title: Iliac crest osteotomy to enhance exposure of the L4-5 interspace in minimally invasive lateral transpsoas interbody fusion: a cadaveric feasibility study.
abstract: OBJECTIVE
  Minimally invasive lateral transpsoas interbody fusion (LTIF) has emerged as a popular surgical technique in a remarkably short period of time. The authors' experience with this procedure and anecdotal evidence in the literature suggest that the iliac crest may occasionally prevent access to the L4-5 interspace during minimally invasive LTIF. The authors propose that removal of a minimal amount of ilium would allow for successful exposure of the L4-5 interspace in those cases with a "high-riding" iliac crest. Therefore, the objective of this study was to evaluate the feasibility of iliac osteotomy to enhance exposure of the L4-5 interspace for minimally invasive LTIF.
  
  
  METHODS
  Twenty L4-5 minimally invasive LTIF procedures were performed on 10 cadavers. The L4-5 minimally invasive LTIFs were successfully completed in 13 of 20 attempts. In the remaining 7 cases, the iliac crest prevented perfect orthogonal access to the L4-5 interspace. An iliac osteotomy was performed until the tubular retractors could be perfectly aligned with the L4-5 interspace and minimally invasive LTIF accomplished. Anteroposterior fluoroscopic images were obtained before and after the osteotomies. The angle between the working instrument and the superior L-5 endplate was measured, as were craniocaudal displacement and the resected iliac area.
  
  
  RESULTS
  Iliac osteotomy enabled completion of L4-5 minimally invasive LTIF in the 7 remaining cases. Iliac resection was minimal; an average of 4.92 cm(2) of iliac surface was resected (range 2.08-8.27 cm(2)) to enable L4-5 access. Adequate working angles were maintained (average 3.3° change after resection) while significant caudal displacement of the tubular system was achieved (average 15.7 mm, range 5.2-27.6 mm).
  
  
  CONCLUSIONS
  A significant portion of patients may have a high-riding iliac crest and that may have had an impact on minimally invasive LTIF in this series; L4-5 cases are rare in relation to midlumbar spine cases in most minimally invasive LTIF patient series. Significant caudal displacement of the tubular system was achieved with minimal iliac osteotomy, ensuring access to the L4-5 interspace in all specimens while maintaining the minimally invasive philosophy behind minimally invasive LTIF.
authors.affiliation: Department of Neurosurgery, Rush University Medical Center, Chicago, IL 60612, USA. ricardo_fontes@rush.edu
authors.forename: Ricardo B V
authors.initials: RB
authors.lastname: Fontes
authors.forename: Vincent C
authors.initials: VC
authors.lastname: Traynelis
mesh_terms: D002102:Cadaver; D005240:Feasibility Studies; D006801:Humans; D007085:Ilium / Q000601:surgery*; D007403:Intervertebral Disc / Q000601:surgery; D008159:Lumbar Vertebrae / Q000601:surgery*; D008866:Microsurgery; D010027:Osteotomy / Q000379:methods*; D013123:Spinal Fusion / Q000379:methods*