Legg-Calve-Perthes disease, commonly known as Perthes disease, is a hip disorder affecting children that is caused by decreased blood flow to the head of the femur. This results in osteonecrosis (also known as “avascular necrosis”) of the proximal femoral epiphysis (femoral head), with resorption, re-ossification and remodeling of the bone. Especially in children under the age of 6, Perthes disease may resolve without sequelae; in older children, however, the bone may fail to remodel to a normal shape leading to disruption of the articular surface and degenerative joint disease later in life.
Structure and Function
The blood supply to the femoral head is made up of three arteries: the medial and lateral femoral circumflex arteries, and the artery of ligamentum teres.
In Legg-Calve-Perthes disease, the blood supply is disrupted by an unknown process, and the bone cells begin to die. This process is termed osteonecrosis.
Loss of blood supply to bone results in ischemia and tissue death. In the regions of ischemia and tissue death, there can be an overall weakening collapse. With time, new blood supply reaches the femoral head, and necrotic bone is removed, resulting in fragmentation and re-ossification.
Notably, and in contrast to the adult form of idiopathic osteonecrosis, Perthes disease in younger children may resolve without sequelae. That is, the bone may remodel to a fairly normal shape and no lingering symptoms. On the other hand, the regenerated bone may remodel to a non-spherical shape producing an abnormal range of motion, an irregular articular surface, and, ultimately, degenerative joint disease of the hip.
Perthes disease begins with a disruption of the blood supply to the head of the femur, which then leads to necrosis, or death, of the tissue.
The exact cause of the disruption of the blood supply is not known, although it is believed to be multifactorial. Some of the factors which have been proposed include hereditary or genetic, predisposing trauma, coagulopathy, collagenopathy, hyperactivity, and passive smoking exposure. These various factors have an association or higher prevalence in patients with Perthes, and are therefore thought to possibly have a causative role.
Another theory links systemic delay in growth and development to the development of Perthes. Delayed bone age has been seen among patients with Legg-Calve-Perthes disease, and therefore, the IGF-pathway has been implicated as a possible cause.
The most common age of presentation for Perthes is about 8 years of age, though patients may be as young as 2 or as old as 12. (Above the age of 12, the condition is more akin to adult osteonecrosis.)
Children with Legg-Calve-Perthes disease typically present with a limp which worsens with activity or at the end of the day, with decreased range of motion. They may experience pain which radiates into the groin, proximal thigh, or knee. There is loss of passive hip rotation on physical exam.
A history of trauma to the painful extremity is sometimes present. Children may often conceal their limp, or not complain of it, but parents or caretakers will notice it. In some cases, the child presents due to an unrelated trauma to the affected limb, and the disease is found incidentally.
The limp that children with Legg-Calve-Perthes disease exhibit is an abductor limp, in which they avoid abduction or internal rotation of the leg.
Additionally, the leg on the affected side may be smaller in size than the contralateral leg due to muscle atrophy.
The definitive diagnosis of Perthes disease is made by x-ray. The disease is primarily classified by radiographic findings, using the Waldenstrom classification. The four stages of Perthes (Figure 1-4) are denoted as initial, fragmentation, reossification, and healed.
In the initial stage, the osteonecrosis process begins. The x-rays may show a dense appearance with flattening of the femoral head joint space widening. There may be only mild symptoms in this stage; parents may notice an altered gait or mild limp.
The fragmentation stage is characterized by revascularization and bone resorption producing collapse. Hip symptoms are most prevalent in this stage, which may present a year or longer.
In the re-ossification stage, new bone appears as the necrotic bone is resorbed. This is the longest stage, and may persist for two years or more.
In the final stage, the femoral head completes its remodeling, with symptoms dependent on the final shape of the femoral head. This stage is labeled the “healed” stage, though that is something of a misnomer: the term refers to the state of the bone’s response and not the state of the hip joint overall. That is, the osteonecrosis process may have abated and the fragmented areas have reconsolidated but unless the shape of the bone has been restored to normal - and it does not necessary do this - symptoms may persist or later degenerative changes may appear.
On x-ray, the femoral head is typically lateralized and more radiodense, and in later stages of disease the femoral head appears flattened.
Other radiographic findings can include changes in the shape of the acetabulum, or the socket of the hip joint.
Another option for imaging is MRI, which has an increase diagnostic accuracy compared to X-ray. Scintigraphy is a method which uses Technetium scanning and can be helpful for diagnosis in the earliest stages of disease.
Laboratory findings are used in the diagnosis of Legg-Calve-Perthes disease primarily to rule out other diseases or illnesses. All laboratory values are typically within normal limits.
Legg-Calve-Perthes disease is a relatively rare disease, with a prevalence of approximately 1 in 10,000 children, but can have devastating long-term consequences on the child’s mobility and quality of life.
The age of onset of Legg-Calve-Perthes disease is most commonly between 4 and 8 years old. In general, it occurs in children under the age of 15 years old. Boys are more commonly affected, with a ratio of male to female of approximately 5:1. In about 10% of all cases, both hips are affected.
Legg-Calve-Perthes disease is more common in children of central European decent, and less common in East Asian and African American populations.
As Perthes is an idiopathic (cause-unknown) disease, the diagnosis can be made only once all other known causes of osteonecrosis have been ruled out. These include hemoglobinopathies, like sickle cell disease or thalassemia, leukemia, lymphoma, idiopathic thrombocytopenic purpura, or hemophilia. Secondary causes of osteonecrosis such as a history of corticosteroid use, traumatic dislocation, septic arthritis, or untreated developmental dysplasia of the hip should be ruled out as well.
Other diseases that cause epiphyseal dysplasia can be mistaken for Perthes, such as multiple epiphyseal dysplasia or spondyloepiphyseal dysplasia. However, these conditions are typically synchronous and symmetric in appearance unlike Perthes. In younger children, Meyer’s dysplasia should be considered as well.
The presence of bilateral osteonecrosis is suggestive of other disease processes, such as multiple epiphyseal dysaplasia. A child with a limp also can be the presentation for septic hip arthritis, or a slipped capital femoral epiphysis, both which should be promptly diagnosed. Additionally, symptoms such as fever, anemia, or leukocytosis should not be missed as these can be clues in ruling out other important conditions.
Treatment Options and Outcomes
Treatment of Legg-Calve-Perthes disease is guided primarily by the stage of disease (itself usually correlated with patient’s age).
The main goal of treatment is maintaining range of motion and containment of the femoral head within the acetabulum. By achieving these goals, one can prevent or minimize deformity of the joint, and achieve greater long-term function.
“Containment” minimizes loss of sphericity as the bone remodels. Containment can be achieved either operatively or non-operatively.
The primary method of treating Perthes is non-operative management consisting of off-loading the hip when it is soft in the fragmentation phase (non-weight-bearing). Motion is maintained by daily exercises at home or with physical therapy. Containment can be achieved with the use of an abduction brace or cast (Figure 5).
In some cases, operative treatment is needed to promote motion with soft tissue releases, or to improve containment with an osteotomy (Figure 6).
Overall, the long-term prognosis for children with Perthes is good; most children are able to return to daily activities without symptoms or limitations.
The most important predictors of long-term prognosis are age at time of diagnosis and the eventual shape and congruity of the femoral head within the acetabulum. Younger patients typically do better, and more spherically-shaped heads and greater degree of congruity of the head within the hip joint portend better outcomes long-term.
Risk Factors and Prevention
A few proposed risk factors include passive exposure to smoke and hyperactivity, although there is no known causality between these risk factors and development of Legg-Calve-Perthes disease.
Although the exact cause of Perthes disease is unknown, many environmental and holistic risk factors have been proposed. One association has been noted between Perthes and attention deficit-hyperactivity disorder. Additional investigation is also being carried out regarding the roles of nutrition and the susceptibility of children to Perthes.
Perthes disease was first described by Henning Waldenstrom. (Dr. Waldenstrom believed the condition was a variant of tuberculosis. The disease is named after the three physicians who independently found that it was not related to tuberculosis: Arthur Legg, Jacques Calve, and Georg Perthes.) Legg-Calve-Perthes disease thus follows “Stigler's Law of Eponymy,” which asserts that no scientific discovery is named after its original discoverer. (Indeed, although the law was named by Stephen Stigler, it discovered by the sociologist Robert K. Merton.) Note that Henning Waldenstrom was not the discoverer of the eponymous Waldenstrom’s Macroglobulinemia; that was Jan G. Waldenstrom, his son. In keeping with Stigler’s Law, we should perhaps mentally misattribute the blood disorder to Dr. Waldenstrom senior.
Osteonecrosis (Avascular necrosis), Bone remodeling
Be able to complete a history and physical exam of the hip in a child. Interpretation an x-ray of Perthes.
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