Legg-Calve-Perthes Disease

Detailed Overview

LCPD typically affects children between the ages of 4 and 10 years, causing hip pain and a limping gait. The disease is self-limiting but occurs over several years through four distinct radiographic stages: initial (necrosis), fragmentation, reossification, and healed. The ultimate goal of treatment is to maintain the spherical shape of the femoral head and ensure it remains contained within the acetabulum during the remodeling phase, thereby preventing early-onset osteoarthritis in adulthood.

Epidemiology & Demographics

Incidence is ~1 in 10,000 children. It is 4-5 times more common in males than females. Peak age of onset is 5-7 years. Bilateral involvement occurs in 10-15% of cases but is usually asymmetric.

Etiological Mechanism

The exact cause of the vascular disruption is unknown (idiopathic). Hypotheses include subtle coagulopathies (e.g., Factor V Leiden, protein C/S deficiency), venous congestion, repetitive microtrauma, and passive smoking exposure.

Primary Causes

Idiopathic disruption of the medial circumflex femoral artery and its branches supplying the capital femoral epiphysis.

• Age and Gender: Males aged 4-10 are at highest risk.
• Skeletal immaturity: Delayed bone age relative to chronological age is common.
• Secondhand smoke: Passive smoking has been strongly correlated with LCPD incidence.
• Thrombophilia: Presence of underlying hypercoagulable states in some patients.

The process begins with an ischemic event that leads to necrosis of the cancellous bone and bone marrow of the femoral head epiphysis. Articular cartilage, nourished by synovial fluid, continues to grow, causing the cartilage to thicken while the bony epiphysis stops growing. A subchondral stress fracture occurs, followed by the fragmentation stage where necrotic bone is resorbed by osteoclasts and replaced by fibrocartilage. Revascularization brings osteoblasts that lay down new bone (reossification). If the femoral head extrudes outside the acetabulum during the softened stages, it heals in a flattened, deformed shape (coxa magna or plana).

Characteristic Clinical Presentation

• Limp (Antalgic Gait): Painless or mildly painful limp, often worse after activity.
• Referred Pain: Pain typically referred to the anteromedial thigh or knee, rarely primarily in the hip.
• Stiffness: Decreased range of motion, particularly in hip abduction and internal rotation.

Physical Examination Signs

• Loss of internal rotation and abduction of the affected hip.
• Positive Trendelenburg sign due to gluteus medius weakness.
• Leg length discrepancy (affected leg may be shorter).
• Thigh, calf, or gluteal muscle atrophy from disuse.

• Coxa Magna: Enlarged, deformed femoral head.
• Premature Osteoarthritis: Degeneration of the hip joint in young adulthood due to incongruency.
• Leg Length Discrepancy: Shortening of the affected limb.

Diagnostic Criteria & Guidelines

Diagnosis is established via anteroposterior (AP) and frog-leg lateral pelvic radiographs demonstrating characteristic findings (sclerosis, fragmentation, or flattening of the capital femoral epiphysis) in a child presenting with typical symptoms.

Differential Diagnosis

• Transient synovitis (typically resolves in 1-2 weeks)
• Slipped Capital Femoral Epiphysis (SCFE)
• Septic arthritis of the hip
• Sickle cell anemia (causing secondary AVN)

Laboratory Tests & Biomarkers

• CBC, ESR, CRP: Typically strictly normal; used to rule out infectious or inflammatory causes.

Imaging Modalities & Findings

• Radiographs (AP and Frog-leg lateral):
• MRI Without Contrast:

• Initial (Necrosis)
  Sclerosis of the epiphysis, joint space widening due to cartilage hypertrophy.
• Fragmentation
  Subchondral fracture (crescent sign), epiphysis appears fragmented. Highest risk of deformity.
• Reossification
  New woven bone appears, replacing the necrotic bone.
• Healed (Remodeling)
  Femoral head is completely ossified. Final shape determines long-term prognosis.

Second-Line & Adjunctive Therapy

Containment bracing (e.g., A-frame orthosis or Petrie casts) to keep the femoral head abducted and internally rotated within the acetabulum during the fragmentation phase.

Surgical & Procedural Management

Surgical containment (e.g., Femoral varus derotational osteotomy [VDRO] or Salter innominate pelvic osteotomy) is indicated for children >8 years, or those with >50% femoral head involvement, or clinical signs of subluxation (loss of containment).

Recommended Lifestyle Changes

• Avoid high-impact, weight-bearing activities (running, jumping).
• Encourage non-weight-bearing activities like swimming or cycling.
• Daily physical therapy exercises to maintain hip abduction.

Patient Counseling & Advice

Counsel parents that the disease process takes 2-5 years to complete. Emphasize that preserving range of motion is crucial. Warn that older age at onset (>8 years) carries a higher risk of permanent deformity and future arthritis.

Follow-Up & Monitoring Schedule

Clinical and radiographic follow-up every 3-4 months until reossification is well underway, then every 6 months until skeletal maturity.

Preventive Strategies

No proven preventative measures since the etiology is idiopathic. Avoidance of secondhand smoke may reduce risk.

Generally good if onset is <6 years of age. Poor prognosis if onset >8 years, female sex, heavy weight, or lateral pillar C involvement.