title: A cadaveric radiographic analysis on the effect of extreme lateral interbody fusion cage placement with supplementary internal fixation on indirect spine decompression.
abstract: METHODS
  Cadaveric Biomechanical and Radiographic Analysis.
  
  
  OBJECTIVE
  The purpose of this study was to quantify the changes in intervertebral height and lateral and central recess areas afforded by lateral interbody fusion cages with 2 supplemental forms of internal fixation in cadaveric specimens.
  
  
  BACKGROUND
  When conservative treatment for symptomatic lumbar stenosis fails, traditional intervention has been direct posterior decompression. The minimally invasive, lateral transpsoas approach may be a viable alternative to direct decompression by providing restoration of the foraminal and intervertebral dimensions, yet few reports have examined the anatomic and radiographic changes that occur using this technique.
  
  
  METHODS
  Computed tomography (CT) scans were taken of 18 intact lumbar (L1-S1) cadaveric specimens under a 400 N preload. Intervertebral height, foraminal areas, and canal area were measured at L3-L4 and L4-L5. Thereafter, the cadaveric specimens were instrumented with lateral cages placed in the central or posterior third of the disk space at L3-L4 and L4-L5 and either (1) lateral plate (n=9) or (2) bilateral posterior pedicle screw fixation (n=9). All constructs were again subjected to a 400 N preload, postinstrumentation CT scans were taken, and changes in intervertebral height and lateral and central recess areas were calculated.
  
  
  RESULTS
  There was no effect of cage placement on any radiographic metric of indirect decompression for either fusion construct. In the lateral plate and pedicle screw groups, respectively, significant increases in average posterior disk height (30.9%, 60.1%), average right (35.3%, 61.5%) and left foraminal area (48.3%, 57.8%), and average canal area (32.3%, 33.3%) were observed. Pedicle screw instrumentation afforded a significantly greater increase in average posterior disk height and foraminal area compared with the lateral plate group, though there was no difference in the average increase in canal area afforded by either form of fixation.
  
  
  CONCLUSIONS
  The radiographic results reported here using a cadaveric model add validity to the underlying rationale described for the minimally invasive lateral approach technique. Increases in disk height, foraminal and canal areas were not dependent on cage positioning within the disk space. As intraoperative placement of a cage in the central portion of the disk is an easier and safer technique, our results suggest that central placement may be preferable in a clinical setting.
authors.affiliation: *Florida Orthopedic Institute and Moffitt Cancer Center †Phillip Spiegel Orthopaedic Research Laboratory, Foundation for Orthopaedic Research & Education ‡University Diagnostic Institute §Center for Spinal Disorders, Florida Orthopaedic Institute, Tampa, FL.
authors.forename: German A
authors.initials: GA
authors.lastname: Marulanda
authors.forename: Aniruddh
authors.initials: A
authors.lastname: Nayak
authors.forename: Ryan
authors.initials: R
authors.lastname: Murtagh
authors.forename: Brandon G
authors.initials: BG
authors.lastname: Santoni
authors.forename: James B
authors.initials: JB
authors.lastname: Billys
authors.forename: Antonio E
authors.initials: AE
authors.lastname: Castellvi
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D019245:Compressive Strength / Q000502:physiology; D019299:Decompression, Surgical / Q000295:instrumentation / Q000379:methods*; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery*; D008161:Lumbosacral Region / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000295:instrumentation / Q000379:methods; D011859:Radiography; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D013130:Spinal Stenosis / Q000000981:diagnostic imaging / Q000601:surgery*; D016474:Weight-Bearing / Q000502:physiology