WO2025117312A1

WO2025117312A1 - Adjustable load sensing hip trunnion trial

Info

Publication number: WO2025117312A1
Application number: PCT/US2024/056824
Authority: WO
Inventors: Brett J. Bell; Darren J. Wilson; Parker HILL; Samuel C. DUMPE; Sied W. Janna
Original assignee: Smith and Nephew Orthopaedics AG; Smith and Nephew Asia Pacific Pte Ltd; Smith and Nephew Inc
Current assignee: Smith and Nephew Orthopaedics AG; Smith and Nephew Asia Pacific Pte Ltd; Smith and Nephew Inc
Priority date: 2023-11-29
Filing date: 2024-11-21
Publication date: 2025-06-05
Anticipated expiration: 2026-05-29

Abstract

An adjustable implant trial (1) includes a trunnion section (100) and a broach (150), the broach being insertable within the bone of a patient during a trialing step. The implant trunnion has a load cell (200) that can measure forces acting on the head (120) of the implant trunnion (e.g., through a trial head attached thereto) during a distraction test. The adjustable implant trial can have a mechanism that alters the neck length of the adjustable implant trial by changing the distance between the implant trunnion and the broach. The adjustable implant trial may also have a mechanism to change the neck offset of the adjustable implant trial.

Description

ADJUSTABLE LOAD SENSING HIP TRUNNION TRIAL

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a non-provisional patent application claiming priority to, and the benefit of the filing date of, U.S. provisional patent application number 63/603,793, which was filed November 29, 2023, the entire contents of which are incorporated herein.

FIELD OF THE DISCLOSURE

[0002] The present disclosure relates generally to orthopedic tools and methods for determining an appropriate size for an implant used as a joint replacement prosthesis. Specifically, the present disclosure relates to systems and methods for aiding a surgeon in selecting the anatomically correct size of a prosthetic device for surgical implantation during total hip arthroplasty (THA).

BACKGROUND OF THE DISCLOSURE

[0003] Inadequate soft-tissue balancing is a major, yet often underemphasized, cause of failure of primary and revision total hip arthroplasty (THA). Moreover, adequate soft tissue tension in the muscles, tendons, and/or ligaments surrounding the hip joint is also difficult to achieve with currently available manual assessment techniques. Accurate soft tissue balancing of the surrounding tendons, ligaments, and muscles to a pre-arthritic state during implant trialing would advantageously restore leg length and femoral offset, while also minimizing post-operative limping and the need for the use of walking aids that are typically observed after such surgical procedures are performed. [0004] The tension required for hip reduction during intraoperative trialing after preparation of both the acetabular and femoral side is a typical starting point for evaluating the hip soft-tissue sleeve. During this intraoperative trialing process, the surgeon assesses the position, stability, leg length, and soft tissue balance of the trial components by checking for combined anteversion, moving the hip through a full range of motion (ROM) into flexion, internal rotation, extension, external rotation, and telescoping the joint. The implant trial sizing devices are repositioned and/or substituted (e.g., with a larger or smaller trial device), if deemed necessary by the surgeon, and the process of intraoperative trialing is repeated. Reductions that are not anatomically correct (e.g., occur with the application of too small or too large of a force) signify that adjustments in offset and/or length are required. Once the trial implants are deemed to have been correctly sized and positioned to produce the correct soft tissue tensioning, the trial implants are exchanged with the final implants.

[0005] Current intraoperative distraction tests for assessing soft tissue balance and prosthetic hip stability include the Shuck test, the Dropkick test, and direct comparison of the limb length by palpation. During these tests, the surgeon subjectively assesses the resistance of the hip muscles to movement by causing the limb to be moved through a series of movements within a passive ROM test while the trial components are in place to determine the necessity for soft tissue release. Failure to bring the hip to full extension, abduct the hip beyond 20°, and/or bend the knee beyond 90°-100 ° (without knee arthritis or previous total knee arthroplasty) serve as indicators to a surgeon that there is a soft tissues tension imbalance. [0006] The Shuck test, which involves applying longitudinal traction in extension while assessing femoral head distraction, is unreliable and prone to error, as the soft-tissue tension in the hip is not uniform and can be influenced by many variables, including, for example, age, sex, presence of generalized laxity, muscle status, duration and type of pathology, type of anesthesia, the degree of dissection, and/or retractor use; furthermore, the Shuck test does not recreate any natural movement that a patient would be anticipated to perform postoperatively. The distraction force exerted by the surgeon during these tests is also not well controlled and, therefore, achieving a baseline measurement (e g., femoral head distraction achieved for a distraction force of a predefined magnitude) for this test is challenging. Further testing for stability by various provocative maneuvers, such as by putting the prosthetic hip in extremes in terms of ROM during trial reduction can also be extremely misleading. In fact, it is common, during exposure for the surgery, for the native hip to dislocate easily without the need for taking the hip to extremes in terms of ROM after the capsule is incised. Similarly, the prosthetic hip at trial reduction (i.e., before capsular repair) can also be found to be spuriously unstable by the surgeon even if it has the same stability and functional biomechanics of the native hip. As a result of the performance of these at times unreliable diagnostic procedures during intraoperative distraction tests, surgeons may erroneously increase the length and/or offset to achieve an unneeded artificial constraint, which actually compromises the functional postoperative outcome for the patient. The detection of impingement and subluxation of the trial devices is also subjective, and adjustment of component orientation after implantation requires repetitive prosthesis extraction, which can potentially jeopardize primary stability, especially in cases with inadequate bone stock.

[0007] Several studies indicate that inadequate soft tissue tension is related to pain (e.g., in the groin and knee), dislocation, reduced ROM of the hip, and limping. With traditional trial reduction assessments, the risk for postoperative dislocation is often a source of concern for both surgeons and patients. It is not uncommon for patients to be provided with functional restrictions after undergoing a THA procedure, which typically includes suggestions to avoid some extreme postures that may increase the risk for hip dislocation. However, the imposition of functional restrictions on a patient has the disadvantages of a slower return to activities by the patient, significant expense, and decreased patient satisfaction. It is thought that the high frequency of the imposition of postoperative functional restrictions may be because intraoperative measurements of ROM by surgeons fail to provide an accurate assessment of what are truly safe postoperative limits to a patient’s ROM.

[0008] Thus, a need exists at present for a more system systematic, quantitative approach for assessing soft tissue tensioning during intraoperative trialing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] By way of example, specific examples of the disclosed device will now be described, with reference to the accompanying drawings, in which: [0010] FIGS. 1 and 2 show features of a load cell installed within an implant trunnion for use in determining forces acting on a trial implant attached thereto during an implant trialing step;

[0011] FIGS. 3-7 show features of an example adjustable implant trial that has the load cell shown in FIGS. 1 and 2 and can adjust a neck length thereof and measure forces acting thereon during the implant trialing step;

[0012] FIGS. 8 and 9 show features of another example adjustable implant trial that has the load cell shown in FIGS. 1 and 2 and can adjust a neck length thereof and measure forces acting thereon during the implant trialing step;

[0013] FIG. 10A schematically shows features of an example system configured to apply a prescribed, calibrated distraction (tension) force to an instrumented adjustable implant trial during a joint distraction test;

[0014] FIG. 10B schematically shows features of a system configured to apply a prescribed, calibrated distraction (tension) force to an instrumented adjustable implant trial during a joint distraction test;

[0015] FIG. 10C schematically shows features of an example load cell suitable for use in the force gauge of the example system shown in FIG. 10B;

[0016] FIG. 11 schematically shows a femoral tracking array attached to a femur to detect relative movements of the femur and pelvis during the joint distraction test;

[0017] FIG. 12 schematically shows a pelvic tracking array attached to a pelvis to detect relative movements of the femur and pelvis during the joint distraction test; [0018] FIGS. 13-19 show features of another example adjustable implant trial that has the load cell shown in FIGS. 1 and 2 and can adjust a neck length thereof and measure forces acting thereon during the implant trialing step;

[0019] FIGS. 20 and 21 show an example in which an implant device has an adjustable trunnion offset from the broach;

[0020] FIGS. 22-25 show features of another example adjustable implant trial that has the load cell shown in FIGS. 1 and 2 and can adjust a neck length thereof and measure forces acting thereon during the implant trialing step;

[0021] FIG. 26 schematically shows features of another example of an adjustable implant trial configured to control and adjust a neck length thereof;

[0022] FIG. 27 schematically shows features of another example of an adjustable implant trial configured to control and adjust a neck length thereof; and

[0023] FIG. 28 schematically shows the steps of a method of use of the example adjustable implant trials disclosed herein.

[0024] FIG. 29 schematically shows features of an example adjustment gauge that can be used with the example adjustable implant trials disclosed herein, in the alternative or in addition to the mechanisms that allow for adjustment of neck length and neck offset, respectively.

[0025] FIG. 30 shows features of an example implant device, in which the trunnion body is adjustable relative to the broach in translation/extension and also a pivoting motion using two (2) actuators. [0026] FIG. 31 shows the broach and the actuators of the implant device shown in

FIG. 30

[0027] FIG. 32 shows an example actuator for the implant device shown in FIG. 30, the actuator comprising a stud, which has a helically threaded portion and a ring gear portion, and a worm gear that is configured to engage with the ring gear portion for rotating the stud.

[0028] FIG. 33 shows the example implant device with the trunnion body extended and pivoted relative to the broach.

[0029] FIG. 34 shows a motorized controller connected to the actuators of the implant device of FIG. 30 by flexible couplers to control rotation of the actuators and, thus, the position and angle of inclination of the trunnion body relative to the broach.

[0030] FIGS. 35-38 show the trunnion body and the broach of the implant device of FIG. 30 in several example extended and/or pivoted positions relative to each other.

[0031] FIGS. 39 and 40 are a side view of another example adjustable implant trial with an adjustable neck length and neck offset.

[0032] FIGS. 41 and 42 show the adjustable implant trial of FIGS. 39 and 40 in retracted and extended positions, respectively.

[0033] The drawings are not necessarily to scale. The drawings are merely representations, not intended to portray specific parameters of the disclosure. The drawings are intended to depict various examples of the disclosure, and therefore are not considered as limiting in scope. In the drawings, like numbering represents like elements. DETAILED DESCRIPTION

[0034] The presently disclosed devices, systems, and methods allow health care professionals (e.g., surgeons) to be able quantify the balance of the forces induced by the surrounding soft tissues (e.g., soft tissue tension) on the femoral trial before the final femoral implant device is inserted. Since the soft tissue tension is now rendered quantifiable, the presently disclosed devices, systems, and methods offer health care professionals the ability to provide a greater degree of personalized treatment to patients, while also reducing the risk of postoperative j oint dislocation, impingement, and unequal limb lengths. By providing quantitative force feedback, it is possible to ascertain information as to whether the cup and stem components of the femoral trial are the correct distance apart (e.g., have the correct offset based on the particular anatomy of the implant patient), which leads to substantially anatomically correct balance of soft tissue tension, which generally offers maximum stability to the joint.

[0035] Furthermore, dynamic assessment of the joint during the trialing process with accurate force feedback obtained from a force calibrated distraction test also can indicate the uniformity of the distribution of such soft tissue tension-induced forces across the joint. Dynamic assessment of the joint during the trialing process will also allow for the determination of peak forces that may occur during the sizing of the trials in cases of prosthetic impingement. This balancing of forces associated with soft tissue tension is crucial in restoring the anatomy of the joint, allowing optimal function of the joint in terms of ROM and pain reduction while also reducing the chances of joint dislocation, prosthetic impingement, and joint wear over time. [0036] The subject matter described herein relates generally to a sensor-based implant trunnion trial component, specifically for determining anatomically correct dimensions for a femoral prosthetic implant, which can measure axial and multi-vector forces induced by soft tissue tension during a navigated hip replacement procedure. The implant trunnion 100 has, within a head 120 thereof, a load cell 200 that is attached, via the trunnion body 110, to a stem component or broach 150 (the terms “stem” and “broach” are used interchangeably herein). An example load cell 200 is shown in FIGS. 1 and 2. In each of the example implant trunnions 100 disclosed herein, the distance between the load cell 200 and the broach 150 can be adjusted. In some examples, the distance can be adjusted using a lead screw and worm gear assembly (see, e.g., example shown in FIGS. 3-7 and example shown in FIGS. 8 and 9). In the example shown in FIGS. 13-21, the distance is adjusted using a telescoping neck portion that slides within a slot formed in the trunnion body 110, with the distance being maintained using retention features and spacers removably insertable over the telescoping neck portion. In still another example, features of which are shown in FIGS. 22-25, a rack-and-pinion mechanism is used to control the distance. In another example, features of which are shown in FIG. 26, the length of the femoral neck can be adjusted by controlling a pneumatic or hydraulic pressure within a chamber internal to the femoral head of the implant trunnion. In another example, features of which are shown in FIG. 27, the length of the femoral neck can be controlled by an elastic member (e g., a spring) positioned within a chamber that is formed internal to the femoral neck and femoral head of the implant trunnion. In another example, features of which are shown in

FIGS. 30-38, the distance between the trunnion body 110 and the broach 150, as well as a pivoting movement therebetween, is controlled using a plurality of actuators, such as, for example, two actuators that connect together the trunnion body 110 and the broach 150.

[0037] Using the example implant devices and methods disclosed herein, the tensionbased forces induced in the trunnion trial component from the soft tissues can be optimally correlated with joint position and displacement of the femoral head during a distraction test (e.g., a shuck test using optical trackers and a pre-determined tensile/traction force exerted by a user through a force gauge). Through the use of force and strain sensors in the implant trunnion, it is possible to quantify the soft tissue tension of the patient at the joint, as well as to reliably assess hip stability through a full ROM. Thus, the example implant devices disclosed herein advantageously facilitate incremental readjustments of the implant devices, along with the bones to which such implant devices are attached, that enable true customization of a patient’s total hip soft tissue tension balance and alignment, especially when used in conjunction with computer-aided surgical techniques.

[0038] FIGS. 1 and 2 show an example of a load cell 200 that is configured to have a femoral head trial (130, see FIG. 13) attached thereto, the size (e.g., diameter) of the femoral head trial corresponding to the specific anatomy of the patient and also to the dimensions of the acetabular cup trial selected by the surgeon. While the examples disclosed herein are described in relation to a femoral trunnion trial component, the present disclosure is not limited to the particular examples disclosed herein and can be implemented in trial devices for other joint replacement procedures that have a need for an adjustable geometry thereof. [0039] In the example shown in FIGS. 1 and 2, the load cell 200 is generally in the form of a hermetically sealed cavity formed within a head 120 of the implant trunnion 100. In this example, the cavity formed internal to the head 120 has dimensions of about 10.5 mm diameter and about 13 mm length. The load cell 200 comprises, located within the cavity, a force measurement device 220. The force measurement device 220 can be, for example, a gamma sterilizable microbutton load cell (Applied Measurements CDFT) rated up to 300-350 N. The dimensions of the example force measurement device 220 are 10 mm in diameter and 3.5 mm in length. The dimensions of the example force measurement device 220 can be 9 mm in diameter and 2.9 mm in length. In some examples, power can be provided to the force measurement device 220 through the bottom surface thereof. The load cell 200 also comprises a power source 236. In this example, the power source 236 is a 3 Volt (V) coin cell battery, having a CR1025 size. The load cell 200 also includes a circuit board 224, on which a micro-controller and communication protocol (e.g., WiFi®, Bluetooth®, etc.) chip are provided. The load cell 200 is used to measure the axial force exerted through the femoral head trial during the trialing procedure and muscle resistance during ROM assessment.

[0040] In some examples, the cavity that is formed within the head 120 can be divided into two sections, thereby allowing the power source 236 to be removed and replaced after use. The load cell 200 includes a lid 214 that is threadably engaged with the internal threads 218 of the head 120 to hermetically seal (e.g., in a liquid- and/or gas-tight manner) the cavity. The implant trunnion 100 is advantageously reusable, after having undergone a suitable sterilization process (e.g., gamma sterilization). Raw mV/V data, which is the ratio of the output voltage to the excitation voltage required for the sensor to work, that is obtained from the force measurement device is converted into engineering units (e.g., Newton (N), pound force (Ibf)). This conversion of the raw mV/V data into engineering units can be done via calibration of the sensor and use of one or more equations for performing the appropriate unit conversions. The processed data is then transmitted, preferably in a wireless manner, to a remote workstation (e.g., any suitable computing device) and integrated into navigation software that is configured to aid the surgeon in performing the trialing step of the surgical procedure.

[0041] The load cell 200 also comprises one or more strain gauges 228 that allow for the measurement of forces that are acting in non-axial directions. These strain gauges 228 can be, for example, in the manner of foil gauges (e.g., QFLG-02-11-3LJB, Tokyo Sokki Kenkyujo Co., Ltd., Japan) that are bonded onto flat surfaces 212 that are formed (e.g., in a precision machining process) on the outer surface of the housing 210 of the load cell 200 or on the head 120. In some examples, the housing 210 forms some or all of the head 120. Preferably, the load cell 200 comprises four (4) strain gauges 228, each of which is located on one of four (4) flat surfaces 212 of the housing 210. These flat surfaces 212 are spaced circumferentially apart from each other at approximately 90° intervals around the housing 210, such that first and second strain gauges 228 are positioned diametrically opposite each other and third and fourth strain gauges 228 are positioned diametrically opposite each other. The strain gauges 228 are bonded onto the respective flat surfaces 212 of the housing 210 using, for example, an epoxy resin and can be protected, in some features, with a layer of silicone rubber disposed over the surface of each of the strain gauges 228. The strain gauges 228 are connected, via signal wires 232 that are routed inside the hermetically sealed cavity, to a 24-bit analog input module, which can be provided on the circuit board 224 and can, in some instances, be integrated with the micro-controller. The data from the strain gauges 228 is transmitted, preferably wirelessly, to the remote workstation and can be integrated into the navigation software that is configured to aid the surgeon in performing the trialing step of the surgical procedure.

[0042] The strain gauges 228 can advantageously be used during dynamic assessment of the joint during the trialing step for indicating the uniformity of force distribution across the joint (e.g., peak forces in cases of prosthetic impingement). The measurement of such forces to ensure proper force balancing has been found to be crucial to restoring the structure of the joint to be anatomically correct, allowing optimal function in terms of ROM and pain reduction. The measurement of such forces has also been found advantageous in reducing the chances of postoperative joint dislocation, prosthetic impingement, and wear over time through optimum location of the trial components during surgery.

[0043] The strain gauges 228 disclosed herein can be used to predict the risk of postoperative impingement and dislocation by detecting an increase in strain at a specified area of the bearing surface during manipulation of the limb during the trialing step. The x- axis, y-axis, and z-axis are perpendicular to each other and represent the medial, anterior, and superior directions, respectively. The external force vector (F_x, F_y, F_z) can be expressed in terms of the outputs of the strain gauges 228 according to the following equation:

[0044] In this equation, T is a calibration matrix and Si (i=l to 4) corresponds to the output of one of the respective four (4) strain gauges 228. The calibration matrix is calculated according to well-established methods for every sensor after use in surgery. The calibration procedures advantageously conform to ASTM E-4 standards (ASTM, 2008). [0045] The load cell 200 also comprises an inertial measurement unit (IMU) sensor (e.g., LSM9DS1) that is configured to determine the angle at which a distraction force is being applied (e g., using one of the systems shown in FIGS. 10A and 10B), so that the angle at which the distraction force is applied can be correlated with the distraction force applied to the instrumented implant trunnion. The IMU comprises sensors, including, for example, accelerometers, gyroscopes, and magnetometers that can be used to measure the posture of bodies and/or surgical tools. Instant posture is captured by the accelerometer, gyroscope, and trigonometry is used to calculate hip ROM after a neutral posture for the limb has been established (e.g., as a zero, or reference, position). The gyroscope and magnetometer are used to obtain geographic orientation for determination of a joint ROM coordination system and to improve the accuracy of the attitude algorithm of ROM measurement of the accelerometer by constant calibration and correction of accumulated errors.

[0046] FIGS. 3-7 show various features of an example of an adjustable implant trial, generally designated 1. In this example, the adjustable implant trial 1 has an implant trunnion 100 that is movable in a linear direction away from a broach 150. The linear direction changes a length of the “neck” of the adjustable implant trial, defined generally as the portion of the trunnion body 110 that extends from and/or between the load cell 200 to the broach 150. The broach 150 is the portion of the implant trial 1 that is inserted within a bone (e.g., a femur) during a trialing step of a joint replacement procedure. The axial adjustment of the implant trunnion 100 relative to the broach 150 is performed using a worm gear mechanism.

[0047] The worm gear mechanism comprises a worm gear 190 that is helically engaged with a worm wheel that is formed on an outer circumferential surface of a collar 180. The collar 180 is attached to an extruded section (see “Attachment” in FIG. 5) of the implant trunnion 100 and is positioned such that a threaded rod 172 can pass axially through the collar 180. The internal circumferential surface of the collar 180 is helically threaded to engage within the helical threads of the threaded rod 172. The worm gear 190 has a worm gear drive 192 that is accessible (e.g., by a surgeon or other user) external from the implant trial 1. A recess 154 is formed within the broach 150, the recess 154 being configured to house a portion of the threaded rod 172 therein. The internal surface of the recess 154 is threaded, the thread size and pitch of the internal surface of the recess 154 being the same as the internal circumferential surface of the collar 180 to form a substantially uninterrupted internally threaded cavity from and/or extending between the implant trunnion 100 and the broach 150.

[0048] A user (e.g., surgeon) applies a rotary input force to the worm gear drive 192, which causes the worm gear 190 to rotate. As the worm gear 190 rotates, the worm wheel and the collar 180 rotate, which in turn causes the threaded rod 172 to retract, or extend into the recess 154 of the broach 150. Thus, rotation of the worm gear 190 causes an axial movement of the threaded rod 172, thereby directly controlling a spacing distance of the implant trunnion 100 away from the broach 150. The worm gear drive 192 can rotate in either direction (e.g., clockwise or anticlockwise) to change the distance between the implant trunnion 100 and the broach 150 in either direction (e.g., closer together when the worm gear drive 192 is driven clockwise or farther apart when the worm gear drive 192 is drive anticlockwise). In the example shown, the threaded rod 172 is an M6 lead screw with a 1 mm thread pitch. At the portion of the threaded rod 172 that extends out of the collar 180 and into the implant trunnion 100, the threaded rod 172 comprises an anti-rotation body 170. The anti-rotation body 170 has a slot in which an anti-rotation pin 174 is inserted. The anti -rotation pin 174 is held within an anti -rotation slot 114 formed in the trunnion body 110 of the implant trunnion 100, so as to maintain the orientation of the implant trunnion 100 relative to the broach 150 as the implant trunnion 100 moves axially relative to the broach 150. The anti-rotation slot 114 advantageously is configured to support a neck length adjustment distance (e.g., the distance between the implant trunnion 100 and the broach 150) from between 0-20 mm, inclusive, which mimics the sizing for the small (S) to extra extra large (XXL) Polar Stem implants available from Smith & Nephew, Inc. The worm gear drive 192 can be configured to accept therein a powered tool insert to allow for adjustment of the neck length in a limited working space for accessing the hip joint.

[0049] FIGS. 8 and 9 show another example of an adjustable implant trial, generally designated 2, that uses a worm gear mechanism for changing a neck length of the implant trial 2. In this example, the recess 156 within the broach 150 is not threaded and the trunnion body 110 is fixedly mounted onto (e.g., attached to, in an immobile, or fixed, manner) the broach 150. The trunnion body 110 has formed therein a cavity 112 that is substantially coaxially aligned with the recess 156 in the broach 150, so that the cavity 112 in the trunnion body 110 and the recess 156 in the broach 150 form a continuous, uninterrupted volumetric space. The worm gear mechanism is fixedly attached within the trunnion body 110 and, at least partially, within the cavity 112 formed in the trunnion body 110. The worm gear 190 is positioned so that the worm gear drive 192 can be accessed and manipulated (e.g., rotated, such as by a tool) from outside of the trunnion body 110. The worm gear 190 is positioned to engage with the worm wheel formed on the outer circumferential surface of the collar 180.

[0050] The collar 180 may be supported by a bearing 118 positioned within the cavity 112. The worm wheel of the collar 180 is in the form of gear teeth that, when the worm gear 190 spins or rotates, engage with the worm gear 190 to cause a corresponding rotary motion of the collar 180. The implant trial 2 also comprises a telescoping extension that is rigidly attached to the end of the threaded rod 172 that protrudes from the cavity 112 of the trunnion body 110. The telescoping extension has a neck 122 and a head 120. The head 120 has the load cell 200 (see FIGS. 1 and 2) contained therein, preferably in a hermetically sealed manner. The neck 122 has a neck body, in which a generally cylindrically-shaped bore 124 is formed. The bore 124 is configured to receive the threaded rod 172 therein and may have a smooth or threaded internal surface thereof. The neck 122 also has, attached to the neck body on an opposite side thereof from the head 120, a neck flange 126. The neck flange 126 is a generally annularly-shaped wall that has a recessed edge 128 that allows for the axial movement of the telescoping extension (e.g., of the neck 122 and the head 120 attached thereto, such as in a unitary, monolithic manner) within the cavity 112 to not be obstructed by the worm gear 190. Thus, the neck flange 126 has a profile that is generally C-shaped, the profile being defined in the plane that is perpendicular to the longitudinal axis of the threaded rod 172, shown generally in FIG. 9. The cavity 112 thus has a corresponding C-shaped region 116 that extends in the longitudinal direction over a full or partial height or thickness of the bearing 118.

[0051] The collar 180 is, similarly to the example adjustable implant trial 1 shown in FIGS. 3-7, internally helically threaded, having a same thread size and pitch as the threaded rod 172. The collar 180 has a portion that extends radially internal to the inner circumferential surface of the bearing 118, so that the collar 180 can rotate within the bearing 118. Thus, the bearing 118 can support the collar 180 in the radial and axial directions. Thus, when the worm gear 190 is rotated, the collar 180 is rotated due to the engagement of the worm gear 190 with the teeth of the worm wheel formed on the outer circumferential surface of the collar 180. This rotation of the collar 180 causes the threaded rod 172 to move along the longitudinal axis thereof, moving the telescoping extension towards or away from the trunnion body 110 depending on the direction of rotation of the worm gear 190. The direction of rotation of the worm gear 190 thus determines whether the threaded rod 172 moves into the recess 156 of the broach 150 or moves (e g., in the direction of extension) or is driven out of the recess 156 of the broach 150. As the threaded rod 172 moves along its longitudinal axis, the telescoping extension also moves an identical distance into or out of the cavity 112 of the trunnion body 110. Thus, rotation of the worm gear 190 causes a change in the distance between the head 120 of the telescoping extension and the trunnion body 110 (and, thus, also the broach 150). [0052] The cavity 112 has, formed on an inner surface thereof, at least one anti-rotation slot 114 formed therein, the anti-rotation slot(s) 114 extending primarily or only in the direction of the longitudinal direction of the threaded rod 172. The neck flange 126 has, formed on the outer surface thereof, at least one anti-rotation ridge that is configured to fit within and slide along the length of one of the anti-rotation slot(s) 114. The neck flange 126 preferably has the same quantity of anti-rotation ridges as there are anti-rotation slots 114 formed on the inner surface of the cavity 112, the anti-rotation ridges being spaced apart from each other circumferentially in the same pattern as the anti-rotation slots 114. The anti-rotation ridge(s) and slot(s) 114 act together as a key that prevents the telescoping extension from rotating relative to the trunnion body 110 as the telescoping extension is extended and retracted relative to the trunnion body 110, such that the adjustable implant trial 2 shown in FIGS. 8 and 9 does not need the anti-rotation pin of the adjustable implant trial 1 shown in FIGS. 3-7.

[0053] In the example shown in FIGS. 8 and 9, the threaded rod 172 is an M4 lead screw, which is fixed within the telescoping extension (e.g., within the neck 122 thereof) by an adhesive thread locker (e.g., Loctite®) and resides, at least partially, within the recess 154 formed in the broach 15 when the telescoping extension is not in an extended position (e.g., in a position that provides about 0 mm of extension from the trunnion body 110). Due to the self-locking behavior that is inherent to worm gear mechanisms, there is no need in either of the example adjustable implant trials 1, 2 shown in FIGS. 3-7 or in FIGS. 8 and 9 for a mechanism that holds/secures the telescoping extension or trunnion body 110, as the case may be, at a specific extension distance relative to the broach 150. In some instances, the collar 180 is fixed within the bearing 118, such that an outer surface of the collar 180 is locked against an inner race of the bearing 118, the inner race being rotatable relative to an outer race of the bearing 118.

[0054] FIG. 10A shows an example system used for applying a prescribed force during a distraction test. This system comprises a force gauge 14 with a grip 16 on one end thereof and a sterile hook 12 on an opposite end thereof. The system also comprises a sterile band 10 that is positioned around the instrumented adjustable implant trial 1-7 as shown in FIG. 10A. The user (e.g., surgeon) hooks the sterile hook 12 onto the sterile band 10, grasps the grip 16, and applies a tension force onto the instrumented adjustable implant trial 1-7, via the sterile hook 12 and the sterile band 10. The magnitude of the tension force is measured by the force gauge 14. The force gauge 14 displays, in real-time, the magnitude of the tension force applied, so that the user can ensure that a prescribed tension force is applied to the instrumented adjustable implant trial 1-7 in a direction of dislocation of the instrumented adjustable implant trial 1-7 from the acetabular cup trial. Thus, if the instrumented adjustable implant trial 1-7 is dislocated from the acetabular cup trial at or below the prescribed tension force, the user can readily determine that the current configuration of instrumented adjustable implant trial 1-7 and/or of the acetabular cup trial is improper, thus indicating to such user that the instrumented adjustable implant trial 1-7 should be adjusted and the distraction test should be repeated.

[0055] FIG. 10B shows an example system used for applying a distraction (e.g., tension) force to an instrumented adjustable implant trial 1-7 during a distraction test. This system comprises force gauge 20 with a grip 24 on one end thereof. On the opposite end, the force gauge 20 is attached to a sterile band 22 that is positioned around the instrumented adjustable implant trial 1-7, as shown in FIG. 10B. The user (e.g., surgeon) grasps the hand grip 24 and applies a tension force onto the instrumented adjustable implant trial 1-7 via the sterile band 22. The magnitude of the tension force is measured by the force gauge 20, for example, by a load cell 30, an example of which is shown in FIG. 10C. The load cell 30 can be provided internal to the outer, generally cylindrically-shaped housing of the force gauge 20. The housing of the force gauge 20 can have cut-outs formed therein or thereon for attachment of the load cell 30 and, particularly, strain gauges 38 of the load cell 30 attached thereto. The force gauge operates 20 because, when the tension force is applied to the instrumented adjustable implant trial 1-7, the load cell(s) 30 of the force gauge 20 will deform as a result of the distraction force being transmitted by the sterile band 22.

[0056] An example of such a load cell 30 is shown in FIG. 10C. As shown, the load cell 30 has a base plate 32 that is secured (e g., internal to), at the four (4) corners thereof, to the housing of the force gauge 20. The base plate 32 has a U-shaped slot 34 that separates, in part, a U-shaped portion 36 of the base plate 32 from the remainder of the base plate 32. It is the geometry of the load cell 30 itself that leads to the deformation of the base plate 32 and, specifically, of the relative deformation of the U-shaped portion 36 and the base plate 32, the strain gauge 38 being positioned to measure the strain caused by the deformation of this U-shaped portion 36. As a distraction force is applied to the instrumented adjustable implant trial through the force gauge 20, the sterile band 22 exerts a tensile force to the force gauge 20, which manifests as an upward force on the U-shaped portion 36 of the load cell 30 (this upward force and motion of the U-shaped portion 36 is shown using the arrow shown in FIG. IOC). As a result of the shape of the U-shaped slot 34 in the base plate32 , the U-shaped portion 36 begins to lift away from (e.g., out of plane, in the direction of the arrow) the remainder of the base plate 32, which is rigidly attached to (e.g., by a fastener at each of the corners of the base plate 32) or unitarily formed (e.g., in a monolithic manner) with the housing of the force gauge 20. As a result of this out-of- plane deformation of the U-shaped portion 36 relative to the base plate 32, the region of the base plate 32 in which the strain gauge 38 is attached is deformed in compression, which the strain gauge 38 can measure to compute the tension force exerted by the user via the measurement of this resulting strain.

[0057] This quantified tension force can then be transmitted, stored, and/or presented to the user. The transmission of this quantified tension force can be wired (e.g., over a serial communication bus, such as a USB connection to the system) and/or wirelessly (e.g., Bluetooth®, Wi-Fi®, NFC, RFID, etc.).

[0058] The force readings obtained from an instrumented adjustable implant trial 1-7 can also be correlated with a known distraction load applied by the external force gauge 14, 20 shown in FIG. 10A (e.g., Series-3 Digital Force Gauge) or FIG. 10B (e.g., one or more strain gauges forming a load cell, an example of which is shown in FIG. 10C). The force gauge 14, 20 is held, by the surgeon grasping the grip thereof, through passive ROM that replicates normal function. The distraction force applied by the surgeon to the resected femoral neck via the force gauge 14, 20 is correlated with forces measured from the instrumented adjustable implant trial 1-7 and are wirelessly transmitted to a computing device (e.g., a tablet, a computer, etc.) for real-time, intraoperative assessment. The neck length and head size can be altered based on the analysis of the data received to obtain an optimum soft tissue tension with the instrumented adjustable implant trial 1-7 in place. This surrogate measure of soft-tissue tension will help guide surgeons on implant choice to reduce potential complications related to the final implant device being too loose (instability) or too tight (stiffness, stress fractures, pain, etc.). The force gauge 14, 20 can have a data connection port (e.g., such as a universal serial bus (USB), or similar port) and/or a wireless communication chip to allow distraction forces to be correlated with femoral neck displacement data obtained from a robotic or surgical navigation platform. [0059] The example systems of FIGS. 10A and 10B can also be integrated into opticsbased navigation systems, examples of which are shown in FIGS. 11 and 12. Such navigation systems can use infrared cameras to obtain positional information based on an infrared light. This infrared light can, in some features, be actively emitted from a reference frame with infrared light-emitting diodes. This infrared light can, in some other features, be passively reflected from trackers 1002 attached to bones, such as the pelvis 1000 and/or the femur 1001, and surgical tools. The use of either of the example systems of FIGS. 10A and 10B, along with the navigation systems shown in FIGS. 11 and 12, would allow implant forces induced by soft tissue tension to be correlated with the degree of displacement obtained from trackers 1002 located on bony structures (e.g., pelvis 1000, see, FIG. 11, or femur 1001, see FIG. 12) during pre-calibrated distraction tests of the trials using the force gauge 14, 20 of either of the systems shown and described relative to

FIGS. 10A and 10B. [0060] In FIG. 12, a femoral tracking array 1002 is attached to the greater trochanter of the proximal femur 1001. In FIG. 11, a pelvic tracking array 1002 is attached to the pelvis 1000. Regardless of the bone to which the tracking array 1002 is attached, the tracking array 1002 is used to track the relative movement of the neck of the adjustable implant trial 1-7 using robotic assistance to determine if the surrounding soft tissue (e.g., muscles, tendons, etc.) of the patient is too tight or too slack during tensioning. Thus, the tracking array 1002 can be used to track the distraction distance between the femur 1001 and the pelvis 1000 when an axial force is applied by a surgeon, using one of the systems of FIGS. 10A and 10B, through the adjustable implant trial 1-7.

[0061] FIGS. 13-19 show features of another example adjustable implant trial 3. The adjustable implant trial 3 includes a broach 150 and an implant trunnion 100. In this example, the implant trunnion 100 comprises two sections, the trunnion body 110 and the telescoping extension, comprising the head 120, the neck 122, and the femoral trial head 130. The telescoping extension comprises the load cell 200 and the IMU described elsewhere herein, both of which are advantageously contained within the head 120. The load cell 200 and the IMU in this example are substantially identical, in form and function, to the load cell and the IMU shown and described in relation to the other examples and, thus, will not be repeated herein again. The head 120 containing the load cell 200 is configured to have the femoral trial head 130 attached thereto. The head 120 containing the load cell 200 and the IMU of the telescoping extension is attached at an end of the neck 122. The trunnion body 110 comprises a longitudinally-extending cavity, into which the neck 122 is insertable. The neck 122 and the cavity have a keyed structure, so that the telescoping extension cannot rotate relative to the trunnion body 110 while the neck 122 is positioned even partially within the cavity of the trunnion body 110. The keyed structure of the neck 122 comprises fin-like structures that are diametrically opposite each other.

The neck 122 has, on opposite sides thereof, plungers 122P positioned on the fin-like structures (e.g., GN615-M2-KN). These plungers 122P are spaced apart from each other at prescribed distances along the length of the neck 122 and are configured to engage within indentations (e.g., hemispherical dimples) that are formed within the cavity at the same spacing as the plungers 122P along the neck 122, so that the plungers 122P nest within the indentations to, at least to some extent, resist axial movement of the telescoping extension relative to the trunnion body 110. The positioning of the plungers 122P and indentations corresponds to predefined neck lengths for the adjustable implant trial 3. In this example, the indentations and plungers 122P are spaced apart from each other every 4 mm, such that the neck length is adjustable in 4 mm increments. Distances shorter than and longer than 4 mm may be used instead. The 4 mm increment spacing mimics the sizing for the small (S) to extra extra large (XXL) Polar Stem implants available from Smith & Nephew, Inc.

[0062] The telescoping extension of the implant trunnion 100 shown in FIGS. 13-19 is designed to accommodate up to four (4) spacers along the length of the neck. The spacers can have any suitable thickness, including the 4 mm thickness of the spacer 270-4 shown in FIG. 19. Thus, the adjustable implant trial can be used to simulate neck lengths of following heights; 0 mm, 4 mm, 8 mm, 12 mm, and 16 mm, these neck lengths corresponding to XS to XXL sizes Polar Stem implants available from Smith & Nephew, Inc. Each spacer is designed to fit the cross-sectional profile of the neck 122 of the telescoping extension. As shown in FIG. 19, the spacer 270-4 has an open side 274 (e.g., defining a 120° wedged section) that facilitates insertion and removal of the spacer 270-4 onto/from the neck 122 of the telescoping extension. One or both of the fin-like structures of the neck 122 has a scale 122S formed or attached thereon, the scale 122S showing a neck length of the implant trunnion 100 as the telescoping extension moves relative to the trunnion body 110.

[0063] FIGS. 18A-18D show various spacer lengths installed over the neck 122 of the telescoping extension. In the example configuration shown in FIG. 18A, a single 4 mm thick spacer 270-4 is installed over the neck 122 of the telescoping extension, such that the implant trunnion 100 provides a 4 mm neck length.

[0064] In the example configuration shown in FIG. 18B, a single 8 mm thick spacer 270-8 is installed over the neck 122 of the telescoping extension, such that the implant trunnion 100 provides an 8 mm neck length. In this example configuration of FIG. 18B, the single 8 mm thick spacer 270-8 can be replaced with two (2) of the 4 mm thick spacers 270-4 shown in FIG. 19.

[0065] In the example configuration shown in FIG. 18C, a single 12 mm thick spacer 270-12 is installed over the neck 122 of the telescoping extension, such that the implant trunnion 100 provides a 12 mm neck length. In this example configuration of FIG. 18C, the single 12 mm thick spacer 270-12 can be replaced with three (3) of the 4 mm thick spacers 270-4 shown in FIG. 19 or even with a combination of an 8 mm spacer 270-8 and a 4 mm spacer 270-4. [0066] In the example configuration shown in FIG. 18D, a single 16 mm thick spacer 270-16 is installed over the neck 122 of the telescoping extension, such that the implant trunnion 100 provides a 16 mm neck length. In this example configuration of FIG. 18D, the single 16 mm thick spacer 270-16 can be replaced with four (4) of the 4 mm thick spacers 270-4 shown in FIG. 19, with two (2) of the 8 mm spacers 270-8 shown in FIG. 18B, or a combination of an 8 mm spacer 270-8 and two (2) 4 mm spacers 270-4.

[0067] FIGS. 20 and 21 show an example of a mechanism by which the trunnion neck offset can be adjusted. The neck offset direction is at least substantially perpendicular to the neck length direction in the example shown. The neck offset direction defines the height of the trunnion body 110 relative to the broach 150. Thus, the mechanism shown in FIGS. 20 and 21 provides manual control of the position of the trunnion body 110 relative to the broach 150 in a one degree of freedom translation stage. The mechanism shown in FIGS. 20 and 21 can be included, for example, in the example adjustable implant trial 3, shown in FIGS. 13-19 and also in the example adjustable implant trial 4, shown in FIGS. 22-25. In the example shown in FIGS. 20 and 21, the trunnion body 110 has feet 292 that are inserted in a mobile manner within a track 290 that is attached to the broach 150. The feet 292 secure the trunnion body 110 to the broach 150. The movement of the trunnion body 110 relative to the broach 150 is controlled by a side-mounted micrometer or screw 280 that is located within a recess formed between the broach 150 and the trunnion body 110. A ball bearing design supports precision motion and durability. The single axis stage is able to travel between neck offset values of -3 mm and +16 mm, inclusive, this range of neck offset values corresponding to the neck offset size range offered by the Polar Stem implants available from Smith & Nephew, Inc.

[0068] FIGS. 22-25 show features of another example of an adjustable implant trial 4, the neck length thereof being adjustable via a rack-and-pinion mechanism 300, which is capable of providing similar functionality to the example adjustable implant trials 1, 2 that utilize a worm gear mechanism. The rack and pinion mechanism 300 is used to provide linear motion of the load cell 200 relative to the trunnion body 110, this linear motion being in the neck length direction. A powered tool insert is connected to the pinion gear drive 322, which is coupled to a combined spur gear 350, pinion gear 320, and ratchet mechanism 360. As the power tool rotates the pinion gear 320 in a first direction (e.g., clockwise), the rotary movement of the pinion gear 320 causes the rack gear 310, which is rigidly attached to the load cell 200 and, thus, also to the head 120, is moved longitudinally, thereby increasing the femoral neck length. The ratchet mechanism 360 comprises a spur gear 350 that is engaged by a pawl 340 to prevent the rack gear 310 from moving in a reverse direction while the pawl 340 is engaged with the spur gear 350. In this example, the spur gear 350 has a circumference of 16 mm with 4 teeth, allowing for a hip femoral trial component to be adjusted precisely in 4 mm increments to mimic the sizing for the S-XXL Polar Stem implants available from Smith & Nephew, Inc. An extension spring 332 is connected to the pawl 340, constantly exerting a moment on the pawl 340 in the direction of a clockwise rotation of the pawl 340, such that contact between the pawl 340 and the surface of the spur gear 350 is maintained throughout the rotation of the pinion gear 320. The pawl 340 is attached to a moving platform 330, which can be adjusted laterally via a button 334 that is accessible from outside of the trunnion body 110. When this button 334 is actuated, the moving platform 330 moves laterally to allow the pawl 340 to disengage from the spur gear 350, so that the rack gear 310 (and the load cell 200 attached thereto) can move in the retraction direction, as far as an unextended position at which the neck length is 0 mm. The rack and pinion mechanism 300 also includes bearings and slip rings along with springs for maintaining orientations of the components thereof.

[0069] FIG. 26 is a schematic illustration of another example of an adjustable implant trial, generally designated 5. In this example, neck length is controlled using a pump 400 and/or pressure regulator 410. A tube is connected between the pump 400 and/or pressure regulator 410 and a chamber defined within the adjustable femoral head 420 and the end of the femoral neck that is positioned internal to the adjustable femoral head 420. The pump 400 and/or pressure regulator 410 control a hydraulic pressure within this chamber by controlling a flow of a pressurized fluid (e.g., air, saline, etc.) into the chamber. Thus, a constant distraction force may be applied by the pump 400 and/or pressure regulator 410 regardless of actuator position.

[0070] The inclusion of a tracking array attached to the great trochanter of the femur (see, e.g., FIG. 12) provides the position of the femoral neck relative to a second tracking array attached to the pelvis (see, e.g., FIG. 11). This configuration assumes that the femur is not tracked in a typical robotic/navigated solution.

[0071] In another example, the distraction distance can be held constant by varying the hydraulic pressure within the chamber at the pump 400 and/or pressure regulator 410. Joint pressure at each hip orientation can be monitored to correlate neck length and leg length with the calibrated force measured from the pressurized fluid. A navigation/robotic surgical system may be used to communicate (e.g., in a wired or a wireless manner) to increase/decrease hydraulic pressure within the chamber in response to a change in displacement (e.g., neck length) in an effort to maintain a constant distraction distance. Based on the hydraulic pressure, the surgical system can recommend an implant assembly configuration to optimize joint pressure throughout the ROM of the joint.

[0072] In an alternative example, the pump 400 and pressure regulator 410 shown in FIG. 26 are not configured as a constant volume device but, rather, are used to bleed excess pressure back to the fluid pump 410 through a relief valve. Thus, this example utilizes a constant volume device such as a fluid filled piston with linear actuator and pressure sensor to modulate and control distraction force. This example advantageously allows for the tracking system 1002 to be omitted, since the distraction distance can be quantified via the fluid volume. In practice, the distraction device would include a bleed port, which would allow air to be purged from the device. Subsequently, once the device has been purged, which can be completed ex-situ by a person (e.g., a surgical assistant), the piston pump position is “zeroed” allowing the distraction distance to be measured as fluid is displaced from the piston to the di stractor.

[0073] In yet another example, a method for leg weight compensation is included, which is of particular interest when used as part of a joint replacement procedure for large or obese patients, in which case the weight of the leg may add force to the device, which could be erroneously attributed to soft tissue tension. Two input parameters are important to the execution of this method. The first input parameter is the orientation of the femur relative to gravity. The second input parameter is the approximate weight of the leg. The first input may be provided by the tracking array along with landmarks describing the femur axis. The leg weight can be estimated by the surgeon or approximated by measuring the force in the actuator through the expected ROM with a relaxed actuator position where soft tissues are expected to be lax. Laxity can be verified by the surgeon manually distracting the device, thus relieving the actuator force. A final alternative to acquire leg weight would be to use the BMI, gender, and thigh circumference of the patient to calculate an estimate of the weight of the leg.

[0074] FIG. 27 is a schematic illustration of another example of an adjustable implant trial, generally designated 6. In this example, the fluid within the chamber is replaced with an elastic member (e.g., spring 440). In this example, the femoral tracking array 1002 located on the greater trochanter (see, e.g., FIG. 12) is necessary to measure the displacement of the actuator at various positions of the femur relative to the pelvis, using the pelvic tracking array 1002 attached thereto. The magnitude of the distraction force may be controlled by the use of interchangeable springs with different spring stiffnesses. In some instances, a preload force applied by the spring 440 may be adjusted by pretensioning the spring 440, such as may be accomplished using a spacer or adjustable screw mechanism, for example.

[0075] The housing/head surrounding the load cell is shaped and configured to have a femoral head trial attached thereto in all of the example adjustable implant trials disclosed herein. [0076] Using the devices, systems, and methods disclosed herein, a more systematic approach is provided for balancing a hip joint during surgery by combining the accuracy of computer navigated surgery for assessing leg length and femoral offset with a controlled force applied manually during the distraction test for assessing the tension in the soft tissues around the hip joint during trial reduction. The method of use is shown schematically in FIG. 28. In a first step, the trial reduction is performed (e.g., the appropriately sized trial femoral implant and cup is inserted into the resected hip joint). In a second step, the calibrated distraction test (e.g., Shuck test) is performed. In a third step, while the distraction force is applied, the limb is moved through a passive ROM, checking for impingement and also that the limb is of the proper length. In a fourth step, the data obtained is analyzed to determine if the soft tissue tension is optimized (e.g., substantially anatomically correct). The second, third, and fourth steps can in some ways be regarded as being performed substantially simultaneously, or concurrently. Thus, during these steps, the amount of force induced by the soft tissues surrounding the hip joint are quantified with the use of load cells and strain gauges of the adjustable implant trial in directions defined by the force exerted by the trunnion on the femoral head. If it is determined that the soft tissue tension is optimized, the implant trials are replaced with the appropriate final implant devices. If it is determined that the soft tissue tension is not optimized, then one or more remedial steps are performed and the method begins again at the first step. Such remedial steps can include altering the neck length of the adjustable implant trial, resitting the broach, and/or re-cutting the femoral neck. As part of the remedial steps, the neck length and neck offset can be adjusted automatically from a single adjustable implant trial, thereby simplifying the workflow, while the placement of strain gauges on multiple faces of the implant trunnion minimizes the risk of dislocation and impingement during passive ROM.

[0077] The angle of the hip joint and the change in displacement between the femoral and pelvic arrays (see FIGS. 11 and 12), which occurs during the trialing step is obtained from the surgical navigation system and correlated with force data, which is obtained from the load cell of the adjustable implant trial, and the magnitude of the distraction force, which is applied by the surgeon during the distraction test using a force gauge. This data can be used to finely tune the selection and placement of the implant trials when the hip is maneuvered in different positions.

[0078] Another example is shown in FIG. 29, in which an adjustment gauge, generally designated 500, is shown. The adjustment gauge 500 allows for relative movement between parts (e.g., the trunnion body and the broach or the broach and the head of the implant trunnion) of the adjustable implant trial that can move relative to each other to be measured. Thus, the adjustment gauge 500 can be implemented in series with, or integrated within, the trunnion body and/or the neck of the telescoping extension thereof. As the limb is moved through the ROM during the trialing step, the adjustment gauge 500 allows for relative movement to occur and for the minimum and maximum values of relative movement to be quantified, so that a surgeon can determine an optimal neck length and/or neck offset for soft tissue tension.

[0079] The adjustment gauge 500 comprises a housing 510 that is generally in the form of a hollow cylinder. A spring 530 and piston 540 are provided within the hollow portion of the housing 510. The spring 530 allows for axial movement of the piston 540 through the housing 510, while simultaneously applying a spring force that resists such movements. The spring 530 can be replaceable to apply different spring forces to resist relative movement. The spring 530 can apply a preload force to the piston 540 that must be overcome before relative movement is possible between the piston 540 and the housing 510. The spring 530 can be replaced to change this preload force applied by the spring 530. The housing 510 has a longitudinally-extending slot 520 formed in an outer surface thereof. The piston 540 has a position marker 550 rigidly attached thereto. The position marker 550 is held captive within the slot 520 formed in the housing 510. The housing 510 also comprises a scale 570 for quantifying the relative position of the piston 540 within the housing 510, as well as relative movement between the piston 540 and the housing 510. The scale 570 is a series of markings and/or numbers that correlate to the distance of relative movement between the piston 540 and the housing 510. The adjustment gauge 500 also has, held slidingly within the slot 520, at least two sliders 560. In the example shown, the two sliders 560 are positioned on opposite sides of the position marker 550 from each other.

[0080] When the piston 540 moves within the housing 510, the position marker 550 moves an identical amount. The sliders 560 are positioned around (i.e., in direct contact with) the position marker 550, preferably with the position marker 550 at a home, undeflected, or nominal position. Thus, when the piston 540 moves relative to the housing 510, the position marker 550 will move the slider 560 in the direction of this relative movement along the length of the slot 520. The sliders 560 advantageously have a frictional fit within the slot 520, so that each slider 560 does not move within the slot 520 unless the slider 560 is contacted (e.g., directly) by the position marker 550 and/or the piston 540, and/or by being manually positioned (e.g., such as during a position reset operation) by a user of the adjustment gauge 500. The piston 540 can move in either longitudinal direction relative to the housing 520, such that the position marker 550 can move the sliders 560 along the slot 520 to quantify the minimum and maximum deflection or relative movement values of the piston 540 relative to the housing 510. The compliance of the spring 530 allows for the surgeon to thus measure the minimum and maximum values in the neck length or neck offset directions in response to the soft tissue tension (e.g., tightness/looseness). The surgeon can use these minimum and maximum values, as indicated by the respective positions of the sliders 560 within the slot 520, to adjust the components of the adjustable implant trial to change the neck length and/or the neck offset, then the sliders 560 are moved against the position marker 550 in the home position and the limb is moved passively through the ROM and the minimum and maximum relative movements are measured again. This process is repeated until the surgeon determines that the neck length and/or neck offset of the adjustable implant trial are anatomically correct for the patient. In some examples, the spring 530 may be positioned on opposite sides of the piston 540 to provide a longitudinally-oriented centering force for the piston 540 within the housing 510.

[0081] The example adjustment gauge 500 shown in FIG. 29 can be used instead of or integrated into the neck offset adjustment mechanism shown in FIGS. 20 and 21. The example adjustment gauge 500 shown in FIG. 29 can also be used instead of or integrated into the neck length adjustment mechanisms shown in FIGS. 3-9 and 13-27. Thus, all of the example adjustable implant trials disclosed herein can have one or more (e.g., a plurality of) the adjustment gauge(s) 500 disclosed in FIG. 29, thereby allowing for such adjustable implant trials to allow for relative movement between the components thereof in at least 2 directions that are transversely (e.g., perpendicularly) arranged relative to each other. In some instances, it may be advantageous for the surgeon to lock one of such adjustment gauges 500 to allow for relative movement of the adjustable implant trials in only one direction.

[0082] FIGS. 30-38 show features of an example adjustable implant trial, generally designated 7. In this example, the trunnion body 710 is movably attached to the broach 750. The trunnion body 710 comprises a head (e.g., 120, see FIG. 1) that fits within the trial head 730. The adjustable implant trial 7 comprises two position adjusters 700, which control a distance and relative angle between the trunnion body 710 and the broach 750. In the example shown, the position adjusters 700 are in the form of motors that can be controlled independently of each other. The position adjusters 700 can be driven in sync (e.g., simultaneously) to change the neck length and neck offset. The position adjusters 700 can be driven independently to vary neck length and change an angle of the trunnion body 710 relative to the broach 750.

[0083] As shown in FIG. 31, the adjustable implant trial 7 comprises, attached to each of the position adjusters 700, a stud 720. Each stud 720 has a collar 740 attached thereto. The trunnion body 710 is omitted from the view shown in FIG. 31 to aid in illustration of the features shown therein. FIG. 32 shows a more detailed view of the stud 720, as well as the structures that control a rotary movement of the stud 720. As shown in FIG. 32, the studs 720 and the collars 740 are each helically threaded to allow for axial movement of the collars 740 along the length of the respective stud 720 upon rotation of the stud 720, as controlled by the respective one of the position adjusters 700. The position adjusters 700 comprise at least a worm gear 726, which threadably interfaces with a ring gear 724 formed continuously along the circumference of the stud 720. The worm gear 726 comprises a worm gear drive 728, which allows a rotary force to be imparted to the worm gear 726, which in turn imparts a corresponding rotary movement of the stud 720 through the engagement of the teeth of the worm gear 726 with the teeth of the ring gear 724. Thus, as the worm gear 726 rotates, the helically threaded portion 722 of the stud 720 is rotated, thereby causing the collar 740, which is threadably engaged with the helically threaded portion 722 of the stud 720, to move along the length of the stud 720.

[0084] FIG. 33 shows the engagement of the collar 740 within a collar recess 712. Thus, the collars 740 are held captive within the trunnion body 710 and cannot move relative to the trunnion body 710. Rather, the trunnion body 710 moves in unison with the collar 740 as the collar 740 moves along the length of the stud 720 upon rotation of the stud 720, as controlled by the respective position adjusters 700. The rotation of the studs 720 can be manually or automatically controlled and may even be adjustable by hand (e.g., using a tool, such as a screwdriver). A second stage gearing may be added to the stud 720 subject to torque requirements.

[0085] FIG. 34 shows an example system, comprising the adjustable implant trial 7, the controller 770, and flexible drive couplings 780. The system advantageously has the same quantity of flexible drive couplings 780 as the adjustable implant trial 7 has position adjusters 700. The controller 770 can comprise, for example and without limitation, motor(s), encoder(s), a power source (e.g., a battery), and associated electronics. In the example shown, the flexible drive couplings 780 receive a rotary input from the controller 770, and transmit this rotary input to the position adjuster 700 with which the flexible drive coupling 780 is operably engaged (e.g., by having the distal end thereof inserted within the worm gear drive 728, as shown in FIGS. 34). The flexible drive couplings 780 are advantageously sufficiently rigid to resist movements thereof while transferring the rotary input from the controller 770 to the corresponding position adjuster 700. As used herein, the ’’distal” end of the flexible drive coupling 780 is the end that engages with one of the position adjusters 700, such that the “proximal” end of such flexible drive coupling 780 is the end that engages with the controller 770.

[0086] FIGS. 35-38 show example relative positions of the trunnion body 710 (and, thus, also the trial head 730) and the broach 750. In FIG. 35, the trunnion body 710 is in a retracted position, in which the neck length (e.g., the distance between the broach 750 and the trunnion body 710) is at a minimum value and the trunnion body 710 is positioned adjacent to (e.g., touching, such as directly touching) the broach 750. In FIG. 36, the trunnion body 710 is in an extended position, in which the neck length (e.g., the distance between the broach 750 and the trunnion body 710) is at a maximum value and the trunnion body 710 is positioned away from the broach 750. In the position shown in FIG. 36, the collars 740 are at the distal ends of the helically threaded portion of the respective stud 720 with which such collar 740 is threadably engaged. [0087] When moving from the retracted position shown in FIG. 35 to the extended position shown in FIG. 36, the position adjusters 700 are controlled (e.g., by the controller 770, through the flexible drive couplings 780) to cause a rotation of the studs 720 in a direction (e.g., anticlockwise) that causes the collars 740 to move along the length of the studs 720 in a direction that increases the distance by which the trunnion body 710 is spaced apart from the broach 750. The position adjusters 700 (and, thus, the studs 720) may be controlled in sync or independently of each other in moving between the retracted and extended positions. A rotation of the studs 720 in an opposite direction (e.g., clockwise) causes the collars 740 to move along the length of the studs 720 in a direction that decreases the distance by which the trunnion body 710 is spaced apart from the broach 750. The studs 720 advantageously are formed to prevent the collars 740 from passing off of the distal ends of the studs 720, which would cause the trunnion body 710 to otherwise separate from the broach 750.

[0088] FIGS. 37 and 38 show the trunnion body 710 rotated relative to the broach 750 by movement of one of the collars 740 into the “retracted” position and the other collar 740 into the “extended” position. The rotated positions shown in FIGS. 37 and 38 are only examples and any position of the trunnion body 710 relative to the broach 750 between the “retracted” position and the “extended” position can be achieved by controlling each of the position adjusters 700 independently of each other.

[0089] By providing independently controlled first and second actuators, independent adjustment of neck length and/or neck offset can be achieved. [0090] FIGS. 39-42 show various features of an example adjustable implant trial, generally designated 8. FIGS. 39 and 40 are side views of the adjustable implant trial 8. The adjustable implant trial 8 is capable of being used to adjust a neck length dimension and a neck offset dimension independently of each other. FIG. 41 shows the adjustable implant trial 8 in a fully retracted position, in which both the neck length dimension and the neck offset dimension are at minimal values. FIG. 42 shows the adjustable implant trial 8 in a fully extended position, in which both the neck length dimension and the neck offset dimension are at maximum values.

[0091] Because the adjustment of the neck length dimension is independent of the adjustment of the neck offset dimension, it is possible for the neck length dimension to be a maximum value and for the neck offset dimension to be a minimum value or for the neck length dimension to be a minimum value and for the neck offset dimension to be a maximum value. Indeed, due to the independent control of the neck length dimension and the neck offset dimension, the neck length dimension can be any dimension between and including the minimum and maximum values thereof and the neck offset dimension can be any dimension between and including the minimum and maximum values thereof. Merely by way of non-limiting example, the adjustable implant trial 8 can have a neck length dimension of 2 mm and a neck offset dimension of 8 mm. By way of further non-limiting example, the adjustable implant trial 8 can have a neck length dimension of 10 mm and a neck offset dimension of 4 mm.

[0092] The adjustable implant trial 8 has a broach 150 and an implant trunnion 100.

The implant trunnion 100 has a trunnion body 110 and a head 120. The head 120 is movable (e g., linearly) relative to the trunnion body 110 in the neck offset direction to change a dimension of the neck offset of the adjustable implant trial 8. The broach 150 has a housing portion 151 and a distal portion 152. In the example shown in FIGS. 38-42, the distal portion 152 and the housing portion are threadably engageable with each other; however, any suitable joining or coupling mechanism for the housing portion 151 and the distal portion 152 is contemplated herein. The housing portion 151 is proximal to the trunnion body 110, relative to the distal portion 152. The trunnion body 110 and, indeed, the entire implant trunnion 100 is movable (e.g., linearly) relative to the broach 150 in the neck length direction to change a dimension of the neck length of the adjustable implant trial 8.

[0093] To accomplish these relative movements between the various components of the adjustable implant trial 8,the adjustable implant trial 8 comprises a neck length motor 146 and a neck offset motor 166.

[0094] The neck length motor 146 is housed at least partially (e.g., entirely) within the housing portion 151 of the broach 150. The neck length motor 146 engages with a threaded rod 142 that is attached to the trunnion body 110. The trunnion body 110 has an adjustment slot 140 formed therein, this adjustment slot 140 being substantially parallel and/or coaxially aligned with the longitudinal axis of the broach 150, or at least the housing portion 151 and/or the neck length motor 146 contained therein. The adjustable implant trial 8 also has, threadably engaged with the threaded rod 142 and contained within the adjustment slot 140, an anti-rotation collar 142. The anti-rotation collar 142 maintains an angular position of the trunnion body 110 relative to the broach 150 while the neck length motor 146 is activated (e.g., driven) to change the neck length dimension of the adjustable implant trunnion 8. Thus, the anti-rotation collar 142 prevents rotation of the trunnion body 110 (and, thus, of the entire implant trunnion 100) relative to the housing portion 151 (and, thus, of the entire broach 150). Thus, the anti-rotation collar 142 prevents rotation of the trunnion body 110 relative to the broach 150, especially when the neck length dimension is being adjusted by activation of the neck length motor 146. In this example, the threaded rod 142 moves longitudinally into or out of the neck length motor 146 to change the neck length dimension. The neck length motor 146 has an internally threaded portion that is rotated to cause this axial movement of the threaded rod 142.

[0095] The neck offset motor 166 is housed at least partially (e.g., entirely) within the trunnion body 110 of the implant trunnion 100. The neck offset motor 166 engages with a threaded rod 162 that is attached to the head 120. The head 120 has an adjustment slot 160 formed therein, this adjustment slot 160 being substantially parallel and/or coaxially aligned with the neck offset motor 166 contained within the trunnion body 110. The adjustable implant trial 8 also has, threadably engaged with the threaded rod 162 and contained within the adjustment slot 160, an anti-rotation collar 162. The anti-rotation collar 162 maintains an angular position of the head 120 relative to the trunnion body 110 while the neck offset motor 166 is activated (e g., driven) to change the neck offset dimension of the adjustable implant trunnion 8. Thus, the anti-rotation collar 162 prevents rotation of the head 120 relative to the trunnion body 110, especially when the neck offset dimension is being adjusted by activation of the neck offset motor 166. In this example, the threaded rod 162 moves longitudinally into or out of the neck offset motor 166 to change the neck offset dimension. The neck offset motor 166 has an internally threaded portion that is rotated to cause this axial movement of the threaded rod 162.

[0096] The neck length motor 146 and the neck offset motor 166 are both connected to and operably powered by one or more electrical power sources (e.g., one or more batteries, which can be rechargeable). Thus, the neck length motor 146 and the neck offset motor 166 may each be connected to a single common power source or may each be connected to a discrete, independent (i.e., not shared) power source. These power source(s) can advantageously be provided within the trunnion body 110, specifically within a cavity formed within the trunnion body 110. In this example, the cavity is formed in-line with (e.g., coaxial to) the adjustment slot 140.

[0097] The head 120 has a load cell (e.g., internal thereto). This load cell can be of any suitable type, according to the examples disclosed herein. An example of such a load cell is shown in FIGS. 1 and 2. The load cell is configured to measure forces exerted on the head 120 during, for example, a distraction test.

[0098] FIGS. 41 and 42 show the adjustable implant trial 8 implanted within a bone, specifically in this example, a femur 1001. In FIG. 41, the components of the adjustable implant trial 8 are adjusted, as described herein, to have the neck length dimension and the neck offset dimension at their respective minimum values. In FIG. 42, the components of the adjustable implant trial 8 are adjusted, as described herein, to have the neck length dimension and the neck offset dimension at their respective maximum values.

[0099] According to this example, an adjustable implant trial 8 for use in a trialing step of a joint replacement procedure is provided. This adjustable implant trial 8 comprises an implant trunnion 100, a broach 150, and first and second position adjusters. The implant trunnion 100 comprises a trunnion body 110, a head 120 configured for attachment to a trial head, wherein the head 120 is at or forms at least a portion of a first end of the trunnion body 110, and a load cell 200 configured to measure forces exerted on the head 120 during a distraction test. The broach 150 is coupled to a second end of the trunnion body and is configured for insertion within an intramedullary cavity of a bone (see, e.g., the femur 1001 in FIGS. 41 and 42) of the patient. The first position adjuster is configured to move the implant trunnion 100 relative to the broach 150 to adjust a neck length dimension of the adjustable implant trial 8. The second position adjuster is configured to move the head 120 relative to the trunnion body 110 to adjust a neck offset dimension of the adjustable implant trial 8. The neck length and neck offset dimensions can be adjusted without removal of the adjustable implant trial 8 from the bone of the patient.

[0100] The example adjustable implant trials disclosed herein can advantageously be heated and cleaned in an autoclave without damaging the components of the load cell 200, thereby allowing for reuse of such adjustable implant trials. The autoclave temperature can be, for example, up to and including 125 °C.

[0101] In the example adjustable implant trials disclosed herein, a 9-axis inertial measurement unit (IMU) sensor can be included within the implant trunnion. This IMU can be used to capture the posture of the joint (e.g., the hip joint) intraoperatively during load measurement and trial reduction. By monitoring hip posture, it is possible to qualitatively record range of motion (ROM) during THA surgery, thereby providing confidence to surgeons and patients as a means of avoiding unnecessary postoperative precautions and to accelerate rehabilitation. The IMU can be calibrated with a standard goniometer. The gyroscope and magnetometer are used to obtain geographic orientation for determination of joint (e.g., hip) ROM coordination. The accelerometer and gyroscope can be used to provide instant posture data and quality of movement (e.g., speed, amplitude, period, etc.).

[0102] Among the benefits provided by using the adjustable implant trials disclosed herein are that it presents a low cost technology for mitigating the risk of impingement and subluxation; acceleration of rehabilitation; unlike in conventional ROM assessment, the assessments performed with such adjustable implant trials disclosed herein do not rely on surgical experience and subjective judgment; and the use of such adjustable implant trials does not require bone pins that are typically used in optics-based navigation systems, which are typically used for accuracy of component positioning, leg length control and ROM detection.

[0103] The examples disclosed herein constitute complementary examples for quantifying the forces exerted through the trunnion on multiple faces; automating the adjustment of the trunnion neck length and offset using a single implant trial; correlating the quantified forces to a known distraction force that is applied to the implant trial manually by the surgeon during passive ROM characteristic of activities of daily living from a force gauge; and correlating leg length and neck offset determined from computer- assisted navigation with a known distraction force applied by the surgeon. Such a coordinated approach facilitates more patient-specific component sizing during the trialing step and builds upon existing tests carried out intra-operatively by surgeons to assess soft tissue tension and leg length/offset at the knees during hip arthroplasty.

[0104] While the present disclosure refers to certain examples, numerous modifications, alterations, and changes to the described examples are possible without departing from the sphere and scope of the present disclosure. Accordingly, it is intended that the present disclosure not be limited to the described examples, but that it has the full scope defined by the language of the specification, and equivalents thereof, as would be understood by persons having ordinary skill in the art. The discussion of any example is meant only to be explanatory and is not intended to suggest that the scope of the disclosure, including the claims, is limited to these examples. In other words, while illustrative examples of the disclosure have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed, and that the descriptions of such examples herein are intended to be construed to include such variations, except as limited by the prior art.

[0105] The foregoing discussion has been presented for purposes of illustration and description and is not intended to limit the disclosure to the form or forms disclosed herein. For example, various features of the disclosure are grouped together in one or more examples or configurations for the purpose of streamlining the disclosure. However, it should be understood that various features of the certain examples or configurations of the disclosure may be combined in alternate examples, or configurations. Any example or feature of any section, portion, or any other component shown or particularly described in relation to various examples of similar sections, portions, or components herein may be interchangeably applied to any other similar example or feature shown or described herein. Additionally, components with the same name may be the same or different, and one of ordinary skill in the art would understand each component could be modified in a similar fashion or substituted to perform the same function.

[0106] As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one example” of the present disclosure are not intended to be interpreted as excluding the existence of additional examples that also incorporate the recited features.

[0107] The phrases “at least one,” “one or more,” and “and/or” as used herein, are open-ended expressions that are both conjunctive and disjunctive in operation. The terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. All directional references (e.g., proximal, distal, upper, lower, upward, downward, left, right, lateral, longitudinal, front, back, top, bottom, above, below, vertical, horizontal, radial, axial, clockwise, and counterclockwise) are only used for identification purposes to aid the reader’s understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of this disclosure. Connection references (e g., engaged, attached, coupled, connected, and joined) are to be construed broadly and may include intermediate members between a collection of elements and relative to movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other. All rotational references describe relative movement between the various elements. Identification references (e.g., primary, secondary, first, second, third, fourth, etc.) are not intended to connote importance or priority but are used to distinguish one feature from another. The drawings are for purposes of illustration only and the dimensions, positions, order and relative to sizes reflected in the drawings attached hereto may vary.

Claims

CLAIMS We claim:

1. An adjustable implant trial for use in a trialing step of a joint replacement procedure, the adjustable implant trial comprising: an implant trunnion comprising: a trunnion body; a head configured for attachment to a trial head, wherein the head is at or forms at least a portion of a first end of the trunnion body; and a load cell configured to measure forces exerted on the head during a distraction test; a broach coupled to a second end of the trunnion body, wherein the broach is configured for insertion within an intramedullary cavity of a bone of the patient; and a position adjuster configured to move the implant trunnion relative to the broach to adjust a neck length and/or a neck offset of the adjustable implant trial without replacing the adjustable implant trial.

2. The adjustable implant trial of claim 1 , wherein the load cell comprises: a plurality of machined surfaces spaced circumferentially around and on or in the head of the implant trunnion; and a plurality of strain gauges, each of which is rigidly attached to one of the plurality of machined surfaces for measuring a strain at the machined surface to which such strain gauge is attached.

3. The adjustable implant trial of claim 2, wherein the load cell comprises: a circuit board for receiving and processing strain signals from the plurality of strain gauges; a power source for providing power to the circuit board; and signal wires that connect the plurality of strain gauges to the circuit board.

4. The adjustable implant trial of claim 2, wherein: the circuit board and the power source are contained within the head of the implant trunnion; and the plurality of strain gauges are on an external surface of the implant trunnion.

5. The adjustable implant trial of claim 2, wherein: the plurality of machined surfaces is a quantity of 4 machined surfaces; the plurality of strain gauges is a quantity of 4 strain gauges; and each of the machined surfaces and strain gauges is circumferentially spaced apart around the head by 90°, such that opposing pairs of the 4 strain gauges are provided 180° apart from each other.

6. The adjustable implant trial of any of claims 1-5, wherein: the broach comprises a longitudinal cavity formed entirely internal thereto; and the position adjuster comprises: a threaded rod that movably extends within the cavity; a collar in a form of a ring gear that is internally threaded and through which the threaded rod extends, wherein the collar is attached to the trunnion body such that a rotary movement of the collar causes a corresponding linear movement of the threaded rod along a longitudinal axis of the cavity; and a worm gear that is threadably engaged with teeth formed circumferentially around the collar that define the ring gear, wherein a rotation of the worm gear causes the rotary movement of the collar; wherein the worm gear comprises a worm gear drive that is accessible from outside the broach to allow for control and input of the rotation of the worm gear; and wherein the linear movement of the threaded rod controls the neck length of the adjustable implant trial.

7. The adjustable implant trial of claim 6, wherein an internal surface of the longitudinal cavity of the broach is threaded.

8. The adjustable implant trial of claim 7, wherein the internal surface of the longitudinal cavity of the broach and the ring gear have a same shape and pitch as threads formed on the threaded rod.

9. The adjustable implant trial of claim 8, wherein the threads of the threaded rod are helical threads.

10. The adjustable implant trial of claim 6, wherein an internal surface of the longitudinal cavity of the broach is not threaded.

11. The adjustable implant trial of claim 6, wherein the worm gear is rotatable in a clockwise direction and an anticlockwise direction to control extension and retraction of the threaded rod along the longitudinal axis of the cavity.

12. The adjustable implant trial of claim 6, wherein the collar is positioned entirely internal to the trunnion body and is rotatably and axially supported by a bearing.

13. The adjustable implant trial of any of claims 1-5, wherein: the head is attached to a neck that is insertable within a cavity formed within the trunnion body, such that the head is attached to the trunnion body by the neck; the cavity formed within the trunnion body comprises recesses formed on an internal surface thereof, the recesses being spaced apart from each other by a prescribed distance; the neck comprises plungers that are formed in an outer surface of the neck and spaced apart from each other by the prescribed distance, the plungers being configured to be depressed into the neck when not aligned with one of the recesses and, when aligned with one of the recesses, to spring into and occupy one of the recesses with which such plunger is aligned, so as to resist movement of the neck within the cavity of the trunnion body unless a force sufficient to depress the plungers is exerted on the head and/or the trunnion body.

14. The adjustable implant trial of claim 13, wherein the neck and the cavity are shaped to prevent rotation of the neck within the cavity.

15. The adjustable implant trial of claim 13, wherein the neck comprises a printed scale of numbers to visually indicate the neck length to the user.

16. The adjustable implant trial of claim 13, comprising one or more spacers that fit around the neck to prevent insertion of the neck into the cavity, wherein the one or more spacers have a thickness that is a same as or a multiple of the prescribed distance.

17. The adjustable implant trial of any of claims 1-5, wherein the position adjuster comprises a rack-and-pinion mechanism configured to control the neck length of the adjustable implant trial.

18. The adjustable implant trial of claim 17, wherein the rack-and-pinion mechanism comprises: a rack gear that is internal to the trunnion body and rigidly attached to the head; a pinion gear that engages with the rack gear to control the neck length of the adjustable implant trial; and a pinion gear drive that is accessible from an exterior of the implant trunnion and is rigidly attached to, so as to co-rotate with, the pinion gear, the pinion gear drive being configured to receive a rotary input that causes a rotation of the pinion gear, which in turn causes a movement of the rack gear in a direction of rotation of the pinion gear to change the neck length of the adjustable implant trial.

19. The adjustable implant trial of claim 18, wherein: the rack-and-pinion mechanism comprises a spur gear that is rigidly attached to, so as to co-rotate with, the pinion gear; the spur gear comprises notches that are formed circumferentially around an outer circumference thereof, a circumferential distance between the notches being a prescribed distance that corresponds to respective neck lengths of final implant devices; and the rack-and-pinion mechanism comprises a pawl that is spring loaded against the outer circumference of the spur gear, such that a distal end of the pawl sequentially engages within each of the notches to prevent rotation of the pinion gear in a direction that would decrease the neck length of the adjustable implant trial.

20. The adjustable implant trial of claim 19, wherein the notches of the spur gear are equally spaced apart from each other around the outer circumference of the spur gear.

21. The adjustable implant trial of claim 19, wherein: the rack-and-pinion mechanism comprises a release button that is accessible from the exterior of the implant trunnion; and the release button is configured such that, when actuated by the user, the pawl is rotated such that the distal end of the pawl is disengaged from the outer circumference of the spur gear and, thus also, the notches of the spur gear to allow for the neck length to be decreased.

22. The adjustable implant trial of any of claims 1-5, wherein the position adjuster comprises at least a first position adjuster and a second position adjuster.

23. The adjustable implant trial of claim 22, wherein the first and second position adjusters each comprise: a threaded rod and comprises a distal portion that has a helically threaded outer surface and a proximal portion that comprises a ring gear formed around an outer circumference thereof; a worm gear that is threadably engaged with teeth that define the ring gear, wherein a rotation of the worm gear causes the rotary movement of the threaded rod; and a collar that is internally threaded and through which the threaded rod extends, wherein the collar is attached to the trunnion body such that a rotary movement of the threaded rod causes a corresponding linear movement of the collar in a direction of a longitudinal axis of the threaded rod; wherein the worm gear comprises a worm gear drive that is accessible from outside the broach to allow for control and input of the rotation of the worm gear; and wherein the first and second position adjusters are independently controlled, such that a neck length and an angle of rotation of the trunnion body relative to the broach can be controlled.

24. The adjustable implant trial of claim 23, wherein the threaded rod and the worm gear are captive within the broach.

25. The adjustable implant trial of claim 23, wherein the collar of each of the first and second position adjusters is rotatably static relative to the trunnion body.

26. The adjustable implant trial of claim 23, wherein the first and second position adjusters are configured such that, when operated in at a same time and with a same rotary input to the respective worm gear drive thereof, the neck length of the adjustable implant trial changes.

27. The adjustable implant trial of claim 26, wherein, when only one of the first and second position adjusters is operated and/or when the first position adjuster is operated differently from the second position adjuster, the trunnion body is rotated relative to the broach.

28. The adjustable implant trial of any of claims 1-21, wherein the position adjuster comprises: a track that is attached to the broach; one or more feet that are attached to the trunnion body and insertable within the track to prevent movement of the trunnion body relative to the broach in a direction of the neck length, wherein the one or more feet are mobile along a length of the track to allow a movement of the trunnion body relative to the broach in a direction of the neck offset; and an adjustment screw that controls, via a rotary movement thereof, the movement of the trunnion body relative to the broach in the direction of the neck offset.

29. The adjustable implant trial of any of claims 1-21, wherein the position adjuster comprises: a track that is attached to the trunnion body; one or more feet that are attached to the broach and insertable within the track to prevent movement of the trunnion body relative to the broach in a direction of the neck length, wherein the one or more feet are mobile along a length of the track to allow a movement of the trunnion body relative to the broach in a direction of the neck offset; and an adjustment screw that controls, via a rotary movement thereof, the movement of the trunnion body relative to the broach in the direction of the neck offset.

30. The adjustable implant trial of any of claims 1-29, wherein the distraction test is a range of motion test to assess whether the adjustable implant trial is an anatomical match for anatomy of a patient undergoing the joint replacement procedure.

31. A method of using an adjustable implant trial in a trialing step of a joint replacement procedure to adjust a neck length and/or neck offset of the adjustable implant trial, the method comprising: providing the adjustable implant trial, which comprises: an implant trunnion comprising: a trunnion body; a head for attachment to a trial head, wherein the head is at or forms at least a portion of a first end of the trunnion body; and a load cell; a broach coupled to a second end of the trunnion body; and a position adjuster; inserting the broach within an intramedullary cavity of a bone of a patient; using the position adjuster to move the implant trunnion relative to the broach to adjust a neck length and/or a neck offset of the adjustable implant trial without replacing the adjustable implant trial; performing a distraction test; and using the load cell to measure forces exerted on the head during the distraction test.