DESCRIPTIVE EPIDEMIOLOGY STUDY OF THE JUSTIFYING PATELLAR INSTABILITY TREATMENT BY EARLY RESULTS (JUPITER) COHORT

Background: Patellar instability is a common injury in young patients and can lead to significant morbidity and arthritis. Its management is controversial. JUPITER (Justifying Patellar Instability Treatment by Early Results) is a hypothesis-driven, multi-center, multi-armed, prospective cohort study developed to describe clinical characteristics and predictors of clinical outcomes in the young patellar instability population. Purpose: To describe the formation of JUPITER and provide a descriptive, epidemiologic analysis of patient demographics and clinical features of the patients in this prospective cohort. Methods: After training and institutional review board approval, surgeons began enrolling patients between 10-30 years of age who sustained a patellar dislocation. Patient demographics, dislocation history, physical exam characteristics, and PROMs were collected. Results: By January 1, 2019, 28 surgeons from 12 sites had prospectively enrolled 661 patients (677 knees) with patellar instability. 62% were female and mean age was 15.8 years. 447 knees (66%) were in the operative group and 230 (34%) in the non-operative group. 55% of knees reported that they had more than 1 dislocation (operative group 73%; non-operative group 27%, p<0.001). Operative treatment was indicated in 39% of first-time dislocators and 85% of recurrent dislocators (p<0.001). Recurrent and operative group patients had more positive physical exam findings than first-time and non-operative group patients on the affected knee (p<0.05 for J-sign, apprehension, crepitus) and the contralateral knee (p<0.05 J-sign, apprehension). The recurrent group was nearly twice as likely to be ligamentously lax (Beighton score 5 or greater) compared to first-time patients (p<0.001). Baseline PROMs varied with the recurrent group having lower Pedi-FABS (p=0.001) and KOOS-QoL (0.008) scores and higher Kujala (0.009), KOOS ADL (0.008), KOOS Sports (<0.001), and Pedi-IKDC (0.014) scores than the first-time dislocator group. Conclusions: The JUPITER Group has been able to accumulate the largest prospectively collected patellar instability database to date. Over half of patients in this group reported they sustained more than one dislocation. Operative management was indicated in 39% of first-time dislocators, 50% of which had sustained an osteochondral fracture, and 85% of recurrent dislocators. Recurrent dislocators were more likely to have positive physical exam findings on both the affected and contralateral knee.