Up to 4 millimeters excessive distal femoral resection in total knee arthroplasty has no significant effect on patellar height and functional score in patient with severe flexion contracture: a retrospective study

Background: Excessive distal femoral resection in patients with severe preoperative flexion contracture has been previously attributed to the joint line elevation after performing total knee arthroplasty (TKA). In this study, the authors investigated the effects of excessive distal femoral cut on the patellar height as well as the outcome of TKA. Methods: This retrospective study included patients with severe flexion contracture (>30 degrees) who underwent TKA. They were divided into two groups according to the size of distal femoral cut: group A (≤9 mm, n=27) and group B (>9 mm, n=22). The functional and radiographic outcomes as well as radiographic indices of patellar height, including adductor ratio, Insall-Salvati index, Blackburne-Peel index, Caton-Deschamps index, and fibular height, were compared between these two study groups. Results: The baseline characteristics of the participants were comparable. The mean femoral cut was 8.3±0.8 in group A and 12.6±0.9 in group B. The mean changes of the adductor ratio, Insall-Salvati index, Caton-Deschamps index, Blackburne-Peel index, and fibular height were not significantly different between the two study groups. As well, the functional and radiographic outcomes of TKA were comparable. No revision surgery was required during the mean follow-up of 51.7±32.4 mo. No genu recurvatum was recorded, and no patient complained of knee instability. Conclusions: An excessive distal femoral cut does not seem to change patellar height in TKA patients, so it could be used safely for patients with a severe preoperative flexion deformity. Level of Evidence: Level IV.