title: Additional sagittal correction can be obtained when using an expandable titanium interbody device in lumbar Smith-Peterson osteotomies: a biomechanical study.
abstract: BACKGROUND
  Insertion of intervertebral fusion devices between consecutive Smith-Peterson osteotomies (SPOs) provides an anterior fulcrum during compression, which has been documented to improve achievable Cobb angle correction. Extension of these principles to an expandable device would theoretically provide greater surgical adjustment for flatback and scoliotic cases than a static cage.
  
  
  OBJECTIVE
  To investigate whether an expandable titanium interbody device would produce greater sagittal correction than a static spacer when used during SPO procedures.
  
  
  METHODS
  Cadaveric research was performed.
  
  
  METHODS
  Seven T10-S1 human specimens were used.
  
  
  METHODS
  Cobb angle changes and range of motion are the physiological measures. No self-report/functional measures were applicable.
  
  
  METHODS
  Bilateral pedicle screws were placed (T11-L5) before Smith-Petersen osteotomy creation from L2 to L4. A transforaminal lumbar interbody fusion titanium expandable implant was placed in each disc space from L2-L3 to L4-L5, which is currently an off-label use of this implant. Initial placement simulated a static spacer, and then incremental device expansion was performed to obtain an intermediate and final height. Lateral fluoroscopic images were taken for Cobb angle evaluation between L2 and L5, and range of motion as observed during application of pure bending moments was captured using a six degree-of-freedom spine simulator. A one-way analysis of variance with Tukey post hoc analysis was performed to determine significant differences (p<.05) between surgical constructs (intact, SPO only, contracted, semiexpanded, and expanded). Study costs were allocated within the research budget of a medical device company, where some authors are salaried employees; another author has been a paid consultant elsewhere. These financial associations were not believed to bias the results.
  
  
  RESULTS
  Change in Cobb angle from L2 to L5 was significantly greater with the interbody spacer compared with SPO alone. Despite an obvious increase in lordosis with expansion height, there were no significant differences between implant expansion states for the L2-L5 Cobb angle. All instrumented constructs were statistically equivalent in every mode of motion once rigid instrumentation was implemented, regardless of expansion state.
  
  
  CONCLUSIONS
  The expandable interbody did have a slight effect on lordotic correction; each additional millimeter in height expansion yielded approximately 1° in correction across the three SPO levels. Even without significant differences between the states, an expandable device may allow the surgeon more control of lordotic correction within the operating room than a static spacer alone.
authors.affiliation: Capital Region Neurosurgery, 1220 New Scotland Road, Slingerlands, NY 12159.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Qandah
authors.affiliation: Globus Medical, Inc., Valley Forge Business Center, 2560 General Armistead Ave., Audubon, PA 19403, USA. Electronic address: nklocke@globusmedical.com.
authors.forename: Noelle F
authors.initials: NF
authors.lastname: Klocke
authors.affiliation: Neurosurgery/Spine-Carilion, 3 Riverside Circle, Roanoke VA 24016.
authors.forename: Jordan J
authors.initials: JJ
authors.lastname: Synkowski
authors.affiliation: Globus Medical, Inc., Valley Forge Business Center, 2560 General Armistead Ave., Audubon, PA 19403, USA.
authors.forename: Suresh R
authors.initials: SR
authors.lastname: Chinthakunta
authors.affiliation: Globus Medical, Inc., Valley Forge Business Center, 2560 General Armistead Ave., Audubon, PA 19403, USA.
authors.forename: Mir M
authors.initials: MM
authors.lastname: Hussain
authors.affiliation: Globus Medical, Inc., Valley Forge Business Center, 2560 General Armistead Ave., Audubon, PA 19403, USA.
authors.forename: Kanaan G
authors.initials: KG
authors.lastname: Salloum
authors.affiliation: Neurosurgery/Spine-Carilion, 3 Riverside Circle, Roanoke VA 24016.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Marvin
authors.affiliation: Globus Medical, Inc., Valley Forge Business Center, 2560 General Armistead Ave., Audubon, PA 19403, USA.
authors.forename: Brandon S
authors.initials: BS
authors.lastname: Bucklen
mesh_terms: D000368:Aged; D001672:Biocompatible Materials; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D007595:Joint Prosthesis; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D056687:Off-Label Use; D010027:Osteotomy; D065289:Pedicle Screws; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D013121:Spinal Curvatures / Q000503:physiopathology / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation*; D014025:Titanium
chemical_list: D001672:Biocompatible Materials; D014025:Titanium
keywords: Cobb angle; Deformity; Expandable; Interbody fusion device; Osteotomy; TLIF