Perthes disease (also called Legg-Calve-Perthes) affects the child’s hip and destroys part of the femoral head.1 The body can completely regenerate this bone or do it only partially and cause a permanent deformity.
It occurs in children between 3 and 12 years and appears more frequently in boys (80%) than in girls (20%). In most cases, it affects only one hip, but in 10% of patients the lesion occurs on both sides, although in these cases it usually does not appear simultaneously.
How Is Perthes Disease Diagnosed?
Laboratory tests for Perthes disease show no appreciable changes, the blood count is usually normal and there can only be a discrete increase in the rate of sedimentation and C-reactive protein.
Conventional Radiology: Radiographic images are the most common method to start the study of a painful hip or pelvis, on suspicion of Perthes disease or another nosological entity, as it is a simple method to achieve, cheap and relatively easy to interpret.2
With the clinical and radiological suspicion of Perthes disease, the study should be completed with more complex examinations that a specialist in orthopedics should request, since they are outside the scope of primary care. These will allow establishing a therapeutic strategy. Among these techniques are the following:
Ultrasound: Useful in the initial assessment of the process and to assess whether or not there is synovitis.
Gammagraphy with technetium-99: It allows an early diagnosis of Perthes disease before radiological changes appear. It is also able to assess the degree of revascularization of the femoral head during the evolutionary process.
Magnetic resonance: Like scintigraphy, it allows early diagnosis of the process, that is, before conventional radiography shows alterations, with the advantage that it provides important information about the shape of the head and the acetabulum and the degree of congruence between them.
Arthrography: It is very useful for visualization of the contour of the femoral head and especially its relation to the acetabulum.3 It allows the orthopedic surgeon to establish the surgical strategy. It’s main indication is in the diagnosis and assessment of the hip “in a hinge.”
Computed tomography – It is not used systematically, although it may be useful in the study of the extent of bone involvement and the three-dimensional structure of the hip.
With a well-performed medical history, a careful physical examination and hip x-rays are usually sufficient to establish an initial diagnosis of Perthes disease in primary care.
However, in the initial phase of the Perthes disease, the differential diagnosis should be made with hip synovitis and septic arthritis in which the initial symptoms are usually very similar.
Normally Perthes disease is not related to falls or bumps in the hip, although it is common for parents to have a problem in their hips or that children take corticosteroid medication for other diseases, are obese or have had a period of rapid growth.
For some reason that doctors do not know, there is not enough blood flowing to the femoral head in Perthes disease. When this happens, some parts of the bone die (this is called necrosis) becoming more fragile and allowing the femoral head to be crushed.
The body will try to eliminate the dead bone and initiate a process of regeneration in the femoral head. The whole process can last several years during which there may be inflammation and consequently pain or lameness. According to the capacity of regeneration of the body, the femoral head will recover or not fully recover its spherical shape.
Usually, the child with Perthes disease refers little or no pain. If there is pain, it usually manifests at the level of the groin but is often referred to in the thigh or knee.
It is frequent, however, that parents notice certain lameness, especially in the afternoon or night, when the child with Perthes disease is tired.
Finally, there may be a decrease in hip mobility with discrete limitation to perform some activities. In these cases, some atrophy of the thigh muscles may even appear.
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