Hemimelia is a type of malformations or a congenital absence of individual bones. These defects include vertebral segment defects (hemivertebra) seen in the German Shorthaired Pointer, apodia (absence of a limb), amelia and hemiamelia (absence of parts of a limb), ectrodactyly ("lobster claw syndrome"), polydactyly (extra digits) seen in the Australian Shepherd, Great Pyrenees and Saint Bernard, anury (no tail) seen in the Cairn Terrier and Cocker Spaniel, brachury (short tail) seen in the Beagle, spina bifida seen in the Bulldog and syndactyly (fusion of bone and/or tissue between two or more digits). Limb deformity and disability are evident from birth. In cats and dogs radial hemimelia is most often seen, although tibial, ulnar and fibular hemimelia also occur. Bilateral hemimelia of the Chihuahua dogs is inherited as an autosomal recessive trait.

Radial hemimelia is a congenital abnormality characterized by the partial or complete absence of the radius. If all or part of the middle bones of a limb are absent, with the proximal and distal portions being present, the hemimelia is called intercalary. The longitudinal hemimelia indicates the absence of one or more bones along the preaxial (medial) or postaxial (lateral) side of the limb. Preaxial longitudinal intercalary radial hemimelia is the most common type of hemimelia in dogs and cats. This condition is usually unilateral, but bilateral absence may occur. The condition is usually noticed soon after birth. Possible causes include dietary mineral deficiencies, genetic predisposition and in utero events of compression, drugs, vaccines, irradiation and nutritional deficiencies. Radial hemimelia can be successfully treated with corrective surgery. Surgical corrections result in satisfactory use of the limb and a better quality of life.


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