Objective:

To evaluate the prevalence and prognosis of postoperative coronal imbalance (CIB) and factors related to its onset and spontaneous improvement in patients with Lenke 5C adolescent idiopathic scoliosis (AIS) who underwent selective thoracolumbar/lumbar fusion (SLF).

Methods:

We measured the radiographic parameters and evaluated clinical outcomes using the Scoliosis Research Society 22 (SRS-22) questionnaire in the Lenke 5C patients with a minimum 2-year follow-up. CIB was defined as C7 plumb line 2.0 cm lateral to the central sacral vertical line (CSVL, C7-CSVL > 2.0cm). We compared the parameters between the patients with CIB group and without CIB (Coronal balanced: CB group).

Results:

A total of 29 patients (mean age at surgery:17.0 years, average FU period: 45.6 months) met our inclusion criteria. CIB was found in ten patients one week after surgery (34.5%), and decreased to 6.9% at final follow-up. Comparative analysis indicated the significant values as follows: age at surgery (17.5/14.7years, P=0.005), LS curve (5.9/11.2°, P=0.02) and L5 tilt (-3.6/-8.1°, P=0.02) in bending film. Greater changes of the LIV disc angle (LDA) which means scoliotic angles between LIV and LIV+1 were significantly associated with spontaneous improvement of CIB (P=0.04). Clinical outcomes were comparable between the CB and CIB group.

Conclusion:

Although CIB was frequently detected in the early postoperative period after SLF, it was mostly corrected spontaneously. Relatively younger age at surgery and less flexible lumbosacral curve may be related with postoperative CIB, and greater changes of the LDA may be associated with spontaneous improvement of CIB.