Component asymmetry in bilateral total knee arthroplasty in the middle eastern population

Purpose

Proper sizing of the femoral and tibial components is an important step in total knee replacement (TKA). When performing bilateral TKA, there is often an opinion that the same size prosthesis as the opposite side will suffice, even though there are reports of anatomical differences between sides. In this study, we quantify the incidence of asymmetry in femoral and tibial component sizes in staged bilateral TKA in a Middle East population.

Methods

This is a retrospective observational study of all patients who underwent uncomplicated bilateral TKA with the same type of prosthesis by two surgeons at the same institute, between January 2013 and January 2019.

Results

There were 123 patients, femoral and tibial component size variationswerepresent in 42patients (34.1%) and 30 patients (24.4%) respectively. The variation was evident in both posterior substituting (PS) and cruciate retaining (CR) designs. The femoral components had a higher variation in size between the sides for both PS and CR designs than the tibial components for both designs. The percentage variation in the size of the femoral component was similar for PS and CR subgroups (32.7% and 33.3% respectively). However, for the tibial component, the size variation was higher for PS design (24.5%) than for CRdesign (18.7%). 7.3% had a side-to-side variation by 2 or more sizes in both femoral and tibial components.

Conclusion

Variations in the size of the femoral and tibial components is common in patients undergoing bilateral TKA. Contralateral component size should not be used as the determinant of component sizes on the other side.