Reoperative neurosurgery in dogs with thoracolumbar disc disease.

OBJECTIVE: To characterize the subset of dogs in our neurosurgical practice that underwent spinal surgery for thoracolumbar (TL) disc herniation and subsequently underwent additional decompressive TL surgery. STUDY
DESIGN: A retrospective case series. SAMPLE POPULATION: Thirty dogs that underwent reoperation for TL disc herniation. A comparison group of Dachshunds that underwent only one decompressive TL disc surgery was also studied.
METHODS: Dogs that underwent reoperation were divided into two groups based on the interval between their first and second surgery. The early reoperation group included those dogs having a second surgery less than 4 weeks after the initial operation. The late reoperation group included those dogs having a second surgery more than 4 weeks after the initial operation. For each Dachshund in the late reoperation group, two Dachshunds that underwent only one decompressive TL disc surgery were selected and formed the comparison group. Dogs in the comparison group were matched with reoperated cases based on the severity of preoperative neurologic deficit and site of disc herniation. These two groups were compared to determine: (1) if age and body weight were risk factors for reoperation, and (2) if dogs had a poorer functional outcome after their second decompressive surgery than did those in the comparison group after their first (and only) decompressive surgery.
RESULTS: A total of 30 of 467 (6.4%) dogs that underwent decompressive TL disc surgery were reoperated. In the early reoperative cases (n = 5 dogs), the inciting cause in all cases was residual compression from disc material at the site of the initial surgery. In the late reoperation group, 22 of 25 (88%) cases had a second disc herniation at a site distinct from the initial lesion. Dachshunds had a significantly higher risk for late reoperation (odds ratio and 95% CI = 3.67, 1.46 to 10.03); other small and medium-sized breeds (<20 kg) were underrepresented. Age and body weight were not significant predictors for reoperation. A total of 21 of 23 (91%) dogs had functional recovery after late reoperation. Complete sensorimotor loss was a significant negative predictor of functional recovery in the late reoperative cases (P = .01). Likelihood of functional recovery in dogs after their second decompressive surgery was identical to the functional recovery of dogs in the comparison group. CONCLUSIONS AND CLINICAL RELEVANCE: Our results show that a second disc herniation occurring at a site distinct from the initial lesion is the most common cause for reoperation and that Dachshunds have a significantly greater risk than other breeds.