Does knee position during wound closure alter patella height following total knee arthroplasty?

Patella infera is a known complication of total knee arthroplasty, and the method of soft tissue closure is a possible contributing factor. The aim of our study was to evaluate the effect of knee position during surgical closure of capsule, subcutaneous tissue and skin on patella tendon length after total knee arthroplasty.

A three arm retrospective cohort study was conducted in a single institution over a 3-year period; 75 patients were divided, by surgeon preference, into three groups (Flexed, Extended and Hybrid) of 25 patients. All groups had standardized prosthesis, intraoperative and postoperative protocols, and differed in knee position at closure. Patellar tendon length was assessed radiologically using Insall Salvati ratio (ISR) and modified Insall Salvati ratio, with a 12-month follow-up. Intraclass correlation coefficients were used to assess intraobserver variability.

There was a small but significant difference in preoperative to initial postoperative ISR change between Flexed and Extended groups (Extended group mean ISR change = -0.05; t = -2.31, P = 0.025, independent samples t-test), which was not sustained at 12 months. The incidence of patella infera was similar in Flexed and Extended groups at 12 months with only one case seen in the Hybrid group.

Our study suggests that knee position during soft tissue closure does not have a sustained impact on patella tendon length after knee replacement. A small but statistically significant reduction in patella height was found in the Extended group initially after surgery but this effect was not sustained at 12 months.