THE CASE
A healthy 6-month-old girl born via spontaneous vaginal delivery to a 33-year-old mother presented to her family physician (FP) for a routine well-child examination. The mother’s prenatal anatomy scan, delivery, and personal and family history were unremarkable. The patient was not firstborn or breech, and there was no family history of hip dysplasia. On prior infant well-child examinations, Ortolani and Barlow maneuvers were negative, and the patient demonstrated spontaneous movement of both legs. There was no evidence of hip dysplasia, lower extremity weakness, musculoskeletal abnormalities, or abnormal skin markings. The patient had normal growth and development (50th percentile for height and weight, average Ages & Stages Questionnaire scores) and no history of infection or trauma.
At the current presentation, the FP noted a leg-length discrepancy while palpating the bony (patellar and malleolar) landmarks of the lower extremities, but the right and left anterior superior iliac spine was symmetrical. The gluteal folds and popliteal fossae were asymmetric, a Galeazzi test was positive, and the right leg measured approximately 2 cm shorter than the left leg. There was no evidence of scoliosis or pelvic abnormalities. Physical examination revealed no ecchymosis or trauma. Orthopedic evaluation by the FP of the hips, knees, and ankles was normal, including negative repeat Ortolani and Barlow maneuvers and normal range of motion. We obtained x-rays of the lower extremities and ordered an orthopedic consultation.
THE DIAGNOSIS
The differential diagnosis included congenital, traumatic, infectious, inflammatory, idiopathic, and neurologic causes.1-3 The most common etiologies of leg-length discrepancies are summarized in TABLE 1.1-3 Radiographic imaging showed a femur length discrepancy, which was determined to be congenital without indication of trauma or disease; therefore, a diagnosis of congenital femoral bowing was made.
Initial orthopedic evaluation revealed a femur length discrepancy of approximately 2 cm. Plain films showed lateral femoral bowing (FIGURE 1A). Regular interval imaging performed at routine well-child examinations at 19 months, 3 years, and 5 years of age showed progression of the femoral length discrepancy from 2 cm to nearly 5 cm, remaining proportionally constant, as well as increasing genu valgum of the right leg up to 12 degrees (FIGURE 1B-D).
DISCUSSION
Congenital femoral bowing, which can present as a leg-length discrepancy in infants, is a relatively rare finding with an incidence of 1 per 52,000 births.4 Our patient presented with an isolated limb deformity, but congenital femoral bowing is recognized as a clinical feature of several skeletal dysplasias (TABLE 2).5
What’s recommended
The American Academy of Pediatrics recommends routine age-appropriate physical examination without specifying leg-length assessment.6 There is insufficient evidence, according to the US Preventive Services Task Force and the American Academy of Pediatrics, regarding the value of routine infant hip and leg-length assessment for developmental dysplasia of the hip and other musculoskeletal abnormalities; however, both agree that abnormal findings require follow-up and management.6-8
Congenital femoral bowing requires plain film diagnosis
Following physical examination, diagnosis of congenital femoral bowing should be confirmed by plain films. Plain radiography remains the main imaging modality for proximal focal femoral deficiency and fibular hemimelia, and appropriate identification of the osseous abnormalities seen on radiographs allows for accurate classification of congenital femoral bowing, prognosis, and surgical planning. (Minor malformations associated with congenital leg-length discrepancies are not typically identified as being part of a larger syndromic diagnosis.4) The patient should subsequently be referred to an orthopedist for monitoring and to establish a long-term management plan.
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