Risk Factors Of Coronal Imbalance After Three-column Osteotomy In Congenital Kyphoscoliosis And Influence Of Sagittal Stable Verterbae On The Postoperative Distal Junctional Kyphosis In Adolescent Idiopathic Thoracic Scoliosis

Part 1:Risk Factors of Coronal Imbalance after Three-column Osteotomy in Congenital KyphoscoliosisObjective.The incidence and risk factors of postoperative Cl have been reported in adolescent idiopathic and degenerative lumbar scoliosis.However,limited data exists for patients with CKS after 3-CO.To investigate the incidence and risk factors of coronal imbalance(CI)after three-column osteotomy(3-CO)in patients with thoracolumbar congenital kyphoscoliosis(CKS).Methods.We reviewed a consecutive series of patients with CKS who underwent posterior-only 3-CO.Coronal curve patterns were classified according to absolute C7 translation values into:Type A,C7 translation<30 mm;Type B,C7 translation ≥30 mm and C7 plumb line(C7PL)shifted to the concave side of the main curve;and Type C,C7 translation ≥30 mm and C7PL shifted to the convex side.CI was defined as C7 translation on either side ≥30 mm.According to C7 translation at the latest follow-up,patients was subdivided into an imbalanced group and a balanced group.Results.One-hundred-thirty patients(mean age:17.7±5.2 years)were recruited.The mean follow-up was 41.3±18.5 months.Twenty-six patients(20%)were identified as having CI at the latest follow-up.Compared with the balanced group,the imbalanced group had a larger proportion of preoperative Type C pattern,higher main curve correction,and greater lowest instrumented vertebra(LIV)tilt before and after surgery.Multiple logistic regression showed that risk factors for CI were preoperative type C pattern,preoperative LIV tilt ≥23.5° and immediate postoperative LIV tilt ≥12.3°.Conclusion.The incidence of CI in patients with CKS after 3-CO was 20%.A preoperative type C pattern,preoperative LIV tilt ≥ 23.5°,and immediate postoperative LIV tilt ≥12.3° were found to be associated with CI at the latest follow-up.Part 2:Influence of Sagittal Stable Verterbae on the postoperative Distal Junctional Kyphosis in Adolescent Idiopathic Thoracic ScoliosisObjective To investigate the influence of relationship between lowest instrumented vertebra(LIV)and sagittal stable vertebra(SSV)on the occurrence of distal junctional kyphosis(DJK)after posterior selective fusion in Lenke 1A scoliosis.Methods A consecutive cohort of 153 patients with Lenke 1A scoliosis who had undergone posterior.selective thoracic fusion were reviewed.SSV was defined as the last vertebra with inferior endplate touched by the posterior sacrum vertical line.According to the relationships between SSV and LIV,the patients were divided into group:LIV<SSV group and LIV>SSV group.Parameters of main thoracic curve and sagittal spinal-pelvic alignment were measured in standing radiographs.And the incidence of DJK was recorded and compared between these two groups.Results The follow-up period ranged from 24 to 69 months.There was no significant difference in demographics,radiographs and scores of SRS-22 between two groups preoperatively.A total of 13 patients who presented with DJK(8.4%)at final follow-up.The incidence of DJK in LIV<SSV group was significantly higher than that in LIV≥SSV group(25.8%vs.4.1%,X2=12.320,P<0.001).There was also no significant difference in radiographic parameters and scores of SRS-22 in patients with and without DJK preoperatively.However,at the latest follow-up,thoracic kyphosis,thoracolumbar kyphosis,sagittal vertical axis and distal junctional angle in DJK group were significantly larger than that in non-DJK group,with pain scores of SRS-22 in DJK group significantly lower than that in non-DJK group.Conclusions The current study revealed the influence of the relationships between SSV and LIV on incidence of DJK after selective fusion in patients with Lenke 1A scoliosis.An LIV location at SSV or more caudal level can significantly decrease the incidence of DJK after selective fusion in patients with Lenke 1A curve.