Prevalence, grading and genetics of hemivertebrae in dogs

Hemivertebrae are the most frequent vertebral malformations in dogs and particularly common in chondrodystrophic dog breeds like the French bulldog, English bulldog, Pug and Boston terrier. Clinical signs caused by hemivertebrae are pelvic limb ataxia and paresis, loss of reflexes, kyphosis, lordosis and scoliosis, incontinence, atrophy and atony of the pelvic limbs due to a compression of the spinal cord. Hemivertebrae can be unilateral or bilateral. The standard diagnostic routine relies on ventrodorsal and lateral x-rays or even computer tomography. A few breeding associations request a mandatory x-ray examination for future breeding dogs to exclude individuals with a high number of hemivertebrae and/or hemivertebra at critical localisations in the thorarcic spine or highly malformed vertebrae. Heritability estimates in French bulldogs indicate that breeding progress can be made using selective breeding and predicting breeding values for future breeding animals.