Decompensation in Selective Thoracic Fusion by Segmental Pedicle Screw Fixation in King type II Adolescent Idiopathic Scoliosis (AIS): Causative Factors and its Prevention

Suk, Se Il; Lee, Sang Min; Kim, Jin Hyok; Kim, Won Joong; Jung, Ewy Ryong; Nah, Ki Ho; Sohn, Hong Moon; Kim, Dong Soo

Abstract

STUDY DESIGN: A retrospective study.
OBJECTIVES
To find the causative factors which induce decompensation after selective thoracic fusion with segmental pedicle screw fixation in King type II AIS. SUMMARY OF LITERATURE REVIEW: Pedicle screw fixation enabling enhanced correction is increasing in use in idiopathic scoliosis. However, there are few reports on the decompensation after selective thoracic fusion with pedicle screw fixation in King type II AIS.
MATERIALS AND METHODS
Thirty-nine King type II AIS patients subjected to selective thoracic fusion with pedicle screw fixation were analyzed after a minimum follow up of 1 year. They were reviewed using standing roentgenograms. Deviation of center of T1 from center sacral line greater than 2 cm was considered decompensation.
RESULTS
Among 39 patients, compensation was in 35 while decompensation in 4 postoperatively. There was no significant differences between the two groups in preoperative thoracic or lumbar curve characteristics such as curve magnitude, apical deviation or apical rotation. There was a significant difference in thoracic curve correction and postoperative T-curve magnitude divided by preoperative L-curve respectively(p= 0.001).
CONCLUSION
Decompensation with selective thoracic fusion with segmental pedicle screw fixation in King type II AIS was not induced by preoperative L-curve characteristics nor derotation maneuver. The factor of decompensation was overcorrection, i.e. if thoracic curve correction was more than 75% or if the magnitude of postoperative T-curve was 30% less than that of preoperative L-curve, there was a high risk of decompensation.