IS Case 600: Avascular necrosis of the right hip

Katherine Kaproth-Joslin, MD

Imaging Sciences URMC

Imaging Sciences URMC 2010
Publication Date: 2011-11-17


The patient is a 6-year-old boy with complaints of leg pain at the ages of 2 and 4.5 years old, now seen for follow-up.


Avascular necrosis of the right hip.


Avascular necrosis of the right hip


Legg-Calve-Perthes (Perthes) disease is a fairly common disorder of the childhood hip, affecting 10.8 of every 100,000 children [1]. The common age of presentation is between 3-7 years, boys more commonly then girls 4:1 [1]. Children often present with limping and pain present only during physical activity [1]. The underlying etiology of Perthes is unknown and is characterized by avascular necrosis of the epiphysis, leading to impaired femoral head enchondral ossification [1]. The proposed mechanism of injury includes repetitive microtrauma, skeletal retardation, and vascular insufficiency [1].

Evaluation of the hip starts with x-ray films in two planes, both establishing the diagnosis as well as enabling classification, prognosis, and treatment follow-up [1]. MRI may be used to diagnosis early Perthes when clinical suspicion is high and plain films are negative. Technetium 99m bone scan can be used to determine the extent of avascular changes before they are evident on plain radiographs [3].

The radiographic appearance of the disease is highly variable depending on the severity of the disease. The stages of Perthes are as follows:

• the initial phase, where growth at the capital femoral epiphysis ceases; the condensation phase, where the cessation of femoral epiphyseal growth leads to a smaller epiphysis and widening of the articular joint space on the affected side;

• the fragmentation phase, where subchondral fracture and linear radiolucency is seen within the femoral head epiphysis;

• the repair phase, where bone is being reabsorbed; and the healing phase, where new bone is being ossified [1, 3].

Several classification systems for Perthes are used, with the most recent based on the height of the lateral pillar of the epiphysis of the femoral head, as measured on the AP x-ray view in the early fragmentation phase [2]. In group A, with the best prognostic outcomes, the lateral pillar remains intact, in group B, at least 50% of the lateral pillar remains standing, and in group C, less then 50% of the lateral pillar remains standing [1, 2]. This system has high prognostic value and good intra-observer reliability. The value of the system increases when the patient’s age at onset of disease is accounted for.


  1. Nelitz M, Lippacher S, Krauspe R, Reichel H. Perthes disease: current principles of diagnosis and treatment. Dtsch Arztebl Int. 2009 Jul;106(31-32):517-23. PMID: 19730720
  2. Herring JA, Kim HT, Browne R. Legg-Calve-Perthes disease. Part I: Classification of radiographs with use of the modified lateral pillar and Stulberg classifications. J Bone Joint Surg Am. 2004 Oct;86-A(10):2103-20. PMID: 15466719
  3. Nochimson G. Legg-Clave-Perthes disease in emergency medicine. Updated: April 14, 2011

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