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One of the goals of total knee arthroplasty (TKA) is to restore of extend the range of motion of the knee joint. A small proportion of patients who are candidates for TKA exhibit fixed flexion contracture (FFC), a condition which prevents the knee from reaching full extension and can be associated with preoperative coronal deformity. In treating FFC, surgeons have two options, either through extensive soft tissue releases or through additional resections of bone on the proximal tibia and distal femur to increase the extension gap. Usually, FFC can be corrected with just soft tissue release, however, sometimes needs to be combined with additional bone resections, especially in cases with varus or valgus coronal deformity. However, additional bone resections beyond 11mm on the femoral side can be associated with knee instability. We therefore asked, is there a relationship between preoperative coronal deformity and intraoperative bone resections required to treat patients with extreme FFC? We analysed 3922 navigated TKA cases undertaken at our institution between March 2007 and October 2022. From this set, we identified 127 patients with extreme fixed flexion contracture (FFC) of greater than 150 and with post-operative FFC less than 50, indicating that the FFC had been resolved. Using simple linear regression and calculating the Pearson correlation coefficients, we related the preoperative coronal deformity to the maximum femoral and tibial resection depths between the medial and lateral sides. We then calculated the statistical significance and coefficient of determination. For the 127 cases, the coefficients of determination were calculated to be 0.19 for the proximal tibia and 0.22 for the distal femur (p 0.025). The correlation coefficients for the relationship between coronal deformity and femoral or tibial resection depths were 0.47 (p 0.025) and -0.43 (p 0.025), respectively. In this study, we determined there was a moderate correlation (indicated as |0.40 – 0.59|) between the tibial and femoral bone resections required to treat extreme FFC in patients with varying degrees of preoperative coronal deformity. In planning to treat extreme FFC, surgeons should pay attention to the preoperative coronal deformity of patients as this will likely be an important factor in determining the required steps in successfully treating the FCC.
Hickey et al. (Fri,) studied this question.