Treatment in Perthes disease is largely related to symptom control, particularly in the early phase of the disease. In the later stages of the disease, there may be increased uptake reflecting a combination of repair of the femoral head and degenerative change in the femoral head and acetabulum 15. 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 2,3īone scan may show reduced uptake in the femoral head in the early stages of the disease, representing the reduced blood supply of osteonecrosis.containment: the amount of lateral subluxation of the flattened femoral head out of the acetabulum.congruence: how well the femoral head contour matches that of the acetabulum.deformity of the femoral head (also assessed on static x-rays and MRI).assessing joint congruence in a variety of joint positions (requires open magnet and dynamic imaging) 2īoth arthrography and dynamic MRI assess three main features 3:.assessing the extent of cartilaginous involvement, important in prognosis.early diagnosis, before the onset of x-ray findings.MRI is gaining an increasing role in a number of scenarios: MRI is increasingly replacing this, in an effort to eliminate pelvic irradiation. Traditionally arthrography performed under general anesthesia with conventional fluoroscopy is performed to assess congruence between the femoral head and the acetabulum in a variety of positions 3. The presence of metaphyseal involvement not only increases the likelihood of femoral neck deformity but also makes early physeal closure with resulting leg length disparity more likely. " sagging rope sign" (thin sclerotic line running across the femoral neck)Īdditionally, tongues of cartilage sometimes extend inferolaterally into the femoral neck, creating lucencies, which must be distinguished from infection or neoplastic lesions 4.proximal femoral neck deformity: coxa magna.femoral head deformity with widening and flattening ( coxa plana).The typical findings of advanced burnt out ( stage 4) Perthes disease are: radiolucency of the proximal metaphysisĮventually, 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.blurring of the physeal plate ( stage 1).apparent increased density of the femoral head epiphysis.asymmetrical femoral epiphyseal size (smaller on the affected side).joint effusion: widening of the medial joint space.established: reduction in epiphysis size, lucencyĪs changes progress, the width of the femoral neck increases ( coxa magna) in order to increase weight-bearing support.early: there may be no appreciable change.The radiographic changes to the femoral epiphyses depend on the severity of osteonecrosis and the amount of time that there has been an alteration of blood supply: healed stage deformity: osteoarthritis risk.Herring classification: lateral pillar involvement.Salter-Thompson classification: extent of femoral head involvement.Catterall classification: extent of femoral head involvement.The radiographic findings are those of osteonecrosis. There are separate systems for staging of Perthes disease:
The investigation of atraumatic limp will often include a hip ultrasound to look for effusion, but ultrasound is unlikely to pick up osteonecrosis. In a small number of patients with Perthes, the radiograph will be normal and persistent symptoms will trigger further imaging, e.g. The best initial test for the diagnosis of Perthes is a pelvic radiograph. In approximately 15% of cases, osteonecrosis occurs bilaterally. Osteonecrosis generally occurs secondary to the abnormal or damaged blood supply to the femoral epiphysis, leading to fragmentation, bone loss, and eventual structural collapse of the femoral head.
The specific cause of osteonecrosis in Perthes disease is unclear.
It is important to be certain that there is no other cause of osteonecrosis (e.g. This may precipitate the presentation or the realization of symptoms that in fact had been long-standing.īlood tests are typically normal in Perthes. Some children have a coincidental history of trauma. Most children present with atraumatic hip pain or limp 3,5,6. Perthes is considered an idiopathic condition, and there are no clear predisposing factors. Presentation is typically at a younger age than slipped upper femoral epiphysis (SUFE) with peak presentation at 5-6 years, but confidence intervals are as wide as 2-14 years 8. Perthes disease is relatively uncommon and in Western populations has an incidence approaching 5 to 15:100,000.īoys are five times more likely to be affected than girls.
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