A novel technique for estimating component sizes in total knee arthroplasty.

Introduction: Intra-operative assessment of total knee arthroplasty (TKA) components is performed with manufacturer specific jigs. Pre-operative templating, patient specific knee cutting blocks and computer-assisted surgeries have also been used to improve alignment and sizing; although the literature shows marginal improvement in functional scores. We propose pre-operative shoe size as a simple measurement tool for estimating the component sizes required for TKA. We investigate the relationship between TKA implant sizes, height, body weight and shoe size.

Methods: Retrospective single centre cohort study of all patients undergoing primary knee arthroplasty over a four-month period (August-November 2015) was conducted. Standard data items recorded during routine admission. The spearman's rank correlation was used to assess the relationship between variables.

Results: One hundred and six patients were included in the final analysis. The mean age of the study group was 67.3 ± 10.1 years (Range 44-90.) There were 42 male patients and 64 female patients. Statistically significant correlations were observed between: Shoe size and femoral component (rho = 0.589, p < 0.05); shoe size and tibial component (rho = 0.718, p < 0.05); shoe size and height (rho = 0.692, p < 0.05); height and femoral component (rho = 0.626, p < 0.05); height and tibial component (rho = 0.674, p < 0.05).

Conclusion: We have demonstrated positive correlation between shoe and TKR component sizes. This relationship allows surgeons to estimate prosthesis size in the pre-operative setting.