Perthes’ disease, also known as Legg-Calve-Perthes’ disease was described by Legg, an American, Calve, a Frenchman, and Perthes, a German at around 1910. It is characterized by loss of circulation to the head of the femur (the ball of the hip) in a growing child resulting in avascular necrosis (death of bone cells in the head of the femur). This is typically followed by revascularization over a period of 18 to 24 months. During the period of revascularization, the bone is soft and liable to fracture under pressure, causing collapse of the head of the femur. Over time, the head of the femur heals and remodels in the collapsed position, resulting in a nonspherical shape. This leads to stiffness and pain.

Various theories have been advanced regarding the cause of Perthes’ disease, but no one knows for sure why there should be a loss of circulation to the head of the femur. We know that in cases of fracture of the neck of the femur where the circulation to the head is cut off, the head of the femur undergoes avascular necrosis, changes similar to those seen in Perthes’ disease. However, in Perthes’ diesease, there is no history of trauma.

We know that it occurs more frequently in boys than girls, from age 3 to 8. Many of these boys tend to be shorter than their peer, suggesting some delay in bone growth and maturation. Could it be that the delay in bone development in the head of the femur somehow causes compression to the arteries that supply it?

The symptoms a child with Perthes’ disease presents depends on the stage of the disease.

In the ischaemia stage, the child may present with an acutely painful hip, due to inflammation of the synovial lining of the joint, or synovitis. He may have a painful limp that developed suddenly over hours.

More frequently, the child presents because of the fracture of the head of the femur that occurs during the stage of revascularization, The child may present with a painful limp that occurred over days or weeks.

Not uncommonly, the patient may go through the whole process of ischaemia with avascular necrosis, revascularization, fracture and collapse, repair and remodelling with no significant symptoms. He may present to the doctor only as a young adult due to pain of degenerative arthritis in the hip, resulting from the Perthes’ disease in childhood.

Perthes’ disease is not preventable, since no one knows what causes it. But there are things one can do to prevent or minimize collapse of the head of the femur. This is discussed in the next section.

When a child presents with acute pain in the hip with a limp, an X-ray is usually taken. In the ischaemia stage, the X-rays may be perfectly normal. The doctor will order blood tests to rule out infection and other acute problems. If necessary, a radionuclide (Technetium) bone scan could be done to confirm the diagnosis.

In the later stages of fracture and collapse, X-ray changes will be quite diagnostic. However, there are some diseases that have X-ray appearances in the hips that mimic Perthes’ disease, including Hypothydroidism (lack of thyroid hormone) and Epiphyseal dysplasia (disease of the growth plates of the body). The doctor may perform other X-rays, and check on the thyroid level in the blood to rule out these conditions.

Once the diagnosis of Perthes’ disease is confirmed, a decision has to be made whether to institute active treatment, and if so, what kind of treatment.

The natural history of Perthes’ disease is such that many children have a good outcome without any active treatment. In the absence of any foolproof test to distinguish those that need treatment from those that do not, the doctor often finds himself in a dilemma. From the little that we know about the disease, there are certain factors that need to be considered when deciding treatment.

1. If the onset of the disease is before age 4, results tend to be good, with or without treatment. The older the child at the onset of disease, the less favorable the result.
2. Is there hip stiffness? If the doctor discovers stiffness on examination, especially tight hip adductors (where the leg cannot be brought out away from the midline), the results are not favorable. In these instances, the patient is usually admitted and placed on traction and physical therapy to relieve the tightness. Sometimes, surgery (hip adductor release) is performed to correct the tightness.
3. Do X-rays of the hips show partial or total head involvement? If the whole head of the femur is involved, the prognosis is less favorable. If only part of the head is involved, and the lateral part of the head is not involved, risk of collapse is much less, and long-term results tend to be better. If X-rays show that the head is well-contained in the acetabulum, results tend to be good. If the head is too large for the acetabulum, or if part of the head extrudes from under the cup, results tend to be poor.

In the past, children with Perthes’ disease were treated with non-weight bearing. They were placed on prolonged bed-rest and cructches, since the thinking was that weight bearing causes the head collapse. This thinking is no longer valid. The contemporary concept is "containment" of the head in the acetabulum, which can be achieved by use of casting and bracing, or surgery. Examples of casting and bracing are the Petrie cast and the Scottish-Rite (Atlanta) brace. These are usually worn for a period of 18 to 24 months. Femoral osteotomy involves cutting the femur just below the hip, and redirecting the head into the acetabulum. The osteotomy is stabilized with surgical hardware, usually plate and screws. Pelvic osteotomy involves cutting the pelvic bone adjacent to the acetabulum, and redirecting the acetabulum to contain the head.

If the head of the femur can be maintained in the acetabulum during the active disease process, and the shape maintained spherical, prognosis is excellent. This tends to happen in children where the onset is before age 4, and where range of motion of the hip is maintained.

If the head of the femur cannot be contained in the acetabulum, and the head flattens, prognosis tends to be less favorable. This tends to happen in older children, with total head involvement, and hip stiffness.

Statistically speaking, 60 to 70% of children with Perthes’ disease do well with no long term disability. With treatment, results are marginally better. Does it mean we should abandon treatment for Perthes’ disease? This is where the controversy remains. Each patient needs to be evaluated individually. Pros and cons of treatment versus non-treatment, and bracing versus surgery need to be considered carefully by the doctor and the parents. Together, a rational approach to the treatment of their child could then be instituted.