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

Clinical article

Restricted access


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.


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.


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.


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:

© AANS, except where prohibited by US copyright law.



  • View in gallery

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

  • View in gallery

    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.

  • View in gallery

    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.

  • View in gallery

    Graph showing the time course of JOA scores.

  • View in gallery

    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.

  • View in gallery

    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.

  • View in gallery

    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.



Airaksinen OHerno ATurunen VSaari TSuomlainen O: Surgical outcome of 438 patients treated surgically for lumbar spinal stenosis. Spine 22:227822821997


Asgarzadie FKhoo LT: Minimally invasive operative management for lumbar spinal stenosis: overview of early and long-term outcomes. Orthop Clin North Am 38:3873992007


Atlas SJKeller RBWu YADeyo RASinger DE: Long-term outcomes of surgical and nonsurgical management of lumbar spinal stenosis: 8 to 10 year results from the Maine lumbar spine study. Spine 30:9369432005


Bogduk N: The lumbar mamilloaccessory ligament: its anatomical and neurosurgical significance. Spine 6:1621671981


Bogduk NWilson ASTynan W: The human lumbar dorsal rami. J Anat 134:3833971982


Carreon LYPuno RMDimar JR IIGlassman SDJohnson JR: Perioperative complications of posterior lumbar decompression and arthrodesis in older adults. J Bone Joint Surg Am 85:208920922003


Costa FSassi MCardia AOrtolina ADe Santis AFornari M: Degenerative lumbar spinal stenosis: analysis of results in a series of 374 patients treated with unilateral laminotomy for bilateral microdecompression. J Neurosurg Spine 7:5795862007


Eule JMBreeze RKindt GW: Bilateral partial laminectomy: a treatment for lumbar spinal stenosis and midline disc herniation. Surg Neurol 52:3293381999


Foley KTSmith MM: Microendoscopic discectomy. Tech Neurosurg 3:3013071997


Goel VKFromknecht SJNishiyama KWeinstein JLiu YK: The role of the lumbar spinal elements in flexion. Spine 10:5165231985


Greenough CGFraser RD: Assessment of outcome in patients with low back pain. Spine 17:36411992


Guiot BHKhoo LTFessler RG: A minimally invasive technique for decompression of the lumbar spine. Spine 27:4324382002


Hindle RJPearcy MJCross A: Mechanical function of the human lumbar interspinous and supraspinous ligaments. J Biomed Eng 12:3403441990


Iguchi TKurihara ANakayama JSato KKurosaka MYamasaki K: Minimum 10-year outcome of decompressive laminectomy for degenerative lumbar spinal stenosis. Spine 25:175417592000


Javid MJHadar EJ: Long-term follow-up review of patients who underwent laminectomy for lumbar stenosis: a prospective study. J Neurosurg 89:171998


Khoo LTFessler RG: Microendoscopic decompressive laminotomy for the treatment of lumbar stenosis. Neurosurgery 51:S146S1542002


Mariconda MFava RGatto ALongo CMilano C: Unilateral laminectomy for bilateral decompression of lumbar spinal stenosis: a prospective comparative study with conservatively treated patients. J Spinal Disord Tech 15:39462002


Niggemeyer OStrauss JMSchulitz KP: Comparison of surgical procedures for degenerative lumbar spinal stenosis: a meta-analysis of the literature from 1975 to 1995. Eur Spine J 6:4234291997


Mayer TGatchel RBetancur JBovasso E: Trunk muscle endurance measurement. Isometric contrasted to isokinetic testing in normal subjects. Spine 20:9209261995


Palmer STurner RPalmer R: Bilateral decompressive surgery in lumbar spinal stenosis associated with spondylolisthesis: unilateral approach and use of a microscope and tubular retractor system. Neurosurg Focus 13:1E42002


Palmer STurner RPalmer R: Bilateral decompression of lumbar spinal stenosis involving a unilateral approach with microscope and tubular retractor system. J Neurosurg 97:2132172002


Perez-Cruet MJFoley KTIsaacs RERice-Wyllie LWellington RSmith MM: Microendoscopic lumbar discectomy: technical note. Neurosurgy 51:1291362002


Prestar FJ: Morphology and function of the interspinal ligaments and the supraspinal ligament of the lumbar portion of the spine. Morphol Med 2:53581982


Schillberg BNyström B: Quality of life before and after microsurgical decompression in lumbar spinal stenosis. J Spinal Disord 13:2372412000


See DHKraft GH: Electromyography in paraspinal muscles following surgery for root compression. Arch Phys Med Rehabil 56:80831975


Sihvonen THerno APaljarva LAiraksinen OPatanen JTapaninaho A: Local denervation atrophy of paraspinal muscles in postoperative failed back syndrome. Spine 18:5755811993


Spetzger UBertalanffy HNaujokat Cvon Keyserlingk DGGilsbach JM: Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part I: anatomical and surgical considerations. Acta Neurochir (Wien) 139:3923961997


Spetzger UBertalanffy HReinges MHGilsbach JM: Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part II: clinical experiences. Acta Neurochir (Wien) 139:3974031997


Thomé CZevgaridis DLeheta OBäzner HPöckler-Schöniger CWöhrle J: Outcome after less-invasive decompression of lumbar spinal stenosis: a randomized comparison of unilateral laminotomy, bilateral laminotomy, and laminectomy. J Neurosurg Spine 3:1291412005


Weiner BKFraser RDPeterson M: Spinous process osteotomies to facilitate lumbar decompressive surgery. Spine 24:62661999


Weiner BKWalker MBrower RSMcCulloch JA: Microdecompression for lumbar spinal canal stenosis. Spine 24:226822721999




All Time Past Year Past 30 Days
Abstract Views 78 78 25
Full Text Views 74 74 12
PDF Downloads 48 48 13
EPUB Downloads 0 0 0


Google Scholar