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Define Perthes Disease. Describe its clinical features, investigations, management and diagnosis.

General Surgery · Final Professional

Definition

Perthes disease (Legg–Calvé–Perthes disease) is idiopathic avascular necrosis of the femoral head epiphysis in a child, followed by revascularisation and remodelling over a period of years. If the head reossifies while deformed, incongruity and premature osteoarthritis result. It typically affects boys aged 4–8 years and is usually unilateral.

Pathology & Stages

The natural history passes through recognised stages: an initial avascular (necrosis) phase; a fragmentation phase (resorption of dead bone); a reossification (healing) phase as new bone forms; and a final remodelling phase. The central concept guiding treatment is ‘containment’ — keeping the softened, biologically plastic head well seated within the acetabulum so it remodels into a congruent, spherical shape.

Clinical Features

A child with an insidious limp and pain in the hip, groin, thigh or (referred) knee, often intermittent. Examination shows an antalgic gait, muscle wasting and restricted movement, especially abduction and internal rotation. The child is systemically well.

DANGER / REMEMBER

A child presenting with knee or thigh pain must always have the hip examined — hip pathology (Perthes, SCFE) classically refers pain to the knee, and the true source is easily missed if only the knee is assessed.

Investigations

Plain radiographs (AP and frog-lateral) show the sequence of changes — early increased density and a smaller epiphysis, a subchondral fracture line (the crescent sign), fragmentation, and later reossification and any deformity/subluxation. MRI is more sensitive in the early stages. Prognostic classifications (Catterall, Herring lateral-pillar) assess the extent of head involvement.

Management

The aims are to relieve pain, maintain hip movement and contain the femoral head so it remodels spherically. Many young children with limited involvement do well with observation, activity limitation, physiotherapy to preserve range, and symptomatic treatment. Containment — by bracing or, more effectively, by femoral or pelvic osteotomy — is used for older children or those with more extensive head involvement or loss of containment. Prognosis is better in younger children and with less femoral head involvement.

CLINICAL PEARL

Two prognostic principles: the younger the child and the less of the femoral head involved, the better the outcome — because a young hip has far more remodelling potential. Treatment revolves around containment.

Differential Diagnosis

A limping child with hip pain has a broad differential that must be considered before settling on Perthes: transient synovitis (benign, post-viral, self-limiting), septic arthritis and osteomyelitis (febrile, toxic, raised inflammatory markers), SCFE (older, often obese adolescent), juvenile idiopathic arthritis, and, rarely, a bone tumour. Age, systemic features, inflammatory markers and imaging distinguish these; bilateral symmetrical ‘Perthes-like’ changes should prompt thought of an epiphyseal dysplasia or hypothyroidism rather than true Perthes.

Complications

The central risk is a deformed, non-spherical femoral head (coxa magna, coxa plana) that is incongruent with the acetabulum, leading to stiffness, hinge abduction and early osteoarthritis in adult life. Loss of containment and lateral subluxation during the fragmentation phase worsen the deformity, which is precisely what containment treatment sets out to prevent.

CLINICAL PEARL

Perthes hinges on two ideas: it is a self-limiting AVN that passes through necrosis → fragmentation → reossification → remodelling, and the whole of treatment is aimed at containment so the plastic head remodels into a round, congruent shape. Younger children with less head involvement need little more than observation.

DANGER / REMEMBER

Because a stiff, irritable hip in a child can equally be septic arthritis, never attribute an acutely painful, febrile hip to Perthes without excluding infection first — the two are managed completely differently and a missed septic hip is disastrous.

Containment of the head in the acetabulum guides treatment.

KEY POINT

Key points TO remember

Idiopathic AVN of the femoral head epiphysis; boys 4–8 y; usually unilateral.
Stages: necrosis → fragmentation → reossification → remodelling.
Insidious limp + hip/thigh/knee pain; ↓ abduction & internal rotation; systemically well.
X-ray shows the sequence; ‘containment’ is the guiding treatment principle.
Younger child + less head involvement = better prognosis; osteotomy for containment when needed.

EXAM TIP

Sources: Maheshwari's Essential Orthopaedics; Apley & Solomon's System of Orthopaedics and Trauma; AO Principles of Fracture Management.

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