The Effect of Duloxetine on Fusion in Rats Undergoing Posterolateral Spinal Fusion

Background: Duloxetine, a serotonin-norepinephrine reuptake inhibitor, is widely used both preoperatively and postoperatively in patients with neuropathic low back pain. This study aimed to determine the impact of duloxetine administration on posterolateral spinal fusion in rats and to evaluate the dose-dependent relationship of this effect. Methods: A pre-established rat model for posterolateral spinal fusion was employed, and four equal groups were formed, each undergoing posterolateral spinal fusion surgery. Except for the control group, the other groups received duloxetine postoperatively starting on day 1 at doses of 30 mg/kg/day, 60 mg/kg/day, and 120 mg/kg/day for six weeks. All rats were sacrificed after six weeks. Fusion status was assessed using manual palpation, radiological examination with plain radiography, and histopathological evaluation. Results: No significant differences were observed between groups in manual palpation scoring or radiological scoring. Histopathological evaluations of new bone formation also showed no significant differences between groups. The number of inflammatory cells was found to be higher in the control group compared to the low- and moderate-dose duloxetine groups (p = 0.012). Neovascularization scores were slightly higher in the control group compared to the duloxetine-treated groups (p = 0.048). Conclusions: In this experimental rat model of posterolateral spinal fusion, duloxetine administration was associated with reduced inflammatory cell infiltration and mildly decreased neovascularization on histopathological evaluation. However, these histological differences did not translate into measurable differences in fusion outcomes, as assessed by manual palpation, radiological scoring, or new bone formation. Overall, postoperative duloxetine treatment did not demonstrate a detrimental effect on spinal fusion success, suggesting that its use for neuropathic pain management may be biologically applicable with respect to fusion healing in this animal model.