Bilateral Tibial Hemimelia: A Case Study

Tibial hemimelia is a longitudinal deficiency of the tibia in which there is either a complete or partial absence of the tibia. Tibial hemimelia is far more rare than fibular hemimelia but it is also more difficult to manage due to the loss of the weight-bearing bone in the lower leg and the absence of controlled knee function. Tibial hemimelia presents bilaterally in only 30% of cases and it is often accompanied by several other abnormalities of the extremities (1). The foot is usually in a grossly supinated position. The femur is often shortened due to a hypoplastic distal femoral epiphysis (2). The thigh section may be smaller in length and circumference because the thigh musculature that would normally attach to the tibia is either absent or abnormal. The proximal end of the fibula is often flat and bowed. Hip subluxation and dislocation are common. There may be knee flexion with popliteal webbing and polydactyly or diplopodia. There may even be central aphalangia ("lobster-claw") of the hands.

There are five types of tibial hemimelia: type 1a, type 1b, type 2, type 3, and type 4. In type 1a tibial hemimelia (as seen in this case), there is complete absence of the tibia with proximal and lateral dislocation of the fibula (3). Previously, a surgical procedure called the Brown procedure was performed on these patients. It involved a fibular centralization with a Symes ankle disarticulation (1). The patient was then fitted with a Symes prosthesis with joints and corset. However, surgical outcomes were generally poor and subsequent surgeries were often required. Thus, this procedure is no longer recommended. For type 1a tibial hemimelia with no functioning quadriceps, knee disarticulations are now often recommended (4). However, if there is marked shortening of the femur, arthrodesis of the femur and fibula may be recommended instead to provide a longer residual limb (2).

This case is that of a young girl born with bilateral type 1a tibial hemimelia. Comorbidities at birth included: bilateral dysplastic hips, a dislocated right hip, shortened and asymmetric femurs, bilateral fusion of the calcaneus and talus, severely supinated feet and abnormalities of the toes. Several genetic tests and other diagnostic studies were performed shortly after her birth and none of them found a cause for the congenital malformation. At 11 months of age, the child underwent successful bilateral ankle disarticulations and calcaneal osteotomies with Boyd type reconstruction and internal fixation (5). She presented in our office with well-healed residual limbs. Skin was in good condition with the exception of significant eczema. She had 40° bilateral knee flexion contractures. Her hips were lax and presented with about 100° of external rotation and 10° of internal rotation bilaterally.

Due to the knee flexion contractures and lack of motor control of the knees, the child was fit with transfemoral stubbie-type prostheses. The prostheses were an exoskeletal design with Symes SACH [*Kingsley Child Symes from Kingsley Mfg. Co., Costa Mesa, CA 92628.] feet. Locking gel liners [*Iceross original, two color, 2mm locking liner without cover from Ossur North America, Alisa Veijo, CA 92656.] were used with a lanyard type locking mechanism for suspension. With these prostheses, the child was able to stand with assistance but ambulation was difficult in part due to her severe hip instability. A custom bilateral torsion control silesian belt was added to the prostheses to internally rotate her hips. This improved her standing stability but she still did not ambulate.

The child is now three years old and is wearing her second pair of prostheses. The design of these prostheses is slightly different from the first pair. The locking gel liners were replaced with BockLite [*Three millimeter Bocklite from Otto Bock Health Care, Minneapolis, MN 55447.] soft inserts for improved cosmesis and weight as well as ease of donning. Unfortunately, the child's knee flexion contractures increased to 55° on the left and 45° on the right so this had to be accommodated for in the new prostheses. The knee flexion contractures and leather thigh tongues were used to achieve self-suspension. A similar custom torsion control Silesian belt was used to provide auxiliary suspension and a reasonable hip position. The transverse plane position of the feet in the second pair of prostheses was changed to better match the hip position with the Silesian belt in place. The child stands in the prostheses with about 40° of hip external rotation and 50° of hip flexion bilaterally. She is able to ambulate with a rolling walker or with moderate assistance from her mother. She alternates between a reciprocal gait and a swing through gait.

The child's rotary hip instability significantly limits her ability to ambulate independently. In addition, her knee flexion contractures inhibit the design, function and cosmesis of the prostheses. While knee disarticulation is often recommended in cases like this one, both the surgeon and the child's mother would like to retain the fibular segments for cosmetic purposes. Surgical correction of her knee flexion and hip external rotation contractures is planned for the near future. This should allow for a significant change in the design and, hopefully, the function of her prostheses.

References

1. Amputation: Surgical Practice and Patient Management. Ed: Murdoch G, Wilson AB. Oxford: Butterworth Heineman, 1996: 225-226.

2. Kostuik JP. Amputation Surgery and Rehabilitation: The Toronto Experience. New York: Churchill Livingston, 1981: 133-135.

3. Sanders G. Lower Limb Amputations: A Guide to Rehabilitation. Philadelphia: F. A. Davis, 1986: 528-531.

4. Atlas of Amputations and Limb Deficiencies: Surgical, Prosthetic and Rehabilitation Principles. 3rd ed. Ed: Smith DG, Michael JW, Bowker JH. Rosemont: American Academy of Orthopedic Surgeons, 2004: 793.

5. Sponseller, P. Clinical and surgical notes from clinic appointments and hospital stays at Johns Hopkins Hospital. 2003-2005.