Weinstein Lovell and Winters Pediatric Orthopaedics 7e

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CHAPTER 30  |  The Child with a Limb Deficiency

and foot anomalies as part of the tibial deficiency ectro- dactyly syndrome, which is inherited as an autosomal dominant trait (166). Treatment in these cases is knee dis- articulation and removal of the segment of distal femur in poorest alignment. Etiology and Epidemiology.  Femoral deficiencies are one of the teratogenic effects of thalidomide. In the modern age, femoral deficiencies are sporadic, unless they are part of a larger syndrome such as femoral hypoplasia–unusual facies syndrome, which exhibits an autosomal dominant inheritance pattern. Clinical Features.  The appearance of patients with femo- ral deficiency is classic and should be easily recognized. It will be bilateral in 15% of the cases. The femoral segment is short, flexed, abducted, and externally rotated. The hip and knee joints exhibit flexion contractures. The proximal thigh is bul- bous and rapidly tapers to the knee joint (Fig. 30-32). Fibular deficiencies are so common in association with PFFD that the valgus foot and other characteristics of fibular deficiency are almost a part of PFFD. PFFD is associated with fibular defi- ciency in 70% to 80% of cases (167). In addition, approxi- mately 50% of the patients will have anomalies involving other limbs (158, 167).

Examination of the hip joint is difficult because of the bulbous thigh and short femoral segment. Pistoning may be apparent because of associated hip instability. The knee is always unstable in the AP direction. Radiographic Features.  Most of the radiographic features were covered in the description of the Aitken classification. In patients with a congenital short femur, the only finding may be slight coxa vara and an anterolateral bow in the femoral shaft. In addition, the findings of fibular deficiency are often evident, as up to 50% of these patients have concurrent fibular deficiency. Other Imaging Studies.  Recently, an MRI classification of femoral deficiency has emerged, which partially addresses the difficulty of the unossified proximal femur on plain radiographs (168). The authors demonstrated that the carti- lage anlage in the proximal femur region was well-visualized with MRI and correlated to the plain radiographic appear- ance over time to the initial MRI. They suggest that an MRI classification should be used in lieu of a plain radiographic classification. Pathoanatomy.  There are few anatomical studies of patients with femoral deficiency. Most of what we know about the pathoanatomy are based on imaging studies. There are pathologic changes throughout the entire limb of varying severity. The acetabulum can exhibit mild dysplasia and retro- version in mild cases, and it can essentially be absent in severe cases. The proximal femur can have delayed ossification and a varus deformity in the intertrochanteric region or there can be a pseudarthrosis. In severe forms, it is completely absent. With regard to the knee, findings can range from mild anterior/pos- terior laxity to complete absence of the cruciate ligaments to severe flexion contracture. As mentioned previously, the lower leg can be normal, but often exhibits fibular deficiency, pos- sibly with severe foot deficiencies that occasionally go along with that disease process. Pirani et al. (169) recently described the MRI appear- ance of the musculature around the hip and proximal femur. Most muscles were hypoplastic, except for the obturator exter- nus and the sartorius, which were hypertrophied. In addition, the obturator externus coursed in an abnormal direction in more severe cases. In describing their MRI classification for PFFD, Maldjian et al. (168) showed, in patients who do not develop pseudarthrosis of the proximal femur, that there is a ­cartilaginous anlage that attaches the proximal femur to the femoral head. Natural History.  Regardless of the severity of the femoral deficiency, children will usually walk at the normal develop- mental age. Children with a mild congenital short femur walk with a slight Trendelenburg gait and have a mild limb-length discrepancy. They often compensate with varying degrees of hip, knee, and ankle flexion on the contralateral side if

FIGURE 30-32.  This photo of a 12-month-old girl who is pulling to the standing position demonstrates the clinical features of PFFD: a very short and bulbous femoral segment, which is flexed, abducted, and externally rotated.