DESCRIPTIVE EPIDEMIOLOGY STUDY OF THE JUSTIFYING PATELLAR INSTABILITY TREATMENT BY EARLY RESULTS (JUPITER) COHORT
Authors: Bishop Meghan E. , Brady Jacqueline M. , Ling Daphne , Parikh Shital , Stein Beth E. Shubin 
Published: March 2019

Background: Patellar instability is frequently seen in young patients and can lead to significant disability 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 obtain sufficient subjects to better describe clinical characteristics and predictors of clinical outcomes in the young patellar instability population. The purpose of this study is to describe the formation of JUPITER and provide preliminary descriptive analysis of patient demographics and clinical features for the initially enrolled patients in this prospective cohort. Methods: After training and institutional review board approval, surgeons began enrolling patients from the 10-25 years age group who sustained a patellar dislocation or subluxation event. Information regarding patient demographics, dislocation history, physical exam characteristics, and baseline validated patient reported outcome scores were collected. Results: As of May 31, 2018, 20 surgeons from 9 different sites had prospectively enrolled a total of 406 patients (142 male, 262 female, 2 not listed; average age 15.1 years old). 269 patients were enrolled in the operative group and 137 patients in the non-operative group. 54.7% of patients reported that they had had greater than 1 dislocation (71.7% in the operative group; 20.4% in the non-operative group). The mean number of recurrent dislocations was 7.6 (Mean operative group 8.3 vs. non-operative group 3.5). 58.7% of first time dislocators were indicated for non-operative treatment while 13.1% of recurrent dislocators were indicated for non-operative treatment (95% CI: 39.1-55.3%, p<0.0001). At the time of first dislocation, 46.3% of participants reported they were participating in a sporting activity, 10.1% were walking, 6.2% were running, 2% were on stairs, and 31.3% reported other activity. 16.7% of the operative group versus 21.2% of the non-operative group reported a contact injury at the time of first dislocation. 32.5% required a manual reduction. Of those who sustained a recurrent dislocation, 5.4% reported a contact injury while 82.4% reported non-contact injury and 9.9% were unsure. 20.7% reported a family history of patellar dislocation. On physical exam, 51.2% (190/369) of patients were noted to have a positive J sign in the involved knee (78.4% mild, 21.2% severe). 35.2% (126/358) were noted to have Beighton hypermobility scores greater than 4. In a multivariable logistic regression model, more severe J-sign was associated with higher odds of redislocation (OR=2.76, 95% CI: 1.60-4.75, p<0.0001) and higher Beighton scores approached significance (OR=1.10, 95% CI: 1.00 -1.20, p=0.06). Pedi-FABS scores (12.5 vs 14.9, p=0.02) and KOOS QOL scores (35.5 vs 41.5, p=0.01) were significantly lower in those who experienced more than one redislocation. Kujala scores were higher in the recurrent dislocators (60.1 vs 55.3, p=0.04). 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. Almost 60% of first time dislocators were indicated for nonsurgical management while only 13% of recurrent dislocators were indicated for non-operative management. Over 80% of recurrent dislocations occurred during a non-contact event. Pedi-FABS scores and KOOS QOL scores were significantly lower in those who experienced more than one redislocation.