“…The combined analysis of the 16 noncomparative studies that contribute data [4,9,13,22,27,30,34,42,53,58,59] reveals 23 complications in 1,154 patients and 1,974 levels treated-this corresponding to a complication rate of 2 and 1.16%, respectively. As can be seen in Table 7, most of the problems were of a cardiopulmonary or neurological nature.…”