Background: At present there is no clear evidence that surgical treatment by fusion operation is more advisable than non-surgical treatment in patients suffering from unspecific chronic low back pain (CLBP). By personal experience a subgroup among the CLBP patients is selected, possibly representing patients with pain from a motion segment/disc, thus making patient selection more specified. Furthermore, selection of level to fuse based on radiological findings has not been found reliable. Therefore a mechanical provocation test has been developed at the clinic. The aim of this randomized study was to compare the outcomes in pain and pain related functions perceived by this specific subgroup of CLBP patients following fusion surgery with those following non-surgical treatment.