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Legg-Calve-Perthes Disease (Coxa plana)

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Topic updated on 07/06/16 10:29am
Introduction
  • Idiopathic avascular necrosis of the proximal femoral epiphysis in children
  • Epidemiology
    • incidence
      • affects 1 in 1200 children
    • demographics
      • 4-8 years is most common age of presentation
      • male to female ratio is 5:1
      • more commonly seen in urban populations versus rural
    • location
      • bilateral in 12%
        • never at the same stage of disease)
    • risk factors
      • positive family history
      • low birth weight
      • abnormal birth presentation
      • children exposed to second hand smoke 
      • Asian, Inuit, and Central European decent
  • Pathophysiology
    • pathoanatomy
      • disruption in vascular supply
        • thought to be associated with a disruption in vascular supply with subsequent revascularization
        • link with abnormal clotting factors (Protein S and Protein C deficiencies) is controversial
        • thrombophilia has been reported to be present in 50% of patients
      • bone collapse and repair (see Waldenström table below)
        • damages result from epiphyseal bone resorption, collapse, and the affect of subsequent repair during the course of disease
        • resorption and remodeling via creeping substitution
  • Associated conditions
    • ADHD
      • has been found to be associated with ADHD in 33% of cases
    • delayed bone age
      • bone age is delayed in 89% of patients
  • Prognosis
    • important prognostic variables
      • age of patient (bone age) at presentation
      • sphericity of femoral head and congruency at skeletal maturity (Stulberg classification)
    • prognosis worse with
      • age (bone age) > 6 years at presentation
      • female sex
      • decreased hip range of motion (abduction)
    • prognosis improved with
      • age (bone age) < 6 years at presentation 
    • natural history
      • long-term studies show that most patients do well until fifth or sixth decade of life in which degenerative changes of the hip become present
        • approximately 1/2 of patients develop premature osteoarthritis secondary to an aspherical femoral head
Stages of Legg-Calves-Perthes (Waldenström)
Initial • Infarction produces a smaller, sclerotic epiphysis with medial joint space widening • Radiographs may remain occult for 3 to 6 mos
Fragmentation •Femoral head appears to fragment or dissolve
• Result of a revascularization process and bone resorption producing collapse and subsequent increased density
• Hip related symptoms are most prevalent
•Lateral pillar classification based on this stage
Reossification Ossific nucleus undergoes reossification as new bone appears as necrotic bone is resorbed • May last up to 18m
Healing or remodeling •Femoral head remodels until skeletal maturity  • Begins once ossific nucleus is completely reossified trabecular patterns returns
 
Classification
 
Lateral Pillar (Herring) Classification
Group A  • lateral pillar maintains full height with no density changes identified • uniformly good outcome  
Group B  • maintains >50% height • poor outcome in patients with bone age > 6 years  
B/C Border • lateral pillar is narrowed (2-3mm) or poorly ossified with approximately 50% height • recently added to increase consistency & prognosis of classification  
Group C  • less than 50% of lateral pillar height is maintained • poor outcomes in all patient  
  • Determined at the beginning of fragmentation stage
    • usually occurs 6 months after the onset of symptoms  
  • Based on the height of the lateral pillar of the capital femoral epiphysis on AP imaging of the pelvis
  • Has best interobserver agreement 
  • Designed to provide prognostic information
  • Limitation is that final classification is not possible at initial presentation due to the fact that the patient needs to have entered into the fragmentation stage radiographically
 
Catterall Classification
Group I 

• involvement of the anterior epiphysis only


Group II
• involvement of the anterior epiphysis with a clear sequestrum  
Group III  • only a small part of the epiphysis is not involved

Group IV • total head involvement  
  • Based on degree of head involvement
  • At risk signs (indicate a more severe disease course)
    • Gage sign 
      • V-shaped radiolucency in the lateral portion of the epiphysis and/or adjacent metaphysis
    • calcification lateral to the epiphysis
    • lateral subluxation of the femoral head
    • horizontal proximal femoral physis
    • metaphyseal cyst
      • added later to the original four at risk signs described by Catterall
 
Salter-Thompson classification
Class A • crescent sign involves <  1/2 of femoral head

Class B • crescent sign involves > 1/2 of femoral head

  • Based on radiographic cresent sign
 
Stulberg classification
  • Gold standard for rating residual femoral head deformity and joint congruence
  • Recent studies show poor interobserver and intraobserver reliability
 
Presentation
  • Symptoms
    • insidious onset
    • may cause painless limp
    • intermittent knee, hip, groin or thigh pain
  • Physical exam
    • hip stiffness with loss of internal rotation and abduction
    • gait disturbance
      • Trendelenburg gait (head collapse leads to decreased tension of abductors) 
      • antalgic limp
    • limb length discrepancy is a late finding
      • hip contracture can exacerbate the apparent LLD
Imaging
  • Plain radiographs
    • AP of pelvis and frog leg laterals
      • critical in diagnosis and prognosis
    • early findings include
      • medial joint space widening (earliest)
      • irregularity of femoral head ossification
      • cresent sign (represents a subchondral fracture)
  • Bone scan
    • can confirm suspected case of LCP
    • decreased uptake (cold lesion) can predate changes on radiographs
  • MRI
    • can provide early diagnosis revealing alterations in the capital femoral epiphysis and physis
  • Arthrogram
    • a dynamic arthrogram can demonstrate coverage and containment of the femoral head
Histology
  • Femoral epiphysis and physis exhibit areas of disorganized cartilage with areas of hypercellularity and fibrillation
Differential Diagnosis
  • Radiographic differential diagnosis
    • multiple epiphyseal dysplasia
    • spondyloepiphyseal dysplasia
    • sickle cell disease
    • Gaucher disease
    • hypothyroidism
    • Meyers dysplasia
Treatment
  • Nonoperative
    • observation alone, activity restriction, and physical therapy
      • indications
        • children < 8 years of age
        • children with lateral pillar A
        • consider activity restriction and protected weight-bearing during earlier stages until reossification is complete
      • technique
        • main goals of treatment are to keep the femoral head contained and maintain good motion
          • containment limits deformity and minimizes loss of sphericity and 
          • lessen subsequent degenerative changes
        • bracing and casting for containment are controversial
        • all patients require periodic clinical and radiographic followup until completion of disease process
      • outcomes
        • good outcome correlates with spherical femoral head
          • 60% do not require operative intervention
          • good outcomes associated with lateral pillar A and Catterall I groups
  • Operative
    • femoral and/or pelvic osteotomy
      • indications
        • children > 8 years of age, especially lateral pillar B and B/C
      • technique
        • femoral osteotomy
          • proximal femoral varus osteotomy to provide containment
        • pelvic osteotomy
          • Salter, triple innominate, Dega or Pemberton osteotomy
          • Shelf arthroplasty may be performed to prevent lateral subluxation and resultant lateral epiphyseal overgrowth
      • outcomes
        • no positive effect has been found for containment surgery performed after initial or early fragmentation stage
        • children with lateral pillar A and those with B under 8 years did well regardless of treatment
        • large recent studies show improved outcomes with surgery for lateral pillar B and B/C in children > 8 years (bone age >6 years)  
        • poor outcome for lateral pillar C regardless of treatment
    • Valgus and shelf osteotomies
      • indications
        • valgus proximal femur osteotomy or shelf osteotomy may be helpful in the setting of hinged abduction
        • shelf or Chiari osteotomies are also considered when the femoral head is no longer containable 
      • hinge abduction
        • hinge abduction is secondary to lateral extrusion of the capital femoral epiphysis producing a hinge effect on the lateral acetabulum during abduction

 

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Qbank (3 Questions)

TAG
(OBQ07.36) A 9-year-old male is brought in for initial evaluation of persistent painless limping favoring the left leg. His symptoms began 6 months ago, and have been progressively worsening. He has nearly full abduction. Radiographs and an MRI are shown in Figures A, B, and C. What is the next most appropriate step in treatment?
Topic Review Topic
FIGURES: A   B   C      

1. Left hip aspiration and culture under fluoroscopic guidance
2. Continued activity limitation and bracing
3. Femoral or pelvic osteotomy
4. Core decompression of the femoral head
5. Work-up for underlying metabolic bone disease

PREFERRED RESPONSE ▶
TAG
(OBQ06.11) A six-year-old boy presents with left leg pain and limping. Radiographs are shown in Figures A and B. The radiographic changes necessary for accurate lateral pillar classification of his disease are usually evident how long after the onset of symptoms? Topic Review Topic
FIGURES: A   B        

1. 1 month
2. 3 months
3. 6 months
4. 12 months
5. 18 months

PREFERRED RESPONSE ▶
TAG
(OBQ05.75) For children with Legg-Calve-Perthes(LCP) disease, all of the following factors are associated with femoral head incongruity and worse clinical outcome EXCEPT: Topic Review Topic

1. Maintenance of less than 50% of lateral pillar height
2. Presentation at 5 years of age
3. Lateral subluxation of the femoral head
4. Calcification lateral to the epiphysis
5. Presence of a radiolucency in the shape of a V in the lateral portion of the epiphysis (Gage sign)

PREFERRED RESPONSE ▶



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