Object: The authors evaluated a new minimally invasive spinal surgery technique to correct degenerative lumbar spinal stenosis involving a split-spinous process laminotomy and discectomy (also known as the "Marmot operation").
Methods: This prospective study randomized 70 patients with lumbar stenosis to undergo either a Marmot operation (40 patients), or a conventional laminectomy (30 patients), with or without discectomy. Spinal anteroposterior diameter, cross-sectional area, lateral recess distance, spinal stability, postoperative back pain, functional outcomes, and muscular trauma were evaluated. The follow up ranged from 10 to 18 months, with a mean of 15.1 months for the Marmot operation group and 14.8 months for the conventional laminectomy group. Compared with patients in the conventional laminectomy group, patients who received a Marmot operation had a shorter mean postoperative duration until ambulation without assistance, a reduced mean duration of hospital stay, a lower mean creatine phosphokinase-muscular-type isoenzyme level, a lower visual analog scale score for back pain at 1-year follow up, and a better recovery rate. These patients also had a longer mean duration of operative time and a greater mean blood loss compared with the conventional group. Satisfactory neurological decompression and symptom relief were achieved in 93% of these patients. Most of the patients (66%) in this group needed discectomy for decompression. The postoperative mean lateral recess width, spinal anteroposterior diameter, and cross-sectional area were all significantly increased. There was no evidence of spinal instability in any patient. One patient with insufficient lateral recess decompression and recurrent disc herniation needed additional conventional laminectomy and discectomy, and one patient with mild superficial wound infection was successfully treated with antibiotics and frequent dressing changes.
Conclusions: A Marmot operation may provide effective spinal decompression. Although this method requires more operative time than a conventional method, it may involve only minimal muscular trauma, spinal stability maintenance, and early mobilization; shorten the duration of hospital stay; reduce postoperative back pain; and provide satisfactory neurological and functional outcomes.