Patella retention versus replacement in total knee arthroplasty; functional and clinimetric aspects.

Introduction: Whether to resurface the patella or not in total knee arthroplasty still remains undecided. Classical scores and questionnaires might not be responsive or demanding enough. This study used two accelerometer based systems to study the hypothesis whether performance based tests are able to detect a difference in patients with or without a resurfaced patella.

Method: In this retrospective study 53 patients were included and divided into a resurfaced group (n = 31) and a non-resurfaced group (n = 22). Both groups were matched on age and longevity of follow up. Patients were clinically assessed using the Knee Society Score (KSS) at various time points. At final follow up patients were also assessed once using the Dynaport Knee Test and the Minimod Gait Test.

Results: The Dynaport Knee Test showed a significant functional advantage for patients with a resurfaced patella [44 vs. 39.7 (P = 0.042)], whereas KSS and The Minimod were not significant (P values ranging from 0.07 to 0.75). Similar to other reports in literature, using the KSS, it was not possible to identify significant difference between patella resurfacing or retaining in total knee arthroplasty, however using a performance based test it was possible to determine significant difference. The found advantage of patella resurfacing may be less due to pain relief but due to a functional benefit during demanding motion tasks. This finding indicates that current measurement tools may not be accurate or specific enough to detect this difference. Therefore, we recommend complementing the classic evaluation tools with an objective functional test, when conducting a randomized trial to answer the indecision whether to resurface the patella or not.