Identifying limitations of a study is hard to accept as an author, but I think it facilitates a better understanding of the study and helps guide future research. The authors list as one of the study limitations a lack of control group receiving sham surgery. They also mentioned the potential placebo effects of surgical and non-surgical treatments, with more placebo effect anticipated in the surgical group.
As Ewa Roos aptly stated, this study may have benefited from a group who received surgery without non-operative treatment. Do you agree? What about other weaknesses of the study?