Quality of life was assessed using the QoL questionnaire SF-12 Health Survey for self-administration, which is a shorter version of the SF-36 Health Survey (QualiMetric Inc., Lincoln, RI, USA) [18]. The results of the SF-12 questionnaire are composed of a Physical Component Summary (PCS) score and a Mental Component Summary (MCS) score and are obtained by standard algorithms. The SF-12 PCS and MCS scores of the US population have a mean of 50, with a standard deviation (SD) of 10. Lower scores mean a worse health status, higher scores a better health status. The written German version of the SF-12 was mailed to the patients and standard scoring algorithms were used to score their responses to the 12 multiple choice questions.

To evaluate the functional health status, the mRS score and the Barthel Index [6, 17] were assessed. The mRS ranges from 0 to 6 and the scores are defined as: (0) no symptoms at all; (1) no significant disability despite symptoms, able to carry out all usual duties and activities; (2) slight disability, unable to carry out all previous activities, but able to look after own affairs without assistance; (3) moderate disability, requiring some help, but able to walk without assistance; (4) moderately severe disability, unable to walk without assistance and unable to attend to own bodily needs without assistance; (5) severe disability, bedridden, incontinent, and requiring constant nursing care and attention; and (6) dead.

Additionally, the Self Evaluation of Health State test, which is a visual analog scale (VAS), was used to evaluate the present subjective health state. In the VAS, 100 points is defined as the best and 0 as the worst imaginable state.

The questionnaires were filled out by the patients themselves or by the help of a close relative.