• SUMMARY

  • Legg-Calve-Perthes Disease is an idiopathic avascular necrosis of the proximal femoral epiphysis in children.

  • Diagnosis can be suspected with hip radiographs. MRI may be required for diagnosis of occult or early disease. 

  • Treatment is typically observation in children less than 8 years of age, and femoral and/or pelvic osteotomy in children greater than 8 years of age.

• EPIDEMIOLOGY

  • Incidence

    • affects 1 in 10,000 children

  • Demographics

    • 4-8 years is most common age of presentation

    • male to female ratio is 5:1

    • higher incidence in urban areas

    • socioeconomic class

      • higher among lower socioeconomic class

    • latitude

      • higher incidence in high latitude (low incidence around equator)

    • race

      • Caucasian > East Asian and African American

  • Anatomic location

    • bilateral in 12%

      • asymmetrical, asynchronous involvement

        • rarely at the same stage of disease

      • symmetrical involvement suggests MED (multiple epiphyseal dysplasia)

  • Risk factors

    • positive family history

    • low birth weight

    • abnormal birth presentation

    • second hand smoke

    • Asian, Inuit, and Central European decent

• ETIOLOGY

  • Pathophysiology

    • osteonecrosis occurs secondary to disruption of blood supply to femoral head

      • followed by revascularization with subsequent resorption and later collapse

        • creeping substitution provides pathway for remodeling after collapse

    • proposed mechanisms

      • possible association with abnormal clotting factors (Protein S and Protein C deficiencies)

        • controversial etiology

        • thrombophilia has been reported to be present in 50% of patients

        • up to 75% of affected patients have some form of coagulopathy

      • repeated subclinical trauma and mechanical overload lead to bone collapse and repair (multiple-infarction theory)

        • damages result from epiphyseal bone resorption, collapse, and the effect of subsequent repair during the course of disease

      • maternal / passive smoking aggravates

  • Associated conditions

    • associated with ADHD in 33% of cases

    • bone age is delayed in 89% of patients

• CLASSIFICATION 

  • Lateral Pillar Classification

    • has best agreement and is most predictive

    • determined during 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

      • 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

Waldenstrom classification

• 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 months
  Fragmentation	Begins with presence of subchondral lucent line (cresent sign) Femoral head appears to fragment or dissolve Result of revascularization process with bone resorption producing collapse with subsequent patchy density and lucencies	Hip related symptoms are most prevalent Lateral pillar classification based on this stage Can last from 6m to 2y
  Reossification	Ossific nucleus undergoes reossification with new bone appearing 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 return

Catteral Calssification

• Emphasizes extent of head involvement and outcome (see groups below)

• Applied during fragmentation stage when the necrotic segment is demarcated from the viable portion 

• Catterall also described head

• At-risk signs that are associated with poor outcomes

  • Gage sign (V-shaped radiolucency in the lateral portion of the epiphysis and/or adjacent metaphysis)

  • Calcification lateral to the epiphysis

  • Metaphyseal cyst

  • Lateral subluxation of the femoral head

  • Horizontal proximal femoral physis

Salter-Thompson Calssification

• 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 hip, knee, groin or thigh pain

  • Physical exam

    • hip stiffness

      • loss of internal rotation and abduction

    • gait disturbance

      • antalgic limp

      • Trendelenburg gait (head collapse leads to decreased tension of abductors)

    • limb length discrepancy is a late finding

      • hip adduction contracture can exacerbate the apparent LLD

• IMAGING

  • Radiographs

    • AP of pelvis and frog leg laterals

      • critical in diagnosis and prognosis

    • early findings include

      • medial joint space widening (earliest) from less ossification of head

        • measured between teardrop and ossification center

      • irregularity of femoral head ossification

        • decreased size of ossification center

        • sclerotic appearance

      • cresent sign (represents a subchondral fracture)

  • Bone scan

    • can confirm suspected case of LCPD

      • decreased uptake (cold lesion) can predate changes on radiographs

    • provides information on extent of femoral head involvement

  • MRI

    • early diagnosis revealing alterations in the capital femoral epiphysis and physis

    • more sensitive than radiograph

  • Perfusion studies predict maximum extent of lateral pillar involvement

  • Arthrogram

    • a dynamic arthrogram can demonstrate coverage and containment of the femoral head

• STUDIES

  • Histology

    • femoral epiphysis and physis exhibit areas of disorganized cartilage with areas of hypercellularity and fibrillation

• DIFFERENTIAL

  • Radiographic differential diagnosis

    • infecitious etiology 

      • septic arthritis, osteomyelitis, pericapsular pyomyositis

    • transient synovitis 

    • multiple epiphyseal dysplasia (MED) 

    • spondyloepiphyseal dysplasia (SED) 

    • sickle cell disease

    • Gaucher disease 

    • hypothyroidism

    • Meyers dysplasia

• TREATMENT

  • Goals

    • resolution of symptoms

      • NSAIDs, traction, crutches

    • restoration of range of motion

      • physical therapy (may exacerbate symptoms), muscle lengthenings, Petrie casting

    • containment of hip

      • improve range of motion, bracing, proximal femoral osteotomy, pelvic osteotomy

        • ensure that femoral head is well seated in acetabulum

  • Nonoperative

    • observation alone, activity restriction (non-weightbearing), and physical therapy (ROM exercises)

      • indications

        • children < 8 years of age (bone age <6 years)

          • young patients typically do not benefit from surgery

        • lateral pillar A involvement

      • technique

        • activity restriction and protected weight-bearing during earlier stages until reossification is complete

        • main goals of treatment are to keep the femoral head contained and maintain good motion

          • containment limits deformity and minimizes loss of sphericity

            • lessen subsequent degenerative changes

        • bracing and casting for containment have not been found to be beneficial in a large, prospective study

        • all patients require periodic clinical and radiographic followup until completion of disease process

      • outcomes

        • good outcomes correlate with a 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

        • proximal femoral varus osteotomy

          • to provide containment

        • pelvic osteotomy

          • Salter or triple innominate osteotomy

          • Shelf arthroplasty may be performed to prevent lateral subluxation and resultant lateral epiphyseal overgrowth

      • outcomes

        • 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) 

           

        • studies sugggest earlier surgery before femoral head deformity develops may be best

        • poor outcome for lateral pillar C regardless of treatment

    • valgus and/or shelf osteotomies

      • indications

        • hinge abduction 

           

          • lateral extrusion of the capital femoral epiphysis producing a painful hinge effect on the lateral acetabulum during abduction

      • abduction-extension osteotomy

        • reposition the hinge segment away from the acetabular margin

        • correct shortening from fixed adduction

        • improve abductor mechanism by improving abductor muscle contractile length

      • Shelf or Chiari osteotomies are also considered when the femoral head is no longer containable

    • hip arthroscopy

      • emerging treatment modality for mechanical abnormalities in the setting of healed LCPD

        • femoroacetabular impingement

    • hip arthrodiastasis

      • indications

        • controversial indications and outcomes

      • technique

        • hip distraction via external fixation

• TECHNIQUE

  • Proximal Femoral Varus Osteotomy (VRDO) 

    •  indications

      • extrusion in early stages of LCPD

    • technique

      • reposition femoral head into acetabulum for containment purposes

• COMPLICATIONS

  • Femoral head deformity

    • coxa magna

      • widened femoral head

    • coxa plana

      • flattened femoral head

    • important prognostic factor

      • Stulberg classification

  • Lateral hip subluxation (extrusion)

    • associated with poor prognosis

      • can lead to hinge abduction

  • Premature physeal arrest

    • trochanteric overgrowth

    • coxa breva

      • shortened femoral neck

    • leg length discrepancy

      • typically mild

  • Acetabular dysplasia

    • poor development secondary to deformed femoral head

    • can alter hip congruency

  • Labral injury

    • secondary to femoral head deformity

      • femoroacetabular impingement

  • Osteochondritis dissecans

    • can lead to loose fragments

  • Degenerative arthritis 

     

    • Stulberg I and most Stulberg II hips perform well for the lifetime of the patient

• PROGNOSIS

  • Important prognostic variables

    • younger age (bone age) < 6 years at presentation is most important good prognostic indicator 

       

    • sphericity of femoral head and congruency at skeletal maturity (Stulberg classification)

    • lateral pillar classification

  • Variables of poor prognosis

    • female sex

    • decreased hip abduction (adduction contracture)

    • heavy patient

    • longer duration from onset to completion of healing

    • stiffness with progressive loss of ROM

    • Catterall "head at risk" signs (see under classification)

  • Natural history

    • long-term studies suggest that most patients do well until fifth or sixth decade of life

    • approximately 1/2 of patients develop premature osteoarthritis secondary to an aspherical femoral head

  • Self-limiting process

    • variable course to final healing from initial ischemic event

    • can take 2-5 years to resolve

  • Differentiated from adult osteonecrosis by its ability to heal and remodel