Legg-Calvé-Perthes Disease

Legg-Calvé-Perthes disease is idiopathic avascular necrosis of the femoral head in childhood, resulting from disruption of the blood supply to the proximal femoral epiphysis. It most commonly presents between four and ten years of age, with a notable male predominance.

The natural history is characteristic, though variable in duration and severity. It comprises sequential phases of necrosis, fragmentation, reossification and, healing.

The central goal of management is containment of the femoral head within the acetabulum during the vulnerable period of active disease. This supports optimal femoral head remodelling and minimises the risk of long-term residual deformity and premature osteoarthritis.

Pathophysiology and natural history

• The cause of the vascular disruption to the proximal femoral epiphysis remains incompletely understood.
• The epiphyseal blood supply relies substantially on relatively vulnerable vessels during this age range, before the more robust, redundant pattern of later childhood and adulthood develops. This is believed to underlie the characteristic age range.
• The disease follows a sequence of pathological phases. The first is avascular necrosis, in which the femoral head bone becomes necrotic but initially retains its normal shape.
• Fragmentation follows, as necrotic bone is progressively resorbed and replaced with new, initially weaker bone. The femoral head is at greatest risk of collapse and deformation in this phase if inadequately protected or contained.
• Reossification follows, as new, more mature bone progressively forms, and finally a healing phase. The entire natural history typically extends over one to several years.
• The shape and sphericity of the femoral head at the end of healing directly determine long-term hip function and the risk of premature osteoarthritis.
• A spherical, well-contained head carries a substantially more favourable prognosis than a flattened, deformed, poorly contained one. This underlies the central treatment goal of supporting containment and remodelling throughout the vulnerable fragmentation phase.

• The characteristic presentation is a gradual onset of limp, with hip, groin, thigh or, given the referred pain pattern, knee pain developing over weeks to months. There is typically no clear preceding traumatic event.
• The condition typically affects a single hip. Bilateral, sequential involvement occurs in a meaningful minority of affected children.
• Examination shows limited hip range of motion, particularly internal rotation and abduction. Some children have a mild Trendelenburg gait, reflecting hip abductor weakness or dysfunction.
• The child generally remains systemically well, without fever or significant systemic upset. This is a useful distinguishing feature from septic arthritis or other significant infection.
• Severity and functional impact vary considerably with the extent of femoral head involvement and, importantly, the age at onset.
• Younger children (generally under approximately six years of age at onset) have a substantially more favourable natural history than older children, because they have greater remaining growth and remodelling capacity.

• Plain radiography of the pelvis is the standard initial investigation. The appearance varies with the stage of disease at assessment.
• Early changes are subtle and include relative femoral head lucency and, subsequently, increased density. More characteristic, later findings are fragmentation and, reossification.
• Serial radiography over the course of the disease supports monitoring of disease stage and progression.
• Magnetic resonance imaging is more sensitive for early disease, before changes are clearly apparent on plain radiography. It also gives more detailed assessment of femoral head containment and the extent of epiphyseal involvement.
• It is a valuable, though not universally required, adjunct, particularly in diagnostic uncertainty or for detailed pretreatment planning.
• Full clinical assessment, including careful exclusion of the alternative diagnoses in the broader differential of hip pain and limp in this age group, is an essential component of evaluation.

• Management is individualised to the child's age at onset, the extent of femoral head involvement, and the degree of femoral head containment within the acetabulum.
• Younger children with limited disease and good initial containment are frequently managed with observation and symptomatic management alone, given the favourable natural remodelling capacity of this lower-risk population.
• Symptomatic management is a foundational component across the full spectrum of severity. It comprises activity modification during significant exacerbation, physiotherapy to maintain hip range of motion, and simple analgesia as required.
• Containment treatment is the central principle for more significant disease. It aims to keep the femoral head positioned and contained within the acetabulum during the fragmentation phase, when the bone is at greatest risk of collapse and deformation.
• It is particularly relevant in older children, given their less favourable natural remodelling capacity, and in those with more extensive head involvement or inadequate containment.
• Containment is achieved by non-surgical bracing, with variable evidence of effectiveness, or, more commonly in contemporary practice for higher-risk disease, by surgical containment procedures (femoral or, less commonly, pelvic osteotomy). These improve the mechanical relationship between the femoral head and acetabulum throughout the vulnerable period.
• Regular, structured orthopaedic follow up is standard throughout the often prolonged natural history. It incorporates serial clinical and radiographic assessment to monitor disease stage and progression and to guide management decisions.
• Long-term follow up should extend beyond resolution of the acute disease, given the substantial risk of long-term hip dysfunction and premature osteoarthritis. This is particularly relevant for children with more extensive disease, older age at onset, or inadequate containment during the vulnerable period.
• Patient and family education and support are needed throughout the often prolonged, uncertain and anxiety-provoking natural history.