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Hemimelia
What are the symptoms?
Fibular hemimelia
This is one of the most common longitudinal limb deficiencies, with an incidence of about 1 in 50,000. The fibular fails to develop in part or whole. The spectrum of abnormality ranges from mild bowing of the leg, to knee joint instability with "knock knee" appearance, unstable ankle with a reverse "club-foot" appearance, and shortening of the lower leg. Sometimes foot, ligament and thigh bone (femoral) abnormalities are associated. The deformity tends to increase with growth, as there is limited growing potential within the affected bone. Since there is often a significant soft tissue deficiency, severe deformity at the ankle often requires a foot amputation known as a "Symes" amputation. Tibial straightening procedures (osteotomies) and limb lengthening procedures can also be undertaken.
Tibial hemimelia
This is a very rare congenital deficiency, with an incidence of about 1 in 1,000,000, in which the tibia fails to develop in part or in whole. Associated problems may include hip and hand abnormalities. There may be associated ligament absence, and an abnormal end of the thigh bone (femur). Many cases are severe, resulting in amputation at or below the knee which may produce a better quality of life and an ability to walk on the affected leg using a prosthetic.
Radial hemimelia
In this condition, the radius fails to develop normally either in part or in whole, causing the position of the hand to tend to drift to the thumb-side of the wrist. Also known as "radial club hand", the incidence is about 1 in 50,000, and mostly occurs without an obvious cause. A range of severity exists, and may be associated with mild or severe hand abnormalities. This may be associated with other disorders such as TAR syndrome that include low platelet count (thrombocytopaenia) or Fanconi anaemia, a form of anaemia. Rarely cardiac, kidney, and tracheal-gullet anomalies are present. Treatment of moderate and severe deformities involves re-aligning the ulna bone using osteotomies and/or external fixators, and centering the wrist on the remaining ulna. Sometimes an absent thumb will be fashioned from an adjacent finger.
Ulna hemimelia
Much less common than radial hemimelia (1 in 150,000), this condition is also known as "ulnar club hand" in which the ulna bone of the forearm fails to develop in part or in whole. The position of the hand tends to drift to the little-finger-side of the wrist and sometimes fingers may be short or absent too. The radius may be fused to the ulna (synostosis). Rarely, there are associated abnormalities of the femur, fibula or shoulder blade. It may be necessary to undertake re-alignment operations of the lower humerus, the radius or ulna. Function in a synostosis may be improved by changing the angle that the forearm sits in rotation.
Background
| Inheritance patterns and prenatal diagnosis 
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