Tibial Hemimelia: Limb Deficiency in Siblings

James E. Russell, M.D.


Summary

Two cases of tibial hemimelia in sibling girls are presented. Typical features and associated deformities are listed. A strong family history of hand and foot deformities was found to be present; and strong genetic counseling against further children, once tibial hemimelia has presented in an offspring, is urged. A plan of surgical management is presented.

Congenital absence of the tibia is a relatively rare limb deficiency and may present in patients in various forms-as a terminal longitudinal complete or incomplete paraxial hemimelia, tibial (Tibia is totally or partially absent, together with appropriate (preaxial) distal elements); or as an intercalary longitudinal complete or incomplete paraxial hemimelia, tibial (Tibia is totally or partially absent, but distal (preaxial) elements are present). The characteristic appearance of the limb in this deformity is that of a flexed knee, severe varus foot deformity with the plantar surface of the foot directed toward the opposite leg or into the perineum11, severe leg-length inequality and malrotation, instability of the knee due to lateral and posterior dislocation of the retained fibular head, reduplication of toes distal to the deformity, and popliteal webbing1.

It is important to differentiate this condition from fibular hemimelia in that (1) the foot and ankle are in varus, not valgus; (2) there is little or no anterior bowing in congenital absence of the tibia and any bowing that is present is more lateral and posterior; and (3) the proximal fibula is dislocated at the knee7.

Deformities associated with tibial hemimelia in the same limb may be absence of one or more rays of the foot, fusion of the tarsal bones, a shortness or partial absence of the fibula9, malformation of the distal femoral condyles, complete absence of the femur, congenital dysgenesis of the proximal femur and congenital subluxation or dislocation of the hip8,10. Upper-limb deformities associated with tibial hemimelia can occur in as many as 50 percent of the cases and include supernumerary digits, partial aphalangia (split-ray or lobster-claw hands), and partial adactylia (floating thumb)2.

Congenital skeletal limb deficiencies are relatively uncommon. Genetically these defects generally appear sporadically and, as a rule, are nonhereditary. The deficiencies are manifest in the fetus during the fourth to seventh postovulatory weeks of pregnancy4.

Congenital absence of the tibia is one of the very few limb deficiencies, if not the only one, that has appeared in siblings or patients with close blood lines1. The Shriners Hospital for Crippled Children in Lexington, Kentucky, is located in the Bluegrass region, near the geographic center of the Commonwealth of Kentucky in proximity to the western border of the Appalachian Mountain range. The makeup of people of this area is largely that of Anglo-Saxon stock, containing many with close bloodlines resulting from inbreeding among families for hundreds of years8. It is from the Appalachian Mountain range that the Lexington Unit draws many of its 84 active amputee-clinic patients.

Case Histories

The purpose of this paper is to report two cases of tibial hemimelia in sibling sisters. These girls exhibit many of the characteristics mentioned above. Fig. 1 reveals the tibial hemimelia deformity of T. M. at the age of one and a half years. Fig. 2 presents X-rays of the leg and foot deformity while Fig. 4 shows comparative X-rays of both feet. The X-rays of the hands shown in Fig. 3 reveal supernumerary fingers and the absence of thumbs. The X-rays demonstrate an intercalary longitudinal complete paraxial hemimelia, tibial limb deficiency. The proximal end of the bowed and thickened fibula is dislocated proximally and laterally. Reduplication of the great toe is obvious. No dislocation of the hips was present in this patient. Subsequently this girl underwent a knee disarticulation and is ambulating well in a standard end-bearing disarticulation prosthesis with outside hinges and a thigh corset. Her gait is good, and she is competing appropriately within her peer group.

In genetic counseling with the patient's parents the clinic-physician chief emphasized that there was a great likelihood a similar deformity might occur in any subsequent children1. The parents indicated that they understood and said that they did not plan to have any other children. However, a sibling sister, M. M. (Fig. 5 ), was conceived and born despite this strong genetic counseling to the contrary. The father and mother had decided on their own to gamble on a normal child because the paternal grandmother had told them that she had had a normal stillborn child with apparently normal limbs. Bilateral lower-limb deformities, similar to those of her sister, are demonstrated, together with hand deformities. The severe foot deformities in both children are characteristic of tibial hemimelia. Fig. 6 and Fig. 7 present X-ray and external views of an intercalary longitudinal complete paraxial hemimelia on the left; and an incomplete tibial hemimelia on the right side. The left hip is subluxed. The present treatment plan for this child is to reduce the left hip and attempt a reconstruction of the left knee joint according to Brown5, which is to be followed in time by a Syme amputation at the left ankle. Subsequently an attempt will be made to Synostose the right tibial fragment to the right fibula; this procedure is to be followed in time by a Syme amputation at the right ankle9.

Over the years, attempts to bring feet with a severe varus deformity into a plantigrade position have been unfruitful and unrewarding even after multiple operative procedures11. The feet have been retained initially to hold the cast on during the reconstruction procedures, but subsequently a Syme amputation usually is carried out in order to fit the child appropriately with a below-knee prosthesis1.

Successful applications of the Brown procedures to produce a lasting functional knee joint have been uncommon. Should the Brown procedure fail in our patient, disarticulation at the knee joint and fitting with a knee-disarticulation prosthesis will be carried out.

Genetic Background

The origins of this family have been traced to Rowan County, Kentucky, which is located in the middle of the Appalachian Mountains of eastern Kentucky. Several members of this family have been affected with upper- and lower-limb deformities, the first apparently being in the paternal grandfather, whose hands are pictured in Fig. 8 . The deformity of the thumbs, according to the grandfather, resembles the "front paws of a coon," and he maintains that the deformities are sure proof that he was "born under the sign of the coon." This type of simple rationalization of sporadic occurrences of physical deformities and other unknown phenomena is common to the mountain folk. As far as the grandfather knows, he was the first person to exhibit any limb deficiencies in his family. Friends of early relatives know of no deformities in this family. The grandfather also states that he was born with a left clubfoot that was apparently treated successfully by casting. The grandfather would not allow us to photograph or view his foot. The grandfather takes pride in being a "damned good carpenter" prior to his retirement several years ago. The father has reduplication of the great toes on both feet, and partial adactylia deformities of both hands. These hand deformities are pictured in Fig. 9 . The hands of a paternal uncle are pictured in Fig. 10 and Fig. 11 . Fig. 12 and Fig. 13 show the reduplication of the great toes of the uncle before ablation of a supernumerary toe on the left side. The male members of this family are not functionally encumbered by the deficiencies in the hands and feet. In addition to the grandfather's claim of being a good carpenter, the father works in a local sawmill and denies any major difficulties.

The exact genetics of the tibial hemimelia limb deficiency are unknown, but the deformity has occurred in the above family associated with a sporadic appearance of hand and foot deformities which, when inherited, became dominant. The association of tibial hemimelia with hand and foot deformities is strong, and caution is urged in genetic counseling.

Shriners Hospital for Crippled Children Lexington, Kentucky

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