Introduction

It is unclear whether the diagnosis and treatment of patellofemoral instability (PFI) has been equitable between racial and socioeconomic groups. This study's purpose was to determine the effects of race and socioeconomic disadvantage on the severity of patellar instability at initial presentation.

Methods

A prospectively enrolled, multicenter cohort study database (JUPITER: Justifying Patellar Instability Treatment by Results) was queried for patients from December 2016-September 2022 with 5-digit zip code data. Patients were excluded if zip code, race, history, treatment, or baseline patient-reported outcome (PROM) data was unavailable. National percentile area deprivation index (ADI) rankings were calculated and stratified by ADI (low (Q1), medium (Q2-Q3), high (Q4)), where higher ADI indicates greater socioeconomic disadvantage. To improve power of analysis, race was categorized into White, Black, or Other race, which included subjects who were Asian, Hispanic, Native American, Native Hawaiian, Indian, Cape Verdean, and multiracial, as well as patients who selected “Other race” but did not specify. Outcomes analyzed included first-time vs. recurrent dislocator status at time of intervention, number of dislocations at time of treatment, type of treatment, presence and location of Outerbridge Grade III/IV chondral lesions, and baseline patient-reported outcome measures.

Results

1215 unique patients (16.6 ± 4.12 years old, 61.7% female) had available zip code, race, ADI, history, treatment, and baseline PROM data. Mean national ADI percentile rank was 38.1 ± 7.6 (Q2-Q3). Patients in the high ADI group were more frequently Black (13% vs. 3.2% in the Low ADI group, p < 0.0001), and patients in the high ADI group had a significantly higher mean BMI than the Low ADI group (24.95 ± 8.5 vs. 23.04 ± 6.34, p = 0.0001). High ADI patients were less likely to undergo chondroplasty (33.8% vs. 45.1%, p = 0.0041) and less likely to undergo osteochondral fracture treatment (9.8% vs. 17.3%, p = 0.0099) than their low ADI counterparts. High ADI patients also had a lower baseline KOOS Pain score than Low ADI patients (66.8 ± 22.4 vs. 71.1 ± 22.5, p = 0.0483) (p=0.0167). There were no significant differences in baseline KOOS QOL, IKDC, or BPII 2.0 based on ADI (p > 0.05). For the generalized linear mixed models, Other race patients were more likely to be First-Time Dislocators, whereas Female patients and patients with a higher BMI were more likely to be a recurrent dislocator. Black race, high ADI, and being both of Black race and High ADI were predictive of an increased number of dislocations at the time of presentation. Being female and older age were each associated with a decreased KOOS Pain score at presentation. Race and ADI did not have a statistically significant association with any of the four baseline PROM scores.

Conclusion

Patellar instability patients with greater socioeconomic disadvantage (higher ADI) were more often Black and had a higher mean BMI than those of lower ADI. Higher ADI was associated with worse pain scores at baseline and a lower likelihood of undergoing chondroplasty and osteochondral fracture treatment. Higher ADI was also associated with more dislocations before initial presentation.