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.