Paper 49: Demographic and Clinical characteristics of patellar instability patients from prospective JUPITER (Justifying Patellar Instability Treatment by Early Results) cohort.
Authors: Brady Jacqueline , Gruber Simone , Veerkamp Matthew , Nguyen Joseph , Heyworth Benton , Tompkins Marc , Green Daniel , Wall Eric ,   The JUPITER Group, Stein Beth Shubin , Parikh Shital , Bishop Meghan 
Published: July 2022

Objectives: The purpose of this study is to provide an objective analysis of patient demographics and clinical features for the young patients with patellar instability. JUPITER (Justifying Patellar Instability Treatment by Early Results) is a hypothesis-driven, multi-center, multi-armed, prospective cohort study developed to better describe demographic and clinical characteristics and predictors of clinical outcomes in the young patellar instability population. Methods: 21 surgeons from 12 institutions enrolled patients between 10-30 years of age who presented with at least one documented patellar dislocation episode. Radiographs and MRI were evaluated for all patients at baseline to confirm patellar dislocation and skeletal maturity status. Patient demographics, dislocation history, physical exam characteristics and baseline validated patient reported outcome (PRO) scores were collected and analyzed. Conservative versus operative treatment was based on treating physician’s preference following standard of care guidelines. The cohort was divided between first-time vs recurrent dislocators and between conservative vs operative treatment. Results: At the end of enrollment in December 2020, a total of 1722 knees with patellar instability were enrolled. The mean age of the cohort was 17.7 years, 62.4% were female. 306 were skeletally immature. 59% of knees reported that they had more than 1 dislocation. ). 71% knees were enrolled in the operative group and 29% in the conservative group. For patients with recurrent dislocation, 89.7% were treated operatively and 10.2% were treated conservative (p<0.001). Operative treatment was indicated in 42.9% of first-time dislocators; 50% were due to presence of an osteochondral fracture. The recurrent and operative group patients were noted to have a higher percent of positive physical exam findings than first-time and conservative group patients on the affected knee (J-sign [p<0.001], apprehension [p<0.001], crepitus [p=0.041]) and the contralateral knee (except for the crepitus test [p=0.648]). The recurrent group was nearly twice as likely to be ligamentously lax (Beighton score of 5 or greater) compared to first-time dislocators (p<0.001). Baseline PROs 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: Based on large prospective cohort of JUPITER group, operative management was indicated in 42.9% of first-time dislocators and 89.7% of recurrent dislocators. Besides osteochondral fracture, recognition of risk factors (young age, contralateral dislocation, anatomic risk factors) may account for higher rates of operative treatment after first-time dislocation. Recurrent dislocators were more likely to have positive physical exam findings on both knees and lower activity scores. However, the knee specific outcome scores were higher in patients with recurrent dislocations which may reflect adaptive mechanisms to improve function. This prospective study provides insights related to demographic information, clinical presentation and baselines PROs of patients with patellar instability. These baseline characteristics would help to identify the at-risk population and compare outcomes in a longitudinal fashion.