The Choice of Lower Instrumented Vertebra in AIS Comparison of Lenke, Suk and Dubousset Criteria

Abstract

Background Distal extension of the selective fusion in AIS is currently among the most explored topics in literature especially for Lenke type 1 and 2 curves and a lot of variability in the distal extension of the fusion is noted among different specialized centers around the world. Methods This is a retrospective descriptive study examining 41 Adolescent Idiopathic Scoliosis (AIS) cases (Lenke type I or II curves) undergoing posterior selective fusion with a minimum follow up of 2 years. We assessed the concordance between Dubousset's, Lenke's and Suk's criteria in the choice of the Lower Instrumented Vertebra (LIV). Baseline and post-operative X-rays of 41 AIS patients presenting with Lenke type I or II curves treated with selective fusion were studied. For each patient, the LIV is determined according to Dubousset's, Suk's and Lenke's criteria. Based on these results, patients are divided into two groups. “Group 1” includes patients where LIV designated by Dubousset's criteria is identical to the LIV designated by Lenke's or Suk's criteria. “Group 2” includes patients where the LIV dictated by Dubousset's criteria is more distal when compared with the LIV dictated by Lenke's and Suk's criteria. The charts of those 41 patients are reviewed at their last post-operative follow-up. The primary outcome measure used to compare those different groups is the frontal balance. The secondary endpoints are the (1) AP Cobb angle of the thoracic curve, (2) the AP Cobb angle of the lumbar curve, (3) the improvement of the Cobb angle of the thoracic curve (% ACT), (4) the improvement of the Cobb angle of the lumbar curve (% ACL), (5) the AP and lateral inclination of the LIV, (6) the AP lumbar Apical Vertebral Translation (AVT-L) and (7) the lateral Cobb angle of D5-D12. Results The LIV recommended by Lenke and the one recommended by Suk's criteria are identical in 70% of cases. The match between the choice based on Dubousset's criteria and the choice accounted by Lenke's or Suk's criteria is obtained for 70% of patients also. In 20% of cases, the LIV recommended by Dubousset's criteria is more distal than the one recommended by Lenke and Suk. Groups' comparison. Preoperatively, the comparison between groups 1 and 2 for the frontal balance and for the secondary endpoints shows no difference. Similarly, non-statistically significant difference was found between both groups for the primary and the secondary endpoints in the immediate post-operative setting and on the last follow-up. Conclusions The 70% accordance rate between Dubousset's criteria and those of Lenke and Suk attributes some validity to Dubousset's criteria. Thus, the statistical study showing no evolution toward a postoperative coronal imbalance or toward a worsening of other structural criteria of the spine curvatures in group 2, which is discordant with the recommendations of Lenke and Suk, prove the validity of the selection criteria of the LIV according to Dubousset. These same results also show that a more extensive distal correction-fusion does nothing for the frontal balance in the immediate postoperative setting, and even after several months of follow-up.