Trial system for knee arthroplasty and expandable tibial tray 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

[0004]

[0001] (Cross - Reference to Related Applications) This application claims priority to U.S. Provisional Patent Application No. 63 / 482,889, filed on February 2, 2023, and U.S. Provisional Patent Application No. 63 / 517,382, filed on August 3, 2023, which are hereby incorporated by reference in their entirety for all purposes.

[0002] (Field of the Invention) This application generally relates to knee arthroplasty, and more specifically, to knee arthroplasty trials and methods for evaluating the compatibility of permanent implants.

Background Art

[0003] Knee arthroplasty, often called knee replacement surgery, is a surgical procedure used, for example, to reconstruct and resurface a knee damaged by arthritis. A total knee arthroplasty (TKA) device 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 fixed to the distal end of the femur (or thigh bone), a tibial tray implant fixed to the proximal end of the tibia (or shin bone), and an insert disposed between them. The femoral and tibial implants each cover the ends of the femur and tibia that form the knee joint, thereby reconstructing the knee. To replace the patellofemoral joint, knee arthroplasty can include a patellar prosthesis for forming a replacement joint surface that replaces the backside of the patella and joins with the femoral implant.

Summary of the Invention

Problems to be Solved by the Invention

[0004] To properly determine the implant size, one or more trials may be used by the surgeon during the surgical procedure. A trial is a temporary component that matches the shape of the final implant to the corresponding size, allowing the surgeon to evaluate the fit of a given size before permanently implanting the final component. The sizing of each of these components must match as closely as possible to the natural anatomical structure. The components of femoral and tibial trials may differ in size in the anterior-posterior (AP) and medial-lateral (ML) directions, and inserts may also be available in many different thicknesses. Therefore, many trials may be necessary to cover all tibial / femoral sizes and insert thicknesses. The trial process can be time-consuming, and multiple trials may be required to find a proper fit. Discrete fixed-height trials can be difficult to insert into and remove from the joint cavity because the optimal fit may be very tight. If the surgeon needs to try multiple thicknesses before being confident that they have selected the correct thickness, this can be time-consuming and frustrating. Shim systems may include sets of shims that can be inserted to increase stack height, but these also require many components, are time-consuming, and can be complex to assemble. Therefore, there is a need for improved trial devices that reduce the total number of fixtures and improve efficiency during the trial reduction process. [Means for solving the problem]

[0005] To satisfy this and other needs, trials, systems, and methods for knee arthroplasty are provided. In particular, a knee arthroplasty trial may include an expandable tibial trial having a screw-driven ramp mechanism for forming a separation between a top plate and a bottom plate. The screw may include stepped increments, thereby making it possible to set the trial to separate 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 to which an articular insert is attached, and a femoral trial configured to mate with the articular insert, thereby mimicking the proper function of the knee.

[0006] According to one embodiment, a trial system for knee arthroplasty includes an expandable tibial tray trial having a top plate and a bottom plate, an actuating screw held 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 actuating screw defines a helical cut having stepped portions, and the expansion ramp includes a pin configured to engage with the actuating helical cut. As the actuating screw rotates, the pin is configured to advance along the helical cut and settle into one of the stepped portions, thereby ensuring that the expandable tibial tray trial expands only to discrete thicknesses.

[0007] A trial system for knee arthroplasty may include one or more of the following features: The expansion ramp may include an inclined body having a pair of vertical support walls defining a channel between them for receiving an operating screw. The pin may be a cross pin extending across the channel between the pair of vertical support walls. The inclined body may define an upper inclined surface providing an inclined surface configured to engage with a corresponding surface on the top plate. The inclined body may include a pair of rails extending from the bottom surface of the inclined body, the rails may be configured to engage with corresponding grooves on the bottom plate. The operating screw may include a head having a drive recess and a shaft defining a helical cut. The helical cut may include a spiral cut that completely penetrates the shaft to form a fully open channel. The trial system may also include an articular insert trial attached to the top plate of an expandable tibial tray trial. The articular insert trial may include a piston having an annular groove configured to engage with a corresponding opening in the top plate so that a spring in the top plate snaps into the groove of the piston, thereby allowing the articular insert trial to be fixed 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 between them. The femoral trial may have an lateral articular surface having a smooth, rounded shape that contacts the articular insert trial, and an lateral surface shaped to match the resected femur having five resection cuts.

[0008] According to one embodiment, an expandable tibial tray trial includes a top plate and a bottom plate configured to nest with each other in a compressed position, and 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 between them 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 inclined body 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 of the expansion trial.

[0009] An 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 actuating screw. The spiral cut may include stepped sections, and when the cross pin is seated in one of the stepped sections, the visible indicator corresponds to one of the discrete heights. The base plate may have a central block section defining a cylindrical through-opening, and the actuating screw may be held in the cylindrical through-opening of the central block section of the base plate. The block section may define a gap on its apical surface such that when one of the indicators is aligned with the gap, the value read by the indicator corresponds to a discrete height of the expandable trial. The head may define a lateral opening that indicates the initial starting position of the expandable trial when aligned with the gap.

[0010] According to one embodiment, the expandable tibial tray trial includes a top plate and a bottom plate configured to nest with each other in a compressed position; an operating screw configured to rotate about an operating axis, the operating screw having a head and a shaft defining a helical cut having stepped portions; and an expansion ramp having an inclined body with a pair of pins having free ends configured to engage with the helical cut of the operating screw. As the operating screw rotates, the pins are configured to advance along the helical cut and settle into one of the stepped portions, thereby ensuring that the expandable tibial tray trial expands only to discrete thicknesses.

[0011] An expandable tibial tray trial may include one or more of the following features: The inclined body may include a base having a closed hole sized and dimensions to receive an actuating screw. The free end of a pin may protrude into the hole so as to advance along the helical cut when the screw is rotated. The pin may be off-axis and offset from one another. The helical cut of the actuating screw may be defined on the surface of the shaft without penetrating the core of the screw. The inclined body may define a plurality of male ramp surfaces having inclined surfaces configured to engage with corresponding female ramp surfaces on a 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) positioning the expandable trial at the surgical site, the expandable trial comprising a top plate and a bottom plate, an operating screw having a helical cut with stepped portions separated by a threaded riser, and an expansion ramp having a pin configured to advance along the helical cut; (3) sliding the expansion ramp along the bottom plate and rotating the operating screw to lift the top plate as the ramp translates forward, the expandable trial expanding to discrete thicknesses once the pin engages with one of the stepped portions. When the pin is in the threaded riser, the expandable trial cannot maintain its height under compression unless it reaches a stepped portion. When it reaches a stepped portion during expansion, the pin retracts into the stepped portion, thereby providing tactile feedback to the user. The operating screw may have one or more visual indicators for specifying a given trial thickness, thereby providing visual feedback to the user.

[0013] Kits are also provided 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) configurations; various types and configurations of instruments, including expandable tibial trials, joint trial inserts, and femoral trials, as well as other components for performing the procedure. [Brief explanation of the drawing]

[0014] A more complete understanding of the present invention, and its associated advantages and features, will be more readily apparent by referring to the following detailed description, when considered in conjunction with the accompanying drawings. [Figure 1]This diagram shows 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] The images show an expandable tibial trial assembly in the fully compressed position and the fully expanded position, according to one embodiment. [Figure 2B] The images show an expandable tibial trial assembly in the fully compressed position and the fully expanded position, according to one embodiment. [Figure 3] A stepped helical screw having a step and a thread riser for engaging with an extension lamp is shown according to one embodiment. [Figure 4A] The figures show a perspective view, a front cross-sectional view, and a side cross-sectional view of an extension ramp having a cross pin configured to engage with the stepped threads of an operating screw, according to one embodiment. [Figure 4B] The figures show a perspective view, a front cross-sectional view, and a side cross-sectional view of an extension ramp having a cross pin configured to engage with the stepped threads of an operating screw, according to one embodiment. [Figure 4C] The figures show a perspective view, a front cross-sectional view, and a side cross-sectional view of an extension ramp having a cross pin configured to engage with the stepped threads of an operating screw, according to one embodiment. [Figure 5A] These show the operating screws that engage with the expansion ramps in the crushed and expanded positions, respectively. [Figure 5B] These show the operating screws that engage with the expansion ramps in the crushed and expanded positions, respectively. [Figure 6A] The screw ramp connections of the cross pins in the crushed and expanded positions are shown, respectively. [Figure 6B] The screw ramp connections of the cross pins in the crushed and expanded positions are shown, respectively. [Figure 7A] The images show tibial trial assemblies in the collapsed and expanded positions, respectively. [Figure 7B] The images show tibial trial assemblies in the collapsed and expanded positions, respectively. [Figure 8A]A cruciate ligament retaining (CR) snap-on insert according to one embodiment, which is attachable to an expandable tibial trial, is shown. [Figure 8B] A cruciate ligament retaining (CR) snap-on insert according to one embodiment, which is attachable to an expandable tibial trial, is shown. [Figure 8C] A cruciate ligament retaining (CR) snap-on insert according to one embodiment, which is attachable to an expandable tibial trial, is shown. [Figure 9A] A posterior stabilizing (PS) snap-on insert according to one embodiment, which is attachable to an expandable tibial trial, is shown. [Figure 9B] A posterior stabilizing (PS) snap-on insert according to one embodiment, which is attachable to an expandable tibial trial, is shown. [Figure 10] A laser marking indicator on an actuating screw for determining insert thickness according to one embodiment is shown. [Figure 11A] Respectively, an expandable tibial trial assembly in a fully collapsed position and a fully expanded position according to one embodiment is shown. [Figure 11B] Respectively, an expandable tibial trial assembly in a fully collapsed position and a fully expanded position according to one embodiment is shown. [Figure 12A] A perspective view of a top plate having an expansion ramp assembly and a bottom view of the top plate according to one embodiment are shown. [Figure 12B] A perspective view of a top plate having an expansion ramp assembly and a bottom view of the top plate according to one embodiment are shown. [Figure 13A] A perspective view of a bottom plate having an expansion ramp assembly and a top view of the bottom plate according to one embodiment are shown. [Figure 13B] A perspective view of a bottom plate having an expansion ramp assembly and a top view of the bottom plate according to one embodiment are shown. [Figure 14] A stepped screw having steps and a screw thread rising portion according to one embodiment is shown. [Figure 15A]A cross-sectional view of an extension ramp having a protruding pin configured to engage with the stepped threads of an operating screw, according to one embodiment, is shown. [Figure 15B] A cross-sectional view of an extension ramp having a protruding pin configured to engage with the stepped threads of an operating screw, according to one embodiment, is shown. [Figure 16A] These show the operating screws that engage with the expansion ramps in the crushed and expanded positions, respectively. [Figure 16B] These show the operating screws that engage with the expansion ramps in the crushed and expanded positions, respectively. [Figure 17A] The images show tibial trial assemblies in the collapsed and expanded positions, respectively. [Figure 17B] The images show tibial trial assemblies in the collapsed and expanded positions, respectively. [Figure 18A] The images show, respectively, a joint insert trial, a apical plate and a basal plate, and a top and bottom view of the expansion assembly of an expandable tibial trial according to one embodiment. [Figure 18B] The images show, respectively, a joint insert trial, a apical plate and a basal plate, and a top and bottom view of the expansion assembly of an expandable tibial trial according to one embodiment. [Figure 19] This shows a slide-on joint insert trial attached to an expandable tibial trial according to one embodiment. [Figure 20A] One embodiment shows a joint insert trial and an expandable tibial trial assembly having locking pins for attaching a modular posterior stabilization (PS) support. [Figure 20B] One embodiment shows a joint insert trial and an expandable tibial trial assembly having locking pins for attaching a modular posterior stabilization (PS) support. [Modes for carrying out the invention]

[0015] Embodiments of this disclosure generally relate to trials, systems, and methods for knee arthroplasty. In particular, a trial for knee arthroplasty may include an expandable tibial trial having a screw-driven ramp mechanism configured to form a separation between a top plate and a bottom plate. The actuating screw may include stepwise increments, thereby allowing the trial to be set to separate heights corresponding to available tibial insert sizes. The expandable tibial trial may include, for example, articular insert trials that slide or snap onto the expandable trial. By utilizing expandable tibial trials representing multiple insert thicknesses in this way, the total number of trials may be reduced, and the efficiency of the trial reduction process may be improved.

[0016] While 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 uses, such as the spine including intervertebral joints, long bones such as the femur, tibia, humerus, clavicle, fibula, ulna, and radius, bones of the foot, bones of the hand, or other suitable bones or joints. While generally described with reference to temporary trials, it will be further understood that similar features may be applied to permanent implants.

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

[0018] Referring here to the drawings, similar reference numerals may refer to similar elements, and Figure 1 shows a whole knee implant trial system 10 according to one embodiment. The whole 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 in order to replace the end of the femur or thigh bone after resection, for example. The tibial trial 14 may be used to approximate a permanent tibial tray implant in order to replace the end of the tibia or shin bone after resection, for example. 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 which are described in more detail herein. The articular insert trial 16 is attachable to the tibial trial 14 and is configured to bond with the femoral trial 12 to mimic proper knee function. Trials 12, 14, and 16 are temporary components that match the shape of the final implant to the corresponding size, allowing the surgeon to evaluate the fit of a given size before permanently implanting the final component into the patient.

[0019] The femoral trial 12 mimics a femoral implant, which curves anteriorly and posteriorly over the distal end of the femur, replicating the natural shape of the original 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 between them. 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 external or lateral articular surface 28 of the femoral trial 12 may form a rounded C-shape or other appropriate shape corresponding to the natural distal femoral surface of the human knee. The femoral trial 12 can be positioned relative to a resected femur. For example, the femoral trial 12 may have a medial or internal surface 30 shaped to match the resected cut at the distal end of the femur. In the illustrated embodiment, the internal surface 30 includes a five-cut osseojunction surface that mates with five corresponding resected cuts to ensure optimal fit. It will be understood that any suitable mating surface can be used for resection in the femoral trial 12 and the corresponding femoral implant.

[0020] The tibial trial 14 mimics a tibial tray implant and replaces, for example, the proximal end of the tibia or shinbone after resection. The tibial tray 14 may be provided in multiple sizes that differ in anterior-posterior (AP) and medial-lateral (ML) orientations to conform to the patient's anatomical structure. 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 with the resection surface of the tibia. The proximal surface 42 is sized and shaped to receive or attach an insert 16, for example, 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, mimicking natural knee movement and providing support during knee flexion and extension. The insert trial 16 includes a body having an upper articular surface 52 and a lower surface 54 on the opposite side, configured to engage with the tibial tray 14. The upper articular surface 52 may be concave and contoured to articulate with the external articular surface 28 of the femoral trial 12. The outer wall 56 of the insert 16 has a common shape, such as a long oval with one side concave, e.g., a bean shape, and may roughly correspond to the outer shape of the tibial trial 14. The insert 16 may be available in various thicknesses, for example, ranging from 10 mm to 30 mm. The insert 16 balances the joint cavity and provides the articular surface 52 when the knee enters its physiological range of motion.

[0022] Referring here to Figures 2A and 2B, an expandable tibial trial assembly 100 according to one embodiment is shown. The expandable trial assembly 100 includes apical and basal 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 Figure 2A, the expandable tibial trial assembly 100 is shown in the fully compressed position. As the screw 106 is rotated, the expansion ramp 108 is pushed forward between the two plates 102, 104, thereby causing expansion between them. The ramp 108 slides along the basal plate 104, lifting the apical plate 102 as the ramp 108 translates forward. In Figure 2B, the expandable tibial trial assembly 100 is shown in the fully expanded position. The actuation screw 106 can be operated using a separate instrument, such as a screwdriver 400, located far forward of the device 100. This forward access allows the surgeon to expand the trial intraoperatively without removing the trial from the joint cavity. In one embodiment, plates 102, 104 can be expanded in discrete increments to match only the thickness corresponding to the thickness of the available tibial insert. The expandable tibial trial 100 can be expanded to the available distinct thickness, thereby enabling 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 may be configured to nest with each other in the collapsed position, as is most commonly seen in Figure 2A. Each of the top plate 102 and the bottom plate 104 includes an upper surface 110 and an opposite lower surface 112. When in the collapsed position, the bottom surface 112 of the top plate 102 may contact the top surface 110 of the bottom plate 104. Each plate 102 includes an anterior side 114 configured for user access and an opposite posterior side 116 that can be initially placed within the surgical site. The external shape of plates 102, 104 may be rounded or curved, similar to tibial tray implants. For example, plates 102, 104 may have a common shape of an elongated oval with one side concave, similar to a bean shape. The anterior side 114 may form an outward convex side as one long side, and the posterior side 116 may include an inward concave side separating the two lobes or wings.

[0024] The top plate 104 may include a composite recess 118 sized and dimensions to accommodate at least a portion of the extension ramp 108. The recess 118 may define an angled or inclined surface 119 corresponding to the inclined surface 160 of the extension ramp 108. As the extension ramp 108 translates forward, the corresponding inclined surfaces 119, 160 slide relative to each other. The upward inclination of the inclined plate 160 converts the horizontal motion of the ramp 108 into vertical motion of the top plate 104, thereby lifting the top plate 104 perpendicular to the bottom plate 102. The top plate 104 may define one or more through-openings 120 configured to connect trial inserts 180A, 180B to the extendable trial 100. The openings 120 may include cylindrical openings configured to receive corresponding supports 190 from the snap-on insert trials 180A, 180B, for example, as described in more detail with respect to Figures 8A-8C.

[0025] The bottom plate 104 may include a central block portion 122 configured to hold an actuation screw 106. The block portion 122 may be centrally located along the front side 114 of the bottom plate 104. The block portion 122 defines a cylindrical through-opening therein, sized and dimensions to hold the actuation screw 106. The sides of the block 122 define inclined or tapered surfaces 124 configured to engage with projections 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 projections 126 may extend forward to engage with the block surfaces 124. The projections 126 may be inclined or tapered inward toward each other from the rear side 116 to the front side 114 of the plate 102. The bottom plate 104 may define one or more through-openings 127 that align with the column openings 120 of the top plate 102.

[0026] The actuation screw 106 is configured to rotate about an actuation shaft 128 between the front end 114 and the rear end 116 of the bottom plate 104. As is most clearly shown in Figure 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 screwdriver 400 to rotate or actuate the actuation screw 106. The drive recess 134 may include a trefoil, hexagon, star, or other suitable recess configured to engage with a screwdriver instrument to apply torque to the actuation screw 106. A lateral opening 136, for example, a circular or oval opening, is provided within the head 130 and may be in fluid communication with the drive recess 134. As will be described in more detail with respect to Figure 10, the lateral opening 136 may function as a zero indicator or starting position for the available extension height. The head 130 also defines several indicators 137, such as etching and / or laser markings, around its circumference, which may provide the user with a visual indication of the height that occurs as the screw 106 rotates.

[0027] The actuation screw 106 may be held within the base 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 pins 140. For example, a pair of cylindrical pins 140 may extend vertically through a block 122, allowing rotation of the screw 106 while holding the actuation screw 106 within the block 122 of the base plate 104. It will be understood that the screw 106 may be constrained to the block portion 122 of the base plate 104 in any suitable manner.

[0028] In one embodiment, the actuarial screw 106 is a stepped helical screw, which ensures that the trial device 100 expands only to a distinct thickness corresponding to the available tibial insert thickness. The shaft 132 of the actuarial screw 106 defines a helical cut 142, which includes a spiral or helical channel cut along the length of the screw body. The helical cut 142 penetrates the shaft 132 completely, forming a channel that is fully open from the surface of the shaft 132 to the core. 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 rises 144 and one or more stepped portions 146. Each thread rise 144 connects to a stepped portion 146. The thread rises 144 may include, for example, a curved or inclined relief having a larger radius than the stepped portion 146. As the screw 106 rotates, the thread rise 144 correlates with the vertical distance the helical cut 142 advances axially. Because the thread rise 144 is steep, the trial 100 cannot maintain its height under compression unless it reaches the step 146. This prevents the user from setting the trial 100 at an intermediate height where a corresponding tibial insert is unavailable. The step 146 may include curved or angled notches or cutouts, which are configured to hold the cross pins 152 and correspond to the thickness of the available tibial inserts. The step 146 may transition to the thread rise 144 via a prominent ridge or apex. The thread rise 144 and the step 146 may extend along one side 148 of the helical cut 142. The opposite side 149 of the helical cut may define a continuous helical or spiral curve. These sides 148, 149 may be inverted or configured for stepped features.

[0029] Referring here to Figures 4A to 4C, an extension ramp 108 according to one embodiment is shown. The extension ramp 108 includes an inclined body 150 and a cross pin 152 configured to engage with a stepped helical screw 106. The inclined body 150 includes a base 154 and a pair of vertical support walls 156 defining an open channel 158 between them for receiving the body of the screw 106. The channel 158 includes a curved or semicircular recess sized and dimensions such as to provide clearance for the screw 106 through which it passes. The central hole axis of the channel 158 is coaxial with the actuation axis 128. The inclined body 150 defines a ramp or upper inclined surface 160 that provides an inclined or sloped surface configured to guide or facilitate the movement of the top plate 102. The sloped surface 160 includes an upward slope from the bottom surface 162 to the top surface 164 of the inclined body 150 and can convert the horizontal movement of the extension ramp 108 into the vertical movement of the top plate 102. The inclined body 150 may include a pair of lower wings 166 extending outward and away from each other along the bottom 162 of the inclined body 150. The wings 166 may provide an upper inclined surface 160 having two separate 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 inclined body 150. The rails 168 may have an L-shaped cross-section with free ends extending outward and away from each other. The rails 168 are configured to fit into corresponding grooves in the bottom plate 104. In this way, the rails 168 are configured to slide along the bottom plate 104 as the actuation screw 106 rotates, providing linear movement of the inclined body 150.

[0030] The expandable trial 100 may initially start with a first thickness equivalent to, for example, a 10 mm tibial insert trial. By using an instrument such as a driver 400, the actuarial screw 106 can 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 stepped 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 has moved the cross pin 152, and thus the mounted ramp 108, forward by a given distance, such as a 1 mm increment. The inclined surface 160 of the ramp 108 is tilted at a 45-degree angle to ensure that the rise of the top plate 102 is equal to the travel of the ramp 108 as it moves along the bottom plate 104. When expanding from 11mm to 12mm, and from 12mm to 13mm, similar increments, for example, of 1mm, may occur. When expanding from 13mm to 15mm, the step 146 of the screw 106 occurs after the cross pin 152 has been pushed 2mm by the screw 106. When expanding from 15mm to 17mm, the same 2mm step may be used. In other words, the amount of expansion is controlled by the location and number of steps 146 of the screw 106, thereby enabling expansion to a given trial thickness.

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

[0032] Highlighting Figures 5A-5B and 6A-6B provides a more detailed view of the movement of the extension ramp 108 due to the rotation of the actuation screw 106. In Figures 5A and 6A, the screw 106 and ramp 108 are shown in the compressed position, with the extension ramp 108 retracted to its furthest forward position. The cross pin 152 extends through the helical cut 142 of the screw 106 and is in the initial starting position. In Figures 5B and 6B, the screw 106 and ramp 108 are shown in the extended position, with the extension ramp 108 extended to its furthest rearward position. As the screw 106 rotates, the cross pin 152 moves along the helical cut 142 of the screw 106 until it reaches the final stage 146. This then causes the inclined body 150 to slide along the bottom plate 104 by the rail 168, pressing the inclined surface 160 against the corresponding inclined surface 119 of the top plate 102, thereby causing the top plate 102 to expand upward. Figures 7A and 7B show the expandable tibial trial 100 in the complete collapse position and the complete expansion position, respectively.

[0033] The expansion ramp 108 is captured by the base plate 104, restricting its movement to one 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 base plate 104, raising the top plate 102 as the ramp 108 moves forward. 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 an uneven load. This expansion trial mechanism makes it possible to represent a number of different tibial insert thicknesses, for example, six different thicknesses, with a single expansion mechanism, thereby simplifying the trial process.

[0034] Referring here to Figures 8A-8C and 9A-9B, examples of modular joint insert trials 180A and 180B are shown. To minimize the number of components and enhance user convenience, the expandable tibial trial 100 may incorporate quick-connect joint insert trials 180A and 180B, for example, featuring snap-on attachment joints. Figures 8A-8B show joint insert trial 180A configured for trialing a cruciate ligament preservation (CR) implant. In the cruciate ligament preservation (CR) procedure, the posterior cruciate ligament (PCL) and intercondylar femoral bone are preserved, which can result in better proprioception, balance, and movement. Figures 9A-9B show joint insert trial 180B configured for trialing a posterior stabilization (PS) implant. In the posterior stabilization (PS) procedure, the posterior cruciate ligament (PCL) and intercondylar femoral bone are resected. The posterior stabilization (PS) implant includes a raised surface or post 188 configured to interlock with a femoral implant. The support column 188 has an articular surface 189 configured to connect with a femoral implant, which can result in better knee flexion and reliable recovery of knee movement.

[0035] Insert trials 180A and 180B may be similar to insert trial 16. In either case, modular insert trials 180A and 180B include a body having an upper articular surface 182 and an opposite lower surface 184 configured to attach to an expandable tibial trial 100. The upper articular surface 182 may be recessed and contoured to articulate with respect to the corresponding femoral trial. The outer wall 186 of inserts 180A and 180B may have a general shape similar to that of the expandable tibial trial 100. As shown in Figures 9A and 9B, the posterior stabilization (PS) insert 180B may further include a raised support 188 extending from the upper articular surface 182. The raised support 188 may be configured to fit into a corresponding box or notch in the center of a femoral component. Insert trials 180A and 180B may have a known thickness so that the corresponding insert thickness can be determined from a value read by the actuation screw indicator 137.

[0036] As best seen in Figure 8C, one or more pegs or pistons 190 may extend from insert trials 180A, 180B to connect the modular insert trials 180A, 180B to the expandable trial 100. The pistons 190 may include a cylindrical support having a circular cross-section that extends downward from the lower surface 184 of the insert 180. The pistons 190 are configured to fit into 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 hold the piston 190 in the opening 120, for example, via a spring 198. Each opening 120 may include a downward extension or housing 194, sized and dimensions such that it is received in a corresponding cylindrical opening 127 in the bottom plate 104 when the trial 100 is fully compressed. The housing 194 defines an internal groove 196 configured to hold a spring 198 within it. Spring 198 may include a sealing spring, an inclined 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, the spring 198 engages with the outer groove 192 of the piston 190, thereby holding the piston 190 in place on the top plate 102. The spring 198 snaps into the groove 192, applying a radial force to the piston 190, thereby enabling the modular insert trials 180A, 180B to be secured to the expandable trial 100. In one embodiment, each insert trial 180A, 180B may include a pair of pistons 190 that align with a spring 198 housed in the top plate 102 of the expandable trial 100. The pistons 190 enable secure attachment of the insert trials 180A, 180B to the expandable trial 100 while facilitating easy connection and disconnection. With these modular articular insert trials 180A, 180B, a single expandable trial 100 can be used to trial both cruciate ligament retention (CR) style and posterior stabilization (PS) insert style. By employing one extension trial 100 with two modular joint inserts 180A and 180B, it becomes possible to replace numerous static tibial insert trials.

[0038] Referring to Figure 10, the operating 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 obtained thickness. In one embodiment, the expandable trial 100 reads the obtained thickness using the method shown in Figure 10. The top surface of the block portion 122 of the bottom plate 104 is laser-marked with the number "1", which is the same for all sizes (e.g., 10, 11, 12, 13, 15, 17). A second number 137 may be engraved and laser-marked on the head 130 of the stepped screw 106. This allows the indicator number 137 to change with the rotation of the screw 106. Since the indicator 137 directly links the expansion of the trial 100 with the displayed thickness, the surgeon can always know what thickness the trial 100 is currently representing.

[0039] In the example shown in Figure 10, at position (a), the opening 136 represents the initial starting position or implant size "10". As the screw 106 is rotated to position (b), the indicator 137 aligns with the gap on the top surface of block 122 of the base plate 104, representing implant size "11". Similarly, as the screw 106 is rotated further, at position (c) it represents implant size "12", at position (d) it represents implant size "13", at position (e) it represents implant size "15", and at position (f) it represents implant size "17". It will be understood that, based on a given expansion, any appropriate trial and implant size can be represented in trial 100. The stepwise increments of the actuarial screw 106 allow the surgeon to expand trial 100 during surgery and set it to separate heights corresponding to the available tibial insert sizes.

[0040] Referring here to Figures 11A and 11B, an expandable tibial trial assembly 200 according to another embodiment is shown. The expandable trial assembly 200 is similar to the expandable trial assembly 100 and includes apical and basal platforms or plates 202, 204, which 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 stepped actuation screw 206 that mates with a protruding pin 252 of the expansion ramp 208 to expand the apical plate 202.

[0041] In Figure 11A, the expandable tibial trial assembly 200 is shown in the fully compressed position. As the actuation screw 206 is rotated, the expansion ramp 208 is pushed forward between the two plates 202, 204, thereby causing expansion between them. The expansion ramp 208 slides along the bottom plate 204, lifting the top plate 202 as the ramp 208 translates forward. In Figure 11B, the expandable tibial trial assembly 200 is shown in the fully expanded position. In one embodiment, the plates 202, 204 may be expanded in discrete increments matching the thickness corresponding to the thickness of the available tibial insert. In an alternative embodiment, the expandable tibial trial 200 may be adjusted to any height between the fully compressed position and the fully expanded position.

[0042] The top plate 202 and the bottom plate 204 may be configured to nest with each other in the collapsed position, as is most commonly seen in Figure 11A. Each of the top plate 202 and the bottom plate 204 includes an upper surface 210 and an opposite lower surface 212. When in the collapsed position, the bottom surface 212 of the top plate 202 may contact the top surface 210 of the bottom plate 204. Each plate 202 includes an anterior side 214 configured for user access and an opposite posterior side 216 that can be initially placed within the surgical site. The external shape of plates 202, 204 may be somewhat rounded or curved, similar to tibial tray implants. For example, tibial trays 202, 204 may have a common shape, such as a bean shape, or an elongated oval with one side concave. The front side 214 may form an outwardly convex side as one long side, and the rear side 216 may include an inwardly concave side that separates the two leaves or wings.

[0043] As is most commonly seen in Figures 12A-12B, the top plate 202 may include a composite recess 218 sized and dimensional to accommodate at least a portion of the extension ramp 208. The recess 218 may define a plurality of angled or inclined surfaces 219 corresponding to the inclined surface 260 of the extension ramp 208. As the extension ramp 208 translates forward, the corresponding inclined surfaces 219, 260 slide against each other. The upward inclination of the inclined surfaces 260 converts the horizontal motion of the ramp 208 into vertical motion of the top plate 202, thereby lifting the top plate 202 perpendicular to the bottom plate 204.

[0044] The top plate 202 may define one or more clips 221 and through slots 223 configured to connect a trial insert 280 to an expandable trial 200. The clips 221 may include a pair of L-shaped extensions on the front side 214 of the top plate 202. The L-shaped clips 221 may extend upward from the top plate 202 and bend toward the rear 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 rear side 216 of the top plate 202 and terminate at a closed end defining, for example, a semicircular recess. As shown in Figure 19, when the insert 280 slides within the slots 223, the clips 221 secure the insert 280 to the top plate 202. It will be understood that sliding, snap-fit, or any other suitable mounting joint may be employed to temporarily attach the insert 280 to the top plate 202. The top plate 202 may also include a hole 217 configured to align with the hole 292 of the articulated insert 280. The hole 217 may include a pair of vertical cylindrical holes 217 located in the center near the front side 216 of the top plate 202. The holes 217, 292 may be configured to receive locking pins 300 for securing any modular rear stabilizing struts, as will be described in more detail with respect to Figures 20A-20B.

[0045] In this embodiment, the top plate 202 may include a plurality of indicators 215 along its anterior surface 214. The indicators 215 may include a plurality of 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 to improve visibility as the top plate 202 moves relative to the bottom plate 204. When the top plate 212 rises to its extended position, the user can read the corresponding height from the corresponding indicator 215 to select the appropriate tibial tray implant.

[0046] As best seen in Figures 13A and 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 front side 214 of the bottom plate 204. The block portion 222 defines a cylindrical through-opening 225 within which the actuation screw 206 is sized and dimensionally positioned. The sides of the block 222 engage 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 for guiding the actuation ramp 208. The slots 224 may include a pair of elongated slots 224 extending substantially parallel to the actuation shaft 228. The slots 224 may include L-shaped notches toward the rear end of each slot 224. The bottom plate 204 may also include a slot 227 that aligns with the corresponding slot 223 of the top plate 202.

[0047] Referring here to Figure 14, the actuation screw 206 is configured to rotate about an actuation axis 228 between the front end 214 and the rear end 216 of the bottom plate 204. Similar to actuation screw 106, 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 screwdriver to rotate or actuate the actuation screw 206. The drive recess 234 may include a triangular recess or other suitable recess configured to engage with a screwdriver instrument such as a screwdriver 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 retaining pin, as described, for example, in trial 100. The shaft 232 of the actuation screw 206 defines a helical cut 242, which includes a spiral or helical channel cut along the length of the shaft 232. The helical cut 242 may be defined on the surface of the shaft 232 with or without penetrating the core of the screw 206. The helical cut 242 may define a channel along which the pin 252 can travel, thereby guiding the movement of the pin 252 and the extension ramp 208.

[0048] In one embodiment, the actuarial screw 206 is a stepped helical screw, which ensures that the device 200 expands only to a distinct thickness corresponding to the available tibial insert thickness. The helical cut 242 may include one or more thread risers 244 and stepped portions 246. Each thread riser 244 connects the stepped portions 246. The thread riser 244 is the vertical distance the helical cut 242 advances axially as the actuarial screw 206 rotates. The stepped portions 246 hold the pin 252 and are configured to accommodate the thickness of the available tibial insert. The stepped portions 246 may include, for example, angled cuts that form an obtuse angle with the thread risers 244. The thread risers 244 and stepped 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 stepped increments 246 of the thread 206 allow the surgeon to expand the trial 200 to discrete heights intraoperatively without removing it from the joint cavity. The trial 200 can be set to one of the distinct heights corresponding to the available tibial insert sizes. Because the thread rise 244 is steep, the trial 200 cannot maintain its height under compression if it has not reached the step 246. This prevents the user from setting the trial 200 to an intermediate height where no available tibial inserts exist. The step 246 may also incorporate a slight back angle to provide height stability while the surgeon is performing range of motion tests.

[0049] In an alternative embodiment, the actuation screw 206 is a continuous helical screw, which ensures that the device 200 can extend to any suitable height along its range of motion. In this embodiment, both sides 248, 249 of the helical cut 142 may include uninterrupted, continuous spiral grooves. The helix may be seamless without stepped regions, allowing for continuous adjustment to any desired height. In this way, the user can steplessly adjust the trial height between the maximum retracted position and the maximum extended position.

[0050] Referring here to Figures 15A and 15B, an extension ramp 208 according to one embodiment is shown. The extension ramp 208 includes an inclined body 250 having a protruding pin 252 configured to engage with a stepped helical screw 206. The inclined body 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 dimensions such that it provides clearance for the screw 206 to pass through. The central hole axis of the hole 258 is coaxial with the operating axis 228. The inclined body 250 defines a plurality of ramps 260 that provide inclined or sloped surfaces configured to guide or facilitate the movement of the top plate 202. The ramp 260 includes an upward inclination from the bottom surface 262 to the top surface 264 of the inclined body 250, and can convert the horizontal movement of the extension ramp 208 into the vertical movement of the top plate 202. The ramp 260 may include, for example, a male ramp having a dovetail or other mating configuration configured to engage with the corresponding inclined surface of a recess 218 in the top plate 202. The ramp 260 may include a pair of parallel ramps 260 located in different planes. For example, a first and second pair of ramps 260 located on either side of the extension ramp 208 can lift the top plate 202 uniformly.

[0051] The extension ramp 208 includes one or more pins 252 that extend into the closing hole 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 hole 258. As is most commonly seen in Figure 15A, the pins 252 may be offset from each other so as to advance along the edge 248 of the helical cut 242. The pins 252 may be offset laterally from the central hole axis and off-axis. The free protruding end of each pin 252 is receivable in the helical cut 242 of the actuating screw 206, which guides the extension ramp 208 as the screw 206 rotates.

[0052] Highlighting Figures 16A and 16B shows in more detail the movement of the extension ramp 208 due to the rotation of the actuation screw 206. In Figure 16, the screw 206 and ramp 208 are shown in the compressed position with the extension ramp 208 retracted to its furthest forward position. The pin 252 extends into the helical cut 242 of the screw 206 in its initial starting position. In Figure 6B, the screw 206 and ramp 208 are shown in the extended position with the extension ramp 208 extended to its furthest rearward position. As the screw 206 rotates, the pin 252 moves along the helical cut 242 of the screw 206 until it reaches the final stage 246. This then causes the inclined body 250 to slide along the bottom plate 204, pressing the inclined portion 260 against the corresponding inclined surface 219 of the top plate 202, thereby causing the top plate 202 to expand upward. Figures 17A and 17B show the expandable tibial trial 200 in the complete collapse position and the complete expansion position, respectively.

[0053] The articular insert 208 may be connected to the apex plate 202, for example, by a snap-fit ​​or sliding joint. The insert 280 may include a body having an upper articular surface 282 and an opposite lower surface 284 configured to attach to the expandable tibial trial 200. The upper articular surface 282 may be recessed and contoured to articulate with respect to a corresponding femoral trial, such as the femoral trial 12. The outer wall 286 of the insert 280 may have a general shape similar to that of the expandable tibial trial 200. In the embodiments shown in Figures 18A-18B, one or more pegs or struts 288 may protrude from the lower surface 284 of the insert 280. The struts 288 are configured to fit into corresponding openings 220 in the apex plate 202, thereby securing the insert 280 to the apex plate. In the embodiment shown in Figure 19, the articular insert 280 includes a slide-on attachment joint. The joint insert 280 slides along the slot 223 of 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 joint insert 280 to the expandable trial 200 by engaging with the groove 290 along the outer wall 286 of the insert 280.

[0054] To further highlight Figures 20A and 20B, a modular posterior stabilization (PS) strut may be incorporated into the articular insert 280 to facilitate the option of using a posterior stabilization femoral implant. The modular strut may be attached to the articular insert 280, for example, using a locking pin 300. As best seen in Figure 20B, the locking pin 300 may include a central cylindrical strut 302, a pair of cylindrical legs 304, and a bridge portion 306 connecting the central strut 302 and the legs 304. The strut 302 may extend vertically upward and be configured to receive a modular strut (e.g., strut 188), and the legs 304 may extend vertically downward from the bridge portion 306 and be fitted into 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 an expandable trial 200. Each leg portion 304 may have an annular groove 308 defined near its free end for snap-on engagement with the joint 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, the spring being stable under load but easily removable.

[0055] In the embodiments described herein, the trial is 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 need to be repeatedly inserted into and removed from the joint cavity. Instead, a single trial can be inserted and expanded to the desired height, thus reducing the number of components, increasing the speed of the procedure, and improving ease of use and usability. Expandable trials allow surgeons to change the size with a single twist of the screwdriver and easily find the appropriate insert thickness. A stepped screw also controls the expansion, ensuring that the trial locks only at the desired expansion height. The stepped screw may also simultaneously provide the user with tactile and / or visual feedback corresponding to the trial thickness.

[0056] Although the present invention is 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, the present invention is intended to cover modifications and variations of the invention provided within the scope of the appended claims and their equivalents. For example, it is explicitly intended that all components of the various devices disclosed above can be combined or modified in any preferred configuration.

Claims

1. This is a trial system for knee arthroplasty. An expandable tibial tray trial having a top plate and a bottom plate; an operating screw held 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. Equipped with, The actuation screw defines a helical cut having a stepped portion, and the extension ramp includes a pin configured to engage with the helical cut of the actuation screw. As the operating screw rotates, the pin is configured to advance along the helical cut and settle into one of the stepped portions, thereby ensuring that the expandable tibial tray trial expands only to a predetermined thickness. A trial system for knee arthroplasty.

2. The system according to claim 1, wherein the extension ramp includes an inclined body having a pair of vertical support walls, and a channel for receiving the operating screw is defined between the pair of vertical support walls.

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

4. The system according to claim 2, wherein the inclined body defines an upper inclined surface that provides an inclined surface configured to engage with a corresponding surface on the top plate.

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

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

7. The system according to claim 6, wherein the helical cut includes a spiral cut that completely penetrates the shaft and forms a fully open channel that is completely open from the surface of the shaft to the core.

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

9. The system according to claim 8, wherein the joint 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 annular groove of the piston, thereby securing the joint insert trial to the expandable tibial tray trial.

10. The system according to claim 8, further comprising a femoral trial having an anterior flange, a pair of posterior condylar flanges, and a distal portion between them, wherein the femoral trial has an lateral articular surface having a smooth, rounded shape that contacts the articular insert trial, and an lateral surface shaped to match a resected femur having five resection cuts.

11. An expandable tibial tray trial, A top plate and a bottom plate are configured to nest inside each other at the crushing position, An actuation screw configured to rotate around an actuation axis, the actuation screw having a head and a shaft defining a helical cut, the head defining a plurality of indicators around the head, The system comprises an inclined body having a pair of vertical support walls defining a channel between them for receiving the actuation screw, and an extension ramp having a cross pin extending across the channel and configured to pass through the helical cut of the actuation screw, As the operating screw rotates, the inclined body translates along the operating axis, expanding the top plate, thereby moving the top plate to the expanded position so that one of the indicators corresponds to a predetermined height of the expanded expandable tibial tray trial. Expandable tibial tray trial.

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

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

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

15. The expandable tibial tray trial according to claim 14, wherein the bottom plate defines a gap on the top surface of the central block portion, and when one of the indicators aligns with the gap, the value read from the indicator corresponds to the predetermined height of the expanded expandable tibial tray trial.

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

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