Rosen & Barkin's 5-Minute Emergency Medicine Consult (419 page)

A special thanks goes to Dr. Harry C. Karydes, who contributed to the previous edition.

CODES

• 984.0 Toxic effect of inorganic lead compounds
  
• 984.1 Toxic effect of organic lead compounds
  
• 984.9 Toxic effect of unspecified lead compound
  

BASICS

• Idiopathic avascular necrosis of the femoral head in children
  
• Genetics:
  
  • Increased frequency with factor V Leiden and anticardiolipin antibodies
    

Exclusively a pediatric disease

• Successive vascular occlusions causing characteristic findings
  
• Growing evidence implicating hypercoagulable states
  
• May be multifactorial
  
• Risk factors include tobacco smoke, wood smoke, low birth weight, birth length <50 cm
  
• Progression through 4 stages of disease:
  
  • Initial stage: Dense femoral head causing intermittent synovitis
    
  • Fragmentation: Femoral head becomes soft and deforms causing loss of motion
    
  • Healing: New bone grows into femoral head
    
  • Residual: Healed femoral head with some deformity
    
• More common in boys: Male > female, 4:1
  
• More common among Caucasians
  
• Most commonly occurs between ages of 3 and 7:
  
  • Range 18 mo–18 yr
    
• Bilateral in 10–15% of cases
  
• Associated with short stature, deprived populations, delayed & disproportionate growth
  

DIAGNOSIS

• Frequently insidious onset
  
• Limp often presenting complaint
  
• Pain:
  
  • Aching in hip, groin, anteromedial thigh, or anteromedial knee
    
  • May be mild
    
  • Aggravated by activity, relieved by rest
    
  • Muscle spasm common complaint early in course of disease
    

• Tenderness over anterior aspect of hip joint
  
• Joint stiffness:
  
  • Limitation of internal rotation seen earliest
    
  • Limited abduction
    
  • Contractures of adductors
    
• Muscle atrophy and shortening of leg on affected side are late findings
  
• Otherwise well appearing and afebrile
  
• May be asymptomatic
  

• Radiographs of hip most important study for diagnosis in ED
  
• Consider and exclude septic arthritis (usually an acute febrile illness)
  

• No specific lab studies diagnostic of Legg–Calvé–Perthes (LCP)
  
• CBC, C-reactive protein (CRP), or ESR, if septic arthritis a concern
  

• Characteristic imaging findings combined with consistent history and physical exam establish diagnosis
  
• Plain radiographs, MRI, and nuclear scintigraphy (bone scan) are the main diagnostic modalities used
  
• Hip radiographs:
  
  • AP & Frog lateral view of affected hip
    
  • Image both hips to detect contralateral disease
    
  • Assess stage, extent, and severity
    
  • Can be normal during 1st 3–6 mo
    
  • Usually abnormal at time of presentation
    
  • 5 stages seen in sequence:
    
    • Cessation of growth at the capital femoral epiphysis; smaller femoral head epiphysis and widening of articular space on affected side
      
    • Subchondral fracture
      
    • Resorption of bone
      
    • Reossification of new bone
      
    • Healed stage
      
• CT:
  
  • Shows precise information on anatomic relationship between femoral head and acetabulum
    
  • May have role in operative planning, staging
    
• MRI:
  
  • Sensitive in the diagnosis of LCP and provides good anatomic images
    
  • Detects abnormalities earlier than plain radiographs
    
  • Used to assess the extent of femoral head infarction
    
  • Variety of findings depending on imaging protocol used
    
• Bone scan:
  
  • Precedes x-ray changes by an average of 3 mo
    
  • Evaluates patterns associated with revascularization and recanalization
    
• US:
  
  • Shows effusion in the hip but is not specific for LCP
    
  • Evaluate for thickening of the synovial membrane
    
  • Evaluate deformity and containment of femoral head
    
• Arthrography:
  
  • Used to evaluate method of treatment
    

Arthrocentesis of hip definitive test to exclude septic arthritis if significant concern for this; may need orthopedic consultation

• Unilateral involvement:
  
  • Transient (a.k.a. toxic) synovitis
    
  • Septic arthritis
    
  • Osteomyelitis
    
  • Sickle cell anemia
    
  • Juvenile rheumatoid arthritis
    
  • Rheumatic fever
    
  • Trauma:
    
    • Femoral neck fracture
      
    • Hip dislocation
      
    • Slipped capital femoral epiphysis
      
  • Tuberculosis
    
  • Tumor
    
• Bilateral involvement:
  
  • Hypothyroidism
    
  • Epiphyseal dysplasia
    
  • Gaucher disease
    

TREATMENT

Clinical course is subacute; less likely to present via ambulance

Not a life-threatening condition; clinical instability mandates identification of alternative diagnosis

• Main ED intervention is pain control
  
• Restrict from vigorous activity
  
• May need crutches if weight bearing painful
  

Ibuprofen: 10 mg/kg/dose PO q6–8h PRN pain

Diazepam: 0.1–0.2 mg/kg/dose (max. 5 mg) PO q6–8h PRN muscle spasm

FOLLOW-UP

Need for admission rare, indicated for:

• Severe pain or muscle spasm not controlled by PO medications
  
• Social considerations; bedrest/care at home not possible
  

• Adequate pain control with PO medications
  
• Orthopedic follow-up arranged in 1–2 wk
  

• Age of onset shown to affect outcome; onset younger than 6 with better outcome, if older than 8, shown to have poorer outcome
  
• For more severe disease, a range of treatment options exists, including conservative treatment, orthotics, traction, and surgical osteotomy, determined by consulting orthopedist
  
• Degenerative arthritis and possible need of a replacement is the main long-term complication
  

Orthopedic consultation to determine further management; may be outpatient

Abrupt onset, presence of fever, unstable patient, or toxic appearance suggest diagnosis other than LCP.

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