Table 4. Risk of Bias Assessment of Included Comparative Observational Studies.

	Parker, et al.19	Gu, et al.21	Lee , et al.22	Mobbs, et al.23	Kotani, et al.24	Wang, et al.25	Wang, et al.26	Schizas, et al.27	Park and Ha29
1 Method of selection of patients identified and appropriateness	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
2 Number of patients deceased or lost to follow-up reported or included in appropriate statistical analysis	No	No	Yes	No	No	No	No	No	No
3 Follow-up period range and mean given (minimum=n)	Unclear	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Unclear
4 Prosthesis models specified	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
5 Clearly defined criteria for measuring outcomes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
6 Valid statistical analysis undertaken	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
7 Data given for deceased patients (information)	No	No	Yes	No	No	No	No	No	No
8 Age range and mean age reported	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes
9 Numbers of males and females given	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes
10 Weight range and mean weight given	No	No	No	No	No	No	No	No	Yes
11 Preoperative diagnoses with percentages of patients given	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes
12 Clinical evaluation independent of operating surgeon	Yes	Unclear	Yes	Unclear	Unclear	No	No	Unclear	Unclear
13 Radiological evaluation independent and blinded to clinical results	No	Yes	Yes	Yes	Unclear	Yes	Yes	Unclear	Unclear
14 Results given for specific models	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
15 Quantification of outcomes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
16 Follow-up data compared with preoperative data (mean and range)	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	No
17 Independence of investigators (no vested interest) stated	No	Yes	No	Unclear	Yes	Yes	Yes	No	Yes
Scores	9	13	14	12	12	13	13	9	11

A positive answer (Yes) to any question counts as 1 point.