title: Perioperative complications of simultaneous versus staged unicompartmental knee arthroplasty.
abstract: BACKGROUND
  The complication risk of staged versus simultaneous total knee arthroplasty continues to be debated in the literature. Previous reports suggest unicompartmental knee arthroplasty provides a more rapid functional recovery than total knee arthroplasty. However, little data exist on whether simultaneous unicompartmental knee arthroplasty can be performed without increasing the perioperative risk compared with staged unicompartmental knee arthroplasty.
  
  
  OBJECTIVE
  We therefore asked if there is an increased risk of perioperative complications with bilateral simultaneous unicompartmental knee arthroplasty.
  
  
  METHODS
  We retrospectively compared 141 patients (282 knees) treated with staged unicompartmental knee arthroplasty with 35 patients (70 knees) treated with simultaneous unicompartmental knee arthroplasty to evaluate perioperative complications and short-term results assessed by Knee Society function scores and the Lower Extremity Activity Scale.
  
  
  RESULTS
  Patients who underwent simultaneous unicompartmental knee arthroplasty had a shorter cumulative operative time (109 versus 122 minutes), a shorter cumulative length of hospital stay (1.7 versus 2.5 days), higher Knee Society function scores at most recent followup (88 versus 73), and higher Lower Extremity Activity Scale (12.0 versus 10.2) without a difference in perioperative complications. The simultaneous cohort was younger (59 versus 63 years of age) and less obese (body mass index 31 versus 33 kg/m(2)) than the staged group.
  
  
  CONCLUSIONS
  Although we found a substantial bias for performing simultaneous unicompartmental knee arthroplasty in younger and less obese patients, these data suggest it can be performed without increasing perioperative morbidity or mortality in this patient population.
  
  
  METHODS
  Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Joint Implant Surgeons, Inc, 7277 Smith's Mill Road, Suite 200, New Albany, OH 43054, USA. BerendKR@joint-surgeons.com
authors.forename: Keith R
authors.initials: KR
authors.lastname: Berend
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Morris
authors.forename: Michael D
authors.initials: MD
authors.lastname: Skeels
authors.forename: Adolph V
authors.initials: AV
authors.lastname: Lombardi
authors.forename: Joanne B
authors.initials: JB
authors.lastname: Adams
mesh_terms: D000367:Age Factors; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods*; D015992:Body Mass Index; D016009:Chi-Square Distribution; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D007902:Length of Stay; D008875:Middle Aged; D009820:Ohio; D011183:Postoperative Complications / Q000209:etiology* / Q000503:physiopathology / Q000601:surgery; D020127:Recovery of Function; D012086:Reoperation; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome