Thoracolumbar disc disease in large dogs: a study of 99 cases.

The records of 99 dogs weighing over 20 kg with thoracolumbar disc disease were reviewed. Two types of disc disease were recognised: degenerative nuclear extrusion (n=63) and degenerative annular protrusion (n=36). Sixty-nine per cent of the affected discs were located between T12-T13 and L2-L3. Of the 63 dogs with degenerative nuclear extrusions, 35 were non-ambulatory and seven had no conscious pain perception at the time of presentation. Decompressive surgery was performed in 55 dogs, four dogs were managed non-surgically and three dogs were euthanased. A successful outcome was achieved in 49 (78 per cent) cases as assessed by the authors and in 53 (84 per cent) cases as assessed by the owners. Mean follow-up time was 11.7 months (range 1.5 to 48 months). Five dogs subsequently lost the ability to ambulate on their hindlimbs. Myelographic investigations in three of these dogs revealed a second thoracolumbar degenerative nuclear extrusion. Of the 36 dogs with degenerative annular protrusions, seven were non-ambulatory at the time of presentation. Fifteen cases had multiple protrusions. Twenty dogs were managed non-surgically, 12 surgically and four were euthanased. A successful outcome was achieved in eight (22 per cent) cases as assessed by the authors and in 19 (52 per cent) cases as assessed by the owners. Mean follow-up time was 9.2 months (range 1.5 to 30 months). The outcome of dogs with annular protrusions was significantly worse compared to the outcome of dogs with nuclear extrusions (P<0.001).