Table 1

Risk of bias assessment using the criteria from the Cochrane Back Review Group

Study	Item
Study	1. Was the method of randomisation adequate?	2. Was the treatment allocation concealed?	3. Was the patient blinded to the intervention?	4. Was the care provider blinded to the intervention?	5. Was the outcome assessor blinded to the intervention?	6. Was the drop-out rate described and acceptable?	7. Were all randomised participants analysed in the group to which they were allocated?	8. Are reports of the study free of suggestion of selective outcome reporting?	9. Were the groups similar at baseline regarding the most important prognostic indicators?	10. Were cointerventions avoided or similar?	11. Was the compliance acceptable in all groups?	12. Was the timing of the outcome assessment similar in all groups?	13. Are other sources of potential bias unlikely?	Score (0/13)
Aboagye et al 39	Unclear	Unclear	No	No	No	No	Yes	Yes	No	Unclear	Unclear	Yes	Yes	4
Bello et al 40	Yes	Yes	Unclear	No	Unclear	No	Yes	Unclear	Yes	Unclear	No	Yes	Yes	6
Bosmans et al 34	Yes	Yes	No	No	No	Yes	Yes	No	Yes	Yes	No	Yes	Yes	8
Carr et al 41	Yes	Unclear	No	No	No	No	Yes	Unclear	Yes	Unclear	No	Yes	Yes	5
Cherkin et al 42	Yes	Unclear	No	No	No	Yes	Yes	Unclear	Yes	Yes	Yes	Yes	Yes	8
Chuang et al 43	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	9
Critchley et al 44	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	Unclear	Yes	Yes	8
van Dongen et al 38	Yes	Yes	No	No	No	No	Yes	No	Yes	Yes	Unclear	Yes	Yes	7
Henchoz et al 45	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Yes	No	Yes	Yes	8
Hlobil et al 46	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	10
Hollinghurst et al 47	Yes	Yes	No	No	No	No	Yes	Yes	Yes	Unclear	Yes	Yes	Yes	8
Hurley et al 48	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	9
Korthals-de Bos et al 35	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	9
Leininger et al 36	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	10
Manca et al 55	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	10
van der Roer et al 53	Yes	Yes	No	No	No	Yes	Yes	No	Yes	Yes	No	Yes	Yes	8
Rosenfeld et al 37	Yes	Unclear	No	No	No	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	8
Seferlis et al 49	Unclear	Unclear	No	No	No	No	Yes	Yes	Unclear	Unclear	Yes	Yes	Yes	5
Smeets et al 50	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	No	Yes	Unclear	8
Torstensen et al 52	Unclear	Unclear	No	No	No	Yes	Yes	Unclear	Yes	Unclear	Unclear	Yes	Yes	5
UK BEAM51	Unclear	Yes	No	No	No	No	Yes	Yes	Yes	Unclear	Yes	Yes	Yes	7
Wright et al 54	Yes	Yes	No	No	No	Yes	No	Unclear	No	Unclear	Unclear	Yes	Yes	5