As a secondary outcome measure we used the Generic Patient-
Specific Scale (GPSS), which assesses individual complaints and
restrictions in a short and efficient way (17). Patients chose their 3
most difficult activities and rated the ability to perform them on an
11-point visual numeric rating scale (VNRS). A score of 10 at the
right-hand end of the VNRS was defined as “I can perform the chosen
function without difficulty”, and 0 at the left-hand end as “I am unable
to perform the chosen function”. A mean score across all activities
was calculated and a minimum change of 3 points was considered as
a clinically important improvement (18, 19). In addition, all patients
completed a modified version of the Fear Avoidance Beliefs Questionnaire
(FABQ) and the Pain Catastrophizing Scale (PCS); 2 factors
possibly influencing our main outcome measure.