How Long and Low Can You Go? Effect of Conformation on the Risk of Thoracolumbar Intervertebral Disc Extrusion in Domestic Dogs

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.

Clinical characterization of thoracolumbar and lumbar intervertebral disk extrusions in English Cocker Spaniels

“…[1][2][3][4]6,12,13,22,27,28 It has been demonstrated that English Cocker Spaniels have a less pronounced chondrodystrophic phenotype than Dachshunds. 5 The vertebral column length relative to the height at the withers (most dorsal aspect of the shoulders between the scapulae) was much higher in Dachshunds than in English Cocker Spaniels, but was similar between English Cocker Spaniels and German Shepherd Dogs. 5 It is therefore possible that different etiologic factors contribute to varying degrees in the development of IVDE in English Cocker Spaniels and Dachshunds.…”

“…[23][24][25] Chondrodystrophy is characterized by disturbed endochondral ossification, so that affected dogs have disproportionally short limbs and relatively long spines. 5,22,26 This was highlighted in a recent study, 5 in which investigators found that dogs with shorter limbs and longer backs were at increased risk of developing thoracolumbar IVDE than were dogs with longer limbs and shorter backs. However, strict criteria to define a breed as chondrodystrophic are lacking, 1,9,27 and it is currently unclear whether English Cocker Spaniels should be considered chondrodystrophic.…”

“…3,4,[8][9][10][11][12] English Cocker Spaniels are also predisposed to IVDE, and this breed is among the 7 breeds at highest risk for this disorder. 2,5,6,13,14 Although anecdotal information suggests a higher incidence of lumbosacral IVDEs in English Cocker Spaniels than in other dog breeds, 15 little is known about characteristics of thoracolumbar and lumbar IVDE in this breed. Therefore, the purpose of the study reported here was to characterize the clinical signs and findings associated with IVDE of these regions in English Cocker Spaniels.…”

A simplified method of walking track analysis to assess short-term locomotor recovery after acute spinal cord injury caused by thoracolumbar intervertebral disc extrusion in dogs

“…Intervertebral disc extrusion (IVDE) is the most common cause of acute spinal cord injury (SCI) in dogs, and chondrodystrophic breeds such as the Dachshund, Cocker spaniel, Basset hound, Beagle, Pekingese, Shih Tzu, Miniature poodle and Bichon frise are commonly represented in the literature (Olby et al, 2003; Ito et al, 2005; Levine et al, 2011; Aikawa et al, 2012; Bergknut et al, 2012; Packer et al, 2013). The high incidence of spontaneous SCI in dogs makes them an important animal model for human SCI (Rice et al, 2009).…”

Surgical treatment of spinal cord compression in client owned dogs with different grades of neurological dysfunction

“…Despite decades of research to identify the new therapeutics, there has been only limited progress toward the beneficial findings. Thoracolumbar intervertebral disk herniation is the most common naturally occurring spinal disease in dogs and results in compressive and contusive SCI [2,7,10]. The most common treatment for SCI is early stabilization of the spinal column followed by surgical decompression and stabilization and minimizing secondary changes [6].…”