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Legg-Calvé-Perthes disease

Legg-Calvé-Perthes disease (LCPD) (more frequently simply referred to as Perthes disease) is idiopathic avascular necrosis (AVN) of the growing femoral epiphysis seen in children, and should not be confused with the Perthes lesion of the shoulder.

It is a diagnosis of exclusion and other causes including sickle cell disease, leukaemia, corticosteroid administration, Gaucher disease, and epiphyseal dysplasia, which tend to be bilateral, must be ruled out 8.

Epidemiology

Relatively uncommon, occurs in approximately 5-15:100,000 children. Boys are affected five times more commonly than girls. Typically seen between the ages of 2 and 14 with a peak around 5-6 years 8

Clinical presentation

The most frequent presenting feature is pain with or without a limp 3,5-6. In 15% of cases both hips are asynchronously involved. 

Radiographic features

The radiographic findings are those of AVN.

Plain film
Early signs
  • joint effusion: widening of the medial joint space
  • asymmetrical femoral epiphyseal size (smaller on affected side)
  • apparent increased density of the femoral head epiphysis
  • blurring of the physeal plate (stage 1: see staging of Legg-Calve-Perthes syndrome)
  • radiolucency of the proximal metaphysis
Late signs

Eventually, the femoral head begins to fragment (stage 2), with subchondral lucency (crescent sign) and redistribution of weight-bearing stresses leading to thickening of some trabeculae which become more prominent.

The typical findings of advanced burnt out (stage 4) Perthes disease are:

  • femoral head deformity with widening and flattening
  • proximal femoral neck deformity: coxa magna

Additionally, tongues of cartilage sometimes extend inferolaterally into the the femoral neck, creating lucencies, which must be distinguished from infection or neoplastic lesions 4. The presence of metaphyseal involvement not only increases the likelihood of femoral neck deformity, but also make early physeal closure with result leg length disparity more likely.

Arthrography

Traditionally arthrography performed under general anaesthesia with conventional fluoroscopy is performed to assess congruency between the femoral head and the acetabulum in a variety of positions 3. MRI is increasingly replacing this, in an effort to eliminate pelvic irradiation.

MRI

MRI is gaining an increasing role in a number of scenarios:

  • early diagnosis, before the onset of x-ray findings, and in designing 
  • assessing extent of cartilaginous involvement, important in prognosis
  • assessing joint congruence in a variety of joint positions (requires open magnet and dynamic imaging) 2

Both arthrography and dynamic MRI asses three main features 3:

  1. deformity for the femoral head (also assessed on static x-rays and MRI)
  2. congruence: how well the femoral head contour matches that of the acetabulum
  3. containment: the amount of lateral subluxation of the flattened femoral head out of the acetabulum
    • when severe this may lead to hinge abduction, whereby rather than rotation and medial movement of the femoral head during hip abduction, the flattened head 'hinges' on the lateral lip of the acetabulum, widening the medial joint space 2-3

Treatment and prognosis

The younger the age at the time of presentation, the more benign disease course is expected and also for same age prognosis is better in boys than girls due to less maturity 5,8. Prognosis is also influenced by the percentage of femoral head involvement and degree of primary deformity of the femoral head and the secondary osteoarthritic changes that ensue. The aim of therapy is to try and maintain good femoroacetabular contact and a round femoral head. 

Bracing may be used in milder cases, although femoral neck and acetabular osteotomies may be required to correct more sever abnormal femoroacetabular malalignment.

In later life, hip replacements may be necessary.

History and etymology

The condition was first described in 1897 by Maydl, with Legg, Calvé and Perthes popularising it in 1910 in separate publications 7.

  • Karel Maydl (1853-1903): Austrian surgeon
  • Aurthur Thornton Legg (1874-1939): American orthopaedic surgeon
  • Jacques Calvé (1875-1954): French orthopaedic surgeon
  • Gerog Clemens Perthes (1869-1927): German surgeon

Differential diagnosis

General imaging differential considerations include:

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