Abstract
Objectives: To measure the size of the working space (WS) and the inclination angle of the tubular retractor (TR) in microendoscopic discectomy (MED) for lumbar disc herniation.
Methods: Forty-five patients were evaluated; L4/5 was affected in 23 patients, L5/S in 21, and L5/6 in one. WS and the inclination angle of the TR were measured using the axial CT image and a plastic template for the TR, both of the actual size. When measuring the WS, the medial one-fourth of the facet joint line was determined, assuming a partial facet resection. To secure access to the edge of the lateral recess, the medial-upper edge of the template was kept on the one-fourth line.
Results: The average WS was 10.7±2.7mm for the patients overall, 9.4±2.1 in L4/5, and 12.0±1.7 in L5/S. The average inclination angle of the TR was 7.9±1.7° for the patients overall, 7.0±1.5° in L4/5, and 8.9±1.2° in L5/S. Each parameter in L4/5 was significantly smaller than that in L5/S. The correlation between the WS and the operation time was significant. Five L4/5 cases had a WS smaller than 8mm, in which a standard rongeur was used with some difficulty.
Conclusion: Preoperative evaluation of the working space gives time to prepare additional surgical instruments, or offers a better opportunity for avoiding difficult cases during the learning period.
