Is there a better derotation manoeuvre in posterior correction of thoracic adolescent idiopathic scoliosis?

Abstract

Background data: Different manoeuvres can be adopted for direct derotation in posterior correction of thoracic adolescent idiopathic scoliosis (AIS). Aim of the study is to evaluate the better manoeuvre in AIS posterior surgery. Methods: 62 consecutive patients affected by AIS (Lenke type 1 or 2), were treated by posterior fusion with pedicle screw-only instrumentation, between 2007 and 2009 at one single institution. Three groups were identified: a Pre-Rod group with the direct derotation procedure done before inserting rods (Pre-R group; n = 22 patients), a Single- Rod group with the derotation done after concave rod insertion (Single R group; n = 20) and a Double-Rod. group after both rods inserted (Double R group; n = 20). There were no statistical differences in the 3 groups, in terms of age, Risser's sign, curve patterns, Cobb main thoracic (MT) curve magnitude and flexibility, extension of fusion, sagittal pre-operative contour and rotation angle (RAsag) of the apical vertebra, measured with axial CT on pre-op and last follow-up control. Results (average FU 3.6 years, range 2.8 to 4.6): The Pre-Rods insertion cases showed a significantly better final correction of apical vertebral rotation (Pre-R 61.9 % Single-R 55.8 % Double-R 50.1 %; p<0.05) and a greater final correction of MT curve (63.4 % vs 61.1 % and 59.1 %; ns) with similar maintenance of initial correction (-1.71degree vs -1.78degree and -1.73; ns). The T5-T12 kyphosis angle was similar before surgery (Pre-R 16.9degree vs Single-R 17.5degree and Double-R 17.2degree): it was reduced at final followup in Single-R and Double-R cases in comparison with Pre-R patients that presented instead a little increase (19.8degree vs 12.5degree and 13.5degree;ns). Lumbar lordosis was similar before surgery (-42.9degree vs -41degree and - 42.1degree) and at final follow-up (-45.1degree vs -44.9degree and -43.2degree; ns). At the latest follow-up, SRS-30 and SF-36 findings were similar between the three groups. Conclusion: The direct derotation procedure resulted more effective both concerning correction of apical vertebral rotation and magnitude of MT curve, when applied to the spine before both rods insertion. The hypokyphotic effect of derotation procedure, registered in Single-R and Double-R groups, was avoided doing derotation before rods insertion.