Study of distal junctional kyphosis of adolescent idiopathic scoliosis following anterior or posterior selective instrumented fusion and its risk factors.

Abstract

Objective To compare the sagittal measurements before and after surgery in patients with adolescent idiopathic scoliosis (AIS) treated with instrumented fusion, and determine the incidence of distal junctional kyphosis (DJK) and its risk factors. Methods Fifty-nine patients with Lenke 1 type A1S underwent anterior or posterior instrumented fusion. In anterior group, including thoracoscopic surgery in 8 cases and mini-open surgery in 19 cases, while in posterior group, including 13 cases with distal pedicle screw fixation and 19 cases with hook constructs. The standing long-cassette anteroposterior and lateral radiographs of spine were taken, and the coronal and sagittal parameters were measured before and after surgery and during follow-up. Results At recent follow-up, the T5-T12, T10,-L2 sagittal measurement and DJK of anterior group increased significantly versus preoperation, the T5-T12 kyphosis, T10,-L2 kyphosis, DJK and L1-S1 lordosis of posterior hook group increased significantly versus preoperation. The postoperative mean T10,-L2 kyphosis and DJK in the posterior hook group were 13.1° and 8.7° compared to 0.1° and -2.2° in the posterior distal pedicle screw group. When postoperative DJK developed in the posterior group, mean postoperative T5-T12 kyphosis, T10,-L2 kyphosis and L1-S1, lordosis 18.5°, 13.6° and 51.1°versus 11.6°, 0.5° and 42.2° preoperatively. When postoperative DJK developed in the posterior group, mean postoperative T10,-L2 was 13.6° kyphosis compared to 2.6° in the posterior group without DJK. Conclusion The AIS patients undergoing selective anterior fusion may develop sagittal decompensation in distal junctional segments without instrumentation for its risk factor of short fusion segments. The AIS patients undergoing selective posterior hook instrumented fusion may develop sagittal decompensation for its risk factor of instability. Key words: Scoliosis; Adolescent; Spinal fusion; Kyphosis