Abstract
Introduction
Many factors can influence post-operative kinematics after total knee arthroplasty (TKA). These factors include intraoperative surgical conditions such as ligament release or quantity of bone resection as well as differences in implant design. Release of the medial collateral ligament (MCL) is commonly performed to allow correction of varus knee. Precise biomechanical knowledge of the individual components of the MCL is critical for proper MCL release during TKA. The purpose of this study was to define the influences of the deep medial collateral ligament (dMCL) and the posterior oblique ligament (POL) on valgus and rotatory stability in TKA.
Materials and Methods
This study used six fresh-frozen cadaveric knees with intact cruciate ligaments. All TKA procedures were performed by the same surgeon using CR-TKA with a CT-free navigation system. Each knee was tested at 0°, 20°, 30°, 60°, and 90° of flexion. One sequential sectioning sequence was performed on each knee, beginning with femoral arthroplasty only (S1), and thereafter sequentially, medial half tibial resection with spacer (S2), ACL cut (S3), tibial arthroplasty (S4), release of the dMCL (S5), and finally, release of the POL (S6). The same examiner applied all external loads of 10 N-m valgus and 5 N-m internal and external rotation torques at each flexion angle and for each cut state. All data were analyzed statistically using two-way ANOVA and paired t-test. A significant difference was determined to be present for P < .05.
Results
There were no significant differences in medial gaps at any sequential step or any tested angle of flexion under valgus loads even after release of the dMCL and the POL compared with those at S1. Internal rotation angles significantly increased after medial half tibial resection with spacer, compared with those after S1, at 0°, 20°, and 30°. Moreover, release of the POL under internal rotation torque resulted in significantly increased internal rotation, compared with that at S1, at 90° of knee flexion. External rotation angles under external rotation torque significantly increased after the ACL cut compared with those at S1 at 0°, and after tibial arthroplasty, significant increase in external rotation angles compared with those at S1 was observed at 60°. Thereafter, significant increase in external rotation angles was seen, at 0°, 30° and 90° after release of the dMCL compared with S1, and significant increase after release of the POL at 30°, 60° and 90° compared to S1. 20°. Rotational angles had correlation with the size of medial gap at 0°, 20° and 90°.
Conclusion
From this study we concluded that retaining of the medial knee structures preserves the valgus and rotatory stability of the knee. Accordingly, to devise a surgical approach of retaining the dMCL and POL has a possibility to improve the outcome after primary TKA.
