► [Deficiency of the proximal femoral segment]
The term proximal focal femoral deficiency is applied to a spectrum of malformations in which aplasia of the proximal femur, deficiency of the iliofemoral articulation, and limb length discrepancy occur in varying degrees (Bryant and Epps 1991) (Fig. 5.31a-c). The defect can occur with or without fibular hemimelia and can be unilateral or bilateral in
Fig. 5.31 a, b. Proximal femoral focal dysplasia in a child. a Immediately after birth, the right femoral head is not ossified, and proximal femoral shaft is bulbous. Classification was uncertain at this time. b A later radiograph taken when the child was 4 years old shows an ossified femoral head within the acetabulum. There is a large gap between the femoral head and proximal femoral shaft because the femoral neck is still unossified. c Postmortem radiograph of a newborn male with splenogonadal fusion and complex limb defects. The right femur is short, proximally deficient, with aplastic femoral head. The acetabulum is dysplastic/absent, and the femur articulates proximally with the ilium. There is significant femoral length discrepancy. The left tibia and fibula, and the left fibula are absent. The right tibia is hypoplastic. Most of the bones in the left foot are lacking. Note also left clubfoot. The upper limbs (not shown) were unaffected. [Reprinted from Hillmann et al. 1987 (a, b, with permission) and Gouw et al. 1985 (c)]
presentation (Stormer 1997). Most commonly, the defect is isolated and unilateral. When bilateral, the defect is often asymmetrical in distribution, with femoral aplasia on one side and femoral hypoplasia on the other. The right side and the male sex are preferentially affected. Four classes of increasing severity have been identified (Levinson et al. 1977; Lange et al. 1978; Goldman et al. 1978). Class A includes cases in which the femur is short, the femoral head is present, and the acetabulum is adequate. In class B, the femur is short and dysplastic and there is a large unossified gap between the femoral head and the distal segment. The acetabulum is adequate or mildly dysplas-tic. Class C proximal focal femoral deficiency con sists of femoral head aplasia, severe dysplasia of the acetabulum, and shortness of the femur with proximal tapering. In class D, only a short, deformed distal femoral segment is found, while both the femoral head and the acetabulum are absent. Function at maturity is primarily dependent upon the extent of the leg-length discrepancy (Koman et al. 1982; Panting and Williams 1978; Kalamchi et al. 1985; Gillespie and Torode 1983). When femoral focal dysplasia occurs in association with skeletal abnormalities involving the upper extremities, a highly specific pattern of rare arm defects is found, such as amelia, per-omelia at the lower end of the humerus, humero-radial synostosis, and defects of the ulna and ulnar rays (Kuhne et al. 1967). For such cases, in which femoral, fibular, and/or ulnar defects tend to be associated, the term femur-fibula-ulna syndrome (FFU complex, OMIM 228200) has been proposed (Lenz et al. 1993). The limb malformations present in the FFU complex are different from those seen in most other types of limb defects. Neither familial occurrence nor associated exogenous factors have been identified. Some evidence favors early somatic mutation (Lenz et al. 1993). The FFU complex has similarities with another pattern of malformations, which includes aplasia/hypoplasia of the ulnas, hypoplasia of the pelvis, aplasia/hypoplasia of the femurs, fibular aplasia, and variable digital abnormalities, as well as ab-sent/dysplastic nails (OMIM 601849) (Kumar et al. 1997). Overlap is also recognized with Fuhrmann syndrome (228930) and with Al-Awadi/Raas-Roth-schild syndrome (276820). The FFU complex is a separate entity from femorofacial syndrome (OMIM 134780), a rare disorder with bilateral femoral hy-poplasia/aplasia and a characteristic facies (short nose with elongated philtrum, thin upper lip, microg-nathia, upslanting palpebral fissure, cleft palate and ear deformities) that also has similarities with the caudal regression syndrome (Daentl et al. 1975; Gleiser et al. 1978). Hypoplasia of both acetabula and short or hypoplastic fibulas are additional consistently found features of this disorder.
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