Confirmation of Long-term In Vivo Bearing Mobility in Eight Rotating-platform TKAs

Abstract

Background Posterior-stabilized rotating-platform prostheses for TKAs were designed to improve contact mechanics at the femoral-polyethylene (PE) interface. Short-term followup studies have shown that the PE bearings rotate with respect to the tibia but might not necessarily track with the femur. It is important to know how kinematics in these designs change owing to longterm in vivo use.Questions/purposes We asked whether there is a significant change in the in vivo kinematic performance of a posterior-stabilized rotating-platform prosthesis at as much as 10 years postoperative. We specifically examined (1) relative femoral component-PE bearing and relative PE bearing-tibial tray motion; (2) relative AP motion of the femoral condyles with respect to the tibial tray; and (3) relative femorotibial condylar translations. Methods In vivo three-dimensional kinematics were evaluated for eight patients at 3 months, 15 months, 5 years, and 10 years after TKA with primary implantation of a posterior-stabilized rotating-platform prosthesis. Each patient performed deep knee bend activity, and threedimensional kinematics were reconstructed from multiple fluoroscopic images using a three-dimensional to twodimensional registration technique. Once complete, relative component axial rotation patterns, medial and lateral condyle motions throughout flexion, and the presence of femoral condylar lift-off were analyzed. Results Overall, tibial bearing rotation was maintained at 10 years postoperatively. There was no statistical difference between postoperative periods for any kinematic parameter except for femoral component-PE bearing axial rotation, which was reduced at the 10-year evaluation versus other assessment periods (p = 0.0006). The lack of statistical difference between postoperative evaluation

Modifications of femoral component design in multi-radius total knee arthroplasty lead to higher lateral posterior femoro-tibial translation

“…Both analysed systems have central pivoting rotating platform designs, which could result in an ipsilateral rollback of one condyle and roll‐forward of the contralateral condyle during deep flexion [13, 29]. Since no significant difference was observed in femoro‐tibial rotation, the observed significant difference in femoro‐tibial translation is most likely caused by an actual rollback, specifically in the G‐CURVE design.…”

Posterior cruciate-retaining total knee arthroplasty exhibits small kinematic changes in the first postoperative year

“…This is noteworthy, as determining the appropriate time to evaluate TKA performance is somewhat controversial and highly dependent on the outcomes to be assessed. At the time of publication, only three longitudinal studies reported fluoroscopic knee kinematics [21, 37, 41]. However, all of these studies examined kinematics for PS‐RP TKAs.…”

“…In another study examining fluoroscopic kinematics of a PS‐RP design [21], patients were recorded performing a deep knee bend at 3 months, 15 months, 5 years, and 10 years after TKA. Only the axial rotation between the femoral component and the polyethylene insert was significantly reduced at the 10‐year timepoint compared to all earlier evaluations [21]. There were no statistical differences in tibial internal rotation, medial condyle AP translation, and lateral condyle AP translation between any of the postoperative intervals.…”

“…These indings are likely a consequence of the increased lexion achieved at 12 months post-TKA. In another study examining fluoroscopic kinematics of a PS-RP design [21], patients were recorded performing a deep knee bend at 3 months, 15 months, 5 years, and 10 years after TKA. Only the axial rotation between the femoral component and the polyethylene insert was signiicantly reduced at the 10-year timepoint compared to all earlier evaluations [21].…”

“…PROMs require at least 1 year after surgery for conclusions to be drawn [7, 24, 29, 30] and provide limited functional information, while quadriceps strength takes at least 6 months to recover [4, 25, 26] and influences gait. Despite the well‐documented changes in muscles and soft tissues, pain, swelling, and patient perception that occur in the year(s) after TKA, limited data suggest that fluoroscopic kinematics of kneel and lunge activities may remain chronometrically stable after posterior‐stabilized rotating‐platform (PS‐RP) TKA [21, 37, 41]. Though periarticular structures continue to change along with the patient’s functional abilities after surgery, prosthetic joint mechanics during kneel, lunge, and step‐up activities may persist over time.…”