Patellar Instability Events Requiring Emergency Department Management - A 20-year Analysis.

Background: Patellofemoral instability (PFI) is a common pediatric knee injury most prevalent among females in late adolescence. This study's purpose was to use a nationally representative database to examine epidemiologic trends in pediatric PFI events requiring management in emergency departments (ED).

Methods: The National Electronic Injury Surveillance System (NEISS) was queried from 2001 to 2020 for cases of knee "dislocation" or "fracture" in patients aged 0-18 years. Case narratives were used to confirm episodes of patellar instability. National estimates were calculated. Seasonal and temporal patterns of injury were assessed overall and within demographic subgroups using bivariate and multivariate analysis.

Results: Study criteria identified an estimated 208,673 cases of patellar instability presenting to United States EDs between 2001 and 2020. The mean annual frequency of injury was 10,434, with time series analysis estimating an increase of 256 dislocations per year (P ​< ​0.001) over the study period. Seasonal injury peaks occurred during the Spring (April-May) and Fall (September-October) months. Males accounted for the majority (59%) of injured patients, and patients aged 15-18 were the most frequently injured age group (48%). A generalized linear model demonstrated that males had a higher rate of dislocations prompting ED management than females and patients aged 10-14 saw a slight increase in the rate of dislocations compared to patients aged 15-18 (P ​< ​0.001). Seasonal variation in injuries was most evident among males and adolescents.

Conclusions: Findings from this study suggest a rising overall frequency of pediatric PFI injuries presenting to the ED. Statistically significant seasonal injury patterns were observed that appeared driven by male adolescent injury. This study highlights novel epidemiologic patterns and improves our understanding of patellar instability events requiring management in the ED.

Key concepts: (1)Temporal trends found a significant rise in the annual number of patellar dislocations requiring an emergent evaluation driven by increases during the Spring and Fall.(2)Seasonal trends were likely driven by an increase in sports participation during the fall and Spring months.(3)Despite patellofemoral instability being more common in females, males were more likely to seek an evaluation at the emergency department after a patellar dislocation.(4)Although both males and females saw an increase in patellar dislocations over the course of this study, males and patients aged 10-18 demonstrated a higher rate and increase of dislocations.

Level of evidence: Level IV - Retrospective Case Series.