Low-Dose Radiation to Prevent Complications of Back Surgery

Overview

More than 10,000 people each year in the United States have "failed back surgery syndrome" caused by scars that form around the outer surface of the spinal cord. Such scarring, known as peridural fibrosis, is common after back surgery known as either lumbar discectomy or laminectomy. Peridural fibrosis may cause recurring low back pain or leg pain after surgery. Operating again to remove the scar tissue often leads to more scarring. Researchers have not previously studied radiation as a way to prevent peridural fibrosis. We will test whether low-dose radiation given 24 hours before surgery will decrease the amount of peridural fibrosis and if this reduction will lead to improved results of surgery. Half of the participants will receive radiation before surgery and the other half will not. We will evaluate patients at followup visits 1, 3, 6, and 12 months after surgery with a physical exam and questionnaire. At 12 months, we will obtain magnetic resonance imaging (MRI) of the lower spine.

Researchers have long known that low-dose radiation inhibits fibroblast and osteoblast activity. Studies in humans have shown that perioperative radiation therapy is a useful way to prevent both keloid and heterotopic bone formation. However, researchers have not previously studied radiation as a means to inhibit peridural fibrosis. Our previous studies of both rat and dog models showed a significant reduction in peridural fibrosis after laminectomy using low-dose external beam radiation (700 cGy) given 24 hours prior to surgery. Based on our results from these animal studies, we will test whether (1) low-dose radiation given 24 hours before surgery will decrease the amount of peridural fibrosis in people and (2) this reduction in peridural fibrosis will lead to improved results of surgery. For this study, we will enroll 46 patients with failed back surgery syndrome believed to be secondary to perineural fibrosis in a randomized, double-blinded, controlled clinical trial. We will assign patients to one of two groups before surgery: preoperative radiation (treatment group) or no preoperative radiation (control group). We will treat half of the patients with external beam radiation before re-exploration and decompression of their peridural fibrosis (treatment group) and perform re-exploration and decompression in the other half without preoperative radiation (control group). All patients will undergo simulation radiation treatment planning and will not know if they received radiation or not. For patients randomized to receive preoperative radiation, we will administer a single dose of 700 cGy to a 6.0-cm-wide field centered on the spinal cord at the affected level, using a 6 MV Varian 600C linear accelerator. We will administer treatment with two fields angled 45 degrees from the vertical plane so that the skin surface for the proposed incision will not be irritated. This should prevent any wound healing problems. Only the radiation oncologist and research assistant will know whether radiation was administered. The patient and the surgeon will be masked as to the treatment. The neurosurgeon co-investigators will perform the same surgical procedure on all patients 24 hours after their radiation (or sham) treatment. We will give all patients preoperative antibiotics. The surgeon will reopen the previous midline posterior lumbar skin incision and dissect the subcutaneous tissue away from the spinous process and laminae. Once the surgeon has adequately exposed the previous surgical site, he or she will place a self-retaining retractor. The surgeon will decompress the nerve by removing the scar tissue from around the nerve root and thecal sac. The surgeon will also remove any intravertebral disc material thought to be causing nerve root compression. On completion of the operation, the surgeon will stop bleeding with electrocautery, irrigate the wound with antibiotic, and close the wound in layers. In general, the hospital stay after surgery is one night. The patient begins gradual ambulation on the evening of surgery. We will administer the North American Spine Society (NASS) Lumbar Spine Outcome Assessment to patients before treatment and at followup visits to assess their physical functioning. We will also use the NASS questionnaire to collect demographic and lifestyle information at baseline and to assess patient expectations regarding treatment and level of satisfaction with the treatment during the followup period. We will do a physical examination and administer the patient-reported questionnaire prior to surgery and at 1, 3, 6, and 12 months after surgery. We will obtain magnetic resonance (MR) imaging of the lumbar spine 12 months after treatment.