title: Influencing segmental balance in isthmic spondylolisthesis using transforaminal lumbar interbody fusion.
abstract: METHODS
  Retrospective cohort study.
  
  
  OBJECTIVE
  The objective of the study was to analyze segmental balance in patients with isthmic spondylolisthesis undergoing single-level transforaminal lumbar interbody fusion (TLIF).
  
  
  BACKGROUND
  Sagittal malalignment of the fused segment was suggested to be associated with degeneration of the adjacent segment. Meticulous surgical technique and particular attention to hardware positioning with the aim to restore segmental balance at the fusion level have been recommended to achieve better long-term clinical outcomes, but no single study addressed all proposed factors.
  
  
  METHODS
  Standard lateral radiographs of the lumbosacral spine in the neutral standing position were retrospectively obtained for 32 patients undergoing single-level TLIF. Preoperative versus postoperative versus final follow-up (12 to 60 mo) values of translational slip (TS), posterior disc space height (PDSH), and segmental lordosis (SL) were compared using paired samples t test. Change in SL postoperatively between groups of next grouping variables: type and position of the interbody device, and rod contouring, was compared using 2-tailed independent samples t test. Association between position of the interbody device and immediate PDSH was addressed with regression analysis postoperatively and at final follow-up.
  
  
  RESULTS
  Mean TS decreased (P<0.001) and mean PDSH increased (P=0.002), but no significant change in SL occurred postoperatively (P=0.811). Increase in SL was observed with ventral positioning of the interbody device (P=0.009) and with bending of connecting rods (P=0.023). During follow-up, there was increase in TS (P=0.002) and decrease in PDSH (P<0.001) and SL (P<0.001) compared with postoperative values. Lower PDSH was found to be associated with more ventral positioning of the interbody device, both postoperatively (P=0.035) and at final follow-up (P=0.029).
  
  
  CONCLUSIONS
  This study demonstrates that reduction of TS and restoration of disc space height are readily achieved with single-level TLIF. However, to establish an increase in SL consistent rod contouring and meticulous anterior placement of the interbody device should be applied. Excessive ventral positioning of the cages might result in insufficient disc space height restoration.
authors.affiliation: Department of Orthopedic Surgery, University Hospital Maribor, Slovenia. gregorrecnik@yahoo.com
authors.forename: Gregor
authors.initials: G
authors.lastname: Recnik
authors.forename: Robert
authors.initials: R
authors.lastname: Košak
authors.forename: Rok
authors.initials: R
authors.lastname: Vengust
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012189:Retrospective Studies; D012447:Sacrum / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*; D013168:Spondylolisthesis / Q000000981:diagnostic imaging* / Q000601:surgery*