Mild component malalignment may not affect the postoperative range of motion in posterior-stabilised total knee arthroplasty

Abstract

INTRODUCTION: The optimal lower limb alignment and component positions in achieving a high flexion angle in posterior-stabilised total knee arthroplasty (TKA) were not well understood. We analysed pre- and post-operative clinical and radiological parameters in patients received TKA for knee osteoarthritis. METHODS: A total of 140 TKAs in 122(98 female, 24 male) patients were recruited. Preand post-operative lower limb long radiographs were measured for mechanical axis and individual component positions in coronal and sagittal planes. RESULTS: The mean (± standard deviation) age of the patients was 68.4±8.0 years. All patients completed 1-year follow-up. The range of motion (ROM) increased from 93.8±20.5to 107.9±14.4 degrees (p<0.001). The mechanical axis improved from 13.3±6.7to 1.9±3.8 degrees varus (p<0.001). Linear regression analyses showed that the preoperative ROM was a predicting factor of postoperative ROM (p<0.001, y=0.4x+70.65, r2=0.32). When classifying the postoperative ROM into poor (<100 degrees), average (100-120 degrees) and good (>120 degrees), significant differences were found in tibial component coronal position and lower limb mechanical axis (p=0.037 and 0.017, respectively). Other radiological parameters were not significant. CONCLUSION: Our data suggest that recreation of neutral lower limb mechanical axis and tibial coronal alignment might improve the ROM after posterior-stabilised TKA. The most significant predicting factor was still preoperative ROM.