“…Besides, 17 (2.62%) studies compared different surgical techniques [ 28 , 53 , 144 , 145 , 186 , 253 , 338 , 358 , 362 , 374 , 390 , 428 , 538 , 552 , 578 , 650 , 651 ] and seven (1.08%) studies evaluated various levels of surgeons’ experience [ 30 , 33 , 36 , 214 , 255 , 294 , 299 ], while in 18 (2.78%) studies, a prediction of pre- or postoperative risk factors was made [ 14 , 39 , 52 , 54 , 98 , 131 , 132 , 143 , 355 , 367 , 389 , 404 , 435 , 448 , 456 , 457 , 604 , 620 ]. Finally, 15 (2.31%) were cost analysis studies [ 57 , 65 , 75 , 90 , 138 , 140 , 142 , 156 , 158 , 226 , 315 , 326 , 328 , 399 , 486 ], 13 papers (2%) studied the patients’ mortality rate [ 31 , 60 , 76 , 258 , 259 , 313 , 320 , …”