eMedicine Specialties > Radiology > Pediatrics

Legg-Calve-Perthes Disease

Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, Consultant Radiologist, North Manchester General Hospital, The Pennine Acute NHS Trust, Manchester UK
Dare Mutiyu Seriki, MBBS, FRCR, MRCP, Staff Physician, Department of Radiology, Hope Hospital, UK; Charles Edward Hutchinson, MD, FRCR, Senior Lecturer, Department of Diagnostic Radiology, University of Manchester; Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute

Updated: May 28, 2008

Introduction

Background

Legg-Calvé-Perthes (LPD) disease is a childhood hip disorder that results in infarction of the bony epiphysis of the femoral head. LPD represents idiopathic avascular necrosis of the femoral head. The disease is bilateral in 10-20% of patients and usually affects children aged 4-8 years. When both hips are involved, they are usually affected successively, not simultaneously. A family history is present in 6% of patients. In adults, the corresponding condition is termed Chandler disease.

Although the etiology is unclear, certain risk factors have been identified in children, including sex, socioeconomic group, and the presence of an inguinal hernia and genitourinary tract anomalies. More specifically, boys are affected 3 to 5 times more often than girls, and the incidence increases in low socioeconomic groups and in children with low birth weight. Determining the prognosis is important at the time of presentation because more than 50% of patients with LPD do not require treatment.^1,2,3

Legg-Calvé-Perthes disease. Stage II disease. Note the slight widening of the left hip joint representing a small joint effusion (see also Image 1 in Multimedia). Joint widening can also be secondary to hypertrophy of the cartilage.

Legg-Calvé-Perthes disease. Axial nonenhanced CT scan through the hip joints in the same patient as in Image 15 in Multimedia more clearly shows the loss of structural integrity of the right femoral head.

Legg-Calvé-Perthes disease. Coronal T2-weighted MRIs show irregularity and flattening of cortical margins of the left femoral epiphysis. Also note a mild joint effusion and subluxation and hinge deformity of the left femoral head.

Legg-Calvé-Perthes disease. Zoomed images of the same patient as in Image 22 in Multimedia show the photopenic defect more clearly.

Pathophysiology

The primary pathologic abnormality in patients with LPD is osteonecrosis resulting in flattening and collapse of the femoral head. The articular cartilage covering the femoral head is remarkably resistant to ischemia and is usually well preserved. The basic underlying cause of LPD is insufficient blood supply to the femoral head. The epiphyseal plate acts as a barrier to the supply of blood in children aged 4-10 years, and the ligamentum teres vessels become nonfunctional, causing the head to be at risk for osteonecrosis. Healing occurs by revascularization of the necrotic femoral head.

The course of revascularization and reconstitution of the femoral head varies. The ultimate shape of the reconstituted femoral head depends on several factors, including the degree and site of necrosis and the magnitude of forces working across the femoral head. In some patients, the femoral head may return to normal, whereas in other patients, coxa plana and shortening and widening of the femoral head may develop. These changes may be associated with osteoarthrosis and intra-articular loose bodies. In most patients, the changes occurring in LPD affect only 1 hip. With bilateral disease, the changes are rarely symmetric.

Frequency

United States

The frequency in the United States is similar to the worldwide frequency.

International

Approximately 1 in 1200 children younger than 15 years is affected.

Mortality/Morbidity

The diagnosis of LPD must be made as early as possible; patients who present after the age of 8 years have a poor prognosis. The prognosis for girls is worse than that for boys, and girls usually have a more severe form of the disease.

The prognosis for patients in whom the onset of LPD occurs before the age of 6 years is favorable, with 80% having a good result; however, in children between 4 years of age and 5 years, 11 months of age who have lateral pillar involvement of classification B/C or C, the prognosis is less favorable.⁴

Race

LPD rarely occurs in blacks.

Sex

The male-to-female ratio is 3-5:1.

Age

Patients with LPD are typically aged 2-12 years. The mean patient age at presentation is 7 years.⁵

Anatomy

The femoral head is spherical and is covered by articular cartilage. The fovea is a just-off-center ovoid depression that serves as an attachment for the ligamentum teres (round ligament). The femoral head is supplied by a vascular ring at the base of the femoral neck from branches arising from the lateral and medial circumflex arteries. The superior and inferior gluteals contribute to the blood supply to a lesser extent. The anterior aspect of the vascular ring is within the joint capsule. Principally, the lateral epiphyseal arteries supply the femoral neck. The artery in the ligamentum teres supplies one third of the arterial supply to the femoral head in children but makes only a small contribution in adults.

Presentation

LPD is a dynamic condition. Results of the physical examination depend on the stage of the disease at the time of presentation. The child often has a limp with groin, thigh, or knee pain. Children who present with knee pain must be carefully examined for hip pathology. As the disease progresses, flexion and adduction contractures may develop, and lateral overgrowth of the femoral head cartilage may cause loss of abduction. Attempts at abduction lead to hinging and possible subluxation of the femoral head. Eventually, the hip may move in only the flexion-extension plane. Progressive loss of movement, adduction contractures, flexion with abduction, and obesity are poor prognostic signs. Lateral subluxation of the femoral head is also associated with a poor outcome.

Several staging schema are used to determine severity of disease and prognosis; these include the Catterall, Salter-Thomson, and Herring systems.⁶

The Catterall classification is based on radiographic appearances and specifies 4 groups during the period of greatest bone loss.

Catterall staging is as follows:

Stage I — Histologic and clinical diagnosis without radiographic findings
Stage II — Sclerosis with or without cystic changes with preservation of the contour and surface of femoral head
Stage III — Loss of structural integrity of the femoral head
Stage IV — Loss of structural integrity of the acetabulum in addition

The Salter-Thomson classification simplifies the Catterall classifications by reducing the groups to 2. The first, called group A, includes Catterall groups I and II; for patients in this group, less than 50% of the head is involved. The second, called group B, includes Catterall groups III and IV; for patients in this group, more than 50% of the head is involved. For both classifications, if less than 50% of the ball is involved, the prognosis is better, whereas if more than 50% is involved, the prognosis is potentially poor.

The Herring classification addresses the integrity of the lateral pillar of the head. In lateral pillar group A, there is no loss of height in the lateral one third of the head, and there is little density change. In lateral pillar group B, there is a lucency and less than 50% loss of lateral height. Sometimes, the head is beginning to extrude from the socket. In lateral pillar group C, there is more than 50% loss of lateral height.

Preferred Examination

Plain radiography remains the major modality for the evaluation of LPD. Staging of the disease is based on plain radiographic findings.^1,7,8

Scintigraphy is a useful technique in early disease when plain radiographic findings may be normal; with scintigraphy, abnormalities become apparent earlier in the course of disease than they do with plain radiography.

CT scans allow early diagnosis of bone collapse and curvilinear zones of sclerosis early in the disease process when plain radiography is less sensitive. CT scans can also demonstrate subtle changes in the bone trabecular pattern.

Ultrasonography is useful in the preliminary diagnosis of transient synovitis of the hip and the onset of LPD.⁹ Hip effusion with capsular distention is well depicted on sonographic images.^{10,11,12,13,14}

MRI is as sensitive as isotopic bone scanning and allows more precise localization of involvement than conventional radiography.^{15,16,17,18,19,20}

Angiography, venography, and arthrography have limited roles in the diagnosis of LPD.

Limitations of Techniques

Plain radiographic findings may be entirely normal in early symptomatic disease.

Although abnormalities become apparent with scintigraphy earlier in the course of disease than they do with radiography, abnormal scintigraphic findings are nonspecific; findings may be positive in patients with trauma, synovitis, and infections.

CT scans allow the early diagnosis of bone collapse, but the use of CT is limited by the comparatively higher radiation dose.

Ultrasonography is useful in the preliminary diagnosis of transient synovitis of the hip and the onset of LPD, but the diagnosis is based on a demonstration of hip effusion, which is a nonspecific finding.

MRI is as sensitive as isotope bone scans and allows more precise localization of involvement than conventional radiography, but the changes seen as bone marrow edema and joint effusions are nonspecific.

Angiography, venography, and arthrography are invasive procedures and do not provide significantly better clinical information for guiding therapeutic options.

Differential Diagnoses

Eosinophilic Granuloma, Skeletal
Septic Arthritis
Sickle Cell Anemia, Skeletal

Radiography

Findings

Legg-Calvé-Perthes disease. Stage II disease. Note the slight widening of the left hip joint, representing a small joint effusion (see also Image 2 in Multimedia). Joint widening can also be secondary to hypertrophy of the cartilage.

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 (see also Image 6 in Multimedia).

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 (see also Image 10 in Multimedia).

Legg-Calvé-Perthes disease. Image shows loss of structural integrity of the left femoral head. Also note the widening and shortening of the femoral neck, and more importantly, the severe subluxation.

Legg-Calvé-Perthes disease. Plain radiograph in an adult patient with residual coxa magna and plana deformity with superimposed joint changes (compare with the CT scans in Images 16-18 in Multimedia).

Early signs on radiographs include the following (see Images above and Images 1-15, 24 in Multimedia)⁷:

Small femoral epiphysis (96%)
Sclerosis of the femoral head with sequestration and collapse (82%)
Slight widening of the joint space caused by thickening of the cartilage, failure of epiphyseal growth, the presence of joint fluid, or joint laxity (60%)
An absence of destruction of the articular cortex, as occurs in bacterial arthritis (destruction of articular cartilage never occurs in LPD)

Late signs on radiographs include the following:

Delayed osseous maturation of a mild degree, a radiolucent crescent line representing a subchondral fracture
Femoral head fragmentation and femoral neck cysts from intramedullary hemorrhage or extension of physeal cartilage into metaphysis, loose bodies, and coxa plana
Coxa magna, or remodeling of the femoral head, which becomes wider and flatter, similar in appearance to a mushroom

Degree of Confidence

Plain radiographs have a sensitivity of 97% and a specificity of 78% in the detection of LPD.

False Positives/Negatives

Severe osteoarthritis and infective arthritis may mimic LPD.