Effect of pregnancy factor on T line corresponding to vertebral level: a multicenter clinical comparative study

Objective To investigate the effect of the pregnancy factor on the line drawn between the highest points of the two iliac crests (T line) corresponding to the vertebral level in a multicenter clinical comparative study. Methods Hospitalized patients selected from the obstetric department or gynecological department, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, were divided into pregnancy group (group P) and non-pregnancy group (group NP). The patients were placed in the lateral position with their back vertical to the bed surface, the patient′s thighs were at an angle of approximately 90 degrees to the trunk, and hip flexion was employed by flexing the patient′s knees to the chest.To determine the highest points of the two iliac crests, a line (T line) was drawn between the highest points using a wire-reinforced epidural catheter.And another vertical line (T′ line) was made between the highest point of the iliac crest on the upper side (not the side in the lateral position) and the ground.Ultrasonography was performed to identify and record the level of T line and T′ line corresponding to the spinous process and lumbar interspace. Results A total of 1 763 cases completed the study, and there were 905 cases in group P, and 858 cases in group NP.Compared with group NP, the rate of T line at L3 spinous process and L3, 4 interspace was significantly increased in group P (P<0.05). Compared with T′ line, the rate of T line at L2, 3 interspace and L3 spinous process was significantly decreased, and the rate of T line at L4 spinous process, L4, 5 interspace and L5 spinous process was significantly increased in group P, and the rate of T line at L3 spinous process, L2, 3 interspace and L3, 4 interspace was significantly decreased, and the rate of T line at L4 spinous process and L4, 5 interspace was significantly increased in group NP (P<0.01). Conclusion The level of T line corresponding to the vertebral level is significantly higher in the pregnant patients than in the nonpregnant patients. Key words: Pregnancy; Ilium; Anatomy