“…Among these studies, 44 met the eligibility criteria; each study is described in eTable 5 in Supplement 1 . 6 , 7 , 8 , 14 , 15 , 16 , 17 , 18 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 Overall, 21 452 patients were included, of whom there were 11 747 females (55%) and 9705 males (45%) with a mean (SD) age of 57 (8) years. Two studies involved a mix of lumbar and cervical populations and were excluded from all quantitative meta-analyses.…”