“…In 10 studies there was a pre-operative patients selection criterion for those submitted to bilateral one stage THR according to ASA grading [1,4,15,24,30,32,34,[40][41][42]. In 3 studies [1,34,41] high risk patients (ASA grades III and IV) were excluded, in 4 studies [15,30,32,40] only patients with grade IV were excluded, and in 3 studies [4,24,42] all grades (ASA grades I,II,III and IV) were included. In 6 studies an analysis of outcome according to ASA grading was reported [4,15,24,30,32,40].…”