Study Of Relationship Between Preoperative Pulmonary Function And Radiographic Parameters In Adolescent Idiopathicscoliosis

Objective: Clinical analysis on radiographic parameters related to preoperativepulmonary function in patients with adolescent idiopathic scoliosis and their clinicalsignificance. To determine values for the volume of right lung, left lung, total lungvolume, and left/right lung volume ratio, allowing comparison between those data andage-matched controls. To determine if lung volume correlated to pulmonary functionretrospectively.Background: Previous research has suggested that the curve degrees and decrease inthoracic kyphosiscontributed to pulmonary impairment.To our knowledge, no study onrelationship between CT determined lung volume and pulmonary function test inscoliosis have been published.Methods:(1)Twenty-four patients with adolescent idiopathic scoliosis had fullassessment of pulmonary function, radiographic evaluation of deformities, and receivedpreoperative CT scan.16females and8males were involved. Radiographicmeasurements obtained including lateral curvature, proximal thoracic curvature, apexdisplacement, vertebral rotation by Nash/Moe method, apical rib-vertebral angledifference(ARVD), kyphotic angle and number of vertebrae in thoracic curve. Weanalysed pulmonary function in relation to deformity.(2)All examinations withpulmonary function test (24examinations) were identified. Three-dimensionalvolumetric reconstruction of lung parenchyma was performed on existing preoperativecomputed tomographic (CT) scans for17idiopathic scoliosis patients. Left, right, totallung volume, left/right ratios and absolute value of right minus left were calculated andcorrelated with pulmonary function tests (PFTs). Linear regression models, usingthree-dimensional lung volume parameters as predictors for VC, FVC, and TLC, werecreated.Results:(1)Average Cobb were52.8(range30-80) degrees with a mean age of14.8 years. Cobb angle of main curve showed significant negative correlation with VC%,FEV1%, FVC%, MVV%, TLC%, DLCO SB%and DLCO SB. Apex displacementdemonstrated a negative effect on TLC%, DLCO SB%and DLCO SB. ARVD fromanteroposterior standing radiograghs showed significant negative correlation with TLC%,TLC, DLCO SB%and DLCO SB. ARVD from anteroposterior supine bendingradiograghs showed significant negative correlation with TLC and DLCO SB. Values ofFEF50%, FEF75%, MMEF%, MVV%and DLCO SB%in patients with number ofvertebrae in thoracic curve≥7were significantly less (P<0.05) compared to those inpatients with number of vertebrae in thoracic curve＜7.(2) Total lung volume waspositively correlated with vital capacity (VC), forced vital capacity (FVC)(P<0.05), andnear-significantly positively correlated with total lung capacity (TLC)(P=0.055). Totallung volume was negatively correlated with forced expiratory flow of25%forced vitalcapacity（FEF50%）, and forced expiratory flow of75%forced vital capacity（FEF75%）,and not correlated with other PFT variables. Absolute value of right volume minus leftvolume was negatively correlated with percentage of predicted values of maximalventilatory volume （MVV%）(P<0.05), and not correlated with diffusion parameters.AIS patients have less total lung volume and right lung volume compared withage-matched controls(P<0.05). Left/right volume ratios for female patients was higherthan values for age-matched controls(P<0.05).Conclusion:(1)Preoperative PFT values in patients with idiopathic scoliosissignificantly reduced, as main curve Cobb angle, apex displacement and ARVD fromanteroposterior standing and supine bending radiograghs increased. PFT values inpatients with proximal thoracic curve Cobb angle≥30were significantly smaller thanthat of proximal thoracic curve Cobb angle＜30; PFT values in patients with numberof vertebrae in thoracic curve≥7were also smaller than that of number of vertebrae inthoracic curve＜7.(2)Total lung volume was positively correlated with vital capacity(VC), forced vital capacity (FVC), and total lung capacity (TLC). Total lung volume andright lung volume of adolescent idiopathic scoliosis patients were less than those of agematched controls. Increase attention to improvement of lung volume asymmetry appears appropriate in order to preserve pulmonary function, and which may prevent percentageof predicted values of maximal ventilatory volume （MVV%）from decreasing.