Legg-Calvé-Perthes Disease (LCPD)

Overview

Definition

Legg-Calvé-Perthes disease (LCPD), also called coxa plana, is a disorder of the hip in which blood supply to the proximal femoral epiphysis is temporarily interrupted, resulting in avascular necrosis and permanent deformity of the femoral head and acetabulum.

Epidemiology

• Population statistics:
  • Affects 1 in 1,200 people in the United States
  • Male-to-female ratio: 4:1
  • Peak incidence between 4 and 8 years of age
  • 90% of cases are unilateral.
  • Highest incidence: White populations
  • Lowest incidence: East Asian populations
  • More prevalent in urban areas in patients with lower socioeconomic status
• Risk factors: 
  • Genetics (10% of cases are familial)
  • HIV (5% of patients have LCPD)
  • Clotting disorders
  • Trauma
  • Steroid use
  • Developmental hip dysplasia 
  • Low birth weight
  • Short stature
  • Exposure to tobacco

Etiology

Legg-Calvé-Perthes disease is a multifactorial disease that is likely caused by a combination of genetic and environmental factors. The exact etiology is unknown, but interruption of the blood supply is the inciting cause.

Proposed mechanisms for interruption of blood supply:

• Trauma
• Synovitis
• Coagulopathies 
• Steroid use

Pathophysiology

There are 4 stages of LCPD:

1. Necrosis: Disruption of blood supply leads to necrosis of subchondral cortical bone or infarction of femoral capital epiphysis.
2. Fragmentation: infarcted bone reabsorbed
3. Reossification: Osteoblastic activity becomes prominent.
4. Remodeling: Femoral head reshapes during patient growth.

Complications

• Deformities of femoral head with disease progression:
  • Coxa magna: widening of femoral head
  • Coxa plana: flattening of femoral head
• Resultant hip incongruence can lead to:
  • Labral tears
  • Osteoarthritis of hip with age

Clinical Presentation

History

• Chief complaint: limp or altered gait
• Pain presents late in the disease course (after 3 months), usually worsens with activity: pain usually mild (limp may be painless) and may be referred to anteromedial thigh or knee
• May be associated with delayed bone age and growth
• Usually lacks systemic symptoms

Clinical findings

• Examination of gait:
  • Antalgic gait: short stance phase due to pain when loading affected hip 
  • Trendelenburg gait: downward tilt of pelvis contralateral to affected hip during swing phase of walking
  • Abductor lurch or intermittent limp, especially after exertion
• Lower extremity exam:
  • Leg-length discrepancy (affected leg is shorter)
  • Atrophy of quadriceps/buttocks muscles from disuse
  • Reduced range of motion of hip joint

Diagnosis

The diagnosis of LCPD is clinical and confirmed through targeted imaging, so a high degree of suspicion is required in the approach to the limping child.

• Labs may be used to exclude other diagnoses: complete blood count (CBC) and erythrocyte sedimentation rate (ESR) to rule out infectious causes of limp
• X-rays looking for pathological deformation of hip: anteroposterior (AP) and frog-leg lateral views
  • Early radiographs may appear normal.
  • Early findings: widening of joint space
  • Caffey’s sign or crescent sign: 
    • Subchondral radiolucent fracture line parallel to articular surface of femoral head
    • May be visible prior to fragmentation
  • Later findings:
    • Fragmentation of femoral ossification center
    • Lateral subluxation and flattening of femoral head
• Magnetic resonance imaging (MRI) and bone scans: may be part of evaluation if diagnosis is in question
  • MRI reveals marrow changes.
  • Bone scan reveals decreased perfusion to femoral head.

Management

Goals of medical therapy

• Eliminating hip irritability and pain
• Maintaining adequate range of motion
• Prevention of femoral epiphysis collapse, containment of femoral head

Conservative management

• Minimal weight bearing and protection of joint until ossification is complete:
  • Hip may be held in abduction by abduction casts or ambulatory braces. 
  • Goal is to promote containment of femoral head within acetabulum.
• Physical therapy and stretching exercises to maintain range of motion and muscle tone
• Nonsteroidal anti-inflammatory drugs (NSAIDs) if needed for pain management
• Children ＜ 6–8 years old have more favorable outcomes to conservative therapy.

Surgical therapy

• Operative procedures include varus femoral osteotomy and Salter osteotomy (goal is containment of femoral head).
• More commonly used in patient > 8 years of age
• Lack of consensus on best treatment

Prognosis

• Generally self-limited (2–3 years)
• Patients left with propensity to degenerative changes: 
  • Most patients function well until their 40s.
  • Hip replacement may be indicated due to chronic osteoarthritis.

Clinical Relevance

Differential diagnosis

• Sickle cell disease (SCD): hemoglobinopathy caused by point mutation in 6th codon of β-globin gene on chromosome 11, which ultimately leads erythrocytes to adopt characteristic “sickle” appearance. Can impair blood flow to femoral head, causing avascular necrosis of femoral head in young children with SCD. May be referred to as osteonecrosis of femoral head (ONFH).
• Developmental hip dysplasia (DHD): congenital disorder of hip joint characterized by hip instability, displayed as subluxation or dislocation, frequently recognized in infants.

Within clinical spectrum of LCPD

Short stature: due to genetics, developmental disorders, and leg-length discrepancy, child may be shorter in stature.

Complication of LCPD

Osteoarthritis (OA): most common form of arthritis, often referred to as “wear and tear” arthritis. Principally a disease of aging, characterized by hyaline articular cartilage loss, but also involving changes to subchondral bone, synovium, and surrounding joint structures. Anatomical abnormalities produced by LCPD increase the risk for degenerative changes of the hip joint and the need for surgical replacement of the hip.