Selection Of Lowest Instrumented Vertebra And Multi-Omics Analysis Of Paraspinal Muscle Imbalance In Idiopathic Scoliosis

Spinal fusion is the mainstay treatment for adolescent idiopathic scoliosis(AIS)patients with Cobb angle exceeding 45 degrees.However,the motion range of fused segments will be lost.For patients in whom the fusion of lumbar curvature is required,preserving mobile segments of the lumbar spine as many as possible is of great significance to maintain the quality of life,reduce the risks of low back pain and distal disc degeneration.Currently,the selection of lowest instrumented vertebra(LIV)mainly relies on standing radiographs.Whether recumbent imaging means,such as recumbent CT,helps for the selection of LIV in AIS patients,is not clear.Bracing is the primary treatment for AIS patients with Cobb angle of 25 to 40 degrees.However,brace therapy can only prevent the progression of the deformities in a certain proportion of patients.The shortcomings of bracing and surgical treatment urge spine surgeons to seek early interventions.Yet interventions for the early stage of idiopathic scoliosis(IS)is lacking,which may be attributed to the unclarified etiology and pathogenesis.Paraspinal muscle imbalance is prevalent in IS patients.However,it is still unclear whether paraspinal muscle imbalance is the cause of spinal deformities in IS or the change secondary to the deformities.Exploring the causal relationship between paraspinal muscle imbalance and IS may help to develop treatment targeting paraspinal muscle imbalance to delay or prevent the progression of IS.This study consists of two parts.In part one,Lenke-5 AIS patients were taken as the object to explore whether recumbent imaging is helpful for the selection of LIV in AIS.In part two,congenital scoliosis(CS)was taken as the control.Through multi-omics comparison of paraspinal muscle imbalance between IS and CS,we aimed to clarify the causal relationship between paraspinal muscle imbalance and IS and explore key genes(proteins)and pathways for paraspinal muscle imbalance in IS.Part Ⅰ.Application of recumbent imaging for the selection of lowest instrumented vertebra in Lenke-5 AISObjective:The selection of LIV is one of the core issues during the surgical treatment of patients with Lenke-5 AIS.Although the proposal of last touched vertebra(LTV)has brought great convenience to the selection of LIV,a considerable number of Lenke-5 AIS patients with the first vertebra proximal to LTV(LTV-1)as LIV displayed satisfactory outcomes.This phenomenon urges spine surgeons to explore more precise strategies for LIV selection.In some Lenke-5 AIS patients,LTV-1 on standing radiographs is touched by central sacral vertebral line(CSVL)on recumbent CT.Whether this characteristic contributes to the selection of LIV in Lenke-5 AIS patients remains unclarified.This study aimed to develop and evaluate a recumbent CT-assisted LIV selection strategy for Lenke5 AIS.Methods:53 Lenke-5 AIS patients who underwent posterior spinal fusion in our center were retrospectively analyzed.Based on whether LTV-1 on standing films was touched by CSVL on recumbent CT or not,patients were divided into the LTV-1 group(n=22)and the LTV group(n=31).Distal fusion to LTV-1 was undertaken in the LTV-1 group,whereas LTV was selected as LIV in the LTV group.Demographic data and surgical information were collected.Radiographic parameters were measured at pre-operation,post-operation and the last follow-up.Quality of life was evaluated using Scoliosis Research Society-22(SRS-22)questionnaire.Results:No statistical differences regarding sex,age at surgery,operative time,blood loss and allogeneic transfusion volume,were observed between groups.Shorter fusion range was observed in the LTV-1 group.Smaller preoperative radiographic parameters,including Cobb angle on bending films,apical vertebral translation,LTV tilt,LTV translation,LTV1 tilt,LTV-1 translation and LTV-1 rotation were observed in the LTV-1 group.Postoperative radiographic parameters were similar between groups except for apical vertebral translation.At final follow-up,greater LIV translation,LIV subjacent disc angle,pelvic obliquity and T2-T12 thoracic kyphosis were observed in the LTV-1 group.There were no significant differences in complication rate,revision rate and SRS-22 questionnaire scores at final follow-up,between groups.Conclusions:For Lenke-5 AIS patients in whom LTV-1 on standing films is touched by CSVL on recumbent CT,distal fusion to LTV-1 is acceptable.Part Ⅱ Multi-omics comparison of paraspinal muscle imbalance between idiopathic scoliosis and congenital scoliosisObjective:Previous studies have validated and analyzed paraspinal muscle imbalance in IS with multiple approaches,such as imaging,histological methods and electromyography.However,it still remains controversial whether paraspinal muscle imbalance is the cause or the consequence of IS.This study aimed to compare paraspinal muscle imbalance between IS and congenital scoliosis(CS),to clarify the causal relationship between spinal deformities and paraspinal muscle imbalance in IS and explore key differential genes(proteins)and pathways for paraspinal muscle imbalance in IS.Methods:Bilateral paraspinal muscles of 5 pairs of IS and CS patients were collected.Transcriptome sequencing was performed to identify differentially expressed genes(DEGs)between muscles on the concavity and that on the convexity in IS and CS.Differentially expressed proteins(DEPs)between muscles on the concavity and that on the convexity in IS and CS,were screened out using liquid chromatography coupled to tandem mass spectrometry.Differential metabolites(DMs)between muscles on the concavity and that on the convexity in IS and CS,were detected with liquid chromatography-mass spectrometry.Bioinformatic analysis of DEGs,DEPs and DMs were conducted.Comparison of DEGs,DEPs and DMs between IS and CS was also implemented.Multiomic analysis of DEGs,DEPs and DMs was conducted to identify pivotal differential genes(proteins)and pathways in paraspinal muscles between the concavity and convexity in both IS and CS.Results:(1)370 DEGs were identified in IS.DEGs in IS were enriched in Gene ontology(GO)terms,including response to external stimulus,system process,cell-cell signaling,signaling receptor binding,molecular function regulator and etc.Kyoto Encyclopedia of Genes and Genomes(KEGG)analysis revealed the enrichment of DEGs in IS in neuroactive ligand-receptor interaction,cytokine-cytokine receptor interaction and calcium signaling pathway and etc.380 DEGs were identified in CS.DEGs in CS were enriched in GO terms,including multicellular organismal process,regulation of multicellular organismal process,system process,receptor ligand activity,receptor regulator activity,signaling receptor binding and etc.KEGG analysis revealed the enrichment of DEGs in CS in neuroactive ligand-receptor interaction,cytokine-cytokine receptor interaction and tight junction.59 DEGs with the same trend of difference in bilateral paraspinal muscles shared by IS and CS were identified,which account for 15.9%of DEGs in IS.(2)105 DEPs were identified in IS.DEPs in IS were enriched in GO terms,such as protein glycosylation,response to metal ion,ATP-dependent chromatin remodeling,calcium ion binding,DNA binding,protein complex binding and etc.KEGG analysis revealed the enrichment of DEPs in IS in pathways,including glycolysis/gluconeogenesis,purine metabolism and hypertrophic cardiomyopathy and etc.48 DEPs were identified in CS.DEPs in CS were enriched in GO terms,such as immune response,potassium ion transport and regulation of cell growth,receptor activity,phosphoglycerate kinase activity and inward rectifier potassium channel activity and etc.KEGG analysis revealed the enrichment of DEPs in CS in pathways,including glycolysis/gluconeogenesis,cellular senescence,Kaposi’s sarcoma-associated herpesvirus infection and etc.8 DEPs with the same trend of difference in bilateral paraspinal muscles shared by IS and CS were identified,which account for 7.6%of DEPs in IS.(3)51 DMs were identified in IS.DMs in IS were enriched in KEGG pathways,including lysine degradation and platelet activation.Only 7 DMs were identified in CS.DMs in CS were enriched in KEGG pathways,including thiamine metabolism,vitamin digestion and absorption,valine,leucine and isoleucine degradation,and platelet activation.Prostaglandin G2 is the only DM shared by IS and CS.(4)Differential expressed genes(proteins)specific for IS at both the level of transcriptome and proteome include ACTN3 and AQP4.Multi-omics integration analysis showed differential activation of pathways including regulation of lipolysis in adipocytes and secretion of aldosterone in IS.No enriched pathways were found based on DEGs,DEPs and DMs in CS.Conclusions:Multi-omics asymmetry in IS is different from that in CS,indicating that there might be some primary imbalance in bilateral paraspinal muscles of IS.Therefore,paraspinal muscle imbalance tends to be the cause of spinal deformities in IS.Differential expressed genes,including ACTN3 and AQP4,and pathways,including regulation of lipolysis in adipocytes and synthesis and secretion of aldosterone,may play important roles in the occurrence and development of paraspinal muscle imbalance and spinal deformities in IS.