Does mismatch of the femoral component aspect ratio influence the range of knee flexion after posterior-stabilized total knee arthroplasty?
OBJECTIVE
To study whether the range of knee flexion (ROF) is affected by geometrical mismatch of the femoral component and the resultant change in the posterior condylar offset (PCO) after high-flexion posterior-stabilized total knee arthroplasty (TKA).


METHODS
One hundred osteoarthritic patients (50 males and 50 females) underwent femoral osteotomy by the anterior referencing technique. The PCO for each patient was measured from lateral radiographs before, during and 2 years after TKA. The thickness of the joint cartilage was measured by magnetic resonance imaging before TKA and added onto the radiographic measurement. The relationship between changes in the PCO and improvements in the ROF before, during and 2 years after TKA were statistically analyzed.


RESULTS
Compared with the preoperative value, the PCO was reduced by (3.45+/-3.28) mm after TKA, with a significantly larger reduction observed in female patients than male patients (P less than 0.05). When examining the subject population as a whole, there was a significant positive correlation between PCO and ROF improvement during TKA (P less than 0.05), but this improvement was not maintained 2 years after TKA (P larger than 0.05). However, when male and female patients were analyzed separately, there was a significant positive correlation between PCO change and ROF improvement for both sexes at both time points (all P less than 0.05).


CONCLUSIONS
Restoration of PCO plays an important role in the optimization of knee flexion even after posterior-stabilized TKA. Femoral components based on Caucasian anatomic characteristics could not match the native anatomy of distal femurs in Chinese population especially female Chinese. Rotated resection of distal femur with anterior re-ferencing technique usually leads to a decreased PCO and therefore reduces maximal obtainable flexion.
Department of Orthopedics, Tianjin Union Medical Centre, Tianjin 300121, China.
Yu-Tao
YT
Jia
Lei
L
Wang
Yu
Y
Zhang
Cong
C
Zhao
Zhen-Hui
ZH
Sun
Jun
J
Liu
D019645:Arthroplasty, Replacement, Knee; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint; D010027:Osteotomy; D016059:Range of Motion, Articular