| Part ⅠThe analysis of correlations between demographic and epidemiological factors and disability of chronic low back painObjectives To describe the epidemiologic features of the disability,quality of life and pain in patients with chronic low back pain(CLBP).The correlations between demographic,epidemiological factors and disability,the quality of life,pain of CLBP patients are analyzed by univariate analysis to screen out and the related factors of disability of CLBP patients and analyze the main dimensions of disability.Materials and methods Patients with CLBP who were admitted to the Spinal Surgery Outpatient Department of the First Hospital affiliated to Naval Military Medical University from February 2021 to August 2021 were recruited for anteroposterial-lateral radiographs of the full spine.Patients who met the inclusion and exclusion criteria were enrolled in this study.Demographic and epidemiological information,Oswestry Disability Index(ODI),Numeric Rating Scale(NRS)scores,SF-36 eight dimension scores of health were collected from patients using a questionnaire.Taking ODI representing the disability of CLBP patients as the dependent variable,according to clinical significance and statistical analysis needs,patients who were enrolled in this study were divided into low degree disability group(mild disability:ODI≤20)and high degree disability group(severe than mild disability:ODI>20),and ODI was converted into ranked ODI(RODI)accordingly.Firstly,demographic,epidemiological factors,NRS scores,SF-36 eight dimension scores of health were compared by univariate analysis between the two groups.Secondly,Spearman correlation test was performed among the demographic and epidemiological factors with statistical significance between the two groups,RODI,10 dimension scores of ODI,NRS scores,SF-36 eight dimension scores of health,and P<0.05 was considered to indicate statistical significance.Results A total of 435 patients with CLBP were enrolled in this study,including 320(73.56%)patients with mild disability,97(22.30%)patients with moderate disability,13(2.99%)patients with severe disability,5(1.15%)patients with being crippled,and 0 patients with being bed bound.There were 320 patients in the low degree disability group and 115 patients in the high degree disability group.The average age of the 435 patients was 36.1±11.6 years old,and 173 of them were male(39.77%),262 of them were female(60.23%),the median ODI was 14.320(73.56%)patients in the low degree disability group with average age being 35.0±10.8 years old and the median ODI being 12,and 133 of them were male(41.56%),187 of them were female(58.44%).115(26.44%)patients in the high degree disability group with average age being 39.1±13.3 years old and the median ODI being 28,and 40 of them were male(34.78%),75 of them were female(65.22%).Univariate comparison between the two groups of CLBP patients demonstrated that age,education,main posture during being not rest,time of maintaining standing posture during being not rest,time of maintaining sitting posture during being rest were statistically significant(P<0.05).With the exception of SF-36 mental health(MH),there were statistically significant differences in clinical outcome parameters between the two groups(P<0.05).The correlation coefficients between age,education,main posture during being not rest,time of maintaining standing posture during being not rest,time of maintaining sitting posture during being rest and RODI were 0.126,-0.174,-0.100,0.094,-0.102,respectively(P<0.05).There was a weak positive correlation between RODI and NRS,a moderate negative correlation between RODI and SF-36 physical function(PF),role physical(RP),a weak negative correlation between RODI and SF-36 general health(GH),role physical(BP),vitality(VT),social function(SF),role emotional(RE),no correlation between RODI and MH,The highest degree of correlation was between RODI and PF(r=-0.470)(P<0.05).Conclusions There are correlations between RODI and NRS、SF-36(excluding MH)and the classification of low and high degree disability has clinical significance.The ODI mainly focuses on the disability of physical function of CLBP patients.Univariate analyses indicate that age,education,main posture during being not rest,time of maintaining standing posture during being not rest,time of maintaining sitting posture during being rest are associated with disability of CLBP.Patients of being oder,lower education level,standing posture during being not rest,longer time of maintaining standing posture during being not rest,shorter time of maintaining sitting posture during being rest have high degree disability and poor quality of life.Part Ⅱ The analysis of correlations between sagittal spinopelvic parameters and disability of chronic low back painObjectives To describe the characteristics of sagittal spinopelvic parameters and analyze the correlations between them in CLBP patients.The correlations between sagittal spinopelvic parameters and disability,quality of life and pain of CLBP patients are analyzed by univariate analyses to screen out the related sagittal spinopelvic parameters of disability of CLBP patients.Materials and methods Partial demographic data including age,sex and body mass index(BMI),as well as clinical outcome parameters including ODI for disability,NRS scores for pain,and SF-36 eight dimension scores for quality of life of the 435 CLBP patients were all derived from Part I.They were also divided into low degree disability group and high degree disability group,and ODI were converted into RODI accordingly.Anteroposterial-lateral radiographs of the full spine of 435 patients with CLBP were collected.Sagittal spinopelvic parameters were measured by two spinal surgeons with more than 2 years of experience,including local parameters,global parameters and combined parameters indicating the matching between local parameters.Transitional vertebra(TV),apical vertebra of thoracic kyphosis and lumbar lordosis,Roussouly Type,position of lumbar vertebra relative to pelvis(PLVRP)were performed any inconsistencies should be referred to another spine surgeon with 10 years of experience for final determination.The interclass correlation coefficients(ICC)of each parameter measured by two surgeons were calculated to evaluate the consistency.Step one,the characteristics of sagittal spinopelvic parameters were described and the correlations were analyzed between sagittal spinopelvic parameters in CLBP patients.Step two,Spearman correlation tests were conducted between the sagittal parameters screened out by univariate analyses between the two groups and the clinical outcome parameters,RODI,10 ODI dimension scores,NRS scores and SF-36 eight dimension scores of health,respectively.The level of significance was P<0.05 for all tests.Results The ICC of each parameter measured by the two surgeons were all above 0.76,showing a high consistency.The average values of each parameter measured by the two surgeons were included in the final analysis.Of the 435 patients,the average or median thoracic kyphosis(TK)36.5°,lumbar lordosis(LL)47.3°,functional thoracic kyphosis(FTK)39.4°,functional lumbar lordosis(FLL)47.6°,lower arc of functional thoracic kyphosis(FTKLA)18.4°,upper arc of functional lumbar lordosis(FLLUA)13.5°,pelvic incidence(PI)46°,sacral slope(SS)33.3°,pelvic tilt(PT)13.4°,sagittal vertical axis offset(SVA)-3.4mm,the absolute values of SVA of 405(93%)patients were<50mm,T1 pelvic angle(TPA)-7.8°,spinosacral angle(SSA)124.5°,T1 spinopelvic inclination(T1SPi)-4.2°,T9 spinopelvic inclination(T9SPi)-9.1°,TK-LL-10°,FTK-FLL-7.5°,PI-LL-0.4°,SS-PT 19.7°,Barrey ratio-0.07,C7 skin periphery distance(C7SPD)35.8mm,lumbar lordosis apical vertebrae skin periphery distance(LLAVSPD)48.7mm,radiological sagittal index(RSI)85.0mm,thoracic kyphosis apical vertebrae(TKAV)T6,thoracic kyphosis apical vertebrae distance(TKAVD)33.7mm,TV L1,transitional vertebrae distance(TVD)0mm,lumbar lordosis apical vertebrae(LLAV)L4,lumbar lordosis apical vertebrae distance(LLAVD)-27.2mm,PLVRP L5,Roussouly Type:Type 2.TK and LL(r=0.420),FTKLA(r=0.557),FLLUA(r=0.519),LL and SS(r=0.818),PI(r=0.469),SSA(r=0.844),SSA and SS(r=0.911),Roussouly Type(r=0.731),FTKLA and FLLUA(r=0.848),FTKLA and T9SPi(r=-0.628),FLLUA and T9SPi(r=-0.640),T1SPi and T9SPi(r=0.740),SVA and T1SPi(r=0.779),Barrey ratio(r=0.970),T1SPi and Barrey ratio(r=0.720),PT and TPA(r=-0.819),SFD(r=0.906),SS-PT and LL(r=0.615),SS(r=0.714),PT(r=-0.754),SFD(r=-0.797).The correlation coefficients between C7SPD and TKAVD,TVD,LLAVD were 0.700,0.640,0.512,respectively.The correlation coefficients between TKAVD and TVD,LLAVD were 0.801,0.594,and the correlation coefficient between TVD and LLAVD was 0.848(p<0.05).Univariate comparisons between the two groups of CLBP patients demonstrated that SSA,SS-PT,C7SPD,TKAV,LLAV,LLAVD,TVD,Roussouly Type were statistically significant(P<0.05).The correlation coefficients between SSA,SS-PT,C7SPD,TKAV,LLAV,LLAVD,TVD,Roussouly Type and RODI were-0.116,-0.115,0.130,0.134,0.122,0.109,0.123,-0.109,respectively(P<0.05).Conclusions The sagittal spinopelvic parameters in patients with CLBP are correlated,and the correlation degree are high for parameters of adjacent segments and with similar functions.The sagittal spinopelvic parameters are correlated with disability of patients with CLBP.Univariate analyses showed that patients with CLBP have high degree disability and poor quality of life with the relatively anteverted spine,the relative retroverted pelvis,the disharmonious spinal morphology.Part Ⅲ The independent factors for disability of chronic low back painObjectives The binary logistic regression analysis is used to adjust the multiple correlation factors screened out by univariate analyses in Part Ⅰand Part Ⅱ to discover the independent factors for disability of CLBP and establish the diagnostic model for disability of CLBP.The sagittal balance of the spine reflected by the parameters is analyzed,and the biomechanical mechanisms of the effect of the sagittal parameters for disability of CLBP are clarified.Materials and methods The demographic,epidemiological data,sagittal spinopelvic parameters as well as ODI of the 435 CLBP patients were all derived from PartⅠ and Part Ⅱ.They were also divided into low degree disability group and high degree disability group,and ODI were converted into RODI accordingly.The demographic,epidemiological factors and sagittal parameters that were statistically different between the two groups in part Ⅰ and Ⅱ were finally included in this study.In order to evaluate the sample size according to the empirical rule,multivariate regression analysis generally requires the sample size of event outcome to be 5-10 times the number of independent variables.Stepwise regression was selected as the screening method of logistic regression variables.The test level of variables entering into the equation was 0.05,and the level of variables taking out of the equation was 0.1.Firstly,logistic regression analysis was conducted with the demographic and epidemiological data with statistically significant differences between the two groups being independent variables and RODI being dependent variable to establish Model 1.Secondly,the demographic,epidemiological data and sagittal parameters with statistically significant differences between the two groups were taken as independent variables and RODI as dependent variable for logistic regression analysis to establish Model 2 as the final model.The nomogram and ROC curve of Model 2 were plotted.The area under ROC curve(AUC)amd determination coefficient(R2)of the two models were calculated and compared respectively to analyze the contribution of sagittal parameters to the disability of CLBP.Bootstrap was used to validate internal validity of the final model and the corrected AUC was calculated to evaluate the stability of the model.Hosmer-Lemeshow goodness of fit was tested to evaluate the consistency of the model and the consistency curve was drawn.P<0.05 was considered statistically significant.Results There were 320 patients in the low degree disability group and 115 patients in the high degree disability group.According to the principle that the number of patients in the high degree disability group is 5-10 times the number of independent variables,the range of independent variables that can be incorporated into the regression equation is about 11-23.In Part Ⅰ and Part Ⅱ of this study,a total of 13 factors were screened out,which conformed to the empirical rule.The two models had statistical significance(P<0.05).The factors included in Model 1 were education and time of maintaining sitting posture during being rest,R2 was 0.039,AUC was 0.630,and factors included in Model 2 were education,time of maintaining sitting posture during being rest,SSA,R2 was 0.063,AUC was 0.658,the comparison between the two models was statistically significant(P=0.0009).The standardized regression coefficients of college diploma,postgraduate diploma,time of maintaining sitting posture during being rest,SSA,were-0.197,-0.211,-0.139,-0.207,respectively and their odds ratios were 0.489(95%CI:0.308,0.778),0.299(95%CI:0.125,0.711),0.875(95%CI:0.772,0.993),0.953(95%Cl:0.925,0.981),respectively.The AUC of the final model before calibration was 0.658(95%Cl:0.600-0.717),and the corrected AUC was 0.654 after 1000 times of internal validation by Bootstrap.Hosmer-Lemeshow goodness of fit test(P=0.664>0.05)showed good consistency.Conclusions Multifactor analyses indicate that education,time of maintaining sitting posture during being rest,spino-sacral angle are independent factors for the disability of patients with CLBP.Patients with lower education level,shorter time of maintaining sitting posture during being rest,relative anteverted spine have high degree disability.The spino-sacral angle(SSA)could comprehensively reflect the sagittal balance in patients with CLBP.The decrease of SSA indicates that the poor sagittal balance will aggravate the disability of patients with CLBP.Part Ⅳ Finite element analysis of lumbar load in different standing and sitting posturesObjectives The bone-ligament finite element models of lumbosacral vertebrae are established by referring to the genuine curvatures of lumbar spine of an asymptomatic volunteer in different standing and sitting postures,and the lumbar load in different postures are analyzed to provide reference for the early intervention of CLBP patients and adopting the correct postures in daily life of the asymptomatic population.Materials and methods An asymptomatic volunteer,male,44 years old,height 168 cm,weight 76 kg,BMI 26.9,was selected from the 435 patients with CLBP.The volunteer adopted supine position and Digital Imaging and Communication Standard(DICOM)format data were obtained by CT scanning from the first lumbar vertebra to the proximal femur.Taked lateral radiographs(from the first lumbar vertebra to the proximal femur)of the volunteer of standing in anteversion position,standing in neutral position,standing in retroversion position,sitting in relaxed back and torso anteversion position,sitting in straight back in neutral position,sitting in relaxed back and torso retroversion position,sitting in relaxed back in neutral position,sitting in relaxed back in neutral position with lumbar support.The igs models of lumbosacral vertebrae were established by using the supine position CT DICOM format data and the finite element models of different postures were established by realigning the spatial positions of each vertebra in the sagittal plane according to the lateral X-ray films of three kinds of standing postures and five kinds of sitting postures.All the models included vertebral bodies,intervertebral discs,bone of the posterior elements,facet joints,seven ligaments.The standing in neutral position model was selected for model validation.Mises stress and distribution,the intervertebral disc pressure(IDP)of different postures were analyzed after loading 400N physiological load to the models.Results Three kinds of standing postures and five kinds of sitting postures finite element models were established and the results of model validation were close to those reported in previous literatures and the models can be used for biomechanical testing.The Mises stress distribution on intervertebral discs shifted from posterior to anterior portion with the body anteversion in standing position.The Mises stress peak values of L3-4,L4-5,L5-S1 discs were greater than those of L1-2,L2-3 discs in all three standing postures and the Mises stress peak values of L3-4,L4-5,L5-S1 discs were lowest in standing in neutral position.The IDP of L3-4,L4-5 discs were highest in standing in retroversion position and lowest in standing in neutral position.While the IDP of L5-S1 discs were highest in standing in anteversion position and lowest in standing in retroversion position.Compared with the sitting in relaxed back and torso anteversion position,sitting in relaxed back and torso retroversion position,the Mises stress distribution on intervertebral discs of lumbar load of sitting in straight back in neutral position was concentrated in the posterior portion.Compared with the sitting in straight back in neutral position,the Mises stress distribution on intervertebral discs was in anterior portion of sitting in relaxed back in neutral position,and then in posterior portion after exposure to the lumbar support(sitting in relaxed back in neutral position with lumbar support).The Mises stress peak values of discs of sitting in relaxed back and torso anteversion position were generally greater than the same level discs in other postures and the Mises stress peak values of L4-5,L5-S1 discs were highest and 1.927 MPa and 2.202 MPa,respectively.The Mises stress peak values of discs in sitting in relaxed back and torso retroversion position were generally greater than the same level discs of sitting in straight back in neutral position(except for L1-2 disc)and the Mises stress peak values of L4-5,L5-S1 discs were highest and 1.416 MPa and 1.875MPa,respectively.The Mises stress peak values of L1-2,L2-3,L3-4 discs decreased of sitting in relaxed back in neutral position compared with that of sitting in straight back in neutral position,however,the Mises stress peak values significantly increased of L4-5,L5-S1 discs,and then the Mises stress peak values of L4-5,L5-S1 discs decreased to similar level of Mises stress peak values in other intervertebral discs after exposure to the lumbar support(sitting in relaxed back in neutral position with lumbar support).There was no significant difference of the Mises stress peak values between sitting in straight back in neutral position and sitting in relaxed back in neutral position with lumbar support.The changes of IDP in sitting postures were consistent with those of Mises stress peak values of discs.Conclusions Different postures effect the distribution and size of lumbar load by changing the lumbar curvature,pelvic orientation and muscle activity.Postures that increase the load of the lumbar intervertebral disc may aggravate the disability of CLBP.The loads of the lumbar intervertebral disc of standing in neutral position,sitting in straight back in neutral position and sitting in relaxed back in neutral position with lumbar support are lower.The correct or use of lumbar braces sitting postures are beneficial for patients with CLBP and the asymptomatic population. |
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