In Perthes disease, the Catterall Group IV classification indicates:

• A Anterior one-quarter of the epiphysis is involved; no structural changes
• B The entire epiphysis is involved — whole head collapse ✓
• C Anterior half of the epiphysis involved; posterior column maintained
• D Three-quarters of the epiphysis involved with central sequestration

Explanation

Catterall's classification of Perthes disease: Group I = anterior quarter involved, no structural changes, good prognosis; Group II = anterior half involved, posterior column maintains structure; Group III = three-quarters involved, central and lateral sequestrum, 'head-within-head' sign; Group IV = entire epiphysis involved (total head collapse). Group IV carries the worst prognosis with very high risk of femoral head deformity and subsequent early-onset OA. Lateral pillar classification (Herring) is now preferred: A (no lateral pillar collapse) = good prognosis; B and C with increasing collapse.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.