Hemimelia

Dysostoses are malformations or a congenital absence of individual bones. They include vertebral segment defects (hemivertebra) seen in 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 Australian Shepherd, Great Pyrenees and Saint Bernard, anury (no tail) seen in Cairn Terrier and Cocker Spaniel, brachury (short tail) seen in Beagle, spina bifida seen in Bulldogs 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. Bilateral hemimelia of Chihuahua dogs is inherited as an autosomal recessive trait.

Treatment of Radial Hemimelia

Radial hemimelia can be successfully treated with corrective surgery. Surgical corrections result in satisfactory use of the limb and a better quality of life.

Malformations of the extremities or parts of them are varied in their manifestations, ranging from absence of a single structure to partial or complete absence of the limbs. 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.

Congenital absence of radius is not common in dog and cats. Congenital deficiencies of the forelimb include segmental deficiencies of the radius and ulna. The affected limb(s) are shortened, deformed and are not functional.

The genetic defects that cause the limb deficiencies are associated with autosomal dominant inheritance; however, other genetic causes include an autosomal recessive inheritance and chromosomal aberrations. In dogs and cats, limb formation occurs from day 23 of gestation to approximately day 35. Congenital malformations of the forelimb occur more frequently than those of the hindlimb, as the forelimb develops earlier.

Adapted from
1. M.R. ALAM, S.Y. HEO, H.B. LEE, J.H. KIM, Y.J. PARK, K.C. LEE, I.H. CHOI, N.S. KIM. Preaxial longitudinal intercalary radial hemimelia in a dog: a case report. Veterinarni Medicina, 51, 2006 (3): 118–123
2. Breur GJ, Lust G, Todhunter RJ. Genetics of canine hip dysplasia and other orthopedic traits, in Ruvinsky A, Sampson, J (eds): The Genetics of the Dog. New York, NY, CABI Publishing, 2001, pps 267-298.
3. LaFond E, Breur GJ, and Austin CC. Breed susceptibility for developmental orthopedic diseases in dogs. Journal of the American Animal Hospital Association 2002; 38: 467-477.