Microsurgical bilateral decompression via a unilateral approach for lumbar spinal canal stenosis including degenerative spondylolisthesis

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Surgical outcome and radiographic changes after microsurgical bilateral decompression via a unilateral approach (MBDU) for lumbar spinal canal stenosis during midterm follow-up periods (> 2 years) have not been reported. The authors retrospectively investigated surgical outcomes after MBDU in patients with lumbar degenerative spondylolisthesis with stenosis in comparison with patients with degenerative stenosis during a minimum follow-up period of 2 years. Radiographic changes at the affected intervertebral level were analyzed during that follow-up period.


Forty-eight patients (23 in the spondylolisthesis group, 25 in the degenerative stenosis group) were included in the study. The average follow-up period was 46 months (range 24–71 months). Surgical outcome was evaluated using the Neurogenic Claudication Outcome Score (NCOS) and the Oswestry Disability Index (ODI). Additionally, the back pain score within the NCOS was also compared. There were no statistically significant differences between the spondylolisthesis group and the degenerative stenosis group with regard to sex, age, follow-up period, operating time, blood loss, surgical sites, approach side, preoperative NCOS, preoperative back pain score, and preoperative ODI. Comparisons were also made between groups using 2 satisfaction measurements at the last follow-up visit. Radiographically, intervertebral angles of 80 sites and slip percentages of 24 sites were measured preoperatively and at the last follow-up.


No patient in either group had additional surgery in the lumbar spine, including fusion procedures. The NCOS, back pain score, and ODI had significantly improved at the last follow-up in both groups. There were no significant differences between the 2 groups in these 3 parameters and the 2 satisfaction measurements at the last follow-up, although those for the spondylolisthesis group indicated a somewhat worse outcome. Intervertebral angles, dynamic intervertebral angles, and dynamic slip percentage did not significantly change after surgery, whereas only slip percentage significantly increased postoperatively (p = 0.0319).


A satisfactory outcome of MBDU persisted for a period longer than 2 years for patients with degenerative spondylolisthesis with stenosis as well as for those with degenerative stenosis. Radiographically in both groups this less invasive procedure was not likely to result in postoperative dynamic instability at the affected level, although the slippage progressed in the spondylolisthesis group.

Abbreviations used in this paper: LSCS = lumbar spinal canal stenosis; MBDU = microsurgical bilateral decompression via a unilateral approach; NCOS = Neurogenic Claudication Outcome Score; ODI = Oswestry Disability Index.

Article Information

Address correspondence to: Kunihiko Sasai, M.D., Ph.D., Department of Orthopedic Surgery, Kansai Medical University, 2-3-1 Shinmachi, Hirakata City, Osaka, 573-1191, Japan. email: sasaik@hirakata.kmu.ac.jp.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Representative MR imaging and CT studies obtained in a 61-year-old woman with lumbar degenerative spondylolisthesis at L-4. A: Sagittal T2-weighted MR image demonstrates compression of the dural sac due to a hypertrophied ligamentum flavum and annular bulging, and redundant nerves above. B and D: Axial T2-weighted MR images at the L4–5 level show compression of the dural sac caused by a hypertrophied ligamentum flavum, osteophytic facet joints, and annular bulging. C and E: Postoperative CT scans show microsurgical bilateral decompression through the left-sided approach. The NCOS in this patient increased from 29 to 81 points after a postoperative period of 51 months. The back pain score increased from 2 points (moderate back pain) to 6 points (none), and the ODI decreased from 17 points to 1 point. Satisfaction measures indicated that the procedure was very successful, with almost complete relief. Also, she would recommend this operation to a friend with the same trouble. Her clinical course was unchanged after the initial improvement.

  • View in gallery

    Representative lateral radiographs from the patient shown in Fig. 1 obtained before the operation (A–C) and 51 months after the operation (D–F). Radiographs show the spine in the flexion (A and D), neutral (B and E), and extension (C and F) positions. The preoperative intervertebral angle, dynamic intervertebral angle, slip percentage, and dynamic slip percentage were −1°, 7°, 17%, and 7%, respectively, and postoperatively changed to 0°, 12°, 22%, and 7%, respectively.


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