Legg-Calvé-Perthes disease

Legg-Calvé-Perthes disease (LCPD or Perthes disease) refers to an idiopathic, avascular necrosis of the femoral head. It may occur unilaterally or bilaterally and typically manifests between the ages of four and ten. Children experience hip pain on weight-bearing, which often projects to the ipsilateral knee and causes an antalgic gait. Early stages are only detectable on MRI but progress of the disease can be tracked and graded using conventional x-ray. Surgery is performed if x-ray reveals signs that indicate an unfavorable prognosis. The aim of surgical intervention is to cover the femoral head as completely as possible with the hip socket, thus retaining its anatomical position. In mild forms of the disease, reduced weight-bearing and physical therapy are indicated. Important prognostic factors include the age of onset and the extent of femoral head involvement.

• Sex: ♂ > ♀ (4:1) ^[1]
• Age: 4–10 years
• Incidence (in children < 15 years): 1–3:20,000 ^[2]

Epidemiological data refers to the US, unless otherwise specified.

• Idiopathic disease
• Multiple factors might promote the development and progress of the condition, including: ^[1]
  • Repetitive microtrauma (e.g., due to child's hyperactivity)
  • Bleeding disorders (e.g., excess factor VII, factor V Leiden, protein S deficiency) ^[3]
  • Genetic factors (e.g., possible mutations in COL2A1 gene) ^[2]
  • Environmental factors (e.g., maternal smoking, secondhand smoke exposure) ^[4][5]

Lateral pillar classification ^[6]

This classification possesses the highest clinical relevance because it correlates best with long-term outcome. The crucial criterion in this classification is the height of the lateral third (“lateral pillar”) of the femoral head.

Other classifications ^[7]

• Catterall classification: refers to the extent of the epiphyseal necrotic area
• Salter-Thompson classification: refers to the extent of subchondral fracture in the early stage of disease
• Stulberg classification: refers to femoral head morphology in the phase of complete healing

Avascular necrosis of the femoral head due to a mismatch between the rapid growth of the femoral epiphyses and the slower development of adequate blood supply to the area

• Antalgic gait (on weight-bearing leg)
• Pain in the hip or the upper leg, sometimes projecting to the knee
  • Insidious onset, pain may fluctuate depending on physical activity ^[8]
  • Often exacerbated by internal rotation
  • FABER test (Flexion, ABduction, and External Rotation) might be positive.
  • Groin tenderness on palpation ^[8]
• Restricted range of movement; is usually present, especially regarding internal rotation and abduction, and can cause the child to limp. ^[9]
• Hinge abduction: refers to the lateral femoral head bumping into the ventrolateral acetabulum when the leg is abducted, possibly involving pain, a palpable clunk, and restriction in the range of movement
• Contralateral involvement in ∼ 10% of cases ^[8]

Legg-Calvé-Perthes disease should be considered in a child with knee pain.

• X-ray (anterior-posterior and frog leg positions ; )
  • Frequently without pathological findings during early stages
  • Increased lucency of the femoral head
  • Flattening and fragmentation of the femoral head
  • Joint space widening
  • “Head-at-risk” signs: prognostically unfavorable radiographic signs (as defined by complementary Catterall classification) ^[10]
    • Lateral calcification
    • Lateral subluxation of the femoral head
    • Lesions extending to the metaphysis
    • Horizontal alignment of the epiphyseal plate
    • Gage sign: triangle-shaped osteoporotic area of increased radiolucency of the lateral femoral head
    • Crescent sign: subchondral lucency representing a fracture
  • See also “Lateral pillar classification” above.
• MRI: indicated if initial imaging is unremarkable but clinical suspicion persists

Differential diagnosis of hip pain in children ^[11]

Pediatric hip pathologies often present as referred pain in the knee! Children or adolescents presenting with nonspecific knee pain and no findings suggestive of knee pathology require prompt assessment of the hip!

Transient synovitis (toxic synovitis) of the hip ^[12]

• Definition: transient (1–2 weeks), self-limiting, nonspecific inflammation and hypertrophy of the synovial membrane of the hip joint
• Epidemiology
  • Common cause of acute hip pain in children
  • Peak incidence: 3–8 years of age ^[13]
  • Sex: ♂ > ♀ (2:1) ^[13]
• Etiology
  • Exact cause is unknown
  • Associated with recent upper respiratory infection and recent gastroenteritis
• Pathophysiology: nonspecific inflammation and hypertrophy of the synovial membrane
• Clinical features
  • Transient acute unilateral and transient hip or groin pain
  • Children may limp or refuse to bear weight on the affected side
  • Possibly limited range of motion (mostly to the extreme abduction and internal rotation position) and tenderness on palpation
  • Recent upper respiratory tract infection in approx. 70% of the patients ^[14]
• Diagnostics
  • Clinical diagnosis
  • Laboratory: mostly normal findings
  • Imaging: to rule out other conditions in presence of physical examination or laboratory findings
    • Normal x-ray findings (anteroposterior view of the pelvis and lateral views of both hips)
    • Effusion on ultrasound that typically improves within days
• Treatment: symptomatic (e.g., rest, NSAIDs)
• Prognosis
  • Typically resolves within 1 week
  • Recurrence in approx. 20% of the children

The differential diagnoses listed here are not exhaustive.

• Conservative treatment: : limited weight bearing, physical therapy
  • Indicated in: ^[15]
    • Young children (< 6 years of age)
    • Mostly undamaged femoral head
    • Lateral pillar A classification
  • Casting and bracing can also be used until femoral head deformity develops or range of motion worsens. ^[16]
• Surgery: femoral osteotomy
  • Indicated in: ^[15]
    • Older children (≥ 6 years of age)
    • Extensive damage to the femoral head (> 50%)
    • Lateral pillar B/C classification
  • Hip arthroplasty can be considered in adults that develop osteoarthritis (see “Complications” below). ^[8]

• Early osteoarthritis of the hip joint due to any of the following: ^[1]
  • Incongruence between the femoral head and acetabulum
  • Shortening of the femoral neck featuring trochanteric elevation, which can manifest as Trendelenburg sign
  • Lateralization and coxa magna (broadening of the femoral head), which can manifest as hinge abduction

We list the most important complications. The selection is not exhaustive.

• Factors associated with a less favorable prognosis include: ^[7][17]
  • Older age of onset (≥ 6 years)
  • Extensive damage to the femoral head (> 50%)
  • Female sex