Makindo Medical Notes

Related Subjects: |Developmental Dislocation (Dysplasia) of the Hip (DDH) |Slipped Upper Femoral Epiphysis (SUFE) |Perthes disease (Osteochondritis of the Hip) |Avascular Necrosis of Femoral head

Perthes Disease 🦴👦 = idiopathic avascular necrosis (osteonecrosis) of the femoral head epiphysis in children. It leads to flattening, fragmentation, and eventual remodelling of the femoral head. Typically affects boys aged 5–7 (range 3–12), 4:1 male predominance, bilateral in ~10%.

📖 About

• Idiopathic avascular necrosis of the proximal femoral epiphysis.
• Vascular supply interruption → bone death → revascularisation cycles.
• Process: necrosis → fragmentation → reossification → remodelling.

⚙️ Aetiology

• Exact cause unknown.
• Proposed mechanism: repeated vascular occlusion of epiphysis with 2–4 week cycles of necrosis/revascularisation.
• 1 in 10,000 prevalence, mostly boys.

🩺 Clinical Features

• Painless limp or hip/knee pain (often referred to knee, misleading ❗).
• ↓ and painful hip abduction & internal rotation (internal rotation affected most).
• No systemic features, knee exam normal.

🔎 Investigations

• Bloods: FBC, ESR, U&E → usually normal (excludes infection/inflammation).
• X-ray:
  • Early: effusion, widened medial joint space, small epiphysis.
  • Later: sclerosis, collapse, flattening (coxa plana), widened neck (coxa magna).
  • Signs: “Sagging rope sign” = thin sclerotic line across femoral neck.
• USS: hip effusion.
• MRI/CT: more sensitive, esp. early disease.

📊 Catterall Classification

• Stage I: small anterior epiphyseal changes, no sclerosis.
• Stage II: bone resorption + sclerosis, partial collapse.
• Stage III: most of femoral head collapsed, “head within head” appearance.
• Stage IV: complete collapse, flat head, sclerosis, metaphyseal changes.

🔎 Differentials

• Transient synovitis
• Septic arthritis (always rule out 🚨)
• Juvenile idiopathic arthritis
• Other osteonecrosis causes: trauma, leukaemia/lymphoma, SLE, haemoglobinopathies, coagulopathies, steroids

💊 Management

• Goals: Contain femoral head in acetabulum → reduce deformity + maintain motion.
• General: activity restriction, analgesia, physiotherapy, range-of-motion exercises.
• Age <6 years: usually conservative, good prognosis 👍.
• Age 6–8: brace (abduction orthosis) ± containment surgery.
• Age >8 years: higher risk of poor outcome → femoral/pelvic osteotomy often needed.
• Prognosis: Outcome depends on % head involvement (>50% involvement = worse outcome). Age >6 years = poorer prognosis.

📌 OSCE / Exam Pearls

• Classic: 6-year-old boy with limp, painful restricted internal rotation, normal bloods.
• Referred knee pain in children with hip pathology is a common trap.
• Best prognosis = <6 years, minimal head involvement.
• Rule out septic arthritis first (well child vs toxic child).

📚 References

• Rockwood & Wilkins’ Fractures in Children, 9th ed.
• Catterall A. The natural history of Perthes’ disease. J Bone Joint Surg Br. 1971.
• NICE CKS: Hip pain in children. 2022.