Background

Although a rare condition (2:100 000), slipped upper femoral epiphysis (SUFE) is one of the most common types of paediatric and adolescent hip disorder. The incidence of SUFE varies with:

1. Sex: SUFE is more common in boys (75% of cases) with the peak incidence occurring at 12 to 15 years compared with 10 to 13 years in girls. Thus, boys tend to have their slip 2 years older than girls. SUFE is rarely reported after the age of 20 years [1].

2. Race [2]: SUFE is more common in those of African and Polynesian descent.

3. Laterality: SUFE is more common on the left side (as is developmental dysplasia of the hip (DDH)). The reason is unknown; it may be related to the sitting posture of right-handed children while writing. The incidence of bilaterality has been reported to be as high as 50%, although the generally accepted incidence is 20%. In children with bilateral involvement, 50–60% present with simultaneous SUFEs and those who present with a unilateral SUFE and subsequently develop a contralateral SUFE do so within 18 months. Younger patients and those with endocrine or metabolic abnormalities are at much higher risk of bilateral involvement.

4. Seasonal variations: this is debatable; some studies have suggested that SUFE is more common in June and July.

Aetiology

Although, the cause is poorly understood, it is believed that increased shear forces or a weak growth plate (the physis) in adolescence predisposes to SUFE. This results in the head of the femur staying in the acetabulum and the neck slipping forward and outward.