Lordosis of lumbar vertebrae in omphalocele: an important factor in regulating abdominal cavity capacity.

PURPOSE: Although it is well known that the tiny abdominal cavity associated with larger omphalocele enlarges rapidly after surgery, the responsible mechanism remains obscure. The authors have studied the curve of lumbar vertebrae and established a hypothesis in which lordosis of lumbar vertebrae plays a major role in changing the capacity of the abdominal cavity.

METHODS

Fifty-three patients with intact omphalocele and 10 normal newborns as the control were studied. The size of omphalocele was determined from the mean value of the length and breadth of the sac. The curve of lumbar vertebrae (lordotic angle) was measured using Cobb's technique on the lateral radiograph serially taken in the supine position.

RESULTS

The mean lordotic angle of 53 patients was 22.2 degrees (range, 0 to 65), which was significantly greater than 11.0 degrees of the control (P <.012). The individual lordotic angle before surgery was significantly correlated with the size of omphalocele (r = 0.668, P <.0001). In serial studies carried out in 15 patients with larger omphalocele, the mean lordotic angle was decreased significantly from 30.5 degrees to 20.0 degrees (P <.009) on the first postoperative day and returned to the control level within a few weeks.

CONCLUSIONS

These results suggest that severe lumbar lordosis may well become an alternative factor to produce visceroabdominal disproportion observed before surgery, and its correction after surgery may well induce the abdominal cavity to rapidly enlarge. It may be speculated that the dehiscence of abdominal rectus muscles associated with omphalocele causes the tension of ventral muscles to decline, and, then, imbalance in tension between ventral (abdominal) and dorsal (back) muscles causes the lumbar lordosis to increase. Accordingly, at the staged procedure, the prosthetic sheet should be attached under moderate tension, and its plication should be carried out at regular intervals to maintain the tension of abdominal rectus muscles.