Effect of Joint Line Elevation after Posterior-stabilized and Cruciate-retaining Total Knee Arthroplasty on Clinical Function and Kinematics / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Joint line (JL) is a very important factor for total knee arthroplasty (TKA) to restore. The objective of this study was to evaluate the early clinical and kinematic results of TKAs with posterior-stabilized (PS) or cruciate retaining (CR) implants in which the JL was elevated postoperatively.</p><p><b>METHODS</b>Data were collected from patients who underwent TKA in our department between April 2011 and April 2014. The patients were divided into two groups based on the prosthesis they received (PS or CR). At 1-year postoperatively, clinical outcomes were evaluated by the American Knee Society (AKS) knee score, AKS function score, and patella score. In vivo kinematic analysis after TKA was performed on all patients and a previously validated three-dimensional to two-dimensional image registration technique was used to obtain the kinematic data. Anteroposterior (AP) translation of the medial and lateral femoral condyles, and axial rotation relative to the tibial plateau, were analyzed. The data were assessed using the Mann-Whitney test.</p><p><b>RESULTS</b>At time of follow-up, there were differences in the AKS knee scores (P = 0.005), AKS function scores (P = 0.025), patella scores (P = 0.015), and postoperative range of motions (P = 0.004) between the PS group and the CR group. In the PS group, the magnitude of AP translation for the medial and lateral condyle was 4.9 ± 3.0 mm and 12.8 ± 3.3 mm, respectively. Axial rotation of the tibial component relative to the femoral component was 12.9 ± 4.5°. In the CR group, the magnitude of AP translation for the medial and lateral condyle was 4.3 ± 3.5 mm and 7.9 ± 4.2 mm, respectively. The axial rotation was 6.7 ± 5.9°. There were statistically different between PS group and CR group in kinematics postoperatively.</p><p><b>CONCLUSION</b>Our results demonstrate that postoperative JL elevation had more adverse effects on the clinical and kinematic outcomes of CR TKAs than PS TKAs.</p>

Kinematic study on tibiofemoral joint after TKA using 2D-3D automatic registration technique / 医用生物力学

Objective To reconstruct the 3D motion of the knee joint after total knee arthroplasty (TKA) and measure the kinematics and the articular contacts between the posterior stabilized TKAs. Methods Sixteen knees undergoing TKAs were scanned by fluoroscopy. An algorithm of automatic registration was developed to match the 3D TKA models and 2D images. The kinematical parameters and articular contact of the tibiofemoral joint was investigated. ResultsThe time for a single image was less than 30 seconds. The in-plane repeatability was within 0.4 mm and 0.5 degree. The application of the high-flex insert didn’t obviously improve the ability of the flexion and the internal/external tibial rotation. When the knee flexed, the contact point on the lateral side moved more posteriorly than that on the medial side. The contact between the post-cam and the femoral prosthesis occurred with the flexion at about 30 degrees. The average range of the contact was within 9 mm. Conclusions The 3D kinematics of the in vivo TKA knee joint was accurately measured by using 2D-3D automatic registration technique. The result can provide references for the biomechanical study of TKA knees and the improvement of TKA prosthesis design.

Development of a force balance telemetry device for total knee arthroplasty / 医用生物力学

Objective A new type of tibial femoral force balancing telemetry device was developed for measuring force balance on the tibial femoral contact surface in knee joint. MethodThe force balance telemetry device was designed imitating the configuration of tibial part of total knee prosthesis, in which force sensors and telemetry circuit were embedded. During total knee arthroplasty(TKA), this device was implanted as a tibial prosthesis to measure tibial femoral force while the knee joint was being placed at different angles. The tension balance was adjusted by releasing soft tissue around knee joint. ResultsThe results indicat that this device has advantage of high accuracy for force measurement (r>0.98，RMS= 65　g), which is sufficient to meet clinical demand. ConclusionsThe measurement of force balance on the tibial femoral contact surface with telemetry device can provide new insight into the estimation of optimal knee prosthesis position and selection of appropriate polyethylene insert.