title: Pain and function in patients after primary unicompartmental and total knee arthroplasty.
abstract: BACKGROUND
  Unicompartmental knee arthroplasty has received renewed interest; however, its short-term advantages over total knee arthroplasty should be weighed against a higher risk of reoperation. Information regarding pain and function after unicompartmental and total knee arthroplasty is therefore needed.
  
  
  METHODS
  Patient-reported data regarding pain and function were collected, at least two years postoperatively and by way of postal questionnaire, from 1344 patients who were listed on the Norwegian Arthroplasty Register as having had an unrevised primary total knee arthroplasty (972 patients) or a unicompartmental knee arthroplasty (372 patients) for the treatment of arthritis. Outcomes were assessed (with a score of zero indicating the worst possible outcome and a score of 100 indicating the best possible outcome) with use of the five subscales from the Knee Injury and Osteoarthritis Outcome Score, the scores from visual analog scales regarding degree of pain and satisfaction with the surgery, and the change in index score (from preoperative to postoperative) on the EuroQol-5D health-related quality-of-life instrument. We also used all forty-two questions from the Knee Injury and Osteoarthritis Outcome Score as outcome measures. To be regarded as clinically significant, the differences needed to be eight units for the Knee Injury and Osteoarthritis Outcome Score outcomes, ten units for the pain and satisfaction scales, and 0.4 unit for the detailed Knee Injury and Osteoarthritis Outcome Score questions.
  
  
  RESULTS
  Unicompartmental knee implants performed better than total knee implants on the Knee Injury and Osteoarthritis Outcome subscales for "Symptoms" (adjusted mean difference, 2.7; p = 0.04), "Function in Daily Living" (adjusted mean difference, 4.1; p = 0.01), and "Function in Sport and Recreation" (adjusted mean difference, 5.4; p = 0.006). Of the forty-two analyses of the detailed questions, four differences were significant. These differences were in favor of unicompartmental knee arthroplasty, but only the question "Can you bend your knee fully?" reached the level of clinical significance.
  
  
  CONCLUSIONS
  We found only small or no differences in pain and function between the scores, at least two years following surgery, of patients who underwent unicompartmental knee arthroplasty and those of patients who underwent total knee arthroplasty; however, patients with unicompartmental knee implants had fewer problems with activities that involved bending the knee.
authors.affiliation: The Norwegian Arthroplasty Register, Department of Orthopaedic Surgery, Haukeland University Hospital, Møllendalsbakken 11, N-5021 Bergen, Norway. stein.lygre@helse-bergen.no
authors.forename: Stein Håkon Låstad
authors.initials: SH
authors.lastname: Lygre
authors.forename: Birgitte
authors.initials: B
authors.lastname: Espehaug
authors.forename: Leif Ivar
authors.initials: LI
authors.lastname: Havelin
authors.forename: Ove
authors.initials: O
authors.lastname: Furnes
authors.forename: Stein Emil
authors.initials: SE
authors.lastname: Vollset
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D009664:Norway; D020370:Osteoarthritis, Knee / Q000601:surgery; D010147:Pain Measurement; D010149:Postoperative Pain / Q000175:diagnosis*; D017060:Patient Satisfaction / Q000706:statistics & numerical data; D011475:Prosthesis Failure; D019919:Prosthesis Implantation / Q000009:adverse effects / Q000379:methods*; D011788:Quality of Life; D016059:Range of Motion, Articular / Q000502:physiology*; D020127:Recovery of Function; D012042:Registries; D011795:Surveys and Questionnaires; D016896:Treatment Outcome