| ?Backgrounds?In recent years,the parameters of sagittal plane,including spinal and pelvic parameters,such as pelvic incidence(PI),pelvic tilt(PT),sacrum slope(SS),lumbar lordosis(LL),and thoracic kyphosis(TK),have been increasingly recognized,as well as the sagittal balance.It has been verified that spinal parameters have been significantly correlated with pelvic parameters,and they play an important role in maintaining sagittal balance through compromise and adjustment.In addition,sagittal parameters have also been verified to be significantly correlated with health-related quality of life(HRQOL).Therefore,compared with coronal plane,more and more importance has been paid by orthopedic surgeons on the restoration of sagittal plane during the spinal deformity surgeries and other orthopedics surgeries.However,too many sagittal parameters and theirs complicated correlations make the researches regarding to sagittal plane of spinal deformities more complicated.The compensatory mechanisms of maintaining sagittal balance have been widely studied that they can occur in spine,pelvis,and/or lower limb areas and the mean objective is to extend the adjacent segments of the kyphotic spine to rebalance the axis of gravity,including:reduction of TK that can be observed in flexible spines,hyperextension of adjacent segments which can also limit the lumbar kyphosis to restore the sagittal balance,retrolisthesis,pelvis retroversion(increase of PT and rotation of the pelvis),knee flexion,and ankle extension;however,it is difficult to recognize which parameters play a key role in maintaining sagittal balance and which parameters are only compensatory mechanisms.LL and TK have been recognized as the two important curves of spinal curve,and their reciprocal relationship has been thought to play an important role in sagittal spinal balance.Therefore,we speculate that regional sagittal parameters(LL and TK)might play a key role in maintaining sagittal balance in asymptomatic subjects and LL-TK match could be used to predict sagittal balance since no regional parameters have been verified to be significantly correlated with sagittal balance and no parameter could represent the compensation of sagittal plane directly.?Objectives?This study was performed to detect the role of regional sagittal parameters(LL and TK)in maintaining sagittal balance in asymptomatic subjects and AIS(Adolescent Idiopathic Scoliosis)patients through observing,collecting and analyzing clinical data,to detect whether regional sagittal parameters(LL and TK)could be used to predict the sagittal balance in elderly patients with unspecific low back pain,to detect whether we could use regional sagittal parameters(LL and TK)to restore the sagittal balance in correction surgery through osteotomy.?Methods?1.Analysis of factors associated with sagittal balance in normal asymptomatic individualsNormal asymptomatic individuals who came to our health care for physical examination from January 2014 to August 2015 were recruited in our study;Part I.Subjects recruited in our study were normal asymptomatic individuals without spinal diseases,and each subject should receive X-ray examination.Demographic data including age and gender,and radiological parameters,including T1 sagittal angle,maxLL(lumbar lordosis calculated by the Cobb method),maxTK(thoracic kyphosis calculated by the Cobb method),SS(Sacrum Slope),PI(Pelvic Incidence),PT(Pelvic Tilt),and SVA(Sagittal Vertical Axis)were collected and analyzed.Subjects were divided into two groups:Group A(n=311),for exploring factors related to sagittal balance and detecting the equation for predicting sagittal balance in normal asymptomatic individuals.The remaining 29 subjects were recruited in Group B for validation this new equation.2.The role of LL-TK(LL minus TK)in predicting the sagittal balance in elderly patients with unspecific low back pain.Elderly patients who went to our clinics for treatment of their complaints about low back pain from January 2012 to January 2014 were recruited in our study;Part III.The exclusion criteria were as follows:lumbar fracture,tumor,lumbar disc herniation or lumbar canal stenosis,infections and other specific diseases which might cause low back pain.Each patient was required to take the whole spine X-ray examination in clinics.All patients provided written informed consent for the study.The specific low back pain was assessed by using Numeric Rating Scales(NRS,0-10).Correlation analysis was performed between SVA and age,NRS and other radiological parameters,and between LL-TK and age,NRS and other radiological parameters.According to whether patients'SVA was larger than 5cm,patients were divided into two groups:Group A(SVA>5cm)and Group B(SVA?5cm).General data and radiological parameters were compared between these two groups.ROC curve was performed to detect the threshold value(cutoff value)of LL-TK and PI-LL as the balance index.The cutoff value of LL-TK and PI-LL were used to assess their effectiveness of predicting sagittal balance.3.The role of LL-TK(LL minus TK)in maintaining sagittal balance before and after correction surgery in AIS patients.Lenke I and Lenke II AIS patients who received correction surgery in our clinic from January 2013 to January 2010 were recruited in this study;Part II.General data were collected,including name,age,gender and Risser sign.Each patient was required to take the whole spine X-ray examination before and after correction surgery.The radiological parameters collected and analyzed in this study included TK(thoracic kyphosis),LL(lumbar lordosis),SS(Sacrum Slope),PI(Pelvic Incidence),PT(Pelvic Tilt),SVA(Sagittal Vertical Axis)and LL-TK(LL minus TK).LL,TK,LL-TK,SS,PT,PI and SVA were compared before and after surgery in each patient,and correlation test between LL,TK and LL-TK before and after surgery was also performed to explore the role of LL-TK in maintaining sagittal balance before and after correction surgery in AIS patients.4.Predictive equation for restoring sagittal balance using regional parametersA total of 311healthy volunteers from January 2014 to August 2015,who met the inclusion and exclusion criteria,were retrospectively reviewed.The inclusion criteria of patients were as follows:a.healthy people without history of spinal disorders or spinal deformity;b.no history of spinal surgery.The exclusion criteria of patients were as follows:a.definite diagnosis of lumbar spinal pathology and spinal deformities;b.tumors or infections;c.hip,knee,and ankle abnormalities.Patients without sufficient radiographic parameters were also excluded from our study.This study was approved by the Institutional Review Board in our university,and all patients in our study provided written informed consent for the study.Demographic data collected was age.Radiographic parameters were measured on each lateral radiograph of the whole spine by two individual surgeons,including maxTK(thoracic kyphosis calculated by the Cobb method),maxLL(lumbar lordosis calculated by the Cobb method),SS(the angle between the horizontal and the sacral plate),PT(the angle between the vertical and the line through the midpoint of the sacral plate to femoral heads axis)and PI(angle subtended by a perpendicular from the upper endplate of S1 and a line connecting the center of the femoral head to the center of the upper endplate of S1).Compared with traditional measurement(TK:usually from T5-T12;LL:usually from L1-S1),maxTK and maxLL were evaluated and analyzed in our study,which could represent the real magnitude of thoracic and lumbar curve as thoracic and lumbar curve in each subject varied among individuals.Patients were randomly assigned into two groups.A cohort of 220 volunteers was recruited in Group A for the development of our predictive formula,and the remaining 91 subjects were recruited in Group B for validation of this new formula.In the first analysis(development of predictive formula),correlation analysis between maxLL and other parameters including age,maxTK,PT,SS and PI was performed.Furthermore,multiple regression analysis was performed to find out the primary contributors to maxLL,and further adjusted multiple regression analysiswas conducted using morphologic parameters to establish predictive radiographic parameters and formula for maxLL.The second analysis was the validation of our newly developed formula.Firstly,the predicated maxLL yielded by our formula and actual maxLL were conducted to detect whether there was significant difference between our predicated maxLL and actual maxLL.Secondly,actual maxLL and predicted maxLL yielded by other 7 formulas were also compared to determine the reliability of our predictive formula,including LL=0.508*PI-0.088*Age+28.6 proposed by Xu et al.,LL=0.45*PI+31.8 proposed by Yamato et al.,LL=0.96*(0.74*PI+0.8)+17.42 proposed by Lee et al.,LL=1.087*(0.548*PI+12.7)+21.61 proposed by Legaye et al.,LL=PI+9 proposed by Schwab et al.,maxLL=-2.72-1.1*PI+1.1*PT-0.31*maxTK proposed by Vialle et al.and LL=45–TK-PI proposed by Rose et al..?Results?1.In Group A,the mean age,T1 sagittal angle,maxTK,maxLL,PT,PI,SS,and SVA was 46.2 years old,20.13~o,36.33~o,47.81~o,15.99~o,47.78~o,31.73~o,and 6.59 mm,respectively.In Group B,the mean age,T1 sagittal angle,maxTK,maxLL,PT,PI,SS,and SVA was 44 years old,21.03~o,39.28~o,51.48~o,15.59~o,48.66~o,33.17~o and 7.62mm,respectively.No significant differences were found in other parameters between male patients and female patients,expect for age(P<0.001).In correlation coefficient analysis,we found a very good correlation between T1 sagittal angle and maxTK,maxLL and SS,SS and PI,and PT and PI;a moderate correlation between maxTK and maxLL and between maxLL and PI;a weak correlation between age and T1 sagittal angle,maxTK,SS,PT,SVA,and between T1 sagittal angle and SVA,SVA and PT,and SVA and PI;and a very weak correlation between T1 sagittal angle and maxLL,maxLL and PT,SVA and maxLL,and PT and SS.Furthermore,the linear regression analysis indicated that age,T1sagittal angle,maxTK,PT and PI were the primary contributors to sagittal balance(SVA),and SVA could be predicted by the following equation:SVA=0.294*age+1.367*T1sagittal angle-1.149*maxLL-0.704*PT+1.378*PI-34.164.Paired t test showed that the predicted SVA calculated by our equation was not significantly different from the actual SVA in Group B(P=0.307).2.129 elderly patients with unspecific low back pain have been recruited in this part.LL-TK was found to be significantly correlated with age,maxLL,maxTK SS,PT,PI,SVA and NRS.According to whether patients'SVA was larger than 5cm,87 patients and 42patients were recruited in Group A and Group B,respectively.There were significant differences in age,maxLL,PT,LL-TK,PI-LL,SVA and NRS between two groups.ROC curve was performed,and the results showed that the cutoff value of LL-TK and PI-LL was 0~o and 13~o,respectively.The positive and negative percentages of using LL-TK and PI-LL to assess sagittal balance in patients with unspecific low back pain was 89%and87%,respectively.3.A total of 76 Lenke 1 and Lenke 2 AIS patients(M:16 and F:60)who received the posterior correction surgery using pedicle screws were included in our study,with the mean age of 15.26 years old.The mean Cobb angle was 48.26±8.6~o,which significantly descreased to 14.15±8.27~o at final follow-up(P<0.001).According to Lenke classification of AIS,37 patients were Lenke 1AN,accounting for 48.7%of total included subjects.The number of Lenke 1A+and Lenke 1A-were 5(6.6%)and 6(7.9%),respectively.A total of9 patients were Lenke 1B,among which 2 patients(2.6%)were Lenke 1B+and 7 were Lenke 1BN(9.2%).12 patients(15.8%)were Lenke 1CN;2 patients(2.6%)were Lenke1C-.There was only 1 patient classified as Lenke 1C+,Lenke 2AN and Lenke 2B-,respectively.Besides,the other 2 patients(2.6%)were Lenke 2CN.Both TK and LL decreased significantly after correction surgery,from 25.51~o to22.11~o(P=0.019),and from 49.32oto 47.19o(P=0.04),respectively.However,no significant change of TK-LL was observed in our study,although TK-LL increased slightly form 23.80~o before operation to 25.09~o at final follow-up(P=0.372).In addition,SS,PT,PI and SVA did not change significantly after the correction surgery.TK was significantly correlated with LL before the operation(r=0.234,P=0.042)and significant correlation was also found after correction surgery(r=0.310,P=0.006).Furthermore,the same change of trend was observed in TK and LL,and significant correlation was also found between the change of TK and LL(r=0.626,P=0.002).4.A total of 220 healthy volunteers were recruited in Group A for the development of predictive formula with the man age of 46.00±16.08 years old.The remaining 91 healthy subjects were recruited in Group B for the validation of newly developed formula with the man age of 46.68±17.17 years old.There were no significant differences of age(P=0.738),maxTK(P=0.433),maxLL(P=0.341),PT(P=0.944),SS(P=0.535)and PI(P=0.727)between Group A and Group B.Correlation coefficient test indicated that correlation was observed between maxLL and maxTK(r=0.564,P<0.001),SS(r=0.783,P<0.001),PT(r=-0.155,P=0.021)and PI(r=0.483,P<0.001).However,no correlations were found between maxLL and age(r=-0.031,P=0.643).Unadjusted multiple linear regression analysis was conducted by using variables that were found to be significantly correlated with maxLL,and the results suggested that maxTK(P<0.001)and SS(P<0.001)were the primary contributors to maxLL,while PT and PI did not play a key role in the morphology of lumbar curves(P=0.477 and 0.629,respectively).Since it was difficult to predict the postoperative values of compensatory parameters such as PT and SS accurately before correction surgery,we removed SS from the multiple regression equation and added morphologic parameters such as maxTK and PI(SS was significantly correlated to PI with r of 0.680)in our regression analysis,which determined the morphology of lumbar lordosis.Adjusted regression analysis showed that maxTK and PI were significantly associated with maxLL,which could be predicted by using the following regression equation:maxLL=0.6*maxTK+0.5*PI+3.In the analysis of validation of predicted formula,there was no significant difference between actual maxLL and predicted maxLL yielded by our formula(48.70±9.46 vs.49.32±7.69,P=0.408).Furthermore,significant correlation was also found between actual maxLL and predicted maxLL.Although no significant difference was also observed between the actual maxLL and predicted LL yielded by Xu et al.'s(P=0.799),and Vialle et al.'s formula(P=0.085),these findings might not be accurate as the Xu et al.'s and Vialle et al.'s formulas were established on the measurement of LL,rather than maxLL,which might be smaller than maxLL,leading to the inaccurate outcomes.In addition,there were significant differences between actual maxLL and predicted maxLL yielded by Yamato et al.'s,Lee et al.'s,Legaye et al.'s,Schwab et al.'s,and Rose et al.'s formula(P<0.001),suggesting great gap between actual maxLL and predicted maxLL yielded by these formulas.?Conclusions?1.Age,T1 sagittal angle,maxLL,PT and PI were the primary contributors to maintaining sagittal balance in normal healthy people.In the normal healthy people,sagittal balance could be predicted by the following equation with good validation:SVA=0.294*age+1.367*T1 sagittal angle-1.149*maxLL-0.704*PT+1.378*PI-34.164.2.LL-TK could be regarded as a very good predictor for sagittal balance in elderly patients with unspecific low back pain,especially combined with PI-LL.3.The same change of LL and TK has been observed,and LL-TK remains contact in Lenke I and Lenke II AIS patients after correction surgery,suggesting that LL-TK might play an important role in maintaining sagittal balance in AIS patients.4.Sagittal balance could be largely restored by restoring LL,and in the correction surgery,LL could be restored by changing TK.5.Based on the predictive equation of sagittal balance,we could accurately assess the situation of sagittal alignment,and make it visible.In addition,restoration of LL in the correction surgery could restore the sagittal alignment.6.Regional sagittal parameters(LL and TK)play an important role in maintaining sagittal balance,which could also be used in restoring sagittal balance. |
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