In slipped capital femoral epiphysis (SCFE), the Southwick slip angle is used to grade severity. An unstable SCFE is defined as:

• A Slip angle > 60° (severe SCFE) regardless of weight-bearing status
• B Acute onset SCFE in a child < 10 years of age
• C Bilateral SCFE occurring within 12 months
• D Inability to bear weight even with crutches due to pain, irrespective of the radiographic grade ✓

Explanation

Loder's classification distinguishes stable SCFE (weight-bearing possible, even with crutches; very low risk of AVN ≈ 0–10%) from unstable SCFE (unable to bear weight; AVN risk 20–50%). This functional definition reflects the degree of displacement across the physis and risk of vascular compromise to the femoral head. Unstable SCFE is an orthopaedic urgency requiring urgent in-situ pinning; delayed treatment markedly increases AVN risk. Severity by slip angle (< 30° mild, 30–60° moderate, > 60° severe) is a separate classification.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.