DEFINITION
Idiopathic interruption of blood supply to the proximal femoral epiphysis in children, leading to avascular necrosis and subsequent remodeling.
• Osteonecrosis and chondronecrosis of the femoral head
• Resorption and renewal of necrotic bone
• May result in coxa plana and coxa magna
HISTORY
Independently described in 1910 by four physicians (Arthur Legg-USA, Jacques Calve-France, Georg Perthes-Germany, Henning Waldenström-Sweden) across four countries as a cause of limping in children.
EPIDEMIOLOGY
INCIDENCE | 5–9 per 100,000 children Higher prevalence at northern latitudes |
• Peak age: 4–8 years; range 18 months – 15 years
• Male predominance → M: F = 5: 1
• Associated with low socioeconomic status and white race
• 10–13% bilateral involvement
ETIOLOGY
Risk Factors
• Systemic growth and developmental disorders
• Low socioeconomic status; passive smoking exposure
• Hyperactivity or ADHD
• Repetitive trauma
• Hemoglobinopathy and coagulopathy
• Hereditary predisposition
PATHOPHYSIOLOGY
Phase | Pathological Changes |
EARLY / NECROSIS | • Synovitis • Necrosis of trabecular bone and bone marrow • Articular cartilage thickening; deep layer necrosis |
FRAGMENTATION | • Vascular granulation tissue invasion of bone marrow • Increased vascularity in cartilage • Osteoclast proliferation and bone resorption |
REOSSIFICATION | • New bone formation on old trabeculae • Woven bone → mature lamellar bone over time |
REMODELING | • Femoral head reshapes until skeletal maturity |
CLINICAL FEATURES
Symptoms
• Insidious onset limp — late presentation is common
• Pain may be absent or mild; exacerbated by activity, relieved by rest
• Pain typically in the groin; may radiate to thigh or knee
• Waxing and waning course; acute onset in some cases
• History of trauma in approximately 17% of patients
Physical Examination
• Restricted hip range of motion — especially abduction and internal rotation
• Early: synovitis and adductor spasm
• Later: antalgic gait and Trendelenburg gait
• Trendelenburg test frequently positive
• Gluteal, quadriceps and hamstring atrophy (disuse)
• Leg length discrepancy (femoral head collapse)
• Laboratory tests: normal
IMAGING
Plain Radiography — Key Findings
• Increased density of the femoral head
• Mild flattening of the superior femoral head
• Widening of the medial joint space
• Irregularity of femoral head ossification
• Crescent sign — present in ~30% of cases
Advanced Imaging
• MRI: Excellent for early diagnosis, especially when radiographs are normal
• Bone scan: Demonstrates avascular zone in early stages
• Arthrography: Useful for evaluating hinge abduction
WALDENSTRÖM CLASSIFICATION
Defines the chronological radiological stages of the disease. Johan Henning Waldenström (1877–1972), Swedish Orthopaedist.
Stage | Duration | Radiological Features |
Initial (Necrosis) | Avg. 6 months | Small, sclerotic epiphysis Medial joint space widening Radiographs may be normal for 3–6 months |
Fragmentation | Avg. 8 mo (2–35) | Subchondral lucent line (crescent sign) Collapse, patchy densities and lucencies Mechanically weakest stage; symptoms most pronounced |
Reossification | Avg. 51 mo (2–122) | New bone formation (woven → lamellar) Femoral head regains roundness |
Remodeling | Until skeletal maturity | Femoral head reshapes toward skeletal maturity |
CATTERALL CLASSIFICATION
Classifies involvement of the femoral head epiphysis into 4 groups. Higher group number indicates worse prognosis.
Group | Extent of Involvement | Key Features |
Group 1 | Anterior epiphysis only | No collapse or sequestrum |
Group 2 | Anterior epiphysis — greater area | Collapse and sequestrum present |
Group 3 | Large portion of epiphysis | Most of epiphysis sequestrated |
Group 4 | Entire epiphysis | Total involvement — worst prognosis |
Catterall 'Head-at-Risk' Signs
• Gage sign: V-shaped radiolucency at lateral epiphysis/metaphysis
• Lateral epiphyseal calcification
• Metaphyseal cyst
• Lateral subluxation of the femoral head
• Horizontal orientation of the proximal femoral physis
LATERAL PILLAR (HERRING) CLASSIFICATION
Assessed on AP radiograph during the fragmentation stage. Evaluates the height of the lateral column of the femoral head epiphysis. Provides prognostic information.
Group | Lateral Pillar Height | Prognosis / Notes |
A | Fully maintained — minimal density change | Best prognosis |
B | > 50% height maintained | Poor prognosis in patients with bone age ≥ 6 years |
B/C | Narrow (2–3 mm) or exactly 50% height | Intermediate group |
C | < 50% height maintained | Poor prognosis in all age groups |
STULBERG CLASSIFICATION
Applied at skeletal maturity. Classifies femoral head shape and acetabular congruence into 5 classes. Predicts long-term arthritis risk.
Class | Femoral Head | Congruence | Long-term Outcome |
I | Completely normal | Spherical-congruent | No osteoarthritis expected |
II | Spherical — with coxa magna, short neck or shallow acetabulum | Spherical-congruent | No osteoarthritis expected |
III | Ovoid/elliptical - > 2 mm deviation from sphericity | Aspherical-congruent | Mild/moderate OA in later life |
IV | Flat (cylinder-like) — flexion/extension preserved, rotation markedly restricted | Aspherical-congruent | Mild/moderate OA in later life |
V | Flat head — resembles adult AVN | Aspherical-incongruent | Severe OA before age 50 |
TREATMENT PRINCIPLES | |
CORE CONCEPT | Containment: maintaining the femoral head within the acetabulum Equalizes forces acting on the femoral head Acetabulum serves as a biological mold for the remodeling femoral head Goal: spherical, congruent hip — prevention of degenerative arthritis |
Conservative Treatment
• Indications: age < 8 years (bone age < 6), Lateral Pillar Group A involvement
• Activity restriction and protected weight-bearing until reossification is complete
• Preservation of hip range of motion
• Containment within the acetabulum
• Abduction casting (Petrie cast) — benefit disputed in large prospective studies
Conservative Treatment Methods
• Skin traction
• Petrie cast (abduction cast)
Surgical Treatment — General Principles
Prerequisites for surgical containment:
• Adequate hip range of motion must be present
• Hinge abduction must be absent
Containment may be achieved by femoral and/or acetabular procedures. No consensus on the optimal technique.
Procedure | Mechanism / Indication | Notes |
Femoral Varus Osteotomy | Redirects lateral epiphysis toward acetabular center | Preferred in early stage (initial/fragmentation) In patients> 8 years 10–15° of varus sufficient Trochanteric apophysiodesis may be added |
Salter Innominate Osteotomy | Increases acetabular coverage from the pelvic side | Redirects acetabulum via ilium osteotomy |
Triple Pelvic Osteotomy | Pelvic-side containment | Comparable outcomes to Salter |
Shelf Acetabuloplasty | Augments lateral acetabular coverage with autologous bone graft | Lateral subluxation, inadequate coverage Hinge abduction Also used as a salvage procedure in late stages |
Femoral Valgus Osteotomy | Moves the deformed area away from the acetabulum | For hinge abduction (congruence improves in adduction) Corrects shortening; improves abductor mechanics |
TREATMENT ALGORITHM — SUMMARY
Parameter | Conservative | Surgical |
Age | < 8 years (bone age < 6) | ≥ 8 years |
Herring Group | A (all ages) and B (< 8 years) | B/C, C and B (≥ 8 years) |
Waldenström Stage | All stages applicable | Preferred in early stage (initial / fragmentation) |