Postoperative outcome after modified unilateral-approach microendoscopic midline decompression for degenerative spinal stenosis

Clinical article

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Object

The object of this study was to assess the feasibility and efficacy of a novel, minimally invasive spinal surgery technique to correct degenerative lumbar spinal stenosis involving a modified unilateral-approach microendoscopic midline decompression.

Methods

In this prospective study, 41 patients with lumbar stenosis were randomly assigned to undergo either a novel, median-approach microendoscopic laminectomy (20 patients) or a conventional laminectomy (21 patients). Spinal anteroposterior diameter, cross-sectional area, lateral recess distance, spinal stability, postoperative back pain, functional outcomes, and muscle trauma were evaluated. Follow-up ranged from 16 to 24 months, with a mean of 17.8 months for the novel procedure group and 18.6 months for the conventional laminectomy group.

Results

Compared with patients in the conventional laminectomy group, patients who received the novel procedure had 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 faster recovery rate. These patients also had less mean blood loss compared with the conventionally treated group. Satisfactory neurological decompression and symptom relief were achieved in 90% of these patients. There was no significant clinical difference compared with the conventional laminectomy group's results. There was no evidence of spinal instability in any patient, and no patient required a follow-up conventional laminectomy.

Conclusions

This novel procedure provides effective spinal decompression. Although this method requires more operating time than a conventional method, it requires only minimal muscle trauma and spinal stability maintenance, and allows for early mobilization. This shortens the hospital stay, reduces postoperative back pain, and leads to satisfactory neurological and functional outcomes. Moreover, with the midline approach, decompression was accomplished without compromising the facet joints, even with a narrow width of lamina.

Abbreviations used in this paper: CPK-MM = creatine phosphokinase muscular-type isoenzyme; JOA = Japanese Orthopaedic Association; VAS = visual analog scale.

Article Information

Address correspondence to: Mitsuru Yagi, M.D., Ph.D., Department of Orthopedic Surgery, Kawasaki Municipal Hospital, 12-1 Saiwai-Ku Shinkawa-Tori, Kawasaki City, 2100013 Japan. email: yagiman@qg7.so-net.ne.jp.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Illustrations showing the tubular retractor centered in the interlaminar position to access both sides.

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    Intraoperative views of modified unilateral-approach microendoscopic midline decompression. A: The base of spinous process. B: Decompression of the L-4 lamina by high-speed drill. C: Decompression of the ligamentum flavum by Kerrison punch. D: Decompression of the contralateral side. E: Decompression of the entry side.

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    A: Bar graph showing operating time for a conventional laminectomy compared with our novel procedure. B: Bar graph showing length of hospital stay after surgery for each procedure. C: Bar graph showing the mean estimated blood loss for each procedure. D: Graph showing the time course of low-back pain (LBP) according to the VAS. E: Bar graph showing the CPK-MM level 24 hours after surgery. F: Bar graph showing the atrophy rate of paravertebral muscle (PVM) 1 year after surgery. Asterisks denote a significant difference between groups. M = month; n.s = not significant; Y = year.

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    Graph showing the time course of JOA scores.

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    Preoperative (A and C) and postoperative (B and D) axial CT (A and B) and MR (C and D) imaging studies obtained in a patient undergoing L4–5 decompression. The postoperative MR images reveal minimal muscle atrophy.

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    Preoperative (A) and postoperative (B–D) CT studies obtained in a patient undergoing L3–4 decompression. Preoperative (A) and postoperative (B) axial images, and postoperative sagittal (C) and coronal (D) images. Postoperative CT images indicate adequate decompression, even in the case of narrow width of lamina.

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    Preoperative and postoperative CT and MR imaging studies obtained in a patient undergoing L5–S1 decompression. Axial preoperative MR image (A) and CT scan (B), and postoperative CT image (C). Sagittal (D and E) and coronal (F) images obtained 1 year postoperatively. Arrows in sagittal images obtained 1 year postoperatively demonstrate the union of lamina and spinous process.

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