Perthes Disease — Management

Perthes disease (Legg-Calvé-Perthes disease, LCPD) is idiopathic avascular necrosis of the femoral head in children, typically affecting those aged 4–10 years. Interruption of the blood supply to the femoral epiphysis leads to bone death, subchondral fracture, resorption, and ultimately revascularisation and reossification. The outcome is determined by the degree of femoral head deformity that develops during the vulnerable avascular phase — a spherical femoral head confers a good prognosis, whereas a flattened or extruded head leads to early hip arthritis.

• Epidemiology: incidence approximately 1 in 10,000 children; male:female ratio 4:1; bilateral in 10–15% (usually asymmetric, sequential); peak onset 5–7 years; white children more commonly affected; lower socioeconomic groups have higher incidence
• Blood supply to the femoral head in children: the lateral epiphyseal vessels (retinacular arteries — branches of the medial femoral circumflex artery) are the dominant supply after age 4; the ligamentum teres contribution is small and insufficient alone; these vessels are vulnerable to interruption by raised intra-articular pressure (effusion), capsular trauma, or ischaemic insult; the precise aetiology of LCPD remains unknown — hypercoagulability, repetitive microtrauma, and vascular anomalies have all been proposed
• Natural history: self-limiting over 2–4 years through the phases of necrosis, fragmentation, re-ossification, and remodelling; the outcome (femoral head sphericity) determines the long-term risk of OA
• Children under 6 at onset have the best prognosis due to greater remodelling potential; children over 8 at onset have the worst prognosis

• Crescent sign (Caffey sign): a subchondral lucency visible on the frog-leg lateral view in Stage I/II; represents a subchondral fracture through the necrotic epiphysis; an early sign of LCPD; best seen on the frog-leg lateral radiograph; implies impending collapse of the femoral head

Two classification systems are routinely used to determine prognosis and guide management decisions in LCPD.

• Herring classification is the most important classification for guiding treatment: Herring A and B in children under 8 years have an excellent prognosis with non-operative management; Herring B/C and C (and B in children over 8) have significantly worse prognosis and are the primary indications for surgical containment
• Catterall "head at risk" signs: indicators of a poor prognosis — lateral calcification lateral to the epiphysis, Gage sign (V-shaped defect in the lateral epiphysis and adjacent metaphysis), metaphyseal cysts, lateral extrusion of the epiphysis, horizontal growth plate; the presence of two or more head-at-risk signs suggests a poorer prognosis and may prompt earlier intervention

• Presentation: insidious onset of hip or knee pain (referred pain to the medial knee from the hip is common — always examine the hip in a child with knee pain); limp (Trendelenburg gait or antalgic gait); reduced hip abduction and internal rotation (earliest loss); stiffness
• Hip examination: reduced abduction and internal rotation are the earliest and most consistent findings; measure abduction in both hips in the supine position; limitation of abduction indicates loss of containment and potential extrusion; assess Thomas test for hip flexion contracture; assess limb lengths for relative shortening
• Trendelenburg sign: positive when the hip abductors (gluteus medius) are weak or the hip is painful — the pelvis drops to the contralateral side during single-leg stance on the affected side
• Differentiate from other causes of childhood hip disease: transient synovitis (usually resolves in 1–2 weeks; inflammatory markers normal or mildly elevated), JIA, developmental dysplasia, septic arthritis (systemic illness, very elevated CRP/ESR), slipped capital femoral epiphysis (adolescents, obesity)

The fundamental principle of LCPD management is containment — keeping the femoral head within the acetabulum during the vulnerable phase of revascularisation and reossification so that the acetabulum acts as a mould to maintain femoral head sphericity. Containment can be achieved non-operatively (abduction orthosis, physiotherapy) or surgically (femoral varus osteotomy, Salter innominate osteotomy, or combined).

• Symptomatic treatment: all patients — analgesia (NSAIDs), activity restriction during painful phases, physiotherapy to maintain hip ROM (particularly abduction), avoidance of impact activity; maintaining mobility of the hip joint during treatment is essential
• Non-operative containment: abduction orthoses (Scottish Rite brace, Atlanta Scottish Rite orthosis) maintain the hip in abduction, directing the femoral head into the acetabulum; evidence for efficacy is limited in randomised trials; used in Herring B patients under 8 years; compliance is a significant problem

• Femoral varus osteotomy: intertrochanteric osteotomy creating varus angulation (neck-shaft angle reduced to approximately 110–115°); the varus position directs the femoral head deeper into the acetabulum (improves containment); fixed with a blade plate or paediatric screw-plate; the main risk is causing a permanent varus deformity and Trendelenburg limp if excessive varus is created; a second procedure to restore the neck-shaft angle may be required if excessive varus is created
• Salter innominate osteotomy: pelvic osteotomy that redirects the acetabulum anterolaterally over the extruded femoral head; acetabular containment is improved by reorienting the socket, not just varus of the femur; maintained with bone graft and fixation; preferred in children with good femoral head coverage but acetabular maldirection; can be combined with femoral varus osteotomy
• Combined femoral + pelvic osteotomy: for the most severe cases; provides maximum containment; longer surgical time and rehabilitation
• Shelf acetabuloplasty: an extra-articular bone shelf is created above the lateral acetabular rim to increase coverage of the extruded femoral head; used as a salvage procedure in late-presenting or previously untreated cases; does not provide true biological containment but provides mechanical coverage and may slow progression of lateral extrusion
• Chiari osteotomy: medialisation osteotomy of the pelvis; increases coverage; used in older children or adults with LCPD sequelae

• The Herring multicentre study (2004): the landmark prospective observational study of LCPD management; demonstrated that: children under 8 years with Herring A, B, or C all had good outcomes regardless of treatment; children 8 years and older with Herring B or B/C had significantly better outcomes with surgical containment compared to non-operative management; Herring C had universally poor outcomes in all treatment groups; this study established the current evidence-based treatment algorithm
• Hinge abduction: in advanced disease (Herring C, large extruded head), the deformed femoral head may hinge on the lateral acetabular rim during abduction rather than gliding smoothly — this hinge abduction causes pain, restricts motion, and can worsen deformity; if hinging is present, surgical containment may worsen the situation; valgus femoral osteotomy (to redirect the better-shaped medial femoral head into the acetabulum) or pelvic shelf procedures may be more appropriate in this scenario
• Long-term outcomes and THA: Stulberg IV and V hips have a very high rate of symptomatic OA by the 4th–5th decade; total hip arthroplasty is eventually required; the technical challenge in Stulberg IV/V is the malformed, large, and flat femoral head combined with an enlarged, shallow acetabulum — standard implants may not fit; dysplastic THA components or modular systems may be required; pre-operative planning with CT is essential
• Distraction arthroplasty (joint distraction): for painful stiff hips in adolescents with Perthes sequelae; an external fixator distracts the joint, off-loading the femoral head and allowing fibrocartilaginous remodelling; evidence limited; used as a joint-preserving bridge before arthroplasty in young patients

• Always examine the hip in a child with knee pain — referred pain from the hip to the medial knee is common in LCPD; a missed hip diagnosis is a serious error
• Herring lateral pillar classification: A (full height), B (>50%), B/C (exactly 50%), C (<50%); assessed during early fragmentation; most important classification for management
• Treatment algorithm: under 6 years — non-operative regardless of grade; 6–8 years Herring B — debated; over 8 years Herring B/C or C — surgical containment (Herring multicentre study evidence)
• Crescent sign: subchondral lucency on frog-leg lateral; Stage I/II; subchondral fracture; early collapse sign
• Stulberg IV/V: flat coxa plana; symptomatic OA by 4th–5th decade; eventual THA; technically challenging due to dysplastic anatomy
• Femoral varus osteotomy: NSA reduced to 110–115°; improves containment; risk of excessive varus + Trendelenburg limp if over-corrected
• Salter osteotomy: redirects acetabulum anterolaterally; improves coverage without varus deformity; combined with femoral osteotomy in severe cases
• Hinge abduction: deformed head hinges on lateral rim during abduction; worsens with containment surgery; consider valgus osteotomy or shelf procedure instead
• Catterall head-at-risk signs: lateral calcification, Gage sign, metaphyseal cysts, lateral extrusion, horizontal growth plate; 2+ signs = poor prognosis indicator
• Age at onset: under 6 = best prognosis (remodelling); over 8 = worst prognosis; the most important single prognostic variable