Weinstein Lovell and Winters Pediatric Orthopaedics 7e

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CHAPTER 30  |  The Child with a Limb Deficiency

absence of a proximal tibia (cartilaginous or bony). This usu- ally (but not always) depends on the presence of a proximal tibial segment. A good radiographic clue is that in patients who have a proximal portion of the tibia, the distal femoral condyle is wider and the ossification of the epiphysis is better than if it is not present. An unusual type of tibial deficiency is that seen in asso- ciation with fibular dimelia. Kumar and Kruger summarized the sporadic reports until 1993 and presented the findings, associated anomalies, and treatments in six patients (102). In this deficiency, the tibia is absent and there is a duplication of the fibula. These patients have a high incidence of other anomalies, including visceral anomalies. The authors recom- mended knee disarticulation if the femur is of normal length and fusion of the fibula to create a sufficient lever arm if there is associated PFFD. Epidemiology and Etiology.  Tibial deficiency is much less common than fibular deficiency, with an incidence reported to be 1 in 1,000,000 live births (126). Also in contrast to fibular deficiency, tibial deficiency can be genetically inher- ited. Although most commonly this is seen as with autosomal dominant inheritance, cases of autosomal recessive inheri- tance have been reported by several authors (127–129). The majority of patients with tibial deficiency will have associated anomalies of the musculoskeletal and other organ systems, with an incidence of approximately 75% (124, 130, 131). Several well-described syndromes include tibial deficiency among the list of findings (127, 132–134), and genetic coun- seling is recommended. Clinical Features.  The typical appearance of an infant with tibial deficiency is a markedly shortened tibia with a rigid equinovarus-supinated foot pointing toward the perineum (Fig. 30-23). Preaxial polydactyly is the classic appearance of the forefoot, although the absence of the preaxial rays or a split foot deformity can also be seen. The fibula is prominent at the proximal lateral aspect of the knee, and the knee is most often unstable to AP and varus/valgus stress testing. The examin- ing physician should actively look for other musculoskeletal anomalies, such as preaxial upper limb polydactyly, hip dislo- cation, or scoliosis. Radiographic Features.  The Jones classification encom- passes many of the radiographic features seen in these patients with respect to the lower leg segment. Other findings include proximal dislocation of the fibula into the distal lateral thigh ­segment, which gives its common appearance on physical exam. As mentioned previously, the distal femoral epiphysis can exhibit delayed or absent ossification in Jones type Ia tibial deficiency. Other radiographic features are those of commonly asso- ciated anomalies, such as hand or foot anomalies (preaxial polydactyly, missing digits, or split hand or foot anomaly), hip anomalies (DDH, PFFD, coxa valga), or spine anomalies (congenital scoliosis).

FIGURE 30-21.  AP radiograph of the lower extremity in a patient with type Ia tibial longitudinal deficiency. Note the severely delayed distal femoral epiphyseal ossification and absence of tibial ossification.

as type II in the original Kalamchi classification. Jones type 3 tibial deficiency is extremely rare and consists of absence of the proximal tibia with presence of the distal tibia. Finally, in type 4 deficiency, there is diastasis of the distal tibiofibular joint, where the talus is wedged between the distal tibia and fibula and can articulate with the fibula alone or the fibula and tibia. The presence or absence of intact extensor mechanism function is the primary initial decision point in the treatment of these children. This usually coincides with the presence or

FIGURE 30-22.  AP radiograph of the lower extremity in a patient with type 1b tibial longitudinal deficiency. Note the increased ossifica- tion of the distal femoral epiphysis as compared to Figure 30-21.