Femoral joint line restoration is a major determinant of postoperative range of motion in revision total knee arthroplasty

Abstract

The purpose of this study was to comprehensively analyze the effects of femoral or tibial joint line elevation and patella height change on the clinical results after revision total knee arthroplasty (RTKA) and to determine which one is the significant factor that should be restored. One hundred and sixty-six RTKA cases (144 patients) with a minimum 2-year follow-up were retrospectively analyzed. Demographic, operative, and clinical data were collected. Tibial and femoral joint line elevations were measured based on the distance from the tibial tubercle and from the adductor tubercle to the distal end of the femoral component, respectively. The patellar position was evaluated using the Insall-Salvati ratio and Blackburne-Peel index. The effects of clinical and radiological variables on the changes of range of motion (ROM) and clinical scores after RTKA were analyzed. Fourteen knees (8.4%) showed a femoral joint line elevation of more than 5mm, and 79 knees (47.6%) showed a tibial joint line elevation of more than 5mm. Patella baja after RTKA was observed in 33 knees (19.9%), and pseudo-patella baja after RTKA was observed in 90 knees (54.2%). The linear mixed model revealed that the femoral joint line position was the only significant factor that affected the change of ROM after RTKA. No statistically significant correlation was observed between variables and postoperative clinical scores. Restoration of femoral joint line was the significant factor that increased postoperative ROM of the knee after RTKA. In complicated revision situations, surgeons should give priority to the restoration of distal femoral joint line to increase postoperative ROM. IV.