All numbers in the tables are medians with corresponding interquartile ranges unless stated otherwise. Difference in continuous data between groups was tested with the Mann-Whitney U test. Difference in categorical data between groups was tested with the x 2 test or Kruskal Wallis test. Pvalues 0.05 were considered statistically significant. Multiple linear regression analyses were performed to analyze the interaction between the different scales of the SF-36 questionnaire and pain rate. All missing data were considered missing at random. In the case that one or more questions were not answered in a specific scale of the SF-36 questionnaire, the mean value of the remaining questions on that specific scale was used for the missing items. When half or more of the questions were not answered, the results of the specific scale were discarded. Statistical analysis was performed by using SPSS 12.0.2 (SPSS, Chicago, IL).