Table 3.

Criteria list for quality assessment of non-controlled studies

A	Patient selection/inclusion adequately described?	Y	N	?
B	Drop out rate described?	Y	N	?
C	Independent assessor?	Y	N	?
D	Co-interventions described?	Y	N	?
E	Was the timing of the outcome assessment similar?	Y	N	?

? score unclear

A: All the basic elements of the study population are adequately described; i.e. demography, type and level of disorder, physical and radiological inclusion and exclusion criteria, pre-operative treatment and duration of disorder

B: Are the patients of whom no outcome was obtained, described in quantity and reason for drop out

C: The data were assessed by an independent assessor

D: All co-interventions in the population during and after the operation are described

E: The timing of outcome assessment should be more or less identical for all intervention groups and for all important outcome assessments