title: Time between the first and second operations for staged total knee arthroplasties when the interval is determined by the patient.
abstract: BACKGROUND
  The purpose of this study was to evaluate the interval between the first and second operations for staged total knee arthroplasties (TKAs) in patients with bilateral knee osteoarthritis. Depending on satisfactory preoperative health status, the patients determined the timing of the second operation. We also analysed correlations between the interval and patient characteristics.
  
  
  METHODS
  Eighty-six patients with bilateral knee osteoarthritis were analysed. The mean follow-up time from the first TKA was 96 months. The side of the first TKA was chosen by the patients. The timing of the second TKA was determined by the patients, depending on their perceived ability to tolerate the additional pain and limitations to activities of daily living.
  
  
  RESULTS
  The median interval between the first and second operations was 12.5 months, with a range of 2 to 113 months. In 43 (50%) patients, the interval was <12 months. There was no difference in the interval between females and males (p=0.861), and no correlation between the interval and body mass index or age. There was weak correlation between the year of the first TKA and the interval (R=-0.251, p=0.020), with the interval getting significantly shorter as the years progressed (p=0.032).
  
  
  CONCLUSIONS
  The median interval between the first and second operations in patients who underwent staged TKAs for bilateral knee osteoarthritis was about 1 year. The results of the current study may help patients and physicians to plan effective treatment strategies for staged TKAs.
  
  
  METHODS
  Level II.
authors.affiliation: Ishii Orthopaedic and Rehabilitation Clinic, 1089 Shimo-Oshi, Gyoda, Saitama 361-0037, Japan. Electronic address: ishii@sakitama.or.jp.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ishii
authors.affiliation: Ishii Orthopaedic and Rehabilitation Clinic, 1089 Shimo-Oshi, Gyoda, Saitama 361-0037, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Noguchi
authors.affiliation: Ishii Orthopaedic and Rehabilitation Clinic, 1089 Shimo-Oshi, Gyoda, Saitama 361-0037, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Takeda
authors.affiliation: Ishii Orthopaedic and Rehabilitation Clinic, 1089 Shimo-Oshi, Gyoda, Saitama 361-0037, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Sato
authors.affiliation: Division of Information Science and Biostatistics, Niigata University Graduate School of Medical and Dental Sciences, 1 Asahimachi Dori, Niigata, Niigata 951-8520, Japan.
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Toyabe
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D003657:Decision Making; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D020370:Osteoarthritis, Knee / Q000601:surgery*; D010358:Patient Participation; D012189:Retrospective Studies; D013997:Time Factors
keywords: Bilateral osteoarthritis; Interval between the first and second operations; Retrospective study; Simultaneous TKA; Staged TKA