title: Frequency, risk factors, and treatment of distal adjacent segment pathology after long thoracolumbar fusion: a systematic review.
abstract: METHODS
  Systematic review.
  
  
  OBJECTIVE
  To systematically review the literature related to distal adjacent segment pathology (ASP) after long thoracolumbar fusions for deformity including frequency, risk factors, frequency differences between adolescents and adults, surgical approach for revision, and revision complications.
  
  
  BACKGROUND
  Spinal deformity surgery complications include ASP. Although ASP at the rostral end of instrumented fusions has been well described, substantially less has been documented about distal ASP.
  
  
  METHODS
  A systematic search was conducted in Medline and the Cochrane Collaboration Library for articles published between January 1, 1983, and March 15, 2012. We included all articles that described distal ASP after long thoracolumbar fusion for deformity. Radiographical ASP (RASP) was defined as evidence of ASP based on imaging, and clinical ASP (CASP) was defined as symptomatic ASP.
  
  
  RESULTS
  Seven retrospective cohort studies met inclusion criteria. Distal CASP developed in 17.7% at 2- 6-year follow-up and 19.8% at 9-year follow-up, whereas reoperation due to CASP was reported in 15.6% at 2 to 6 years and 14.4% at 9 years. Distal RASP was more frequent (44.7%-65.5%). Preoperative sagittal imbalance was associated with increased risk of distal ASP. There was increased risk of CASP in patients with higher postoperative fractional curve and increased risk of RASP in younger patients and those with preoperative disc degeneration, longer fusions, circumferential procedures, and postoperative L5-S1 disc space narrowing. No studies meeting inclusion criteria compared distal ASP in adults and adolescents or defined the best approach or complications for distal ASP revision.
  
  
  CONCLUSIONS
  Low-quality evidence suggests a cumulative rate of 18% to 20% for CASP and 45% to 65% for RASP after long thoracolumbar fusion for spinal deformity during 9-year follow-up. Low-quality evidence suggests an association between preoperative sagittal imbalance and distal ASP, with greater risk of distal ASP in patients with sagittal imbalance. Low-quality evidence suggests increased risk of CASP in patients with higher postoperative fractional curve and increased risk of RASP in younger patients and those with preoperative disc degeneration, longer fusions, circumferential procedures, and postoperative L5-S1 disc space narrowing.
  
  
  METHODS
  1. The risk of developing new symptoms secondary to distal adjacent segment pathology following long thoracolumbar fusion for deformity is approximately 18–20% during a period of 9 years follow up, and most of these patients will require revision surgery. Strength of Statement: Weak. 2. The risk of developing distal adjacent segment pathology may be higher in those with preoperative sagittal imbalance, preoperative disc degeneration, longer fusions, circumferential procedures, and postoperative L5–S1 disc space narrowing. Strength of Statement: Weak.
authors.affiliation: University of Virginia Health Sciences Center, Department of Neurosurgery, Charlottesville, VA 22908, USA.
authors.forename: Manish K
authors.initials: MK
authors.lastname: Kasliwal
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Shaffrey
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Lenke
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Dettori
authors.forename: Claire G
authors.initials: CG
authors.lastname: Ely
authors.forename: Justin S
authors.initials: JS
authors.lastname: Smith
mesh_terms: D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology* / Q000601:surgery; D055959:Intervertebral Disc Degeneration / Q000473:pathology* / Q000601:surgery; D008159:Lumbar Vertebrae / Q000473:pathology* / Q000601:surgery; D012307:Risk Factors; D013123:Spinal Fusion / Q000009:adverse effects* / Q000379:methods; D016896:Treatment Outcome