Acute slipped capital femoral epiphysis: The importance of physeal stability

Abstract

Background Slipped upper femoral epiphysis (SUFE) was traditionally classifi ed as (1) acute: there are abrupt symptoms and signs developing over a short period of time (<3 weeks), (2) chronic: patients present with pain in the groin, thigh, and knee that varies in duration, often ranging from months to years and (3) acute on chronic: initially, patients have chronic symptoms, but develop acute symptoms as well following a sudden increase in the degree of slip. The authors thought that this classifi cation was cumbersome and misleading since it did not include a consideration of the stability of the slipped epiphysis. Therefore they introduced and investigated the concept of slip stability and its effect on the outcome of treatment. Methods They retrospectively reviewed the charts and radiological tests of 55 patients with SUFE in 3 centres in the USA between 1975 and 1991. Patients with underlying endocrine and metabolic bone diseases were excluded. All patients were treated with internal fi xation. Patients were divided into two groups: • Stable slips: a patient was able to ambulate and weight bear • Unstable slips: a patient was unable to ambulate with or without crutches. Results There were 25 stable slips and 30 unstable slips. Avascular necrosis of the femoral head (AVN) developed in 47 % of unstable slips but in none of the stable hips (P = 0.0003). However, there were several confounding factors whose effects were not possible to explore. For example, an unintentional reduction of the slip occurred in 26 unstable slips (out of 30) and in only 2 of the stable slips (out of 25). Conclusion Slip stability based on the above clinical defi nition was an important prognostic factor for the development of AVN and a poor outcome.