Table 3.

Overview risk of bias for surgical, including epidural injections versus conservative therapy

References	Randomisation adequate?	Allocation concealed?	Groups similar at baseline?	Patient blinded?	Care provider blinded?	Outcome assessor blinded?	Co-interventions avoided or similar?	Compliance acceptable?	Drop-out rate described and acceptable?	Timing outcome assessment similar?	Intention-to-treat analysis?	Total
Buttermann [2]	?	?	+	−	−	−	−	na	−	−	?	1
Osterman [12]	+	+	−	−	−	−	−	na	+	+	+	5
Peul [13]	+	+	+	−	−	−	−	na	+	+	+	6
Weinstein [22]	+	+	+	−	−	−	−	na	+	+	+	6
Weber [19]	+	+	?	−	−	−	?	na	+	+	?	4

na not applicable

? = Unsure