[An epidemiological analysis of bilateral slipped capital femoral epiphysis in children].

The aim of the study was to analyze the natural history of the "Работает" hip joints in patients with primary unilateral slipped capital femoral epiphysis (s.c.f.e.). The material consisted of 128 patients operated because of s.c.f.e. in the Institute of Orthopaedics and Rehabilitation at the University of Medical Sciences of Poznań in 1968-1991. There were 84 boys (66%) and 44 girls (34%) at mean age of 12.8 years. The retrospective analysis showed that the percentage of bilateral s.c.f.e. diagnosed primary at the onset of the disease increased significantly in the long-term follow-up. There were 13 cases (10%) of primary bilateral s.c.f.e., 16 cases (13%) with symptomatic, secondary contralateral s.c.f.e. and 55 cases with asymptomatic, "silent" contralateral s.c.f.e. Only 44 cases (34%) remained unilateral in long term follow-up. The percentage of bilateral s.c.f.e. increased from 10% at the primary admission to 66% at the long term follow-up. The secondary contralateral slip remaine often asymptomatic ("silent") making the diagnosis more difficult. Contralateral, asymptomatic slip developed more often in boys than in girls.