Effects On The Thoracic Balance And Lung Morphology With Pedicle Screws In Correcting Adolescent Idiopathic Scoliosis

Objectives: To sure the effects on the thoracic balance and lung morphology incorrecting AIS by means of posterior fusion with pedicle screws.Methods：In the first section,we retrospectively reviewed43thoracic AIS patientswho underwent posterior fusion with pedicle screws in our hospital from October2010to August2012. The main curve of all patients were the main thoracic curve withright-side. The main thoracic curve have a mean angle of59.43°(range35.08°–101.87°,SD of16.54°).There were12males and31females with a mean age ofmean14.87years(range10–18years,SD of1.54).Full-length,standing lateral andanteroposterior radiographs and spinal CT,were available for all patientspreoperatively. We designed two indicators including TRMC and TRAT which areused to evaluate thoracic balance.We measured the Cobb angle of the main thoraciccurve，AVB-R and TRMC by means of anteroposterior radiographs. We reconstructedthe CT sections of apical vertebra by means of MPR technique. We measuredTRAT,RHI,VTand RAsag in the CT sections. The SAQ was performed by the patientsthemselves preoperatively. The correlation analysis were performed between TRMC,TRAT with the above-mentioned parameters. In the second section, all cases weresame with the first section and preoperative examination and data preparation weresame with the first section.We measured RAsag，MLdev and RAml in the CT sectionsof apical vertebra. Other parameters were same with the first section. In the third section,we retrospectively reviewed28thoracic AIS patients who underwent posteriorfusion with pedicle screws in our hospital from apri2011to August2012. The maincurve of all patients were the main thoracic curve with right-side. The main thoraciccurve have a mean angle of61.74°(range39.71°–101.87°,SD of16.94°).There were9males and19females with a mean age of mean15.19years(range10–18years,SD of1.56).Full-length,standing lateral and anteroposterior radiographs and spinalCT,were available for all patients before surgery and1week after surgery. Wemeasured the Cobb angle of the main thoracic curve，AVB-R and TRMC by means ofanteroposterior radiographs before and after surgery. We measuredCCTA,CVTA,TTA,TRAT,RHI,RAsag and RAml in the CT sections of apical vertebrabefore and after surgery. We reconstructed the lung morphology and measuredVr,Vl,Vt,LVR,LLH,RLH,and TLH before and after surgery.We compared thedifference of the above-mentioned parameters.Results: The correlation between the TRMC and AVB-R was statisticallysignificant(R=0.94,P﹤0.01); the correlation between the TRAT and RHI wasstatistically significant(R=0.613,P﹤0.01). The statistical significance was found inthe correlation between TRMC and TRAT with the Cobb angle of the main thoraciccurve,RAsag,VT and SAQ(P﹤0.01). The statistical significance was found in thecorrelation between RAsag,MLdev and RAml with the Cobb angle of main thoraciccurve, VT,AVB-R,TRMC,RHI and TRAT (P﹤0.01).Except the order of correlationcoefficient between three angles and TRAT was MLdev> RAml> RAsag,the order ofcorrelation coefficient between three angles and other parameters were RAml>MLdev> RAsag. The correlation between RAsag,MLdev and RAml with SAQ wasstatistically significant(P﹤0.05), the order of correlation coefficient was RAml>MLdev> RAsag. In the third section, The Cobb angle of main thoracic curve, RAsag、RAml、AVB-R,RHI,TRMC and TRAT after surgery showed significantly correction compared with these parameters before surgery(P﹤0.01, except RAsag P﹤0.05). Thecorrection rates of these parameters were79.01％,19.57％,55.27％,57.28％,27.27％54.21％and45.24％, respectively. There were no statistical significance about thoseparameters including VI,Vr,Vt and LVR before and after surgery(P>0.05). The LLHand TLH after surgery were higher than those before surgery(P﹤0.01). The RLH aftersurgery were higher than it before surgery(P﹤0.05). There were no statisticalsignificance about CVTA and TTA before and after surgery(P>0.05). The CCTA aftersurgery was smaller than it before surgery(P﹤0.01).Conclusion：TRMC andTRAT are good parameters evaluating the thoracic balance.RAml is the best parameter evaluating thoracic deformity among RAml,RAsag andMLdev.The thoracic deformity showed significantly correction and the thoracicbalance achieved significantly correction recovering after surgery. The lungmorphology also changed significantly afte surgery. The bilateral lung height werehigher than those before surgery, but the lung volume had no changes.