Legg-Calvé-Perthes (Perthes) disease is a self-limiting disorder characterized by avascular necrosis (AVN) of the femoral head in children. The condition results in temporary loss of blood supply to the proximal femur, leading to necrosis and subsequent remodeling and healing.

Perthes disease affects approximately 1 in 10,000 children, with a male-to-female ratio of 4:1. Peak incidence occurs between 5-7 years of age. The disease is typically unilateral (80%) but can involve both hips (20%) in up to 20% of cases.

Perthes disease progresses through four radiographic stages:

• Initial stage (0-3 months): Femoral head appears smaller (coxa plana) due to loss of blood supply and necrosis
• Fragmentation stage (3-8 months): Resorption of necrotic bone with new bone formation; femoral head appears fragmented
• Reossification stage (8-12 months): Progressive recalcification and healing of femoral head
• Healing/Healed stage (12+ months): Complete remodeling and bone resorption; residual deformity determines long-term prognosis

The primary goal of treatment is to keep the femoral head contained within the acetabulum during the healing phase, as acetabular support promotes optimal remodeling and reduces residual deformity.

Prognosis is determined by age at onset, extent of femoral head involvement (lateral pillar classification), and effectiveness of containment during healing.

Common presenting complaints:

• Painless limp or antalgic gait (most common)
• Hip or groin pain (may be referred to knee)
• Thigh or groin pain worse with activity
• History of recent viral illness or upper respiratory infection in some cases

Physical examination findings:

• Limp or reduced hip motion
• Restricted hip abduction and internal rotation
• Positive Trendelenburg sign or drop
• Hip flexion contracture
• Pain with internal rotation and abduction
• No fever (critically important to distinguish from septic arthritis)

Key feature: Pain is present but minimal relative to severity of radiographic changes. Systemic symptoms (fever, weight loss, malaise) are absent.

Plain Radiography (First-line):

• Anteroposterior (AP) and frog-lateral (internal rotation) views of pelvis and hips
• Shows femoral head collapse, increased density, fragmentation, or reossification depending on disease stage
• Bilateral films essential to assess contralateral hip

MRI (High sensitivity for early diagnosis):

• Best modality for detecting AVN before radiographic changes become apparent
• T2 sequences show edema and confirm blood supply loss
• Useful when clinical suspicion high but plain films normal

Bone scintigraphy (Technetium-99m):

• Shows decreased uptake in avascular area
• Less commonly used now due to radiation and MRI availability

Laboratory tests: Not typically needed. ESR, CRP normal. Exclude infection if clinical presentation includes fever or systemic symptoms.

Age as prognostic factor:

• Age <6 years: Excellent prognosis even with extensive femoral head involvement due to greater remodeling capacity
• Age 6-8 years: Intermediate prognosis; Herring classification guides intensity of treatment
• Age >8 years: Poorer prognosis; significant risk of residual deformity; surgical containment frequently required

Primary goal: CONTAINMENT — keeping the femoral head within the acetabulum during the healing phase to promote optimal remodeling.

Treatment options based on presentation and risk:

• Observation/Conservative management (Low-risk cases): Herring A patients or very young children with mild involvement. Activity restriction with protection from impact sports. Regular clinical review and radiographic assessment
• Physiotherapy: Hip flexibility exercises, abductor strengthening, gait training. Important adjunct to all treatment approaches
• Abduction bracing (Intermediate-risk): Maintains hip in abduction and internal rotation, centering femoral head in acetabulum. Examples: Petrie brace, A-frame orthosis, Toronto brace
• Surgical containment (High-risk, older children): Femoral derotation osteotomy, varus osteotomy, or pelvic osteotomy to surgically position femoral head into acetabulum. Used when conservative methods inadequate or child >8 years with significant involvement

Activity restrictions: Avoid high-impact activities (running, jumping, contact sports) during active disease. Swimming, cycling, walking permitted. Gradual return to activities as healing progresses.

Note: Perthes disease is primarily an orthopaedic condition. Pharmacological treatment is adjunctive to mechanical containment. No disease-modifying agents exist.

Initial assessment steps:

• Detailed history: limp duration, pain pattern, functional impact, recent illness
• Physical examination: gait assessment, hip range of motion, Trendelenburg sign, absence of fever
• Plain radiographs (AP and frog-lateral): establish diagnosis, determine disease stage and severity
• Classify by Herring lateral pillar involvement
• Assess bilateral hips (20% bilateral involvement possible)

Establish baseline for treatment decisions:

• Document age at diagnosis (critical prognostic factor)
• Determine disease stage (initial, fragmentation, reossification, healed)
• Assess extent of femoral head involvement
• Evaluate hip abduction and internal rotation limitations

Monitoring parameters:

• Serial radiographs every 3-6 months during active disease: assess progression through stages
• Hip range of motion: track abduction and internal rotation limitations
• Gait assessment: document limp resolution with treatment
• Brace compliance and tolerance if used
• School and activity participation: functional outcomes

Bilateral Perthes (20% of cases): Usually sequential rather than simultaneous. Second hip typically diagnosed 6-12 months after first. Prognosis generally favorable for both hips if age <6 years at first presentation. Requires bilateral radiographic assessment and coordinated bilateral treatment if needed.

Young children (<6 years): Excellent remodeling capacity — even extensive femoral head involvement (Herring C) often achieves good outcomes with conservative management. Surgical intervention rarely necessary.

Older children (>8 years): Reduced remodeling capacity — Herring B and C patients at high risk of residual deformity. Surgical containment more frequently required. Poor prognosis if untreated or inadequately contained.

Systemic conditions: Increased incidence in endocrine disorders (hypothyroidism, growth hormone deficiency) and metabolic bone disease. Screen for these conditions, particularly in cases with atypical presentation.

Imaging stewardship: Diagnosis made primarily on plain radiographs. MRI reserved for atypical presentations or very early disease when radiographs normal. Avoid unnecessary advanced imaging; serial plain films sufficient for monitoring disease progression.

Medication stewardship: NSAIDs and paracetamol are adjunctive; use for short-term pain management to facilitate function, not as primary treatment. Avoid chronic NSAID use; physiotherapy and mechanical containment are foundation of therapy.

Specialist referral: Refer to pediatric orthopedics all confirmed cases of Perthes disease. Indications for surgical intervention include: Herring C classification, age >8 years with significant involvement, failure of conservative containment, development of coxa plana with functional limitation.

Overtreatment prevention: Young children (<6 years) with Herring A involvement may require only observation and activity modification. Avoid unnecessary bracing in low-risk cases.

Overall prognosis: Perthes disease is self-limited; the femoral head will eventually remodel and heal regardless of treatment. Treatment goal is to optimize the shape of the femoral head at completion of remodeling, reducing long-term complications.

Age <6 years: Excellent prognosis overall. Even patients with extensive femoral head involvement (Herring C) achieve good remodeling with conservative management. >90% achieve near-normal femoral head shape.

Age 6-8 years: Intermediate prognosis. Herring A and early B patients usually achieve good outcomes with conservative management. Herring C patients benefit from more aggressive containment.

Age >8 years: Reduced remodeling capacity. Herring C patients have significant risk of residual deformity (coxa plana, hip pain) without surgical containment. Outcomes worse in this age group.

Long-term complications: Residual hip deformity (coxa plana) may lead to early osteoarthritis in adulthood, particularly if femoral head coverage is inadequate. Hip pain, hip flexion contracture, and functional limitation may persist into adulthood in some cases.

Follow-up into adulthood: Patients with history of Perthes disease should be counseled about increased risk of hip osteoarthritis in middle adulthood. Emphasize importance of activity modification, weight management, and early treatment of hip symptoms.

• American Academy of Orthopaedic Surgeons (AAOS): Guidelines on Legg-Calvé-Perthes disease
• International Hip Dysplasia Institute: Evidence-based recommendations for Perthes disease management
• Pavlik Study Group: Long-term outcomes of Perthes disease treatment strategies
• Australian Orthopaedic Association: Perthes disease management in children
• eTG - Therapeutic Guidelines: Perthes disease in children