Blood loss, operating time, and positioning of the patient in lumbar disc surgery.

Many textbooks and papers on lumbar disc surgery still, nearly 40 years after the first description of a variant of the kneeling position, pay no attention to the positioning of the patient. In this study, the association between intraoperative blood loss, operating time, and position of the patient was studied in 436 patients undergoing a standard macrosurgical operation for lumbar disc herniation. Prone position on bolsters was used in 216 cases, 192 of which were primary operations, and a frame-supported kneeling position in 220, 203 of which were primary operations. The mean blood losses in prone versus kneeling positions in the primary operations were 376 ml and 150 ml, respectively (P less than 0.001), and the mean operating times were 74 minutes and 52 minutes, respectively (P less than 0.001). The 99% confidence interval for the difference between the mean operating times was from 15 to 29 minutes. A moderate nonlinear positive correlation was found between intraoperative blood loss and operating time. No intraoperative complications attributable to the position of the patient emerged. On the basis of the findings in this study, the use of kneeling position is strongly advocated.