Abstract
Introduction
Achieving high flexion after total knee arthroplasty (TKA) is one of the most important clinical results, especially in eastern countries where the high flexion activities, such as kneeling and squatting, are part of the important lifestyle. Numerous studies have examined the kinematics after TKA. However, there are few numbers of studies which examined the kinematics during deep knee flexion activities. Therefore, in the present study, we report analysis of mobile-bearing TKA kinematics from extension to deep flexion kneeling using 2D-3D image matching technique.
Materials and Methods
The subjects were 16 knees of 8 consecutive patients (all women, average age 75.9), who underwent primary mobile-bearing PS TKA (P.F.C. sigma RP-F: Depuy Orthopedics Inc., Warsaw, IN, USA) between February 2007 and May 2008. All cases were osteoarthritis with varus deformity. Postoperative radiographs were taken at the position of extension, half-squatting and deep flexion kneeling 3 month after the surgery, and the degrees of internal rotation of the tibial component was measured by 2D-3D image matching technique. Pre- and post-operative ROM was recorded. Then, we compared the absolute value and relative movement of tibial internal rotation between extension, half-squatting and deep flexion kneeling, and evaluated the correlation of the ROM and the internal rotation.
Results
The mean preoperative ROM was from -12 to 118 degrees. After the surgery, ROM was from -2 to 123 degrees. Clinical scores of all cases were significantly improved after surgery. Internal rotation of tibial component was -6.8 to 9.7 (mean, 1.7) degrees at half-squatting position, and -7.2 to 13.6 (mean; 1.9) degrees at kneeling position. There was no correlation between maximum flexion angle and tibial rotation during flexion. There was significant negative correlation between tibial internal rotation angle in extension and tibial rotational movement from half-squatting to deep flexion kneeling (R; -0.824, P<0.05).
Discussion
The internal rotation of the tibia during high flexion is well known as medial pivot movement in intact knee. And several reports have suggested that the medial pivot movement is related to maximum flexion angle after TKA. In the present study, we showed that there was significant negative correlation between the tibial internal rotation angle in extension and tibial rotational movement from half-squatting to deep flexion kneeling. This result suggested that the internal rotation of the tibial component in extension prevent the medial pivot movement of the knee during deep flexion. Therefore, the rotational alignment of tibial component may have the effect to the flexion angle after TKA.
