title: Minimally invasive lateral retroperitoneal transpsoas interbody fusion for L4-5 spondylolisthesis: clinical outcomes.
abstract: OBJECTIVE
  In this study the authors report on the clinical outcomes, safety, and efficacy of lateral retroperitoneal transpsoas minimally invasive surgery-lumbar interbody fusion (MIS-LIF) at the L4-5 disc space in patients with spondylolisthesis. This approach has become an increasingly popular means of fusion. Its most frequent complication is lumbar plexus injury. Reported complication rates at the L4-5 disc space vary widely in the literature, bringing into question the safety of MIS-LIF for the L4-5 region, especially in patients with spondylolisthesis.
  
  
  METHODS
  The authors retrospectively reviewed prospectively acquired multicenter databases of patients with Grade I and II L4-5 spondylolisthesis who had undergone elective MIS-LIF between 2008 and 2011. Clinical follow-up had been scheduled for 1, 3, 6, 12, and 24 months postoperatively. Outcome measures included estimated blood loss, operative time, length of hospital stay, integrity of construct, complications, fusion rates, visual analog scale (VAS), Oswestry Disability Index (ODI), and 36-Item Short Form Health Survey (SF-36).
  
  
  RESULTS
  Eighty-four patients with L4-5 MIS-LIF were identified, 31 of whom met the study inclusion criteria: 26 adults with Grade I and 5 adults with Grade II L4-5 spondylolisthesis who had undergone elective MIS-LIF and subsequent posterior percutaneous pedicle screw fixation without surgical manipulation of the posterior elements (laminectomy, foraminotomy, facetectomy). The study cohort consisted of 9 males (29%) and 22 females (71%) with an average age of 61.5 years. The mean total blood loss was 94 ml (range 20-250 ml). The mean hospital stay and follow-up were 3.5 days and 18.2 months, respectively. The average score on the ODI improved from 50.4 preoperatively to 30.9 at the last follow-up (p < 0.0001). The SF-36 score improved from 38.1 preoperatively to 59.5 at the last follow-up (p < 0.0001). The VAS score improved from 69.9 preoperatively to 38.7 at the last follow-up (p < 0.0001). No motor weakness or permanent deficits were documented in any patient. Correction of deformity did not have any neurological complications. All patients had improvement in anterolisthesis. Residual postoperative listhesis across cases was noted in 4 patients (12.9%). Transient anterior thigh numbness (Sensory Dermal Zone III) was noted in 22.5% of patients.
  
  
  CONCLUSIONS
  With its established surgical corridors through the retroperitoneum and psoas muscle, the MIS-LIF combined with posterior percutaneous pedicle screw fixation/reduction is a safe, reproducible, and effective technique for patients with symptomatic degenerative spondylolisthesis at the L4-5 vertebral segment.
authors.affiliation: Department of Neurosurgery, University of South Florida, Tampa, USA. AmirAhmadianmd@gmail.com
authors.forename: Amir
authors.initials: A
authors.lastname: Ahmadian
authors.forename: Sean
authors.initials: S
authors.lastname: Verma
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Mundis
authors.forename: Rod J
authors.initials: RJ
authors.lastname: Oskouian
authors.forename: Donald A
authors.initials: DA
authors.lastname: Smith
authors.forename: Juan S
authors.initials: JS
authors.lastname: Uribe
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000009:adverse effects / Q000379:methods*; D011446:Prospective Studies; D016658:Psoas Muscles / Q000601:surgery*; D011859:Radiography; D012187:Retroperitoneal Space / Q000601:surgery; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000009:adverse effects / Q000379:methods*; D013168:Spondylolisthesis / Q000000981:diagnostic imaging / Q000601:surgery*; D016896:Treatment Outcome