The effect of patella resurfacing on pain outcomes following primary knee arthroplasty: Comparing cruciate retaining and Posterior Stabilized Implants

Knee arthroplasty surgery involves either resurfacing or retaining of the patella. Whether or not to resurface remains controversial, with anterior knee pain a concern in both cases. Differences in pain outcomes between these procedures may be affected by implant type, specifically cruciate retaining (CR) or posterior stabilized (PS) designs. The purpose of this study was to test for associations between patella resurfacing and pain outcomes as measured by utilization data, comparing CR and PS implants. We identified knee arthroplasty cases in Nova Scotia, Canada from 2016-2024 through the Canadian Joint Replacement Registry (CJRR). Using health utilization data for proxy measures, pain visits within 90 days of discharge and a narcotics prescription (Rx) filled in the 30 to 90-day period following discharge were measured. Inverse probability treatment weighted, hierarchical logistic models were run separately for CR and PS observations. The association between patella resurfacing and the probability of a visit for pain or narcotic Rx was tested, controlling for confounders. The t-statistic with a 95% confidence was used for statistical significance. There were 6101 CR and 6956 PS observations. A lower percentage of CR cases had the patella resurfaced (18.6% [CI 17.7%-19.6%]) compared to PS cases (71.5% [CI 70.4%-72.6%]). For CR cases, the adjusted Odds Ratio (OR) of both proxies for pain where the patella was resurfaced were higher, specifically 1.98 [CI 1.65-2.37; p-value = 0.0002] for a pain visit and 1.40 [CI 1.17-1.68; p-value < 0.0001] for a narcotics Rx. Resurfacing was associated with a lower probability of a pain visit for PS cases (OR 0.81 [CI 0.69-0.94, p-value=0.0061]) but was not statistically significant for narcotics. Using health utilization data as a proxy measure for pain, our study finds a CR implant design has higher odds of post-surgical pain when the patella is resurfaced compared to a PS design.