plate 202. The holes 217, 292 may be configured to receive a locking pin 300 for securing an optional modular posterior stabilization post, as will be described in more detail with respect to FIGS.

[0045] In this embodiment, the top plate 202 may include multiple indicators 215 along its anterior surface 214. The indicators 215 may include multiple markings or etchings, such as lines and numbers, that represent the corresponding height of the tibial tray implant. The indicators 215 may be provided on both sides of the block 222 for better visibility as the top plate 202 moves relative to the bottom plate 204. Once the top plate 212 is raised to the extended position, a user may read the corresponding height from the corresponding indicator 215 to select the appropriate tibial tray implant.

[0046] As best seen in FIGS. 13A-13B , the bottom plate 204 may include a central block portion 222 configured to hold the actuation screw 206. The block portion 222 may be centrally located along the forward side 214 of the bottom plate 204. The block portion 222 defines a cylindrical through opening 225 sized and dimensioned to hold the actuation screw 206 therein. The sides of the block 222 may mate with grooves 226 in the top plate 202, thereby maintaining uniform vertical movement of the top plate 202 relative to the bottom plate 204. The bottom plate 204 may define one or more slots 224 that guide the actuation ramps 208. The slots 224 may include a pair of elongated slots 224 extending generally parallel to the actuation axis 228. The slots 224 may include an L-shaped notch toward the rear end of each slot 224. The bottom plate 204 may also include a slot 227 that aligns with a corresponding slot 223 in the top plate 202 .

[0047] 14 , the actuation screw 206 is configured to rotate about an actuation axis 228 between the anterior end 214 and the posterior end 216 of the bottom plate 204. Similar to the actuation screw 106, the actuation screw 206 includes a head 230 and a shaft 232. The proximal end of the head 230 may define a drive recess 234 configured to receive an instrument, such as a driver, to rotate or actuate the actuation screw 206. The drive recess 234 may include a triangular recess or other suitable recess configured to engage a driver instrument, such as the driver 400, to apply torque to the actuation screw 206. The actuation screw 206 may define an annular groove 238 between the head 230 and the shaft 232. The annular groove 238 may include a semicircular recess configured to receive a portion of a fixation pin, for example, as described for the trial 100. The shaft 232 of the actuation screw 206 defines a helical cut 242 comprising a spiral or helical-shaped channel cut along the length of the shaft 232. The spiral cut 242 may be defined in the surface of the shaft 232, with or without passing through the core of the screw 206. The spiral cut 242 may define a channel for the pin 252 to travel along, thereby guiding the movement of the pin 252 and the extension ramp 208.

[0048] In one embodiment, the actuation screw 206 is a stepped helical thread, which ensures that the device 200 only expands to a discrete thickness corresponding to the available tibial insert thickness. The helical cut 242 may include one or more thread risers 244 and step portions 246. Each thread riser 244 connects a step portion 246. The thread riser 244 is the vertical distance that the helical cut 242 advances axially as the actuation screw 206 rotates. The step portions 246 are configured to retain the pin 252 and correspond to the available tibial insert thickness. The step portions 246 may include, for example, angled cuts that form an obtuse angle with the thread riser 244. The thread risers 244 and step portions 246 may extend along one side 248 of the helical cut 242. The opposite side 249 of the helical cut 242 may include a continuous helical or spiral curve. The step increments 246 of the screw 206 allow the surgeon to intraoperatively expand the trial 200 to discrete heights without removing it from the joint cavity. The trial 200 can be set to one of the discrete heights corresponding to available tibial insert sizes. Because the thread riser 244 is steep, the trial 200 cannot maintain its height under compression if it does not reach the step 246. This prevents the user from setting the trial 200 to an intermediate height where no tibial inserts are available. The step 246 can also incorporate a slight back angle to provide height stability while the surgeon performs range-of-motion testing.

[0049] In an alternative embodiment, the actuation screw 206 is a continuous helical thread, ensuring that the device 200 can be expanded to any suitable height along its range of motion. In this embodiment, both sides 248, 249 of the helical cut 142 can include a continuous, uninterrupted spiral groove. The helix can be unbroken, with no graduated areas, allowing for continuous adjustment to any desired height. In this way, the user can adjust the trial height continuously between a fully retracted position and a fully extended position.

[0050] 15A-15B, an extension ramp 208 is shown according to one embodiment. The extension ramp 208 includes a ramp 250 having a protruding pin 252 configured to engage the shoulder screw 206. The ramp 250 has a base 254 and a pair of vertical walls 256. The base 254 defines a through hole 258 for receiving the body of the screw 206. The hole 258 may include a closed cylindrical opening sized and dimensioned to provide clearance for the screw 206 to pass therethrough. The central bore axis of the hole 258 is coaxial with the actuation shaft 228. The ramp 250 defines a plurality of ramps 260 that provide an inclined or sloped surface configured to guide or encourage movement of the top plate 202. The ramps 260 may include an upward slope from the bottom surface 262 to the top surface 264 of the tilter 250 to convert horizontal movement of the extension ramps 208 into vertical movement of the top plate 202. The ramps 260 may include, for example, male ramps having a dovetail or other mating configuration configured to mate with corresponding sloped surfaces of the recesses 218 in the top plate 202. The ramps 260 may include a pair of parallel ramps 260 located in different planes. For example, first and second pairs of ramps 260 may be located on either side of the extension ramp 208 to uniformly lift the top plate 202.

[0051] The expansion ramp 208 includes one or more pins 252 that extend into the obturator foramen 258. The pins 252 may include a pair of protruding pins 252, for example, one at the top and one at the bottom of the foramen 258. As best seen in FIG. 15A , the pins 252 may be offset from one another to follow along the edge 248 of the spiral cut 242. The pins 252 may be offset laterally from the central foramen axis and may be off-axis. The protruding free end of each pin 252 is receivable in the spiral cut 242 of the actuation screw 206 to guide the expansion ramp 208 as the screw 206 is rotated.

[0052] 16A-16B, the movement of the extension ramp 208 due to rotation of the actuation screw 206 is shown in more detail. In FIG. 16, the screw 206 and ramp 208 are shown in a collapsed position with the extension ramp 208 retracted to its most forward position. The pin 252 extends into the spiral cut 242 of the screw 206 in an initial starting position. In FIG. 6B, the screw 206 and ramp 208 are shown in an extended position with the extension ramp 208 extended to its most rearward position. As the screw 206 rotates, the pin 252 moves along the spiral cut 242 of the screw 206 until it reaches the final step 246. This, in turn, causes the ramp 250 to slide along the bottom plate 204 and press the ramp portion 260 against the corresponding ramp surface 219 of the top plate 202, thereby expanding the top plate 202 upward. 17A-17B show the expandable tibial trial 200 in a fully collapsed position and a fully extended position, respectively.

[0053] The articular insert 208 may connect to the top plate 202 using, for example, a snap-fit or a sliding joint. The insert 280 may include a body having an upper articular surface 282 and an opposing lower surface 284 configured to attach to the expandable tibial trial 200. The upper articular surface 282 may be concavely contoured to articulate against a corresponding femoral trial, such as the femoral trial 12. The outer wall 286 of the insert 280 may have a general profile similar to that of the expandable tibial trial 200. In the embodiment shown in FIGS. 18A-18B , one or more pegs or posts 288 may protrude from the lower surface 284 of the insert 280. The posts 288 are configured to fit into corresponding openings 220 in the top plate 202, thereby securing the insert 280 to the top plate. In the embodiment shown in FIG. 19 , the articular insert 280 includes a slide-on attachment joint. The articular insert 280 slides along the slot 223 in the top plate 202, and the clip 221 secures the insert 280 to the top plate 202. For example, the clip 221 temporarily secures the articular insert 280 to the expandable trial 200 by hooking into a groove 290 along the outer wall 286 of the insert 280.

[0054] 20A-20B, modular posterior stabilized (PS) posts may be incorporated into the articular insert 280 to readily provide the option of using a posterior stabilized femoral implant. The modular posts may be attached to the articular insert 280 using, for example, a locking pin 300. As best seen in FIG. 20B, the locking pin 300 may include a central cylindrical post 302, a pair of cylindrical legs 304, and a bridge portion 306 connecting the central post 302 and the legs 304. The post 302 may extend vertically upward and be configured to receive a modular post (e.g., similar to the post 188), and the legs 304 may extend vertically downward from the bridge portion 306 and fit within the articular insert 280. The articular insert 280 may define a pair of holes 292 that align with corresponding holes 217 in the top plate 202 of the expandable trial 200. Each leg 304 may define an annular groove 308 near its free end for snap-on engagement with the articular insert 280. Similar to the piston 190, the groove 308 may be configured to receive a spring to provide a temporary connection to the trial assembly that is stable under load yet easily removable.

[0055] In the embodiments described herein, the trials are expandable, which reduces the total number of instruments and improves efficiency during the trial reduction process. Unlike static systems, expandable trials do not have multiple components that must be moved repeatedly in and out of the joint space. Instead, a single trial can be inserted and expanded to the desired height, reducing the number of components, speeding the procedure, and improving ease and usability. The expandable trials allow the surgeon to change sizes with a single twist of a driver, making it easy to find the appropriate insert thickness. The shoulder screw also controls expansion, ensuring the trial locks only at the desired expansion height. The shoulder screw may simultaneously provide the user with tactile and / or visual feedback corresponding to the trial thickness.

[0056] While the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the present invention cover all modifications and variations of the present invention provided they come within the scope of the appended claims and their equivalents. For example, it is expressly intended that all of the elements of the various devices disclosed above can be combined or modified in any suitable configuration.

Claims

1. 1. A knee arthroplasty trial system, comprising: an expandable tibial tray trial having a top plate and a bottom plate; an actuation screw retained in the bottom plate; and an expansion ramp configured to slide along the bottom plate and lift the top plate as the ramp translates anteriorly; Equipped with the actuation screw defines a helical cut having a stepped portion, and the expansion ramp includes a pin configured to engage the helical cut of the actuation screw; When the actuation screw is rotated, the pin is configured to advance along the spiral cut and fit into one of the stepped portions, thereby ensuring that the expandable tibial tray trial only expands to a discrete thickness. Knee arthroplasty trial system.

2. The system of claim 1 , wherein the expansion ramp includes a ramp having a pair of vertical support walls defining a channel therebetween for receiving the actuation screw.

3. The system of claim 2 , wherein the pin is a cross pin extending across the channel between the pair of vertical support walls.

4. The system of claim 2 , wherein the ramp defines an upper beveled surface that provides a beveled surface configured to mate with a corresponding surface on the top plate.

5. The system of claim 2 , wherein the tilter includes a pair of rails extending from a bottom surface of the tilter, the rails configured to fit into corresponding grooves in the bottom plate.

6. The system of claim 1 , wherein the actuation screw includes a head having a drive recess and a shaft defining the helical cut.

7. The system of claim 6 , wherein the helical cut comprises a spiral cut that extends completely through the shaft to form a completely open channel.

8. The system of claim 1 , further comprising an articular insert trial attached to the top plate of the expandable tibial tray trial.

9. 9. The system of claim 8, wherein the articular insert trial includes a piston having an annular groove configured to fit into a corresponding opening in the top plate such that a spring in the top plate snaps into the groove in the piston, thereby securing the articular insert trial to the expandable tibial tray trial.

10. 9. The system of claim 8, further comprising a femoral trial having an anterior flange, a pair of posterior condylar flanges, and a distal portion therebetween, the femoral trial having an outer articular surface with a smooth, rounded shape that contacts the articular insert trial, and a medial surface shaped to match a resected femur having five resection cuts.

11. 1. An expandable tibial tray trial, top and bottom plates configured to nest within one another in a collapsed position; an actuation screw configured to rotate about an actuation axis, the actuation screw having a head and a shaft defining a helical cut, the head defining a plurality of indicators around its circumference; an inclined body having a pair of vertical support walls defining a channel therebetween for receiving the actuation screw, and an expansion ramp having a cross pin extending across the channel and configured to pass through the helical cut of the actuation screw; As the actuation screw rotates, the ramp translates along the actuation axis, expanding the top plate and thereby moving the top plate to an expanded position such that one of the indicators corresponds to a discrete height of the expanded trial. Expandable tibial tray trial.

12. The expandable tibial tray trial of claim 11 , wherein the indicator includes a series of numbers laser marked on the head of the actuation screw.

13. The expandable tibial tray trial of claim 11 , wherein the spiral cut includes stepped portions, and when the cross pin is seated in one of the stepped portions, the visual indicator corresponds to one of the discrete heights.

14. 12. The expandable tibial tray trial of claim 11, wherein the bottom plate has a central block portion defining a cylindrical through-opening, and the actuation screw is retained in the cylindrical through-opening in the central block portion of the bottom plate.

15. 15. The expandable tibial tray trial of claim 14, wherein the bottom plate defines a gap in a top surface of the block portion, and when one of the indicators aligns with the gap, the indicator reading corresponds to the discrete height of the expansion trial.

16. The expandable tibial tray trial of claim 15, wherein the head defines a lateral opening that, when aligned with the gap, indicates an initial start position of the expandable trial.

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