A Nationwide Cohort Study of Slipped Capital Femoral Epiphysis

Objectives: To describe the epidemiology of Slipped Capital Femoral Epiphysis (SCFE), examine associations with childhood obesity and socioeconomic deprivation, and to explore factors associated with diagnostic delays. Design: Historic cohort study using linked primary and secondary care data from the Clinical Practice Research Datalink (CPRD) and Hospital Episode Statistics (HES). Setting: All contacts with healthcare services, including emergency presentations, outpatient appointments, inpatient admissions, and primary care visits within the United Kingdom National Health Service. Patients: All individuals <16 years old with a diagnosis of SCFE and whose electronic medical record was held by one of 650 primary care practices in the UK between 1990 and 2013. Main outcome measures: Annual incidence, missed opportunities for diagnosis, and diagnostic delay. Results: Over the 23-year period the incidence remained constant at 4.8 (95% CI 4.4 to 5.2) cases per 100,000 0-16 year olds. There was a strong association with socioeconomic deprivation. Pre-disease obesity was also strongly associated with SCFE; mean pre-disease z-score of BMI 1.43 (95%CI 1.20 to 1.68) compared to the UK reference mean. Diagnostic delays were common with most children (75.4%) having multiple primary care contacts with relevant symptomatology, and those that presented with knee pain having significantly longer diagnostic delay (median 161 [IQR 27-278] days) than those with hip pain (20 [5-126]) or gait abnormalities (21 [7-72]). Conclusions: SCFE has a strong association with both area-level socioeconomic deprivation and pre-disease obesity. The majority of patients with SCFE are initially misdiagnosed and those presenting with knee pain are particularly at risk