classification of Perthe's disease

Last reviewed 01/2018

Classification of Perthes disease

A fourfold classification of the condition in relation to extent of the involvement of the femoral head has been proposed by Catterall:

• grades of involvement are as follows:
• I - central involvement
• II - central involvement with collapse
• III - nearly whole head involvement
• IV - whole head involvement
  
  
• but the reliability and prognostic value is limited (1)
• this classification was supplemented with “head at risk signs”
• these were associated with a poorer prognosis
• signs include:
• Gage's sign - a radiolucent defect between the lateral epiphysis and metaphysis
• calcification lateral to the epiphysis
• metaphyseal cysts
• lateral subluxation
• horizontal growth plate (2)

An alternative classification based on the height of the lateral pillar of the epiphysis of the femoral head (as seen on an AP x-ray view) in the early fragmentation phase has been described by Herrring in 1992.

• the three choices include:
• the lateral pillar is intact
• at least 50% of the lateral pillar remains standing
• less than 50% of the lateral pillar remains standing (1)
  
  
• this has a greater prognositic value and also a greater inter-observer reliability than the Catterall classification
• predictive value is higher when the patient's age at the onset of the disease is also taken into consideration (1)

Reference:

• (1) Nelitz M, Lippacher S, Krauspe R, Reichel H. Perthes Disease Current Principles of Diagnosis and Treatment Dtsch Arztebl Int. 2009 July; 106(31-32): 517–523.  
• (2) The Pediatric Orthopaedic Society of North America (POSNA) 2012. Legg-Calve-Perthes Syndrome