title: Overlapping Surgery in the Ambulatory Orthopaedic Setting.
abstract: BACKGROUND
  The practice of a surgeon performing procedures in two operating rooms during overlapping time frames has been described as concurrent surgery if critical portions occur simultaneously, or overlapping surgery if they do not. Although recent media reports have focused on the potential adverse effects of these practices, to our knowledge, there has been no previous research investigating outcomes of overlapping procedures in orthopaedic surgery.
  
  
  METHODS
  A retrospective review of an institutional clinical database from 2012 to 2015 was utilized to collect data from all surgical cases (including sports medicine, hand, and foot and ankle) performed at an ambulatory orthopaedic surgery center. Patient demographic characteristics, types of procedures, operating room time, procedure time, and 30-day outcomes including complications, unplanned hospital readmissions, unplanned reoperations, and emergency department visits were collected. The amount of overlap time between cases was also analyzed. Pearson chi-square tests, Student t tests, and logistic regression were used for statistical analysis.
  
  
  RESULTS
  Of 3,640 cases performed, 68% were overlapping procedures and 32% were non-overlapping. There was no difference in the mean age, sex, body mass index, American Society of Anesthesiologists rating, or Charlson Comorbidity Index between patients who had overlapping procedures and those who did not. Comparison of overlapping surgery cases and non-overlapping surgery cases revealed no difference in the mean procedure time (70.7 minutes compared with 72.8 minutes; p = 0.116) or total operating room time (105.4 minutes compared with 105.5 minutes; p = 0.949). Complications were tracked for 30 days after procedures and yielded a rate of 1.1% for overlapping surgeries and 1.3% for non-overlapping surgeries (p = 0.811). Stratification based on subspecialty surgery also demonstrated no difference in complications between the cohorts. Fifty percent of overlapping cases overlapped by <1 hour of operating room time, but 7% overlapped by >2 hours. The rate of complications was found to have no association with the amount of overlap between cases (p = 0.151).
  
  
  CONCLUSIONS
  Overlapping surgery yields equivalent patient operating room time, procedure time, and 30-day complication rates as non-overlapping surgery in the ambulatory orthopaedic setting. Further investigation is warranted for inpatient orthopaedic procedures and across all orthopaedic subspecialties.
  
  
  METHODS
  Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Departments of Orthopaedic Surgery (A.L.Z., D.C.S., D.Y.D., C.B.M., T.P.V., and B.T.F.) and Epidemiology and Biostatistics (D.B.), University of California at San Francisco, San Francisco, California Alan.Zhang@ucsf.edu.
authors.forename: Alan L
authors.initials: AL
authors.lastname: Zhang
authors.affiliation: Departments of Orthopaedic Surgery (A.L.Z., D.C.S., D.Y.D., C.B.M., T.P.V., and B.T.F.) and Epidemiology and Biostatistics (D.B.), University of California at San Francisco, San Francisco, California.
authors.forename: David C
authors.initials: DC
authors.lastname: Sing
authors.affiliation: Departments of Orthopaedic Surgery (A.L.Z., D.C.S., D.Y.D., C.B.M., T.P.V., and B.T.F.) and Epidemiology and Biostatistics (D.B.), University of California at San Francisco, San Francisco, California.
authors.forename: Debbie Y
authors.initials: DY
authors.lastname: Dang
authors.affiliation: Departments of Orthopaedic Surgery (A.L.Z., D.C.S., D.Y.D., C.B.M., T.P.V., and B.T.F.) and Epidemiology and Biostatistics (D.B.), University of California at San Francisco, San Francisco, California.
authors.forename: C Benjamin
authors.initials: CB
authors.lastname: Ma
authors.affiliation: Departments of Orthopaedic Surgery (A.L.Z., D.C.S., D.Y.D., C.B.M., T.P.V., and B.T.F.) and Epidemiology and Biostatistics (D.B.), University of California at San Francisco, San Francisco, California.
authors.forename: Dennis
authors.initials: D
authors.lastname: Black
authors.affiliation: Departments of Orthopaedic Surgery (A.L.Z., D.C.S., D.Y.D., C.B.M., T.P.V., and B.T.F.) and Epidemiology and Biostatistics (D.B.), University of California at San Francisco, San Francisco, California.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Vail
authors.affiliation: Departments of Orthopaedic Surgery (A.L.Z., D.C.S., D.Y.D., C.B.M., T.P.V., and B.T.F.) and Epidemiology and Biostatistics (D.B.), University of California at San Francisco, San Francisco, California.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Feeley
mesh_terms: D000328:Adult; D000553:Ambulatory Care; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000009:adverse effects / Q000379:methods*; D010359:Patient Readmission; D011183:Postoperative Complications / Q000209:etiology; D012189:Retrospective Studies; D055815:Young Adult