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 descent 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 Lateral Pillar (Herring) Classification Group A Lateral pillar maintains full height with no density changes identified Consistently good outcome Group B Maintains >50% height Poor outcome in patients with bone age > 6 years Group B/C 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 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 (crescent 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 Catterall Classification Based on degree of head involvement Group I Involvement of the anterior epiphysis only Group II Involvement of the anterior epiphysis with a central sequestrum Group III Only a small part of the epiphysis is not involved Group IV Total head involvement Salter-Thompson Calssification Salter-Thompson classification <i>Based on radiographic crescent sign</i> Class A Crescent sign involves < 1/2 of femoral head Class B Crescent sign involves > 1/2 of femoral head 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 crescent 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 infection 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