Abstract
Intervertebral disc extrusion (IVDE) is a common neurological disorder in certain dog breeds, resulting in spinal cord compression and injury that can cause pain and neurological deficits. Most disc extrusions are reported in chondrodystrophic breeds (e.g. Dachshunds, Basset Hounds, Pekingese), where selection for ‘long and low’ morphologies is linked with intervertebral discs abnormalities that predispose dogs to IVDE. The aim of this study was to quantify the relationship between relative thoracolumbar vertebral column length and IVDE risk in diverse breeds. A 14 month cross-sectional study of dogs entering a UK small animal referral hospital for diverse disorders including IVDE was carried out. Dogs were measured on breed-defining morphometrics, including back length (BL) and height at the withers (HW). Of 700 dogs recruited from this referral population, measured and clinically examined, 79 were diagnosed with thoracolumbar IVDE following diagnostic imaging ± surgery. The BL:HW ratio was positively associated with IVDE risk, indicating that relatively longer dogs were at increased risk, e.g. the probability of IVDE was 0.30 for Miniature Dachshunds when BL:HW ratio equalled 1.1, compared to 0.68 when BL:HW ratio equalled 1.5. Additionally, both being overweight and skeletally smaller significantly increased IVDE risk. Therefore, selection for longer backs and miniaturisation should be discouraged in high-risk breeds to reduce IVDE risk. In higher risk individuals, maintaining a lean body shape is particularly important to reduce the risk of IVDE. Results are reported as probabilities to aid decision-making regarding breed standards and screening programmes reflecting the degree of risk acceptable to stakeholders.
Highlights
Chondrodystrophy and Intervertebral Disc Extrusion (IVDE)Intervertebral disc extrusion (IVDE) is the most common spinal neurological disorder in domestic dogs [1]
Rupture of the dorsal annulus fibrosis (AF) leads to extrusion of this degenerated disc material into the spinal canal. This is in contrast to disc protrusion, where dorsal bulging of the AF and nucleus pulposus (NP) can lead to impingement of the spinal cord; the NP is retained within the AF
The aim of the current study was to investigate the relationship between relative thoracolumbar vertebral column (‘back’) length and intervertebral disc extrusion (IVDE) in a wide range of morphologically diverse breeds focussing on IVDE in the thoracolumbar vertebral column only, which is more likely to be directly affected by back and leg morphology than the cervical vertebral column, and is most commonly affected, with 85% of cases found in this region [29]
Summary
Chondrodystrophy and Intervertebral Disc Extrusion (IVDE)Intervertebral disc extrusion (IVDE) is the most common spinal neurological disorder in domestic dogs [1]. IVDE can result in spinal cord compression and injury which may be associated with pain, sensory and motor deficits, that can significantly compromise quality of life [2]. In severe cases this may result in permanent loss of function, with owners choosing to euthanise their dog or nurse them long-term as paraplegics [3], in some cases using carts for mobility [4]. In chondrodystrophic dogs, altered epiphyseal chondroblastic growth and maturation results in disproportionate dwarfism [6], manifested as a ‘long and low’ morphology In these breeds, IVDE commonly occurs between 3–7 years of age [7], following a degenerative process, chondroid metaplasia. The demographics of dogs affected by these two types of disc disease are divergent, with differences in breed and age, and characteristics of the diseases such as speed of disc degeneration, frequency of disc calcification and spinal level affected, as recently reviewed [14]
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