Percutaneous Endoscopic Lumbar Discectomy for the Treatment of Recurrent Lumbar Disc Herniation: A Meta-analysis

Table 2

Results of risk assessment of bias in cohort studies.

Study	Selection	Comparability	Outcome	Total
Chen (2015)[10]	★★★★	★	★	6
Lee (2009)[6]	★★★★	★★	★★★	9
Lee (2018)[12]	★★★★	★★	★★★	9
Liu (2017)[13]	★★★★	★★	★★★	9
Wang (2020)[16]	★★★★	★★	★★★	9
Yao (2017)[14]	★★★★	★	★★★	8
Yao (2017)[14]	★★★★	★	★★★	8