Background In Denmark the numbers of primary total knee arthroplasty (TKA) operations annually increase. In the year 2000 was performed approximately 2,500 operations and in 2008 was performed more than 7,500 total knee arthroplasty operations, and there appears in all countries to be similar tendency. Meanwhile, the prevalence of overweight and obesity has increased markedly over the last 50 years. Approximately 13% of the Danish population is obese. For several years the association between obesity and knee osteoarthritis (OA) has been recognized, and osteoarthritis is the most frequent indication for total knee arthroplasty(80%).
The purpose of this study is to investigate whether weight loss interventions before primary total knee arthroplasty will improve quality of life and functional level, reduce pain and risk of early and late postoperative complications.
Sample size Significance level is set to 5% by using a 2-sided analysis and the power is set at 80%. Based on an expectation of a difference in patient-reported outcome scores in between the groups at 8%, as measured by SF-36 12 months postoperatively, standard deviation (SD) 13 must be include 41 participants in each group. To allow a drop-out rate of 20% the group size increases to 51 participants in each group. In total 102 participants.
Statistical analysis, The two groups scores at 12 months postoperatively, and the two groups' change in the primary outcome measurer, from 1 week before surgery to 12 months postoperatively, compared with t-test or Mann-Whitney test rang sum depending on data distribution.
