| BackgroundAdolescent idiopathic scoliosis(AIS)is traditionally defined as a structural threedimensional spinal deformity in persons aged 10 to 18 years.Rigo type A curve with brace treatment has a much higher risk to fail and produces more obvious compensatory proximal thoracic curves.Based on prior clinical observations and biomechanical research studies,we speculate that better in-brace correction pressures may influence the likelihood of vertebral growth plate stress remodeling and the chance of curve regression.PurposeThis study aimed to analyze the clinical features of the compensatory proximal thoracic curves with Rigo type A AIS patients at the termination of brace treatment;evaluate the imaging parameters,balance,and aesthetic corrective outcomes of different pressures of Rigo-Chêneau braces on patients with Rigo type A AIS;and subsequently,determine the effects of brace pressure on the von Mises stress of vertebral growth plates.MethodsIt was to retrospective investigate outcome in terms of the incidence of compensatory proximal thoracic curves for Rigo type A AIS patients receiving Rigo-Chêneau braces management between 2016 and 2020 at our center.Clinical features such as spinal balance and truncal cosmetics were assessed and analyzed in patients with compensatory proximal thoracic curves after bracing.A 3D finite element model(FEM)of one scoliotic Rigo type A3 spine with a compensatory proximal thoracic curve,consisting of growth plates attached to rigid C2 to L5 vertebrae,was developed using computed tomography images.Different corrective pressures were estimated by the mechanical principles of the Rigo-Chêneau brace and then applied to the FEM.The changes that occurred in AIS imaging parameters,balance,aesthetics,and stress distribution on the growth plates were investigated in the AIS model.Results(1)Retrospective study: Seventy-two(29 with the compensatory proximal thoracic curves)patients met the inclusion criteria.Their average age was 14.1 ± 3.3 years at treatment onset and the mean brace treatment period was 2.0 years(median).At the termination of treatment,the rate of main thoracic curves progression was 9.7%(7 of 72),and the rate of surgery or progression to ≥ 50° was 4.2%(3 of 72).The compensatory proximal thoracic curves remained uncorrected in 6.9%(2 of 29)of the cases and increased in 7.0%(3 of 43)of the cases.(2)Finite element analysis: From the perspective of AIS imaging parameters,when the corrected pressure of the left lumbar region was 0.035 MPa,the Cobb angle correction rate was the highest,the major thoracic curve Cobb angle correction rate was 23.0%,and the compensatory proximal thoracic curve Cobb angle correction rate was 27.8%.From the perspective of stress distribution on the growth plates,when the corrected pressure of the left lumbar region was 0.014 MPa,the concave/convex stress ratios of the cranial growth plates of the apical T2 and T7 were the smallest,1.355 and 0.996,and the posterior/ anterior stress ratios of the cranial growth plates of the apical T2 and T7 were relatively small,0.781 and 1.739.Conclusions(1)Rigo type A AIS patients have achieved good short-term efficacy of major thoracic curves after Rigo-Chêneau bracing,but a small number of patients with compensatory proximal thoracic curves.(2)The apical growth plate asymmetrical compressive loading in the major thoracic curve and compensatory proximal thoracic curves was inverted by adjusting the left lumbar region corrective pressure of the Rigo-Chêneau brace,and the variation trend between AIS 3D imaging parameters and vertebral growth plate stress distribution was inconsistent. |
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