EQUINE VETERINARY EDUCATION / AE / AUGUST 2020
441
and the cranial end plates of T1 and T2; the bone was otherwise eburnated (Fig 5). There was a rim of new bone around the articular margins of the intervertebral symphyses and extensive new bone on the ventral aspects of the vertebral bodies of C7, T1 and T2, the extent of which had not been appreciated radiologically (Fig 1b). The facets for the articulations of the first and second ribs on both the left and right sides had periarticular modelling.
Discussion
In the majority of Equidae in the current report it seems likely that the underlying cause of intervertebral disc disease was not infection. However, in small animals discospondylitis is defined as bacterial, or less commonly fungal or algal, spinal infection, usually haematogenous, beginning as an infection of end plates of the vertebral bodies through the highly vascular and slow-flowing metaphyseal and epiphyseal capillary beds with secondary involvement of the intervertebral disc (Kerwin 2015; Ruoff et al. 2018). The mean and median ages of the Equidae in this case series was lower than the mean age of the majority of horses presented for lameness or poor performance to both clinics (Parkes et al. 2013). It is also lower than the reported age of horses with discospondylitis (Foss et al. 1983; Nixon et al. 1984; Adams et al. 1985; Stadler et al. 1988; Furr et al. 1991; Hillyer et al. 1996; Colbourne et al. 1997; Sweers and Carsten 2006; Garcia et al. 2015). The advanced nature of the radiological abnormalities at the time of diagnosis, despite clinical signs having been recognised in six Equidae for ≤ 2 months, suggests that radiological changes probably predated clinical signs. No horse had a history of known trauma. The cause of intervertebral disc disease therefore remains open to speculation. It was suggested that such radiological abnormalities may reflect the end-stage of cervical vertebral stenosis, based on a horse which presented with ataxia (Speltz et al. 2006). However, in the current series only three of the horses had concurrent enlargement of the articular process joints at the same level as the intervertebral disc disease and narrowing of the dorsoventral height of the vertebral canal was not a major feature. It is notable that in four cases there was subtle to severe subluxation of the affected vertebrae. Vertebral malalignment may be due to angular deformation, which is potentially reducible, although contributing to segmental instability, or a translational defect, more correctly referred to as spondylolisthesis, based on the human literature (Jiang et al. 2011). Spondylolisthesis is reported in humans as a consequence of trauma or disc degeneration in the cervical spine. In cervical degenerative spondylolisthesis in human patients, degeneration of the disc and the articular process joints occurs first, in association with neck pain, which is considered to be the initial symptom.
a)
b)
c)
Fig 5: Osseous specimens from Horse 5 (see Fig 1). a) Lateral oblique image of the seventh cervical (C7) to second thoracic (T2) vertebrae. b) The caudal aspect of C7. c) The cranial aspect of T2. There is very extensive modelling on the ventral aspects of C7 to T2. There is major destruction of the caudal end plate of C7 and the cranial aspect of T2. There are severe bilateral costovertebral joint osteophytes of the first and second ribs.
© 2019 EVJ Ltd
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92
