Structural changes occurring at the surgical site long after hemilaminectomy in small-breed dogs with type I thoracolumbar intervertebral disk herniation.

Hemilaminectomy is the most common surgical procedure for type I thoracolumbar intervertebral disk herniation (TL-IVDH). Despite the clinical relevance of postoperative morphological assessment to predict postoperative complications, only a few studies have evaluated long-term changes at the surgical site, such as those affecting the spinal cord and vertebrae, after hemilaminectomy for type I TL-IVDH. This retrospective study describes postoperative changes at the surgical site, including disk height, in dogs that had undergone hemilaminectomy and subsequently experienced late recurrence. Nineteen dogs were eligible for inclusion in this study. The disk height index (DHI) at the initial affected site was significantly reduced compared to the time of initial onset. The maximal spinal cord compression rate at the initial affected site at the time of recurrence decreased significantly compared to that at the time of initial onset. Two dogs had bone regrowth at the site of first surgery at the time of recurrence. No recurrence of disk herniation or spinal cord injury caused by bone regrowth was observed at the surgical site. In conclusion, structural changes such as decreased DHI and bone regrowth were observed at the surgical site a long time after hemilaminectomy, but these changes were not the direct cause of the neurologic signs observed at recurrence.