Structural characteristics and predicted functional capacities of epaxial muscles in chondrodystrophic and non-chondrodystrophic dogs with and without suspected intervertebral disc herniation- a preliminary study

Epaxial muscle atrophy is related to spinal diseases in dogs. However, the influence of intervertebral disc herniation (IVDH) on the functional capacity of epaxial muscles has not been investigated. We aimed to estimate force and power-generating capacity of epaxial muscles in chondrodystrophic Dachshunds and non-chondrodystrophic Border terriers bred for similar purposes. Further we aimed to compare these features in Dachshunds with and without IVDH. Cadavers of Dachshunds (n = 16) and Border terriers (n = 7) were investigated with MRI. In the absence of clinical information, MRI findings were used to categorize the Dachshunds into affected (n = 8) and non-affected (n = 8). Epaxial muscle mass, muscle belly length, fascicle length, architectural index and physiological cross-sectional area (PCSA) were obtained through dissections, pain and exercise history through questionnaires. Difference between groups and effect of covariates were assessed with ANCOVA models. Dachshunds had greater muscle mass in M. splenius, M. longissimus capitis and M. iliocostalis thoracis (all P < .05). Dachshunds had higher PCSA in M. semispinalis complexus (P = .004) and M. iliocostalis lumborum (P = .016) than Border terriers, which had longer muscle fascicles in these muscles (P = .004 and P = .002, respectively). Affected Dachshunds had longer muscle fascicles than non-affected Dachshunds in M. longissimus thoracis et lumborum (P = .004) and M. longissimus cervicis (P = .011). Body weight had a significant impact on all muscle variables, but pain and exercise had none. Dachshund epaxial muscles have greater potential for force production than those of the Border terrier. This may imply that Dachshunds, due to predisposition to IVDH, require more spinal stability provided by the epaxial muscles.