Regarding the possibility of anterior vascular injury from the posterior approach to the lumbar disc space: an anatomical study.

STUDY DESIGN: Anatomical study with magnetic resonance imaging data. OBJECTIVE: To document the distances between the major retroperitoneal vessels and the anterior lumbar disc spaces; to determine the effect of patient positioning on these relationships; and to discuss ways to deal with vascular injury. SUMMARY OF BACKGROUND DATA: It is well known that there are major vascular structures anterior to the lower lumbar spine. Vascular injury during posterior approaches, however, remains a problem. These anatomical relationships have not been determined in vivo, and there are no data on the effect of turning the patient prone, and onto bolsters. METHODS: A random sampling of 49 women and 48 men was made. All examinations were performed in magnetic resonance scanners operating at 1.5 T. Measurements were made using electronic calipers on axial T2-weighted images. Post hoc studies were done on a smaller number of patients, to determine the effect of prone positioning. RESULTS: At the L4-L5 level, 66% of the common iliac arteries in women and 49% of those in men were within 5 mm of the anterior aspect of the disc space. At L5-S1, these numbers dropped to 23% for women and 19% for men. No relationship between the age of the patient and the distance from disc space to blood vessel was found. There was little change in these measurements between the supine and prone positions. The use of bolsters to decompress the abdominal contents in the prone position did not significantly alter the disc-artery distances. Venous relationships were also documented. CONCLUSION: The lower lumbar spine is confirmed to frequently be very close to the major retroperitoneal vessels. Turning the patient prone and placing the patient on bolsters does not change this relationship. This is part of the reason why vascular injuries may occur during routine lumbar spine surgery. Spine surgeons should be able to recognize and initiate treatment of such injuries.

Changes in the size of the lateral ventricles in the normal-term newborn following vaginal delivery.

BACKGROUND: This is a study of the size of the lateral ventricles in a population of normal-term newborns following vaginal delivery. OBJECTIVE: To assess the time course for the lateral ventricles to change from closed to open following vaginal delivery. MATERIALS AND METHODS: A total of 143 normal-term newborns had a videotaped cranial ultrasound examination during the period from 1 to 156 h after birth. Many had from one to three additional examinations when returning for well-baby checks. Three methods [overlapping intervals (smoothed percentages), life table, and geometric distribution] were used to construct the approximate distributions of completely closed, partially open, and open ventricles. RESULTS: Using smoothed percentages it was estimated that within 12 h of birth, 80% of newborns had closed lateral ventricles, 19% had partially open ventricles, and only 1% were completely open. The estimated median time from birth to partially open ventricles was in the period 36 to 60 h. The life table gave the estimated median time to partially open ventricles as 74 h. Fitting the data to a geometric distribution gave an estimated mean of 63 h. CONCLUSION: The majority of normal newborns have closed lateral ventricles following vaginal delivery and these are partially opened by day 3 after birth.