Legg-Calve-Perthes Disease

Rapid growth occurs in relation to development of the blood supply of the secondary ossification centers in the epiphyses, causing interruption of adequate blood flow and making these areas prone to AVN. Interruption of the blood supply to the bone results in necrosis, removal of the necrotic tissue, and its replacement with new bone.

Bone replacement may be so complete and perfect that completely normal bone may result. The adequacy of bone replacement depends on the age of the patient, the presence of associated infection, the congruity of the involved joint, and other mechanical and physiologic factors. Necrosis may occur after trauma or infection, but idiopathic lesions can develop during periods of rapid growth of the epiphyses.

The cause is not known, but children with LCPD have delayed bone age, disproportionate growth, and a mildly shortened stature. LCPD may be idiopathic, or it may result from a slipped capital femoral epiphysis, trauma, steroid use, sickle-cell crisis, toxic synovitis, or congenital dislocation of the hip.

LCPD usually occurs in children aged 4-10 years (mean age, 7 years). It occurs more commonly in boys than in girls (male-to-female ratio, 4:1). The condition is rare, occurring in approximately 4 of 100,000 children. A British study reported an incidence of 2.8 per 100,000 persons aged 14 years or younger.[2]

A population-based design study demonstrated that patients with a history of LCPD seem to have a higher risk of severe injury than those without the disease. This risk may be due to a tendency for more hyperactive behavior among LCPD patients, especially females.[3]

The prognosis for patients with LCPD can be good; it depends on the completeness of involvement of the epiphyseal center. The severity of involvement of the femoral head, its subsequent healing, and proper joint space preservation all help determine when and to what degree an athlete will be able to participate in sports. The functional result depends on the amount of deformity that develops when the structure is softened. Overall, the prognosis for recovery and sports participation after treatment is very good for most individuals.

The short-term prognosis is related to femoral head deformity at the completion of the healing stage. Risk factors include the following:

• Clinical onset at an older age
• Extensive femoral epiphyseal involvement
• Femoral head containment
• Reduced range of motion in the hip
• Premature closure of the growth plate

The long-term prognosis is related to the potential for osteoarthritis of the hip as an adult.[4]  It is worse for patients with metaphyseal defects, those in whom the disease develops late in childhood (age ≥10 years), and those who have more complex involvement of the femoral head with residual deformity; degenerative arthritis occurs in nearly 100% of these patients. This rate is in comparison to patients who are younger than 5 years when the problem develops; the incidence of degenerative arthritis is negligible in this younger population.

The results of one small retrospective study found that total hip replacement can be considered a possible option for patients who had LCPD in childhood. Alhough a high rate of neurologic complications was noted, these were possibly related to inadequate soft-tissue release or excessive limb-lengthening.[5]

The earliest sign of Legg-Calvé-Perthes disease (LCPD) is an intermittent limp (abductor lurch), especially after exertion, with mild or intermittent pain in the anterior part of the thigh. LCPD is the most common cause of a limp in the 4- to 10-year-old age group, and the classic presentation has been described as a painless limp. The patient may present with limited range of motion of the affected extremity. The most common symptom is persistent pain.

Hip pain may develop and is a result of necrosis of the involved bone. This pain may be referred to the medial aspect of the ipsilateral knee or to the lateral thigh. The quadriceps muscles and adjacent thigh soft tissues may atrophy, and the hip may develop adduction flexion contracture. The patient may have an antalgic gait with limited hip motion.

Pain may be present with passive range of motion and limited hip movement, especially internal rotation and abduction. Children with LCPD can have a Trendelenburg gait resulting from pain in the gluteus medius.

Laboratory studies and radiography may supplement medical history-taking and physical examination in the assessment of a child with a limp.[6]

Differential diagnoses include osteomyelitis, pyogenic arthritis, transient synovitis, abscess of the psoas muscle, juvenile rheumatoid arthritis, hemophilia, slipped capital femoral epiphysis, infection, and neoplasm.

Recommended studies include a complete blood count (CBC) with differential and measurement of the erythrocyte sedimentation rate (ESR); however, findings may be normal.

Obtain hip radiographs, including anteroposterior and frog-leg lateral views of the pelvis, to establish the diagnosis.[6, 7] (See the images below.)

Initial radiographs can be normal, but radiographic changes can be divided into five distinct stages representing a continuum of the disease process, as follows:

• Stage 1 - Cessation of femoral epiphyseal growth
• Stage 2 - Subchondral fracture
• Stage 3 - Resorption
• Stage 4 - Reossification
• Stage 5 - Healed or residual stage

Early radiographic changes may reveal only a nonspecific effusion of the joint associated with slight widening of the joint space, metaphyseal demineralization (decreased bone density around the joint), and periarticular swelling (bulging capsule). This is the acute phase, and it may last 1-2 weeks. Decreasing bone density in and around the joint is noted after a few weeks.

With advancing disease, the joint space between the ossified head and acetabulum widens as the necrotic ossification center appears denser than the surrounding structures. Narrowing or collapse of the femoral head causes it to appear widened and flattened (coxa plana). A varus deformity of the femoral neck may occur as a result of damage to the femoral head growth center and overgrowth of the greater trochanteric apophysis.

Eventually, the disease may progress to collapse of the femoral head, increase in the width of the neck, and demineralization of the femoral head. The final shape of this area depends on the extent of necrosis and the degree of collapse. All of the findings are correlated with disease progression and the extent of necrosis. This is the active phase, and it can last 12-40 months.

A bone scan can be used to evaluate the site for avascular necrosis (AVN).

Consultation with an orthopedist is recommended. Goals in the treatment of Legg-Calvé-Perthes disease (LCPD) include the following:

• Eliminating hip irritability
• Restoring and maintaining good range of motion in the hip
• Preventing femoral epiphyseal collapse
• Attaining a spherical femoral head when the hip heals

Initial therapy includes minimal weightbearing and protection of the joint, which is accomplished by maintaining the femur abducted and internally rotated so that the femoral head is held well inside the rounded portion of the acetabulum. Abduction and rotation of the femur are accomplished by means of either the use of orthotic devices (bracing) or surgery (osteotomy). The Scottish Rite brace achieves containment by abduction while allowing free knee motion.

Results of surgical containment appear to be better than those of nonsurgical containment (orthosis). Surgery does not speed healing of the femoral head, but it does cause the head to reossify in a more spherical fashion.

Surgical management typically involves either femoral osteotomy to redirect the involved portion within the acetabulum or innominate osteotomy. The two procedures yield equivalent results, but femoral osteotomy may cause shortening of the limb, leading to a chronic limp.[8, 9, 10, 11, 12, 13, 14]  A systematic review and meta-analysis by Adulkasem et al found that for severe LCPD, combined osteotomy was the most effective procedure.[15]

In a Norwegian study of Perthes disease (ie, LCPD), Wiig et al followed 358 patients for 5 years and determined that proximal femoral varus osteotomy provided the best results in children 6 years and older with hips having more than 50% femoral head necrosis at the time of diagnosis.[8] They found no significant difference between physiotherapy and abduction orthosis and therefore suggested abandoning abduction orthosis for Perthes disease. For children younger than 6 years, no difference in outcome was determined for any of the three treatments.

A study by Kim et al suggested that contrary to conventional belief, a greater varus angulation may not produce better preservation of the femoral head following proximal femoral varus osteotomy.[16]

A meta-analysis of the medical literature addressing the effectiveness of surgical and nonsurgical treatment of LCPD suggested that there is minimal evidence to determine the most appropriate treatment.[17] This research also provides some evidence that nontreatment may be as effective as orthotic or surgical intervention.

Pailhé et al conducted a prospective study of 45 patients who underwent triple osteotomy of the pelvis for the treatment of LCPD.[18] The mean follow-up period of the study was 15.2 years. The investigators concluded that triple osteotomy provides satisfactory, reproducible long-term results.

Because LCPD is a local self-healing disorder, treatment consists of protection of the joint by allowing new bone formation to occur and restore a spherical femoral head. The aim is to prevent the development of any of the following:

• Irregular contouring, flattening, or mushrooming of the head
• Shortening and broadening of the neck
• Flattening of the vertical wall of the acetabulum

The development of any of these conditions can result in osteoarthritis at an early age.