Hemimelia – a birth defect involving a unilateral or bilateral underdevelopment of the distal portion of the upper or lower limb. The defected bone can be shortened or completely undeveloped (aplasia). There are two types of hemimelia – transverse and longitudinal.
Transverse hemimelia is a congenital absence of a portion of a limb (as opposed to amelia, in which the entire limb is absent). It is clinically similar to a state after amputation (hence it is sometimes called “congenital amputation”). Longitudinal hemimelia is a partial absence of one of the components of a limb in the longitudinal axis (in phocomelia there is a complete lack of a portion of a limb). It is simply an underdevelopment and shortening of the bone building the limb.
The defect most commonly involves the following bones:
- fibula - fibular hemimelia
- tibia - tibial hemimelia
- radius - radial hemimelia
- ulna - ulnar hemimelia.