In Legg-Calve-Perthes disease, the Catterall Group III hip is characterized by:

• A More than 50% of the femoral head involved but with a posterior pillar of intact bone supporting the head ✓
• B Less than 50% of the femoral head involved with no collapse
• C Entire femoral head involvement with metaphyseal reaction and dead-appearing epiphysis
• D Only the anterior portion of the femoral head involved

Explanation

Catterall classification of Perthes disease: Group I = anterior quarter of head, no collapse; Group II = anterior half, intact posterior/medial columns (pillar); Group III = three-quarters of head, intact posterior pillar (but small and sclerotic), high risk of collapse; Group IV = entire head (whole head dense/fragmented). Group III corresponds to Lateral Pillar (Herring) classification Group B/B-C border. The 'Catterall head-at-risk' signs (Gage sign, calcification lateral to epiphysis, lateral subluxation, horizontal physis, metaphyseal cysts) increase the risk of poor outcome.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.