Problems associated with the use of the knee-chest position for operations on lumbar intervertebral discs.

A number of authors have described the advantages of the knee-chest position for operations on lumbar intervertebral discs (Lipton 1950; Taylor, Gleadhill, Bilsland and Murray 1956; Wayne 1967). Wayne listed the advantages as simplicity of positioning, ease of maintenance of good ventilation, avoidance of epidural venous engorgement, excellent exposure of the interlaminar space and decreased risk of injury to major prevertebral vessels and organs. He showed that vena caval pressure was minimal in this as compared with other positions even in obese patients, and assumed that this low venous pressure existed in the epidural and vertebral veins. Similar studies by Pearce (1957) demonstrated low venous pressure with the patient in the prone supported posture.