Fibular hemimelia, sometimes known as paraxial fibular hemimelia or longitudinal fibular deficiency, is a condition in which a child is born with part or all of the fibula missing. Together with the tibia, the fibula is a bone in the lower leg. While the slender fibula is located on the outside of the leg, the thicker tibia is situated on the inside. Fibular hemimelia typically makes the affected limb shorter and causes the foot to bend inwards and down. Various treatments are available depending on the severity of the deformity, ranging from special footwear to limb lengthening surgery, or amputation and the fitting of an artificial body part, or prosthesis.
Although fibular hemimelia is the most frequent cause of deformed bones in the legs, its cause is unknown. The deformity often affects only one limb, and the disorder is more common in men than women. Sometimes there may be other associated deformities affecting the tibia, the femur, or thigh bone, and the foot. A number of different systems are used to classify fibular hemimelia, with classes ranging in severity from relatively mild to severely disabling. Each class is associated with a particular treatment plan and outlook.
In one classification system, what is called type IA fibular hemimelia refers to the condition where only part of the fibula is missing. Type IB describes the state where a third to a half of the fibula is missing and the amount of bone that remains is not sufficient to support the ankle. In type II, the most severe, there is no fibula at all.
The treatment of type IA fibular hemimelia does not always involve surgery because, in milder cases, walking may be possible with the use of a heel lift. A heel lift is an extra piece added to a shoe in order to effectively equalize the lengths of the legs. Sometimes, with only a small difference in leg lengths, a technique known as contralateral epiphysiodesis may be used in order to shorten the opposite leg. This procedure, which stops the bone from growing, is timed carefully to coincide with the final growth phase in adolescence, with the aim of leaving the normal leg slightly short. For a larger difference in leg length, and where the ankle and foot are not too misshapen, surgery can be performed which extends the shortened limb.
Type IB fibular hemimelia is treated similarly to IA, although operations may also be required to correct the angle of the ankle and stabilize the foot. For type II, a number of different surgical procedures may be necessary. The foot is sometimes removed early in life and a prosthesis may be used to enable efficient walking.