MAGNETIC-RESONANCE-IMAGING ANALYSIS OF PERCUTANEOUS DISCECTOMY - A PRELIMINARY-REPORT

Twenty-one consecutive patients (27 lumbar discs) were treated by percutaneous discectomy for lumbar herniated disc disease from July 1988 through March 1989. Twenty-six discs in 20 patients were evaluated with preoperative and postoperative magnetic resonance images graded by a neuroradiologist blinded to the clinical and prior imaging results. Fifteen patients were treated by one-level percutaneous discectomy and six patients by two-level percutaneous discectomy. The disc herniations were graded with respect to size, type, location, and hydration status on the magnetic resonance image scans. The postoperative magnetic resonance images were obtained 2-6 months after percutaneous discectomy. Early clinical outcomes after percutaneous discectomy were compared with the various magnetic resonance imaging parameters. Overall, treatment for thirteen patients (62%) was considered clinically successful (decrease or elimination of pain) after percutaneous discectomy, whereas treatment for eight (38%) patients was considered to clinically fail (persistence of pain) with follow-up ranging from 1 to 6 months postoperatively. Three of the patients in whom treatment failed have been subsequently treated successfully by laminotomy and discectomy. On the average, there is a small absolute decrease (5% of the anteroposterior diameter of the spinal canal) in the size of disc herniations when treated by percutaneous discectomy. Although this study is limited by a small sample size and lacks statistical significance, it appears that an early clinical success after percutaneous discectomy may be related to a few magnetic resonance imaging parameters. Early successful outcome appears more likely in a patient with a type II disc herniation (protrusion/bulge) and a disc herniation that has been shown to decrease in absolute size by greater than 10% of the anteroposterior diameter of the spinal canal from preoperative to postoperative (for example, if a disc herniation measured 38% preoperatively and 28% postoperatively, the absolute change in size is 10%).