The purpose of this study is to evaluate the post-operative range of motion (ROM) of the knee related to the anterior-posterior femoral translation on the tibia observed during surgery in cruciate-retaining total knee arthroplasty (TKA) using a navigation system. Our hypothesis is that the intraoperative anterior-posterior femoral translation is correlated with the post-operative ROM in patients undergoing cruciate-retaining TKA.
The subjects were 20 patients involving 23 joints. The passive maximum ROM was measured before and 1 year after surgery. In addition, we evaluated the intraoperative anterior-posterior femoral translation that was measured after inserting a tensor device from 10° to 120° of knee flexion. The starting point of the anterior-posterior femoral translation was defined as when the femur started to move posteriorly. The anterior-posterior femoral translation 120 was set as the amount of femoral movement from 10° to 120°.
The subjects were divided into those with an increased or maintained ROM (group A) and those with a decreased ROM (group B). There were no significant differences between the two groups in terms of the age or pre-operative ROM. The starting point of the anterior-posterior femoral translation was significantly earlier in group B (58.0 ± 5.7° for group A, 48.7 ± 3.2° for group B) (P < 0.05). Regarding the anterior-posterior femoral translation 120, Group B showed a larger amount of femoral movement posteriorly than group A (13.0 ± 6.5 mm for group A, 19.0 ± 6.2 mm for group B) (P < 0.05).
III.
The present study shows that intraoperative anterior-posterior femoral translation has a significant correlation with the post-operative ROM in patients undergoing cruciate-retaining TKA. If the starting point of the anterior-posterior femoral translation is early and the anterior-posterior femoral translation 120 is large, there is likely to be a decrease in the post-operative ROM.