Association of hardware removal with secondary osteonecrosis following femoral neck fractures: a systematic review and meta-analysis

Table 2 Quality assessment of each included study by the Newcastle–Ottawa scale (NOS)

Study	Selection				Comparability	Outcome measurement		Statistical analysis		Total score
Study	Patient definition^a	Representativeness of patients^b	Selection of controls^c	Definition of controls^d	Control for important factor^e	Reliability of outcome measure^f	Validity of outcome measure^g	Sample size^h	Statistical methodⁱ	Total score
Ai et al. [2]	1	1	1	1	1	1	1	0	1	8
Chang et al. [13]	1	0	1	1	0	1	1	1	1	7
Pei et al. [9]	1	1	1	1	0	1	1	1	1	8
Wang C et al. [10]	1	1	1	1	1	1	1	1	1	9
Wang T et al. [5]	1	1	0	1	1	1	1	1	1	8

^aThe inclusion/exclusion criteria are clearly defined
^bHow were cases selected? (e.g., random sample)
^cControls were derived from the same community as patients
^dControls defined as individuals without avascular necrosis of the femoral head
^eConfounding factors have been well adjusted
^fThe measure of avascular necrosis of the femoral head has documented reliability
^gThe measure of avascular necrosis of the femoral head has documented validity
^hThe sample size was justifed
ⁱThe statistical analysis was clearly presented and was appropriate

ISSN: 1749-799X