The association between surgeon grade and radiographic implant alignment following oxford unicompartmental knee replacement.

Abstract

Introduction: Unicompartmental knee replacement (UKR) is a technically challenging operation. Component alignment can influence implant longevity and knee function post-operatively. This study aimed to investigate implant alignment following UKR performed by consultants compared to trainees.

Methods: 100 Oxford UKRs performed by trainees and consultants were analysed. Two blinded surgeons independently assessed post-operative knee radiographs on four parameters: flexion/extension of femoral component, posterior slope of tibial component, and varus/valgus of femoral and tibial components. Logistic regression was performed to predict the probability of implant malpositioning outside the optimal position range.

Results: Median varus/valgus angles for femoral components did not differ significantly between trainees and consultants (p = 0.92), nor did the angles for tibial components (p = 0.43). Posterior tibial slope measurements showed a significant difference between trainees and consultants (7.08° [IQR 5.2-9.30], and 5.35° [IQR 2.65-7.05], respectively; p < 0.01). Median flexion/extension angles for femoral components also differed significantly between trainees and consultants (-14.45° [IQR -19.2 to -9.85] and -10.2°[IQR -13.55 to -6.95], respectively; p < 0.01). A greater proportion of implants positioned by trainees were classified as outliers for this parameter (46% versus 20%, p < 0.01; aOR 5.39, 95% CI 2.05-14.18, p < 0.01). However, no differences in the proportion of outliers was found when trainees were directly supervised by consultants (p = 0.73).

Conclusions: Trainees achieved adequate component alignment within optimal ranges for most parameters however were more prone to positioning the femoral component in excessive flexion. Greater emphasis on achieving optimal flexion/extension positioning of the femoral component during surgical training and direct supervision may improve the outcomes of patients undergoing an Oxford UKR by trainees.