Adult visitors to the outpatient clinic of the Department of Surgery and also staff at 4 different Dutch hospitals were asked to participate in this study. The 4 hospitals were located in different regions (both rural and urban) and consisted of 1 university hospital and 3 teaching hospitals. Since it was not possible to perform a prospective sample size calculation, we chose to include a minimum of 250 individuals at each hospital. We considered this to be a large enough population to be representative of the whole population. We constantly monitored the age and sex of the respondents in order to obtain comparable group sizes. As data collection took several days at each hospital, after each day we checked the numbers of men and women and the distribution across different age categories. When differences arose, specific sex and/or age groups were approached to participate in the day(s) that followed.
The study consisted of a short questionnaire in which the postal code, age (as a continuous variable and subdivided into 3 categories (18–39, 40–64, and over 64 years)), sex, and work status (student, working, retired, unemployed, unfit for work, or other) of the subjects were recorded. When participants were actively employed at the time of filling out the questionnaire, they were requested to report whether they considered their employment to be blue-, pink-, or white-collar (i.e. very physically demanding, moderately physically demanding, or not physically demanding). After this, they were asked whether they had a history of lower extremity surgery and—if this was the case—how long ago. In addition, they were asked whether they were currently scheduled for lower extremity surgery. Next, they were presented with the Dutch version of the lower extremity functional scale (LEFS) (Hoogeboom et al. 2012 (link)) The LEFS has 20 items in 4 categories. For each question, 0 to 4 points can be earned, so 80 points can be earned in total—indicating maximal lower extremity function (Binkley et al. 1999 (link)) The Dutch version of the LEFS has been validated using the SF-36 as a reference and proved to have good internal consistency, good reliability, and good construct and discriminant validity, while showing no floor or ceiling effects (Hoogeboom et al. 2012 (link)).
Individuals were excluded if they had had lower extremity surgery within 1 year of filling out the questionnaire. Participants who were scheduled for lower extremity surgery were also excluded. Missing data in the LEFS were treated according to the instructions of the developers of the questionnaire (Stratford et al. 2005 ). When questionnaires contained more than 4 missing answers, or 3 missing within 1 domain, they were excluded (Stratford et al. 2005 ).
We obtained data on socioeconomic status (SES) from the Netherlands Institute for Social Research (Sociaal Cultureel Planbureau). For all postal codes, a number is available that reflects the SES of that particular area. This figure ranges from −6.7 to +3.1, where 0 represents the average SES for the Netherlands.
The study consisted of a short questionnaire in which the postal code, age (as a continuous variable and subdivided into 3 categories (18–39, 40–64, and over 64 years)), sex, and work status (student, working, retired, unemployed, unfit for work, or other) of the subjects were recorded. When participants were actively employed at the time of filling out the questionnaire, they were requested to report whether they considered their employment to be blue-, pink-, or white-collar (i.e. very physically demanding, moderately physically demanding, or not physically demanding). After this, they were asked whether they had a history of lower extremity surgery and—if this was the case—how long ago. In addition, they were asked whether they were currently scheduled for lower extremity surgery. Next, they were presented with the Dutch version of the lower extremity functional scale (LEFS) (Hoogeboom et al. 2012 (link)) The LEFS has 20 items in 4 categories. For each question, 0 to 4 points can be earned, so 80 points can be earned in total—indicating maximal lower extremity function (Binkley et al. 1999 (link)) The Dutch version of the LEFS has been validated using the SF-36 as a reference and proved to have good internal consistency, good reliability, and good construct and discriminant validity, while showing no floor or ceiling effects (Hoogeboom et al. 2012 (link)).
Individuals were excluded if they had had lower extremity surgery within 1 year of filling out the questionnaire. Participants who were scheduled for lower extremity surgery were also excluded. Missing data in the LEFS were treated according to the instructions of the developers of the questionnaire (Stratford et al. 2005 ). When questionnaires contained more than 4 missing answers, or 3 missing within 1 domain, they were excluded (Stratford et al. 2005 ).
We obtained data on socioeconomic status (SES) from the Netherlands Institute for Social Research (Sociaal Cultureel Planbureau). For all postal codes, a number is available that reflects the SES of that particular area. This figure ranges from −6.7 to +3.1, where 0 represents the average SES for the Netherlands.