Influence of Derotation Connectors on 3D Surgical Correction of Adolescent Idiopathic Scoliosis

STUDY DESIGN: Monocentric study comparing results of simultaneous translation on 2 rods (ST2R) with derotation connectors (prospective series) or without derotation connectors (retrospective series) in Adolescent Idiopathic Scoliosis (AIS) surgery.OBJECTIVE: The objective of this study was to assess if derotation connectors influence axial, coronal, and sagittal results in AIS surgery.SUMMARY OF BACKGROUND DATA: Conventional reduction techniques remain limited in their ability to reduce axial torsion. Direct vertebral derotation technique accomplishes partial axial derotation but decreases thoracic kyphosis.METHODS: Monocentric study including AIS surgeries performed using ST2R technique with derotation connectors (group D+, n=44) or without derotation connectors (group D-, n=24). The axial intervertebral rotation was measured between apical and neutral vertebra on pre and postoperative computed tomography scan. T test was used to compare mean values. ANCOVA analyzed the influence of connectors and covariates on the primary outcome, which was the difference between preoperative and postoperative intervertebral rotation.RESULTS: The mean axial torsion gain in the D+ group was 23% (+3.84 degrees, 95% confidence interval, +1.95/+5.73). In the D- group, mean axial torsion increase of 4% (-0.42 degrees, 95% confidence interval, -1.19/+2.03). The result was significantly different between the 2 groups (P=0.005). The coronal correction of the main curve angle was 80% in the D+ group and 64% in the D- group (P=0.004). Kyphosis correction was similar between the 2 groups (P=0.3) with significant increase of thoracic kyphosis in the whole series (P=0.02) and no patients with postoperative hypokyphosis <10 degrees. Multivariate analysis confirmed the influence of derotation connectors on both axial and coronal correction (P<0.05).CONCLUSIONS: The use of derotation connectors in the surgical treatment of AIS significantly improved axial and coronal correction compared to nonuse of connectors without compromising the sagittal plane.