Aetiology

The aetiology of SCFE is unknown in most cases. Obesity is recognised as the most strongly associated risk factor.[5][11][12][13] Obesity increases the shear stress across the physis, weakens it, and causes the characteristic displacement in SCFE.

Hormonal involvement associated with the adolescent growth spurt may also provide insight into the aetiology of SCFE. The physis weakens at puberty, possibly due to the effect of circulating gonadotrophins.[7] The weakening effect of testosterone on the physis offers a causative hypothesis for the higher incidence in males. The lower incidence in female adolescents may be due to oestrogen increasing the strength of the physis and narrowing its width. SCFE is associated with endocrine disorders, but the majority of children with SCFE are obese.[7][15] One study found increased leptin levels in patients with SCFE, regardless of obesity status.[16]

Radiotherapy is a risk factor for SCFE.[17] There is no evidence of a genetic predisposition.

Pathophysiology

The characteristic weakening and widening of the physis is due to a variety of factors such as obesity, rapid growth during adolescence, and endocrine disorders.[2][7] These factors induce stress around the hip joint and apply shear force at the growth plate. The growth plate is intrinsically weak. Excess weight, the stress of an adolescent growth spurt, and changing hormone levels result in physeal weakness which that allows the epiphysis to displace anteriorly and superiorly relative to the metaphysis.

Classification

Acute, chronic, acute-on-chronic[4]

This traditional classification system is based on symptom duration:

  • Acute: prodromal symptoms lasting <3 weeks prior to an acute fracture-like event

  • Chronic: symptoms lasting >3 weeks

  • Acute-on-chronic: symptoms lasting >3 weeks with a sudden onset of increased pain and irritation.

Stable/unstable[5]

This classification is based on weight-bearing ability:

  • Stable: can bear weight with or without support. This classification accounts for nearly 90% of all SCFE cases.[6][7]

  • Unstable: unable to bear weight with or without support.

This classification is the most widely accepted.[1][5][7][8]

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