Practice Essentials
Legg-Calvé-Perthes disease is the eponym given to idiopathic osteonecrosis of the femoral head resulting from compromise of the tenuous blood supply to this area. [1] It was described approximately 100 years ago as a unique disease entity affecting the pediatric population. [2] Legg-Calvé-Perthes disease may result in femoral head deformity and degenerative joint disease. The femoral head may be distorted permanently. The younger the age of onset of Legg-Calvé-Perthes disease, the better the prognosis. Children older than 10 years have a very high risk of developing osteoarthritis. Most patients have a favorable outcome. Prognosis is proportional to the degree of radiologic involvement. [3, 4, 5, 6, 7]
The exact etiology of Legg-Calvé-Perthes disease remains unclear, but it is likely multifactorial and may include genetic predisposition, environmental exposures, and/or socioeconomic factors. [8] Some specific suggested causes include trauma, an inflammatory process, a disorder of the epiphyseal cartilage, abnormalities in the vasculature, [9] increased blood viscosity such as thrombophilia, abnormalities in growth hormone, maternal smoking, and second-hand smoke exposure. [8, 10]
Pathophysiology
The pathophysiology and temporal sequence of events in Legg-Calvé-Perthes disease remains unclear; however, the following scenario is generally accepted:
The blood supply to the femoral head is interrupted. [11]
Bone infarction and necrosis affects the articular cartilage, subchondral bone, and the bony epiphysis. [10]
Revascularization occurs and new bone ossification starts. In some cases, patients may have normal bone growth and development.
With progression of the disease, bone resorption, delayed bone formation, and subchondral fracture occurs. This microdamage is usually the result of normal physical activity, not direct trauma.
This may result in deformities in the femoral head, epiphyseal growth plate, and possible lesions in the metaphysis. [10]
Epidemiology
One in 1200 children younger than 15 years are affected by Legg-Calvé-Perthes disease; however, the incidence varies among demographic groups, with a reported range of 0.4-29 per 100,000 children. [12] A British study reported an incidence of 2.8 per 100,000 persons aged 14 years or younger. [12]
Legg-Calvé-Perthes disease is most commonly seen in persons aged 3-12 years, with a median age of 7 years. The disease is familial approximately 10% of the time. [13]
Legg-Calvé-Perthes disease is a self-limited disease if not treated. Outcome varies widely. In 10-24% of patients with Legg-Calvé-Perthes disease, involvement is bilateral. [1]
Whites are affected more frequently than persons of other races. Males are affected 4-5 times more often than females.
In a study of girls with Legg-Calvé-Perthes disease, of the 451 patients who presented at a single large urban children's hospital with a diagnosis of Legg-Calvé-Perthes disease, 82 (18.2%) were female. The average age at presentation for girls was 6.58 years. [14]
In a cross-sectional retrospective analysis of US pediatric hospitalizations for the surgical management of Legg-Calvé-Perthes disease (LCPD) using the Kids' Inpatient Database, LaGreca et al found that the rate of hospital admissions for LCPD surgery has continued to decrease since 2000. The decrease in admissions was noted as being significant for all age groups. [15]
Signs and symptoms
Symptoms of Legg-Calvé-Perthes disease usually have been present for weeks, because the child often does not complain. Radiographs of the hip should always be considered for a child complaining of thigh or knee pain.
History may reveal the following:
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Hip or groin pain, which may be referred to the thigh
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Mild or intermittent pain in anterior thigh or knee
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Limp
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Usually no history of trauma
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Progressively increased pain with physical activity, usually relieved by rest. [13]
Physical examination findings and symptoms may include the following:
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Decreased range of motion (ROM), particularly with internal rotation and abduction
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Painful gait
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Muscle spasm
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Limp
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Leg length inequality due to collapse of the femoral head
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Thigh, calf, and buttocks muscle atrophy: Circumferences on the involved side may be smaller than on the unaffected side, secondary to disuse.
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Short stature, resulting from deformity of the femoral head.
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Roll test: With patient lying in the supine position, the examiner rolls the hip of the affected extremity into external and internal rotation. This test should invoke guarding or spasm, especially with internal rotation.
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Trendelenburg sign: While standing, the patient lifts one leg up at a time; because of muscle weakness on the affected side, the pelvis drops to the opposite side. [13]
Diagnosis
Plain radiographs of the hip, including anteroposterior and frog-leg views, are the preferred diagnostic tests.
When the diagnosis of Legg-Calvé-Perthes disease is unclear, initial laboratory studies can aid in ruling out other diagnoses. CBC count, erythrocyte sedimentation rate, and C- reactive protein evaluation may be helpful to evaluate for suspected infection.
Hip aspiration with fluid analysis can be performed if a septic joint is suspected.
Multiple radiographic classification systems exist, based on the extent of abnormality of the capital femoral epiphysis. Waldenstrom, Catterall, Salter and Thompson, and Herring are the 4 most common classification systems. [4, 6, 16, 17, 18, 19, 20, 21, 22]
The Herring classification is generally determined at the beginning of the fragmentation stage radiographically, about 6 months after presentation of initial symptoms. It is based on the height of the lateral pillar on the anteroposterior radiograph, with classifications as follows [23, 24] :
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Group A: The lateral pillar is at full height with no density changes. This group has a consistently good prognosis.
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Group B: The lateral pillar maintains greater than 50% height. There will be a poor outcome if the bone age is greater than 6.
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Group C: Less than 50% of the lateral pillar height is maintained. All patients will experience a poor outcome.
Treatment
Legg-Calvé-Perthes disease does not require emergent inpatient care. The focus should be on administering appropriate analgesic medication. Bed rest and abduction stretching exercises are recommended. Nonsurgical containment allows the femoral head to stay within the acetabulum, where it can be molded. Various casts, braces, and crutches are used for containment.
In a meta-analysis by Adulkasem et al of the treatments for Legg-Calvé-Perthes disease, combined osteotomy was found to be the most effective modality, followed by femoral varus osteotomy and then Salter innominate osteotomy. [25]
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Legg-Calvé-Perthes disease. Image shows subchondral sclerosis and radiolucency in the left femoral head (stage II disease). The femoral head is slightly smaller on the left than the right.
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Legg-Calvé-Perthes disease. The left subchondral radiolucency is more readily demonstrated on a frog-leg view and represents subchondral fracture.
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Legg-Calvé-Perthes disease. Image shows left femoral subchondral sclerosis and radiolucency.
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Legg-Calvé-Perthes disease. Image shows left femoral subchondral sclerosis and radiolucency.
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Legg-Calvé-Perthes disease. Image shows flattening and early fragmentation of the left femoral head with the presence of femoral neck cysts. The femoral head is obviously smaller on the left than on the right.
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Legg-Calvé-Perthes disease. Image shows loss of structural integrity of the right femoral head. Also note lateral extrusion of the right femoral head.
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Legg-Calvé-Perthes disease. Coronal T1-weighted image demonstrates irregularity and distortion of the right femoral head in this 7-year-old child with known Legg-Calvé-Perthes disease. Image courtesy of Radiopaedia.org, contributed by Dr. Roberto Schubert, published at http://radiopaedia.org/cases/legg-calve-perthes-disease-4.
