A New Angled Chisel for Microendoscopic Decompressive Laminotomy.

STUDY DESIGN: A retrospective comparative series study OBJECTIVE:: To describe a new angled chisel (NAC) that facilitates the osteotomy in Microendoscopic decompressive laminotomy (MEDL), and to analyze the clinical and radiological outcomes using the tool.

SUMMARY OF BACKGROUND DATA: MEDL for lumbar spinal stenosis is a minimally invasive surgery. The paraspinous unilateral approach for bilateral decompression can preserve the posterior structure better than other methods. The resection of the medial facet on the approach side is technically difficult, however, because the working space is limited and the retractor is difficult to place properly. Because of these limitations, either the inferior articular process on the approach side tends to be resected excessively, which can lead to facet fracture and instability, or the superior articular process tends to be resected insufficiently, which can result in residual symptoms. The ideal decompression of the medial facet consists of sufficient resection to the deep portion, especially lateral recess of the spinal canal, and adequate facet preservation. Special curved devices to obtain optimal resection have been developed, but these devices have not effectively improved the osteotomy. I developed a new angled chisel to allow an osteotomy at the desired angle.

METHODS: Forty patients underwent MEDL with use of the NAC (NAC group) and forty patients underwent the same procedures without the NAC (control group). The osteotomy-angle of the medial facet on the approach side and VAS score were analyzed.

RESULTS: The average osteotomy-angle of the medial facet was significantly smaller in the NAC group. The radiological and clinical results were significantly better in the NAC group.

CONCLUSION: The NAC was useful tool that sharpen the osteotomy-angle of the medial facet and thereby improved the clinical course.