The natural evolution of postoperative distal adding-on in adolescent idiopathic scoliosis / 中华骨科杂志

ABSTRACT

Objective To investigate the natural evolution of postoperative distal adding-on in Lenke 1A and 2A adoles-cent idiopathic scoliosis(AIS)patients,and to explore the risk factors for the progression of distal adding-on.Methods From Ju-ly 2006 to July 2012,a total of 197 AIS patients with Lenke 1A or 2A curves underwent posterior selective thoracic instrumenta-tion and fusion surgery.Among which,44 patients(22.3%)with postoperative distal adding-on were recruited in this study.There were 39 female and 5 male,with an average age of(15.0±2.1)years.The mean Cobb angle of main thoracic curve was 49.3°±9.3°. The first postoperative radiograph indicating distal adding-on and the last follow-up radiograph were comparedmake the measure-ment of the disc angle below lowest instrumented vertebra(LIV),and the distance between the vertebra below LIV(LIV+1)and cen-tral sacral vertical line(CSVL).Distal adding-on could be classified into progressive group and non-progressive group according to its natural evolution during follow-up.If the disc angle increased> 5°or the LIV+1-CSVL distance increased>5 mm,the pa-tients were assigned into progressive group; Otherwise, the patients were assigned into non-progressive group. Using Student T test, χ2test or Fisher exact test, the predicted risk factors for progression were screened for further Logistic regression. Results Among the 44 patients enrolled in the study,17 patients(38.6%)had progressive adding-on while 27 patients(61.4%)had non-progressive adding-on.The Risser sign was significantly lower in progressive group than non-progressive group(t=4.399,P<0.001). Besides,more patients had LIV proximal to substantially stable vertebra(SSV)in progressive group than non-progressive group (Fisher exact test value=18.142,P<0.001).The improvement of shoulder imbalance was significantly better in progressive group than non-progressive group(t=3.011, P=0.002). According to Logistic regression, the low Risser sign and LIV proximal to SSV were independent risk factors for progression of distal adding-on.Moreover,the self-image domain of SRS-22 Scores was remark-ably lower in progressive group than non-progressive group(t=2.321,P=0.014).Conclusion Distal adding-on could be classi-fied into progressive group(40%)and non-progressive group(60%)according to its natural evolution.The risk factor for its progres-sion included skeletal immaturity and LIV proximal to SSV.Moreover,the progression of distal adding-on might compensate for the shoulder imbalance during follow-up.