Increasing hospital admissions for patellar instability: a national database study from 2004 to 2017

Objectives: Epidemiology of patellar instability is not fully characterized, as some studies have produced conflicting information or been drawn from limited populations. In this study, we used the Pediatric Health Information System (PHIS) database to examine trends in admissions for patellar instability throughout the United States. We hypothesized that there would be an increasing rate of patellar instability admissions in recent years. Secondarily, we examined how demographic factors and insurance status relate to admissions for patellar instability.Methods: This study queried the Pediatric Health Information System (PHIS). Patients with ICD 9 & 10 codes 8363, 8364, 71,785, M221.0, S83.001, S83.002, S83.003, S83.004, S83.005, and S83.006, were abstracted from PHIS. We included all patients admitted with patellofemoral dislocations that were reported in the PHIS database between 1 January 2004 and 30 April 2017. The rate of patellar instability admissions was examined as well as demographic factors and insurance status.Results: An estimated total of 25,413 admissions for patellar instability were identified by the search of the PHIS database; 15,444 (60.8%) were female patients and 9,966 (39.2%) were male. The adjusted number of admissions per reporting hospital significantly increased over the years studied (r = 0.775, p < 0.001), from 14.5 admissions per reporting hospital in 2004 to 86.0 admissions per reporting hospital in 2016. Of all patellar instability admissions, 55.0% were white, 20.4% were black, 1.7% were Asian, and 22.9% were unknown race. A larger number of admissions occurred in patients with insurance status other than Medicaid in every year data were collected.Conclusions: Based on a PHIS database search, pediatric hospital admissions for patellar instability are steadily increasing. The majority of patients admitted for patellar instability are female, white, and have insurance other than Medicaid. Males admitted for patellar instability tended to be older than females admitted for the same.Level of evidence: II.