Table 2.

The quality of the included nonrandomized controlled studies assessed with the Newcastle-Ottawa Scale.

Study	Selection				Comparability	Outcome assessment			Total quality score
	Representativeness of the treatment arm	Selection of the comparative treatment arm(s)	Ascertainment of treatment regimen	Outcome was not present at the start of the study	Comparability between patients in different treatment arms: age, preoperative conditions	Assessment of outcome with independency or with records	Adequacy of follow-up duration (more than three months)	Lost to follow-up (acceptable - less than 10%)
Ruiz-Mesa et al. 2017 [18]	☆	☆	☆	☆	☆	☆	☆	☆	8
Mencucci et al. 2018 [34]	☆	☆	☆	☆	☆☆	☆	☆	☆	9
Ruiz-Mesa et al. 2018 [35]	☆	☆	☆	☆	☆	☆	☆	☆	8
Escandon-Garcia et al. 2018 [36]	☆	☆	☆	☆	☆☆	☆		☆	8
de Medeiros et al. 2019 [37]	☆	☆	☆	☆	☆☆	☆	☆	☆	9
Singh et al. 2019 [38]	☆	☆	☆	☆	☆☆	☆	☆	☆	9
Rodov et al. 2019 [39]	☆	☆	☆			☆		☆	5
Bohm 2019	☆	☆	☆	☆	☆	☆	☆	☆	8
Lin et al. 2019 [41]	☆	☆	☆	☆		☆		☆	6

Each item can get at most one star (☆) in “selection” and “outcome assessment,” and two stars (☆☆) at most in “comparability.” The total number of stars ranges from 0 to 9; studies that score 0 to 3, 4 to 6, and 7 to 9 are considered have a low, moderate, and high quality, respectively.