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

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.