Classification of Perthes Disease

Cateral

Stage 1
- Anteromedial portion of head & no collapse
Stage 2
- More head involved & may be fragmentation but uninvolved pillars of bone limit collapse
Stage 3
- More head involved & metaphyseal reaction with ↑ collapse
Stage 4
- Whole head involved with severe collapse & metaphyseal reaction

Salter-Thompson

Lateral portion of femoral capital epiphysis intact
Lateral portion of femoral capital epiphysis collapsed

Herring

Normal height of lateral pillar of femoral capital epiphysis
Less than 50% reduction in height of lateral pillar
More than 50% reduction in height of lateral pillar