Outcomes of Selectively Unresurfaced Patellae with a Partial Lateral Facetectomy in Primary Total Knee Arthroplasty.

Background: Not resurfacing the patella during primary total knee arthroplasty (TKA) has steadily increased as implants and techniques have improved. However, limited data exist on the acceptable arthritis severity to leave the patella unresurfaced and the subsequent effect on patient-reported outcome measures (PROMs). This study evaluated PROMs in matched cohorts of unresurfaced and resurfaced patellae, accounting for patellar osteoarthritis severity and lateral patellar facetectomies.

Methods: A consecutive series of primary TKAs was retrospectively reviewed. There were 871 patellae selectively unresurfaced, of which 667 (76%) had an aggressive lateral facetectomy. The remaining 1,064 patellae were resurfaced. The TKAs with unresurfaced patellae were matched to TKAs with resurfaced patellae based on demographics and patellar osteoarthritis severity. There were 140 TKAs in each matched group, which did not differ by demographics (P ≥ 0.334) or osteoarthritis severity (P ≥ 0.999). The PROMs were compared between groups at a mean of 2.7 years (range, 1 to 10) at a significance level of 0.05.

Results: The matched groups did not differ by postoperative knee-specific PROMs (P ≥ 0.225), nor improvement from the preoperative baseline score (P ≥ 0.193). A greater percentage of patients who had unresurfaced patellae and a lateral facetectomy achieved minimal clinically important differences (MCIDs) for the Knee Injury and Osteoarthritis Outcome Score (94, 89, 86%) and pain with stairs (88, 85, 81%) compared to patella groups without a lateral facetectomy, despite lacking statistical significance (P ≥ 0.295). The change in PROMs for patients who had moderate to severe patellofemoral arthritis grade ≥ 2 was not different between patella groups (P ≥ 0.382).

Conclusions: Study results show that patients who had unresurfaced and resurfaced patellae have similar PROMs after TKA regardless of patello-femoral osteoarthritis severity. An aggressive lateral facetectomy when leaving the patella unresurfaced may help achieve PROM MCIDs more frequently.