Abstract
Purpose
Degenerative osteoarthritis of the knee usually shows arthritic change in the medial tibiofemoral joint with severe varus deformity. In TKA, the medial release technique is often used for achieving mediolateral balancing, but there is some disagreement regarding the importance of pursuing the perfect rectangular gaps. Our hypothesis is that the minimal release especially in MCL is beneficial regarding on retaining the physiological medial stability and knee kinematics, which leads to improved functional outcome. Therefore, the purpose of this study is to examine the thickness of the tibia resection if the extent of the medial release is minimized to preserve the medial soft tissue in TKA.
Patients and Methods
Thirty TKAs were performed for varus osteoarthritis by a single surgeon. In the TKA, femoral bone was prepared according to the measured resection technique, bilateral meniscus and anterior cruciate ligament were excised. After the osteophytes surrounding the femoral posterior condyle were removed, the knee with the femoral trial component was fully extended and the amount of the tibial bone cut was decided for the 10mm tibial insert by referring to the medial joint line of the femoral trial component. After the every bone preparation and placement of all the trial components, If flexion contracture due to the narrow extension gap was found, additional tibial bone cut or medial soft tissue release were performed.
Results
MCL deep layer release was performed following the medial meniscus removal in all the TKAs, additional tibial bone cut was performed for three cases, but there was no additional medial soft tissue treatment in any TKAs. Final extension gap in the medial side was 21.2 mm, the average of the tibial insert thickness actually used was 10.6 mm, and the thickness of all the femoral implant at the distal part was 9 mm, therefore the residual medial extension gap in extension was averaged 1.8 ± 0.54 mm. On the other hand, the thickness of the tibial bone cut in the lateral side was various from 11 mm to 16 mm (average was 12.9 ± 1.13 mm).
Discussion and Conclusions
All the TKAs in this study were performed to create the proper medial stability in extension without excessive medial release by cutting the adequately thck tibial bone, which lead to thicker tibia resection than the applied tibial insert in the lateral side. As lateral laxity is necessary for the medial pivot movement of the normal knee, slight lateral laxity can be accepted with TKA. The balance between lateral laxity and medial stability in both extension and flexion has not been well elucidated, further studies are necessary regarding on in vivo kinematic.
