title: Expandable vs Static Cages in Transforaminal Lumbar Interbody Fusion: Radiographic Comparison of Segmental and Lumbar Sagittal Angles.
abstract: BACKGROUND
  One criticism of transforaminal lumbar interbody fusion (TLIF) is the inability to increase segmental lordosis (SL). Expandable interbody cages are a relatively new innovation theorized to allow improvement in SL.
  
  
  OBJECTIVE
  To compare changes in SL and lumbar lordosis (LL) after TLIF with nonexpandable vs expandable cages.
  
  
  METHODS
  We performed a retrospective cohort study of patients who were ≥18 years old and underwent single-level TLIF between 2011 and 2014. Patients were categorized by cage type (static vs expandable). Primary outcome of interest was change in SL and LL from preoperative values to those at 1 month and 1 year postoperatively.
  
  
  RESULTS
  A total of 89 patients were studied (48 nonexpandable group, 41 expandable group). Groups had similar baseline characteristics. For SL, median (interquartile range) improvement was 3° for nonexpandable and 2° for expandable (unadjusted, P = .09; adjusted, P = .68) at 1 month postoperatively, and 3° for nonexpandable and 1° for expandable (unadjusted, P = .41; adjusted, P = .28) at 1 year postoperatively. For LL, median improvement was 1° for nonexpandable and 2° for expandable (unadjusted, P = .20; adjusted, P = .21), and 2° for nonexpandable and 5° for expandable (unadjusted, P = .15; adjusted, P = .51) at 1 year postoperatively. After excluding parallel expandable cages, there was still no difference in SL or LL improvement at 1 month or 1 year postoperatively between static and expandable cages (both unadjusted and adjusted, P > .05).
  
  
  CONCLUSIONS
  Patients undergoing single-level TLIF experienced similar improvements in SL and LL regardless of whether nonexpandable or expandable cages were placed.
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Yee
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Jacob R
authors.initials: JR
authors.lastname: Joseph
authors.affiliation: Department of Neurology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Samuel W
authors.initials: SW
authors.lastname: Terman
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Paul
authors.initials: P
authors.lastname: Park
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D016268:Internal Fixators; D008141:Lordosis / Q000000981:diagnostic imaging / Q000209:etiology / Q000601:surgery*; D008159:Lumbar Vertebrae; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000295:instrumentation*; D016896:Treatment Outcome
keywords: Expandable cage; Interbody cage; Minimally invasive; Spine; TLIF; Transforaminal lumbar interbody fusion