In-vivo knee kinematics in rotationally unconstrained total knee arthroplasty

Effect of single-radius design on in vivo kinematics during stair activities after total knee arthroplasty

BACKGROUND

The single-radius design is one of the major total knee arthroplasty (TKA) designs and widely used all over the world. The objective of this study was to compare in vivo kinematics between the anteroposterior (AP) single-radius design with mediolateral (ML) single-radius (Non Restricted Geometry; NRG) and ML dual-radius (Triathlon) during stair activities.

METHODS

A total of 21 knees in 18 patients (NRG group: 10 knees in 7 patients, Triathlon group: 11 knees in 11 patients) with a clinically successful posterior stabilized TKA were examined. Under fluoroscopic surveillance, each patient performed stair ascending and descending motions. In vivo kinematics were analyzed using 2D/3D registration technique. The knee flexion angle, rotation angle, varus-valgus angle, AP translation of the femorotibial contact point for both the medial and lateral sides of the knee, and post-cam engagement were evaluated.

RESULTS

There were no significant differences between the two groups in rotation angle and AP translation at each flexion angle. Examining the varus-valgus angle, the NRG group showed varus position at an early flexion angle during both stair activities.Post-cam engagement was observed in both groups during both stair activities. The mean flexion angle of engagement in the NRG group, the post of which was located anterior to the Triathlon, was larger than that in the Triathlon group during both stair activities.

CONCLUSION

Despite the same AP single-radius TKA, ML single-radius might affect varus motion at an early flexion angle.

Can Computer-Assisted Total Knee Arthroplasty Support the Prediction of Postoperative Three-Dimensional Kinematics of the Tibiofemoral and Patellofemoral Joints at the Replaced Knee?

The aim of this study was to analyze the extent to which postoperative patellofemoral joint (PFJ) kinematics assessed at 6-month follow-up after total knee arthroplasty (TKA) mimics the intraoperative kinematics after final component implantation. The study hypothesis, already proved in terms of tibiofemoral joint (TFJ) kinematics, is that the intraoperative assessment of PFJ kinematics after component implantation is also capable of predicting postoperative knee kinematics during activities of daily living. Twenty patients selected for TKA with patellar resurfacing were implanted using surgical navigation, including patellar component positioning via a novel computer-assisted procedure. This allowed for intraoperative TFJ and PFJ kinematic assessment after final component implantation. At 6-month follow-up, all patients were contacted for follow-up control; in addition to clinical examination, this implied postoperative kinematics assessments by three-dimensional video fluoroscopy of the replaced knee during standard activities of daily living. Several traditional PFJ, as well as TFJ, rotations and translations were calculated intra- and postoperatively and then statistically compared. Good postoperative replication of the intraoperative measurements was observed for most of PFJ variables analyzed, as well as those for TFJ. Relevant statistical analysis also supported the significant consistency between the intra- and postoperative measurements. Pertaining to the present findings on a statistical basis, intraoperative measurements performed at both TFJ and PFJ kinematics using a surgical navigation system under passive conditions, are predictive of the overall knee kinematics experienced at postoperative follow-ups by the same replaced knees in typical activities of daily living.

Change in knee biomechanics during squat and walking induced by a modification in TKA size

The purpose of this study is to analyze the effects of TKA under-dimensioning during daily activities. A regular ("control") size and an undersized design of the same fixed bearing asymmetric PS prosthesis were analyzed during walking and squat using finite element analysis. The two models showed similar internal-external rotations and antero-posterior displacements during both activities. Slightly higher displacements, wider contact areas and lower contact pressure were found in the control size. Post-cam engagement angles were similar on both sizes. Changes in TKA size slightly affected knee kinematics and kinetics, with post-cam related differences leading to minor changes in kinetic patterns.

High congruency MB insert design: stabilizing knee joint even with PCL deficiency

PURPOSE

PCL management and choice of insert design and mobility in total knee arthroplasty are still debated in the literature. Consequently, the purpose of this study was to analyze the biomechanics of a fixed and a mobile bearing total knee arthroplasty with conventional and ultra-congruent insert during walking and squat activities, using finite element analysis, and to check the performance in a knee with healthy and deficient PCL.

METHODS

The study was based on an already validated and published knee model. Fixed bearing and mobile bearing cruciate-retain designs were selected for this study. Implant kinematics and kinetics were calculated, following previously experimental tests, during a walking cycle and a loaded squat in a knee with intact and with deficient PCL.

RESULTS

Mobile bearing design, due to its higher congruency, was able to complete the task in intact and deficient PCL conditions, with similar internal-external femoral rotation and with a slight higher anterior translation of the one of the intact knees. Such outcomes were also in agreement with the results of different experimental studies of native knee specimens under similar boundary conditions. Contrariwise, fixed bearing design was able to accomplish the task only in healthy PCL conditions.

CONCLUSION

Results demonstrated how the high congruency of the mobile bearing design is able to guarantee proper knee stability and kinematics even when the PCL is deficient. Instead, the fixed bearing insert, with lower congruency, is not able, in the absence of the PCL, to stabilize the joint inducing irregular kinematic pattern and component dislocation. Surgeons will have to consider these findings to guarantee the best outcome for the patient and the related change in stability in case of PCL deficiency.

An Anatomical-Based Subject-Specific Model of In-Vivo Knee Joint 3D Kinematics From Medical Imaging

Biomechanical models of the knee joint allow the development of accurate procedures as well as novel devices to restore the joint natural motion. They are also used within musculoskeletal models to perform clinical gait analysis on patients. Among relevant knee models in the literature, the anatomy-based spatial parallel mechanisms represent the joint motion using rigid links for the ligaments’ isometric fibres and point contacts for the articular surfaces. To customize analyses, therapies and devices, there is the need to define subject-specific models, but relevant procedures and their accuracy are still questioned. A procedure is here proposed and validated to define a customized knee model based on a spatial parallel mechanism. Computed tomography, magnetic resonance and 3D-video-fluoroscopy were performed on a healthy volunteer to define the personalized model geometry. The model was then validated by comparing the measured and the replicated joint motion. The model showed mean absolute difference and standard deviations in translations and rotations, respectively of 0.98 ± 0.40 mm and 0.68 ± 0.29 ° for the tibia–femur motion, and of 0.77 ± 0.15 mm and 2.09 ± 0.69 ° for the patella–femur motion. These results show that accurate personalized spatial models of knee kinematics can be obtained from in-vivo imaging.

Total Knee Arthroplasty Kinematics

Knee kinematics is an analysis of motion pattern that is utilized to assess a comparative, biomechanical performance of healthy nonimplanted knees, injured nonimplanted knees, and various prosthetic knee designs. Unfortunately, a consensus between implanted knee kinematics and outcomes has not been reached. One might hypothesize that the kinematic variances between the nonimplanted and implanted knee might play a role in patient dissatisfaction following TKA. There is a wide range of TKA designs available today. With such variety, it is important for surgeons and engineers to understand the various geometries and kinematic profiles of available prostheses. The purpose of this review is to provide readers with the pertinent information related to TKA kinematics.

Changes in total knee arthroplasty design affect in-vivo kinematics in a redesigned total knee system: A fluoroscopy study

BACKGROUND

Journey II Bi-Cruciate-Stabilized knee system was designed to overcome the complications of Journey Bi-Cruciate-Stabilized, including ilio-tibial band inflammation and episodes of dislocation. The purpose of this study was to assess differences in knee kinematics between the first and second-generation design by means of video-fluoroscopy. Re-designed prosthesis in-vivo kinematics was analyzed during activities of daily living and results were eventually compared with those of the previous system, as reported in a previously published study. It was hypothesized that changes in components' design influences replaced knee's kinematic patterns.

METHODS

Sixteen patients (3 males, 13 females) implanted with the redesigned prosthesis were assessed by video-fluoroscopy during stair-climbing, chair-rising and leg-extension at 8 months of follow-up. Patterns of axial rotation and antero-posterior motion of the medial and lateral femoral condyles were obtained. Range of Motion and International Knee Society Score were recorded pre- and post-operatively. Student t-tests were applied to compare the mean of each interesting variables.

FINDINGS

The comparison of the kinematics of the two designs revealed similar patterns of axial rotation, with progressive femoral external rotation in flexion and reduced absolute values of displacement for the new system. Reduced posterior displacements of the medial and lateral condyles were observed in Journey II patients. In terms of absolute location, the lateral condyle in the redesigned prosthesis showed a more anterior position on the tibial-baseplate embedded coordinate system at maximal flexion.

INTERPRETATION

Design changes in the recently-introduced total knee system contributed to modify its in-vivo knee kinematics as demonstrated by video-fluoroscopy.

In vivo kinematics of knee replacement during daily living activities: Condylar and post-cam contact assessment by three-dimensional fluoroscopy and finite element analyses

In total knee replacement, the investigation on the exact contact patterns at the post-cam in implanted patients from real in vivo data during daily living activities is fundamental for validating implant design concepts and assessing relevant performances. This study is aimed at verifying the restoration of natural tibio-femoral condylar kinematics by investigating the post-cam engagement at different motor tasks. An innovative validated technique, combining three-dimensional fluoroscopic and finite element analyses, was applied to measure joint kinematics during daily living activities in 15 patients implanted with guided motion posterior-stabilized total knee replacement. Motion results showed physiological antero-posterior translations of the tibio-femoral condyles for every motor task. However, high variability was observed in the position of the calculated pivot point among different patients and different motor tasks, as well as in the range of post-cam engagement. Physiological tibio-femoral joint rotations and contacts at the condyles were found restored in the present knee replacement. Articular contact patterns experienced at the post-cam were found compatible with this original prosthesis design. The present study reports replaced knee kinematics also in terms of articular surface contacts, both at the condyles and, for the first time, at the post-cam. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1396-1403, 2017.

Kinematic analysis of stair climbing in rotating platform cruciate-retaining and posterior-stabilized mobile-bearing total knee arthroplasties

INTRODUCTION

The aim of our study was to compare and contrast the effects of two types of mobile-bearing total knee arthroplasties (TKA), namely, the cruciate-retaining (CR) and posterior-stabilized (PS) TKAs, on clinical outcomes and in vivo kinematics during stair climbing.

MATERIALS AND METHODS

The Press-Fit Condylar Sigma rotating platform was used for both CR and PS TKAs. Patient-reported outcomes were assessed using the 2011 Knee Society Score. Quadriceps muscle strength was evaluated by isokinetic dynamometry. In vivo kinematics were evaluated using periodic sagittal plane radiographic images obtained during stair climbing to quantify anteroposterior (AP) tibiofemoral translation, implant flexion and axial rotation angles using image-matching techniques. Outcomes were evaluated in 20 TKAs, which had been undergone with clinical success, including ten knees with CR types and ten knees with PS types.

RESULTS

There were no significant differences between the CR and PS TKA groups (p > 0.05) in isometric extensor torque (1.0 ± 0.2 and 1.1 ± 0.6 N m/kg, respectively) or patient-reported score for stair climbing function (4.0 ± 0.5 and 3.8 ± 0.9, respectively). Both types of TKAs showed stable AP translation in the mid range of knee flexion and paradoxical translation in the low range of flexion, with limited rotation, during stair climbing. There were no significant differences between the CR and PS TKA groups (P > 0.05) in anterior translation from 80° to 40° of knee flexion (4.2 ± 1.2 and 3.5 ± 1.6 mm, respectively), posterior translation from 40° to 10° of knee flexion (2.3 ± 1.9 and 2.0 ± 1.5 mm, respectively), and total external rotation (2.8° ± 4.9° and 0.5° ± 5.0°, respectively).

CONCLUSIONS

Both CR and PS types of rotating platform mobile-bearing TKAs provided reproducible knee joint kinematics during stair climbing and equivalent clinical outcomes.

LEVEL OF EVIDENCE

IV.

[Total knee arthroplasty. Patient-specific instruments and implants]

This article describes the concept and surgical technique of patient-specific total knee arthroplasty. Patient-specific implants and instruments are designed and fabricated based on computed tomography (CT) data of the leg. The disposable patient-specific drill guides and cutting-jigs are manufactured taking into consideration the anatomical and biomechanical axes of the knee joint and mediating the efficient pre-navigation of the osseous saw-cuts, without the need for additional navigation or balancing aids. The surgical plan is made on the basis of the CT data. The implantation technique comprises the following steps: distal femoral resection, tibial resection, balancing and femur preparation, tibia preparation, optional patellar resurfacing, trialling of the test components, and implantation of the final components. By using this patient-specific implant system, which includes not only personalized, single-use instruments, but also individualized implants, the surgeon is able to provide endoprosthetic treatment that broadly restores the patient's own knee anatomy and knee kinematics. Preliminary studies have proven the concept and data on this technology are promising so far; however, like a new implant, they are usually limited. In particular, comparative long-term clinical data are still to come.

[Individualized total knee arthroplasty]

This article describes the rationale and the surgical technique of patient-specific uni-, bi-, or three-compartmental knee arthroplasty using the second generation (G2) of ConforMIS™ technology. The patient-individual implants and instruments are designed and fabricated based on data from a preoperative computed tomography of the lower limb. The disposable patient-specific drill guides and cutting-jigs are manufactured under consideration of the anatomical and biomechanical axes of the knee joint and mediate efficient pre-navigation of the saw-cuts on the femoral and tibial bone without the need for an additional navigation or balancing device. The surgical technique for all types of knee resurfacement comprises the steps of cartilage removal, knee balancing in extension and flexion, sparing bony cuts, final preparation of femur and tibia, trialling, cementing of components and final choice of tibial insert. The use of individualized three-dimensional image-derived resurfacing implants, as well as personalized single-use instrumentation, facilitates the surgeon to perform an almost anatomical knee resurfacement that has the potential to restore almost normal knee kinematics. The limited data on this novel technology is promising, however long-term clinical data is needed for final evaluation of this technology.

Variations in morphological characteristics of prostheses for total knee arthroplasty leading to kinematic differences

BACKGROUND AND PURPOSE

The aim of this study is to compare kinematics during weight-bearing deep knee-bending motion in patients after bilateral total knee arthroplasty (TKA) of two types: 1) a conventional ScorpioFlex prosthesis and 2) a contemporary redesigned non-restrictive-geometry (NRG) prosthesis installed by the same surgeon.

METHODS

We enrolled 15 patients who underwent conventional ScorpioFlex posterior-stabilised TKA in one knee and contemporary NRG TKA on the contralateral side (the same surgeon). During fluoroscopic examination, each patient performed weight-bearing deep knee bending. Motions among all components were analysed using a two- to three-dimensional registration technique.

RESULTS

The mean maximum flexion was 108° (SD 8) and 120° (SD 9) after ScorpioFlex and NRG TKAs, respectively; there were statistically significant differences between the groups. From extension to maximal flexion, the medial condyle translated by 4.8mm (SD 1.2) and 5.4mm (SD 2.4) posteriorly after ScorpioFlex TKA and NRG TKA, respectively. The lateral femoral condyle moved 8.4mm (SD 1.5) and 12.2mm (SD 2.1) posteriorly after ScorpioFlex TKA and NRG TKA, respectively. There were no significant differences in medial condyle translation between the groups except for the lateral condyle. The total amount of tibial axial rotation during extension to flexion was 5.1° (SD 1.8) after ScorpioFlex and 13.2° (SD 3.4) after NRG TKAs; there were statistically significant differences between the groups.

CONCLUSIONS

NRG resulted in much better maximum flexion, lateral condyle movement and tibial internal rotation than did ScorpioFlex TKAs. The observed kinematic differences are most likely caused by variations in the morphological characteristics of the two implants.

A new protocol from real joint motion data for wear simulation in total knee arthroplasty: stair climbing

In its normal lifespan, a knee prosthesis must bear highly demanding loading conditions, going beyond the sole activity of level walking required by ISO standard 14243. We have developed a protocol for in vitro wear simulation of stair climbing on a displacement controlled knee simulator. The flexion/extension angle, intra/extra rotation angle, and antero/posterior translation were obtained in patients by three-dimensional video-fluoroscopy. Axial load data were collected by gait analysis. Kinematics and load data revealed a good consistence across patients, in spite of the different prosthesis size. The protocol was then implemented and tested on a displacement controlled knee wear simulator, showing an accurate reproduction of stair climbing waveforms with a relative error lower than 5%.

Difference in knee rotation between total and unicompartmental knee arthroplasties during stair climbing

PURPOSE

The purpose of this study was to compare knee kinematics during stair walking in patients with simultaneous total knee arthroplasty (TKA) and unicompartmental knee arthroplasties (UKA). It was hypothesized that UKA would reproduce more normalized knee kinematics than TKA during stair ascent and descent.

METHODS

Six patients who received UKA in one knee and TKA in the other knee were included in the study. For this study, a four-step staircase was assembled with two force platforms being positioned at the centre of the second and third steps. Each patient was attached with 16 reflective markers at both lower extremities and was asked to perform five roundtrip trials of stair climbing. Kinematic parameters including stance duration, knee angle, vertical ground reaction force (GRF), joint reaction force, and moments were obtained and analysed using a10-camera motion system (VICON, Oxford, UK). Nonparametric Friedman test was used to compare the results between two arthroplasty methods and between stair ascent and descent.

RESULTS

Compared to TKA, UKA knees exhibited significantly greater degree of rotation in transverse planes (5.0 degrees during ascent and 6.0 degrees during descent on average), but showed no difference in terms of the other parameters. When comparing the results during stair ascent with descent, overall greater knee angle, vertical GRF, joint reaction force, and moment were observed during stair descent.

CONCLUSIONS

Both UKA and TKA knees have shown overall similar knee kinematics, though UKA knee may allow greater degree of rotation freedom, which resembles normal knee kinematics during stair walking.

Three-dimensional implant position and orientation after total knee replacement performed with patient-specific instrumentation systems

Patient-specific instrumentation systems are entering into clinical practice in total knee replacement, but validation tests have yet to determine the accuracy of replicating computer-based plans during surgery. We performed a fluoroscopic analysis to assess the final implant location with respect to the corresponding preoperative plan. Forty-four patients were analyzed after using a patient-specific system based on CT and MRI. Computer aided design implant models and models of the femur and tibia bone portions, as for the preoperative plans, were provided by the manufacturers. Two orthogonal fluoroscopic images of each knee were taken after surgery for pseudo-biplane imaging; 3D component locations with respect to the corresponding bones were estimated by a shape-matching technique. Assuming that the corresponding values at the preoperative plan were equal to zero, discrepancies were taken as an indication of accuracy for the systems. A repeatability test revealed that the technique was reliable within 1 mm and 1°. The maximum discrepancies for all the patients for the femoral component were 5.9 mm in a proximo-distal direction and 4.2° in flexion. Good matching was found between final implantations and preoperative plans with mean discrepancies smaller than 3.1 mm and 1.9°.

Design and kinematics in total knee arthroplasty

PURPOSE

Posterior stabilised (PS) total knee arthroplasty (TKA) design development that focused on restoring normal knee kinematics was followed by the introduction of reason-guided motion designs. Although all PS fixed-bearing knee designs were thought to have similar kinematics, reports show they have differing incidences and magnitudes of posterior femoral rollback and axial rotation. In this retrospective comparative study between two guided-motion total knee systems, we hypothesised that kinematic pattern has an influence on clinical and functional outcomes.

METHODS

This study represents the continuation of a previously reported clinical and kinematics analysis. We retrospectively reviewed 347 patients treated with two different TKA designs: Scorpio NRG (Stryker Orthopedics) and Journey Bi-Cruciate Stabilised (BCS) knee system (Smith & Nephew). Two hundred and eighty-one patients were assessed clinically. Patients were divided into groups according to implanted TKA. Clinical evaluation with the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire was performed. Fifteen Scorpio NRG and 16 Journey BCS patients underwent video fluoroscopy during stair climbing, chair rising/sitting and step up/down at six months of follow-up.

RESULTS

At an average 29 months of clinical follow-up, patients with Journey BCS TKAs reported better clinical results. Stiffness was more frequently reported in the Journey group (5.2 % vs 1.2 %), whereas anterior knee pain was observed in the Scorpio NRG group (1.9 %) only. Both prosthetic models reported different posterior translation of the medial and lateral contact points (CP) in all analysed motor tasks during knee flexion (BCS 10-18 mm; NRG Scorpio 2-3 mm). Both designs produced progressive external rotation of the femoral component relative to the tibia during flexion.

CONCLUSIONS

Journey BCS showed statistically significant better KOOS results. The higher posterior femoral rollback observed in the kinematic assessment of this design, associated with a better patellofemoral design, may be the reason for better clinical outcome. The reported cases of stiffness and anterolateral joint pain could be attributed to excessive medial and lateral tibiofemoral posterior translation. The NRG group demonstrated good axial rotation, but this was not coupled with physiological kinematic patterns. Patellofemoral pain can be explained by a less friendly femoral-groove design. TKA clinical-functional outcome and complications were highly influenced by the bearing geometry and kinematic pattern of prosthetic designs.

In vivo kinematics of medial unicompartmental osteoarthritic knees during activities of daily living

Few studies exist describing unicompartmental osteoarthritic knee kinematics. Moreover, the role of the anterior cruciate ligament (ACL) in the determination of knee kinematics has not been fully described. The objective of the current study was to analyze the in vivo kinematics of knees with medial osteoarthritis (OA) and intact ACL during closed and open chained motion. Eight patients scheduled for UKA diagnosed with primary medial OA underwent knee CT-scans and video-fluoroscopy. Fluoroscopic analysis included stair climbing, chair rising and leg extension. Three-dimensional bone positions were obtained from each image by iterative procedures using a CAD-model-based shape-matching technique. Patterns of axial rotation and anterior-posterior (AP) motion of the medial and lateral femoral condyle were obtained with specific software. The femur reported an overall external rotation relative to the tibia from extension to flexion in all tasks. Average AP translation of the medial femoral condyle were smaller in open-chained tasks than in weight-bearing conditions. Average AP motion of the lateral femoral condyle reported an overall posterior translation with knee flexion. The absent natural "screw-home" mechanism and the lack of medial condyle posterior translation was explained by bone-cartilage defects and meniscal degeneration. Relevant findings were the kinematic pattern differences between weight-bearing and open chained activities, suggesting that in biphasic muscle contraction and unloaded conditions, the function of the cruciate ligaments was not physiological. The kinematics of knees with medial OA and intact ACL differed from healthy knees.

Three-dimensional motion analysis of the human knee joint: comparison between intra- and post-operative measurements

PURPOSE

To compare intra-operative knee joint kinematic measurements immediately after total knee replacement with those of the same patients post-operatively at 6-month follow-up.

METHODS

Fifteen patients who underwent total knee arthroplasty were analysed retrospectively. Eight were implanted with one prosthesis design and seven with another. The intra-operative measurements were performed by using a standard knee navigation system. This provided accurate three-dimensional positions and orientations for the femur and tibia by corresponding trackers pinned into the bones. At 6-month follow-up, the patients were analysed by standard three-dimensional video-fluoroscopy of the replaced knee during stair climbing, chair rising and step-up. Relevant three-dimensional positions and orientations were obtained by an iterative shape-matching procedure between the silhouette contours and the CAD-model projections. A number of traditional kinematic parameters were calculated from both measurements to represent the joint motion.

RESULTS

Good post-operative replication of the intra-operative measurements was observed for most of the variables analysed. The statistical analysis also supported the good consistency between the intra- and post-operative measurements.

CONCLUSIONS

Intra-operative kinematic measurements, accessible by a surgical navigation system, are predictive of the following motion performance of the replaced knees as experienced in typical activities of daily living.

LEVEL OF EVIDENCE

Prognostic studies--investigating natural history and evaluating the effect of a patient characteristic, Level II.