Catterall's 1971 landmark study asks whether early radiographs can predict the final shape of the femoral head in Perthes' disease. It reviews 97 hips in 89 children and proposes a four-group classification based on the degree of epiphyseal involvement. The central question: does extent of involvement at diagnosis define natural history and guide treatment?
When a child presents with Perthes' disease, the most important question is not age or sex — it is how much of the epiphysis is involved.
Before Catterall, treatment decisions were guided by age and sex alone, and results across series were incomparable because no shared classification existed. This paper gave the field a common language and, crucially, showed that prognosis is set at diagnosis by disease extent.
In practice: Group I patients need activity restriction, not aggressive treatment. Group II patients over age 4 are the group where abduction bracing or containment surgery earns its keep. Group III and IV patients have poor outcomes regardless of conventional non-operative treatment. These are the hips where containment surgery (varus derotation osteotomy or abduction bracing) is most seriously considered, particularly when 'head at risk' signs are present.
The 'head at risk' concept is the actionable clinical pearl: Gage's sign, lateral calcification, subluxation, and a horizontal physis on AP radiograph identify the hips most likely to extrude the anterolateral fragment outside the acetabulum during remodeling. Spotting these signs early is what separates a watchful attending from a reactive one.
Herring's lateral pillar classification (1992) was explicitly developed as a refinement of Catterall's framework. Understanding Catterall is prerequisite knowledge for understanding why lateral pillar height became the dominant prognostic variable in modern practice.
Catterall's 1971 landmark study asks whether early radiographs can predict the final shape of the femoral head in Perthes' disease. It reviews 97 hips in 89 children and proposes a four-group classification based on the degree of epiphyseal involvement. The central question: does extent of involvement at diagnosis define natural history and guide treatment?
When a child presents with Perthes' disease, the most important question is not age or sex — it is how much of the epiphysis is involved.
Before Catterall, treatment decisions were guided by age and sex alone, and results across series were incomparable because no shared classification existed. This paper gave the field a common language and, crucially, showed that prognosis is set at diagnosis by disease extent.
In practice: Group I patients need activity restriction, not aggressive treatment. Group II patients over age 4 are the group where abduction bracing or containment surgery earns its keep. Group III and IV patients have poor outcomes regardless of conventional non-operative treatment. These are the hips where containment surgery (varus derotation osteotomy or abduction bracing) is most seriously considered, particularly when 'head at risk' signs are present.
The 'head at risk' concept is the actionable clinical pearl: Gage's sign, lateral calcification, subluxation, and a horizontal physis on AP radiograph identify the hips most likely to extrude the anterolateral fragment outside the acetabulum during remodeling. Spotting these signs early is what separates a watchful attending from a reactive one.
Herring's lateral pillar classification (1992) was explicitly developed as a refinement of Catterall's framework. Understanding Catterall is prerequisite knowledge for understanding why lateral pillar height became the dominant prognostic variable in modern practice.