THE EFFECTS OF NONSTEROIDAL ANTIINFLAMMATORY DRUGS ON POSTERIOR SPINAL FUSIONS IN THE RAT

Study Design. This was a prospective study to determine the potential effects of indomethacin on spinal fusions in the rat. Objectives. To d etermine if indomethacin exerts a deleterious effect on spinal fusions in the rat model. Summary of Background Data. Nonsteroidal antiinflam matory drugs are a class of compound that affect bone osteogenesis dur ing fracture healing and heterotopic ossification. Spinal fusion is a process that occurs via osteogenesis and, therefore, may be similarly affected. Methods. Thirty-nine adult, Sprague-Dawley rats underwent a three-level posterior spinal fusion. Fusion was performed using morsel ized autogenous vertebral bone graft obtained via caudectomy and stabi lized using a cerclage wiring technique. The 39 rats were divided into two groups consisting of 17 study animals and 22 control animals. The control group was injected with 1.5 cc of 0.9 normal saline subcutane ously for 12 weeks, whereas the test animals were injected on an ident ical schedule using 3 mg/kg of indomethacin sodium salt. Two control a nimals died, and three animals in the treatment group died of drug-rel ated complications. Twelve weeks after surgery, all animals were kille d, and the involved spinal segments were evaluable if the spinal segme nts exhibited decreased scaled micromotion. Results. Sixty segmental l evels in 20 control animals were assessed. Overall, 27 of 60 levels (4 5%) achieved fusion. In the indomethacin-treated group, 42 levels in 1 4 animals were evaluated. Overall, four of 42 levels (10%) achieved a fusion. Chi-square analysis demonstrated a significant difference (P < 0.001) between the control and indomethacin-treated groups. Conclusio ns. This study raises serious questions about the inhibitory effects o f nonsteroidal anti-inflammatory drugs on spinal fusion. Clinically, t he wide-spread use of nonsteroidal anti-inflammatory drugs in the post operative period after spinal fusion may need to be avoided.