Research

Study Design:
Radiographic analysis on the characteristics and behavior of the lumbosacral hemicurve in idiopathic left lumbar curves exceeding 40 degrees and its potential role in coronal trunk imbalance.

Objective:
To determine if magnitude or rigidity of the lumbosacral hemicurve predisposes to coronal decompensation preoperatively and postoperatively in adolescent idiopathic scoliosis that have a left lumbar curve exceeding 40 degrees as a component of the curve pattern.

Methods:
The study design was a retrospective radiographic review of 50 patients. The lumbosacral hemicurve was measured from L4 to perpendicular. Flexibility of this hemicurve was measured on the right side bending film using the intercrestal line and the sacral alar notches as horizontal references.

Results:
Overall, 84 percent (42/50) demonstrated preoperative decompensation greater than one centimeter. Eighty-six percent (36/42) were left decompensated. Of the 28 patients with more than 20° of L4 tilt to horizontal, 96 percent (27/28) were decompensated preoperatively with left decompensation persisting postoperatively in 63 percent. Lumbar right side bending films revealed the lumbosacral hemicurve did not achieve correction to neutral in 80 percent (40/50), averaging 5.5°.
A more structural lumbosacral hemicurve (corrected to < 5 degrees of neutral) was significantly related to preoperative coronal decompensation in the combined group and in the King II subgroup. Sacral obliquity correlated significantly with preoperative decompensation in King I curves, as well as, in the combined group. Postoperatively, significant correlation continued to be observed between sacral obliquity and trunk imbalance in the King I curves and the combined group. Iliac obliquity was significantly correlated to preoperative imbalance of the trunk in Type I curves and the combined group. Iliac obliquity was significantly related to postoperative decompensation in the combined group.

In conclusion, intrinsic properties of the hemicurve including obliquity of the sacrum and rigidity correlate with imbalance in the curve patterns studied. 'At risk' signs for persistent postoperative coronal decompensation include iliac and sacral obliquity noted on the preoperative standing full-length radiographs.