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Q1: What is the likely diagnosis and how does it typically present?
Legg-Calvé-Perthes (LCP) disease, also known as idiopathic avascular necrosis of the proximal femoral epiphysis, is one of the more insidious causes of a limp in the paediatric population. It commonly presents between the ages of 5 and 7, although it has been reported in children ranging from the ages of 2 to 16. Although its aetiology remains unclear, it is three times more common in boys and has been shown to be associated with protein C and protein S deficiencies as well as various other thrombophilias.
Clinically, LCP disease presents with a slowly developing and gradually worsening limp, that may or may not be painful. Associated pain is usually activity related and relieved by rest. The pain is usually localised to the groin, inner thigh, or knee region. On examination, these children will have a positive Trendelenburg test and have limited abduction and difficulty medially rotating their affected leg. Often, they also have trouble with hip motion. With disease progression, necrosis of the femoral head leads to further degeneration and immobilisation of the hip, which can then progress to disuse atrophy of the buttocks, thigh, and calf muscles.1
Q2: What are alternative differential diagnoses in a child with a limp?
The differential diagnosis list for a child with a limp is quite extensive and can include various hormonal, metabolic, orthopaedic, and genetic causes. Frequent causes of limp also vary by age group. In the 4–11 year old age group, the most common causes of a limping gait are: septic arthritis, osteomyelitis, tarsal coalition, transient monoarticular synovitis, juvenile rheumatoid arthritis, LCP, slipped capital femoral epiphysis, and neoplasias such as osteoid osteomas or osteochondromas.2 Many of these common causes can be diagnosed by laboratory evaluation such as erythrocyte sedimentation rate for transient monoarticular synovitis, rheumatoid factor and antinuclear antibody testing for juvenile rheumatoid arthritis, and presence of a febrile course for septic arthritis or osteomyelitis.
Epidemiologically, LCP disease has been shown to be associated with a myriad of external factors such as lower socioeconomic group, advanced maternal age, later born children, short stature, low birth weight, delayed bone age, and breech birth. LCP also demonstrates a higher incidence in Asian and eastern European populations and a decreased incidence in African- Americans and native Americans. Trauma can be related to the onset of symptoms but is not implicated as a direct cause.
LCP disease is diagnosed and staged by radiography. Radiographs should be taken in the anteroposterior and frog-leg lateral position and are used to determine the progressive stage of the disease. The four classification stages for LCP disease are (1) initial, (2) fragmentation, (3) reossification, and (4) healing.3 Radiographic findings can also be used to determine prognosis. Poor prognosis is generally associated with the degree of deformity of the femoral head and acetabulum, female sex, and age of onset after 8 years of age. Definitive diagnosis of LCP must be done by technetium bone scan or magnetic resonance imaging to show the avascular necrosis of the femoral head and subsequent acetabulum-femoral deformity.
Therapy for LCP disease depends on the child and severity of the illness, active treatment is not required for all children. The main treatment, when indicated, is containment of the femoral head within the acetabulum by casting, immobilisation, or more invasive surgical methods. In the majority of children, LCP disease is a local, self healing disorder. The acetabulum undergoes bony remodelling with subsequent improvement in femoral head deformities. The long term prognosis is directly related to the onset of symptoms and degree of residual femoral head deformity and results in an increased incidence of degenerative osteoarthritis in adulthood. It was recently shown that up to 80% of LCP disease patients who underwent containment, remained active, pain-free, with a good range of motion up to 40 years after onset of symptoms, regardless of radiographic appearance.4