Inhibition of peridural fibrosis after laminectomy using low-dose externalbeam radiation in a rat model

OBJECTIVE: Clinical studies have revealed a significant association between the presence of extensive postlumbar discectomy peridural scar formation a nd the reoccurrence of low back and radicular pain. Low-dose perioperative radiation therapy has been shown to inhibit scar formation. Its effect on p eridural fibrosis, however, has not been studied. METHODS: Thirty male Sprague-Dawley rats underwent L5 laminectomies. Ten ra ts each received a single fraction of 700-cGy external beam radiation to th e lumbar spine 24 hours before surgery; 10 vats each received 700 cGy 24 ho urs after surgery. The remaining 10 rats served as a control group. All of the rats were killed 30 days after surgery. The spines were harvested, and axial histological sections through the laminectomy defect were evaluated. Each specimen was scored for extent, density, and arachnoidal involvement b y fibrosis. RESULTS: There was a statistically significant difference between the treat ment and control groups regarding the extent of fibrosis along the dura (P < 0.001), the density of fibroblasts (P < 0.005), and the arachnoid involve ment (P < 0.01). There was no difference in fibrosis reduction between the groups receiving pre- and postlaminectomy radiation. CONCLUSION: Low-dose external beam radiation therapy administered before or after laminectomy in a rat model significantly decreases the extent, densi ty, and arachnoidal involvement of peridural fibrosis. This technique may i mprove the outcome of patients who undergo reoperations for recurrent radic ular and/or low back pain after successful lumbar discectomy in whom there is a significant amount of peridural fibrosis.