title: In-Hospital Complication Rates and Associated Factors After Simultaneous Bilateral Versus Unilateral Total Knee Arthroplasty.
abstract: BACKGROUND
  Data comparing complication rates following simultaneous bilateral total knee arthroplasty with those of unilateral total knee arthroplasty are conflicting. The purpose of this study was to compare in-hospital complication rates following simultaneous bilateral versus unilateral total knee arthroplasty and to determine factors associated with in-hospital complication rates in a large cohort of patients identified from the Nationwide Inpatient Sample (NIS).
  
  
  METHODS
  The 2004 to 2007 NIS data set was used to identify 407,070 total knee arthroplasties: 24,574 simultaneous bilateral and 382,496 unilateral total knee arthroplasties. Complications, based on International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes, were categorized as none, minor, major, or mortality. Covariates included comorbidities, demographic information, payer type, and hospital total knee arthroplasty volume. Multiple logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs).
  
  
  RESULTS
  Simultaneous bilateral total knee arthroplasty was associated with significantly higher odds of an in-hospital complication compared with unilateral total knee arthroplasty: OR, 1.51 (95% CI, 1.42 to 1.62) for minor complication; OR, 1.30 (95% CI, 1.14 to 1.47) for major complication; and OR, 2.51 (95% CI, 1.66 to 3.80) for mortality. Patients with greater numbers of medical comorbidities were more likely to have an in-hospital complication. Compared with whites, African-American and Asian/Pacific Islander groups had significantly higher odds of a minor complication. Female patients were less likely than male patients to have an in-hospital complication. Patients who were less than sixty-five years old at the time of surgery had significantly reduced odds of a minor complication and mortality compared with patients who were seventy-five years of age or older. Compared with hospitals with a very-high volume of total knee arthroplasty procedures performed (≥850), lower-volume hospitals had significantly increased odds of minor complications and mortality.
  
  
  CONCLUSIONS
  While complication rates following either unilateral or simultaneous bilateral total knee arthroplasty are low, simultaneous bilateral total knee arthroplasty was associated with higher odds of in-hospital complications, including mortality, compared with unilateral total knee arthroplasty. Patient demographic information, preoperative health status, payer type, and hospital total knee arthroplasty volume were all significant factors in complication rates following bilateral total knee arthroplasty.
  
  
  METHODS
  Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: OrthoCarolina Research Institute, Inc., 2001 Vail Avenue, Suite 300, Charlotte, NC 28207. E-mail address: susan.odum@orthocarolina.com.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Odum
authors.affiliation: OrthoCarolina Hip and Knee Center, 2001 Vail Avenue, Suite 200-A, Charlotte, NC 28207. E-mail address: Bryan.springer@orthocarolina.com.
authors.forename: Bryan D
authors.initials: BD
authors.lastname: Springer
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D015897:Comorbidity; D005260:Female; D006801:Humans; D007297:Inpatients; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000145:classification / Q000453:epidemiology* / Q000208:ethnology; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data; D012307:Risk Factors; D012737:Sex Factors; D014481:United States / Q000453:epidemiology