title: Influence of perioperative complication severity on 1- and 2-year outcomes of low back surgery.
abstract: BACKGROUND
  Several factors potentially influence outcomes of surgery, including perioperative complications. Complications may take many forms and the Clavien-Dindo (CD) classification is designed to categorize them by degree of severity. The aim of this study was to evaluate the influence of perioperative complications by severity categorization on the 1-and 2-year pain and disability outcomes for patients who received low back surgery.
  
  
  METHODS
  Data used for the study involved a purposive sample (N = 477; 8.1%) from a spine outcomes registry of 5876 patients who received spine surgery and encountered complications. All complications were categorized using the CD classification and were collapsed according to distribution frequencies, i.e., Grade I-II and Grade III-V. Adjusted and unadjusted regression analyses were used to determine the association between CD classification and 1- and 2-year outcomes.
  
  
  RESULTS
  The majority of surgical complications were Grade III-V (N = 358; 75.1%), with two incidences in which death occurred. For the unadjusted models, there were no significant associations between CD classification categorizations for 1-year outcomes; however, 2-year outcomes were significantly worse (P <0.05) for those with Grade III-V categorization. When adjusted and controlled for baseline characteristics, CD classification did not influence 1-or 2-year pain and disability outcomes.
  
  
  CONCLUSIONS
  When control variables are considered, the severity of perioperative surgical complications does not appear to influence 1- or 2-year pain and disability outcomes.
  
  
  METHODS
  Level 4.
authors.affiliation: Department of Orthopedics, Duke University School of Medicine, 2200 W Main St, Durham, NC, 27708, USA. james.grainger@dm.duke.edu.
authors.forename: James
authors.identifier: http://orcid.org/0000-0002-8207-1368
authors.initials: J
authors.lastname: Grainger
authors.affiliation: Department of Orthopedics, Duke University School of Medicine, 2200 W Main St, Durham, NC, 27708, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hammett
authors.affiliation: Division of Neurosurgery, Duke University Medical Center, 200 Trent Drive #1l, Durham, NC, 27710, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Isaacs
authors.affiliation: Department of Orthopedic Surgery, Duke University, 2200 W. Main St. B230, Durham, NC, 27708, USA.
authors.forename: Chad
authors.initials: C
authors.lastname: Cook
mesh_terms: D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D017116:Low Back Pain / Q000175:diagnosis / Q000601:surgery*; D008159:Lumbar Vertebrae; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement / Q000379:methods*; D011183:Postoperative Complications / Q000175:diagnosis / Q000453:epidemiology*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013123:Spinal Fusion / Q000009:adverse effects*; D013997:Time Factors; D016896:Treatment Outcome
keywords: Low back surgery; Lumbar spine; Outcomes; Perioperative complications