Abstract
Background
Data on varus-valgus and rotational profiles can be obtained during navigated total knee arthroplasty (TKA). Such intraoperative kinematic data might provide instructive clinical information for refinement of surgical techniques, as well as information on the anticipated postoperative clinical outcomes. However, few studies have compared intraoperative kinematics and pre- and postoperative clinical outcomes; therefore, the clinical implications of intraoperative kinematics remain unclear.
In clinical practice, subjects with better femorotibial rotation in the flexed position often achieve favorable postoperative range of motion (ROM); however, no objective data have been reported to prove this clinical impression. Hence, the present study aimed to investigate the correlation between intraoperative rotation and pre- and postoperative flexion angles.
Materials and Methods
Twenty-six patients with varus osteoarthritis undergoing navigated posterior-stabilized TKA (Triathlon, Stryker, Mahwah, NJ) were enrolled in this study. An image-free navigation system (Stryker 4.0 image-free computer navigation system; Stryker) was used for the operation. Registration was performed after minimum soft tissue release and osteophyte removal. Then, maximum internal and external rotational stress was manually applied on the knee with maximum extension and 90° flexion by the same surgeon, and the rotational angles were recorded using the navigation system. After knee implantation, the same rotational stress was applied and the rotational angles were recorded again. In addition, ROM was measured before surgery and at 1 month after surgery. The correlation between the amount of pre- and postoperative tibial rotation and ROM was statistically evaluated.
Results
The amount of tibial rotation at registration was positively correlated with that after surgery (p < 0.05). Although the amount of tibial rotation at maximum extension was not correlated with ROM, the amount of rotation at 90° flexion at registration was positively correlated with pre- and postoperative ROM (p < 0.05). Moreover, the amount of tibial rotation at 90° flexion was positively correlated with postoperative ROM (p < 0.05).
Conclusion
It is well known that preoperative ROM affects postoperative ROM. Our results showed that better tibial rotation at 90° flexion predicts favorable postoperative ROM, suggesting that flexibility of the surrounding soft tissues as well as the quadriceps muscles is an important factor for obtaining better ROM. Further evaluation of navigation-based kinematics during TKA surgery may provide useful information on ROM.
