title: Risk factors for and assessment of symptomatic pseudarthrosis after lumbar pedicle subtraction osteotomy in adult spinal deformity.
abstract: METHODS
  Retrospective review of prospectively collected data.
  
  
  OBJECTIVE
  To assess the prevalence, risk factors, and clinical outcomes for pseudarthrosis after a lumbar pedicle subtraction osteotomy (PSO).
  
  
  BACKGROUND
  There exists no large series that examines pseudarthrosis rates of PSOs.
  
  
  METHODS
  Data of 171 consecutive patients with adult deformity who underwent a lumbar PSO by 2 surgeons at a single institution with a minimum 2-year follow-up were analyzed. Pseudarthrosis diagnosed through sagittal malalignment and instrumentation failure noted on radiograph was confirmed intraoperatively.
  
  
  RESULTS
  Eighteen (10.5%) of 171 patients developed pseudarthrosis after a PSO. Eleven of the 18 patients (6.4% of all patients, 61.1% of the 18 patients with pseudarthrosis) had pseudarthrosis at the PSO site, L3 being the most common; other locations included the lumbosacral junction (4/18), thoracolumbar junction (2/18), and upper thoracic spine (1/18). Preoperative pseudarthrosis level was a predictor of the postoperative level of pseudarthrosis (93%). Fifteen of the 18 patients (83%) had no interbody fusion directly above or below the PSO site, 16 (88%) had a history of pseudarthrosis at the time of PSO surgery and 2 of 3 patients who had prior radiation to the lumbar region developed pseudarthrosis. Most pseudarthroses occurred within the first 2 years (n = 13/18), between 2 and 5 years (n = 3/18), and more than 5 years (n = 2/18) postoperatively. Prior pseudarthrosis (P < 0.0001), pseudarthrosis at the PSO site (P < 0.0001), prior decompression in the lumbar region (P = 0.0037), prior radiation to the lumbar region (P < 0.0001), and presence of inflammatory/neurological disorders (P < 0.0036) were identified as risk factors. All 18 patients with pseudarthroses required revision surgery (posterior-only surgery, n = 12; anteroposterior surgery, n = 6) due to loss of sagittal alignment and pain. The mean pre-revision Scoliosis Research Society score was 85, post-revision score was 95 (P = 0.0166), and the mean pre-revision Oswestry Disability Index score was 42.5, post-revision score was 34.5 (P = 0.0203).
  
  
  CONCLUSIONS
  The overall prevalence of pseudarthrosis was 10.5% of which 61% occurred at the actual PSO site and Scoliosis Research Society and Oswestry Disability Index scores improved significantly after pseudarthrosis repair.
  
  
  METHODS
  4.
authors.affiliation: *University of North Texas Health Science Center Fort Worth, TX and †Department of Orthopaedic Surgery, Washington University School of Medicine, St Louis, MO.
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Dickson
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Lenke
authors.forename: Keith H
authors.initials: KH
authors.lastname: Bridwell
authors.forename: Linda A
authors.initials: LA
authors.lastname: Koester
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001863:Bone Screws; D004185:Disability Evaluation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008161:Lumbosacral Region / Q000601:surgery; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D011183:Postoperative Complications / Q000175:diagnosis* / Q000209:etiology / Q000601:surgery; D011542:Pseudarthrosis / Q000175:diagnosis* / Q000209:etiology / Q000601:surgery; D012189:Retrospective Studies; D012307:Risk Factors; D012447:Sacrum / Q000601:surgery; D013122:Spinal Diseases / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000601:surgery; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult