title: Evaluation of indirect decompression of the lumbar spinal canal following minimally invasive lateral transpsoas interbody fusion: radiographic and outcome analysis.
abstract: BACKGROUND
  The surgical treatment of lumbar stenosis traditionally includes laminectomy for direct decompression of the spinal canal. Selected patients with spinal stenosis may also require lumbar fusion. Minimally invasive lateral transpsoas interbody fusion has the ability of placing a large interbody cage that can increase disc height and distract the spinal level. The purpose of this study was to examine the concept of indirect decompression of the spinal canal in patients with co-existing lumbar spinal stenosis undergoing lateral transpsoas interbody fusion.
  
  
  METHODS
  We reviewed 25 consecutive spinal stenosis patients with instability undergoing lateral transpsoas interbody fusion without laminectomy. All patients had relevant symptoms of back pain, leg pain, and/or spinal claudication and met standard criteria for lumbar fusion. Patients were evaluated by outcome analysis scales (VAS scores, Oswestry disability index and treatment intensity scale). Postoperative MRI scans, when available, were evaluated for change in canal dimensions. Statistical significance was assessed by paired t-test, which compares the mean change. There were 25 patients in the study (mean age 61 years). 15 patients had grade I spondylolisthesis. VAS for back pain intensity improved from 7.74 to 2.07 and for frequency from 7.91 to 2.22. VAS for leg pain intensity improved from 7.24 to 1.87 and frequency from 7.41 to 2.35. All improvements were statistically significant (P<0.0001). The Oswestry disability index improved from 55.1 to 16.4 (P<0.0001), and treatment intensity scale improved from 14.6 to 3.7 (P<0.0001). Radiographic evaluation in 20 treated levels (15 patients) found an increase in dural sac dimension of 54% in the anterior-posterior plane and 48% in the medial-lateral plane (P<0.0001). The calculated area of the dural sac increased an average of 143% (range of - 10.4% to + 495%).
  
  
  CONCLUSIONS
  Indirect decompression of spinal stenosis can be achieved with lateral transpsoas interbody fusion with improved clinical outcomes. Pre-op and post-op MRI scans showed a significant increase in dural sac dimensions. The mechanism for this indirect decompression may relate to stretching and unbuckling of the spinal ligaments and a decrease in intervertebral disc bulging. Further studies are needed to determine which stenosis patients undergoing this surgery are most appropriate for indirect decompression alone over laminectomy.
authors.affiliation: Department of Neurological Surgery, Weill-Cornell Medical College, New York-Presbyterian Hospital, New York, USA. ere2006@med.cornell.edu
authors.forename: E H
authors.initials: EH
authors.lastname: Elowitz
authors.forename: D S
authors.initials: DS
authors.lastname: Yanni
authors.forename: M
authors.initials: M
authors.lastname: Chwajol
authors.forename: R M
authors.initials: RM
authors.lastname: Starke
authors.forename: N I
authors.initials: NI
authors.lastname: Perin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019299:Decompression, Surgical / Q000379:methods*; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology / Q000601:surgery; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D012189:Retrospective Studies; D013116:Spinal Cord / Q000473:pathology / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*; D013130:Spinal Stenosis / Q000473:pathology / Q000601:surgery*; D016896:Treatment Outcome