POSTURE FOR SURGERY OF THE PROLAPSED LUMB AR DISC

For surgery of the lumbar disc, with a posterior route, the patient is placed either in a prone, or a knee-chest, or a lateral position. The y aim at facilitating the surgical access in decreasing local bleeding and collapsing the dural sheat. This benefit, as a result of the main tenance of the pressure in the epidural venous system at a low level, is obtained through the absence of any abdominal compression as well a s the posture. In the prone position, the abdominal compression and th e increase of the physiologic lordosis impair the systemic venous retu rn and carry the risk of cardiac arrest. In addition to these adverse effects, the conventional knee-chest position increases the haemodynam ic repercussions in modifying the distribution of blood volume and inc reasing the potential risk of mediastinal compression and air embolism . The lateral position generates only minor haemodynamic modifications , except in the obese. However it is difficult to stabilize the patien ts' position and to maintain the alignment of the spine. Therefore it is used the less one. The postural risks of all three positions are nu merous and include mainly the compression of nerves, vessels and skin. Finally the selection of the position depends basically on morphologi cal criteria and the adaptative capacities of the patient. The optimal position is the one offering a low pressure level in the spinal venou s system, while maintaining the venous return.