The extent of laminectomy affects pain-related behavior in a rat model of neuropathic pain

One of the unresolved questions in neuropathic pain research is whether we can prevent or reverse mechanical hyperalgesia by rhizotomy or ganglionectomy. However, one of the obstacles in answering that question is lack of a standardized surgical procedure used in experimental ganglionectomy. We tested the hypothesis that laminectomy performed during ganglionectomy induces lumbar column deformity. We further examined whether spinal deformity is a source of pain-related behavior. Five conditions were studied. Fifth and sixth lumbar (L5 and L6) ganglionectomy were performed in rats using either minimal or extensive laminectomy technique. Two other groups had minimal and extensive laminectomy without ganglionectomies. A final control group had no surgery. Sensory responsiveness of the plantar aspect of the hind paw was repeatedly tested, and a plain radiograph in anteroposterior projection was made to assess the extent of deformity by measurement of deformity angles. Hyperalgesia resulted in groups with extensive laminectomy regardless of performance or absence of ganglionectomy, while in groups with minimal laminectomy there was no increase in pain-related behavior. Lateral deformity of the spine was observed in rats with or without ganglionectomy, confirming that laminectomy can produce deformity. The extent of deformity was more pronounced in rats exposed to the extensive laminectomy. Our results indicate that laminectomy can produce spine deformity and that there is a direct relationship between the extent of laminectomy and the development of mechanical hypersensitivity. The data presented suggest that there is a need for standardization of laminectomy procedure in rat experimental pain models.