| BackgroundSpondylolisthesis is a common disease in spine department of orthopedics.this disease can cause various symptoms such as low back pain、radiating pain of lower extremities、neurogenic intermittent claudication and so on.According to the mechanism of spondylolisthesis,this disease can be classified as isthmic spondylolisthesis、degenerative spondylolisthesis、developmental spondylolisthesis、traumatic spondylolisthesis and some other kinds,and among population almost 70%of spondylolysis are found in the L5 segment.As we all know,among the spine sequence,lumbosacral region sustains the greatest shear force than other sections,further more the isthmus is one of the important factors limiting the forwarding of lumbar vertebrae,as a result when shear force turns greater than what the L5 isthmus can sustain,the isthmic spondylolisthesis can occur very easily.Pelvic incidence which attracts intensive concentration recently,is a parameter which describes the anatomic relationship of L5 lumbar vertebrae and hip joint which is below the L5 vertebrae,and it can also measure the sloping degree of the sacrum to a great extent.After an individual develops to maturation,pelvic incidence always stays stable constantly and its another characteristic is that it keeps constant and unchangeble when this individual changes his position.An individual with great individual pelvic incidence,his sloping degree of sacrum tends to be horizontal and apparently the upper endplate of first sacrum tends to be vertical.So to maintain the balance of body gravitational force,other spinal segments will bring out a series of compensatory alteration,such as the increasing of lumbar lordosis and other linkable changes.After these alterations,the shear force lumbosacral region bears turns out to be greater which makes the occuration of L5 isthmic spondylolisthesis become more possible.Therefore based on this compensatory theory,a great many of scholars believe that pelvic incidence has a very important impact on the occuration of L5 isthmic spondylolisthesis which cannot be neglected,in another words,pelvic incidence is regarded as a predicting factor of L5 isthmic spondylolisthesis further more.Spino-pelvis,as a compounding complex,makes an individual body keep stable position to maintain the balance of body gravitational force with as least energy as possible.In anatomy,the lumbosacral region is the connecting part of spine and pelvis,and sustains the greatest shear force than other sections.Once the L5 isthmic spondylolisthesis occurs,the balance of spine and pelvis will definitely be broken,and as a result a series of sagittal parameters will alter to satisfy the compensatoration and adaption.Quite a few scholars believe that after the occuration of L5 isthmic spondylolisthesis,pelvis and sacrum will still alter including that pelvis will rotate adaptively and the angle between pelvis and sacrum will tend to be 90°,therefore this will definitely lead to the increasing of lumbar lordosis,which is regarded as a linkable move.These following up alterations just make sure that the line of gravity still locate on the hip joint which guarantees the balance of body gravity acquired again.Intervertebral disc is an essential structure to buffer the longitudinal pressure of spine,which has been proved to degenerate from the age of 20～30.The degeneration of lumbar intervertebral disc is regarded as the basis of plenty of lumbar degenerative diseases and plays a crucial role in both the occuration and development of these diseases.When degenerated intervertebral disc bulged、herniated,it may probably press the spinal cord、never roots and the cauda equine,which would make the patients suffer from symptoms such as the spastic paralysis below the pressed plane、never roots radiating pain、the functional disorder of urination and defecation and so on.There are various risk factors that have been proved to accelerate the degeneration.The aging of patients will decrease the water content of the nucleus pulposus of intervertebral disc,so the degeneration of lumbar intervertebral disc is regarded as one of the natural functional degenerations in human beings.In addition,over weight,or in another words great BMI(body mass index,BMI)can act as another risk factor of the degeneration of lumbar intervertebral disc since it can increase the longitudinal pressure of spine exerting on the adjacent intervertebral disc.The female gender of older individuals、facet joint arthritis have also been proved to be the risk factors of degeneration of lumbar intervertebral disc.A good deal of researchs have demonstrated that the pelvic incidence and lumbar lordosis in both patients with L5 isthmic spondylolisthesis and patients with L5 degenerative spondylolisthesis are greater than normal population significantly.For those patients with L5 isthmic spondylolisthesis,the L5/S1 intervertebral disc plays an essential role in limiting the forwarding of L5 vertebrae.Meanwhile greater pelvic incidence means that the upper endplate of first sacrum tends to be more vertical,which will definitely increase the shear force exerting on the lumbosacral region,and this is believed to accelerate the degeneration of L5/S1 intervertebral disc.There are numerous factors that are able to accelerate the progress of isthmic spondylolisthesis,and lots of researchs have demonstrated that there is a close relationship between the degree of lumbar intervertebral disc degeneration and the slipping rate of lumbar spondylolisthesis,and many scholars believe the degeneration of lumbar intervertebral disc is likely to be one of the cuases that accelerate the progress of L5 isthmic spondylolisthesis,and some scholars move forward a step to demonstrate that the severe degree of spondylolisthesis can have an impact on the morphology of spine.In recent years,it draws more and more attention that many scholars try to explain the progress of lumbar spondylolisthesis from the angle of spino-pelvic sagittal parameters,but many scholars debate on this controversial mechanism and till to now there is no a theory that convinces all scholars.This research makeS efforts to explore the interaction effect of spino-pelvic sagittal parameters and the progress of L5 isthmic spondylolisthesis by analyzing the relationship of spino-pelvic sagittal parameters、the slipping degree of L5 isthmic spondylolisthesis and the degree of L5/S1 intervertebral disc degeneration.Objective1.To investigate the relationship of spino-pelvic sagittal parameters、the slipping degree of L5 isthmic spondylolisthesis and the degenerating degree of L5/S1 intervertebral disc.2.To explore the interaction effect of spino-pelvic sagittal parameters and the progress of L5 isthmic spondylolisthesis by.Method1.Selection of analyzed objects.From September 2013 to September 2017,83 patients diagnosed with L5 isthmic spondylolisthesis were included in this study.Imaging materials include standing lumbar X-ray(front position、lateral position and bilateral oblique position are all required)and sagittal lumbar MRI.The inclusion criteria include:(1)patient age must be greater than 20 years old:(2)patients who must be diagnosed with L5 isthmic spondylolisthesis definitely,and both lateral isthmic spondylolisthesis and bilateral isthmic spondylolisthesis are included;(3)patients who do not have spinal history of surgery preciously.The exclusion criteria include:(1)patients who do not have all imaging materials we need,such as those do not have lumbar lateral X ray、those whose lumbar X ray do not contain bilateral femural heads、those who do not have lumbar lateral MRI and so on;(2)patients who were diagnosed with other lumbar degenerative diseases,such as spondylolisthesis in other lumbar segments、scoliosis and so on;(3)patients who were diagnosed with degenerative L5 spondylolisthesis or those were diagnosed with traumatic L5 spondylolisthesis;(4)patients who do not have other essential data,such as weight、specific age and so on.Ultimately,83 patients who meeted all the criterias above were included into this research.Among these 83 patients,the average age is 51.75±11.05 ranging from 21～79 years old,and the average weight is 62.15±9.97 ranging from 43～91kg.There are 30 males and 53 females.2.Measurement of parameters.Both spinal sagittal parameters and pelvis sagittal parameters were measured on the standing lateral lumbar X ray,and we needed to measure these parameters below:(1)pelvic incidence(PI):the included angle of the straight line which connects the middle point of the S1 upper endplate and the middle point of two femur heads and the vertical line of the S1 upper endplate;(2)lumbar lordosis(LL):the included angle of the vertical line of L1 upper endplate and the S1 upper endplate;(3)slipping rate of L5 vertebrae(SR):the ratio of the sagittal distance that L5 vertebrae slipped to the sagittal length of the S1 upper endplate.The degree of L5/S1 intervertebral discs degeneration was assessed on the lateral lumbar MRI by using the modified Pfirrmann disc grading system.In detail 2 surgeons of spine department of orthopedics from our hospital assessed the the degree of L5/S1 intervertebral discs degeneration on the lateral lumbar T2 weighted MRI in the PACS(picture archiving and communication systemsp,PACS),which contains patients imaging information,by by using the modified Pfirrmann disc grading system.According the grade,these two surgeons gave a corresponding score,such as 1 score means grade Ⅰ and 8 scores means grade Ⅷ.This makes sure that patients with high scores has severe degenerated L5/S1 intervertebral disc.3.Grouping of analyzed objects.In this research,we divided respectively patients into several groups according their own pelvic incidence、the modified Pfirrmann grade of L5/S1 intervertebral disc and the slipping rate of L5 vertebrae.In detail,we divided all patients into three groups according their pelvic incidence,low PI group(pelvic incidence<45°)、normal PI group(45°<pelvic incidence<60°)and high PI group(pelvic incidence>60°),based on the classifying criteria of SDSG(Spinal Deformity Study Group,SDSG)and then we compared and analyzed the difference of the degenerated degree of L5/S1 intervertebral disc、the slipping rate of L5 vertebrae and lumbar lordosis among these three groups;then we divided all the patients with normal pelvic incidence into low slipping rate group(with slipping rate<25%)and moderate slipping rate group(with 25%<slipping rate<50%)and compared and analyzed the difference of lumbar lordosis between these two groups(in this classification,there were no patients with severe slipping rates,so we did not compare severe slipping rate group to other two groups);in the final we divided all the patients with normal pelvic incidence group into moderate disc degeneration group(with modified Pfirrmann grade 4 or grade 5)、lowly severe disc degeneration group(with modified Pfirrmann grade 6)and highly severe disc degeneration group(with modified Pfirrmann grade 7 or grade 8)and compared and analyzed the difference of lumbar lordosis and slipping rate among these three groups(in this classification,there were not patients with highly normal or lowly degenerated disc,so we did not compare these patients to other two groups).4.Methods of analysis and statisticsAll statistics data in this research were analyzed using software SPSS 20.0.We used one way ANOVA(one way analysis of variance,ANOVA)to conduct the test of significance among three groups data and we used LSD(least significant difference,LSD)method or Tamhane method to compare the mutual difference of two group among three groups.We used independent t test to compare the difference of two groups.In terms of the test level,in this research p<0.05 means that the difference is significant.Result1.Basic statistics of all objects.From September 2013 to September 2017,there are 94 patients diagnosed with L5 isthmic spondylolisthesis,but 11 patients of them met the exclusin criteria and we excluded these patients.Finally,among these 83 patients,the average age is 51.75±11.05 ranging from 21～79 years old,and the average weight is 62.15±9.97 ranging from 43～91kg.There are 30 males and 53 females.2.Differences based on pelvic incidence.We divided all patients into three groups according their pelvic incidence,low PI group(pelvic incidence<45°、group A)、normal PI group(45°<pelvic incidence<60°、group B)and high PI group(pelvic incidence>60°、group C),based on the classifying criteria of SDSG(Spinal Deformity Study Group,SDSG)and then we compared and analyzed the difference of the degenerated degree of L5/S1 intervertebral disc、the slipping rate of L5 vertebrae and lumbar lordosis among these three groups.Ultimately there are no significant difference on the weight and age among group A、group B and group C(p>0.05).The degree of L5/S1 intervertebral disc degeneration in group C is more severe than both that of group A and group B significantly(p<0.05)and the degree of L5/S1 intervertebral disc degeneration in group B is more severe than that of group A significantly(p<0.05).The lumbar lordosis in group C is greater than both that of group A and group B significantly(p<0.05)and the lumbar lordosis in group B is greater than that of group A significantly(p<0.05).In terms of the slipping rate,there is an significant difference on the slipping rate between group C and group A,the slipping rate of group C is greater than that of group A(p<0.05).The average slipping rate of group B is slightly greater than that of group A but there is no significant between group A and B(p>0.05).3.Differences based on the degree of L5/S1 disc degeneration.We divided all the patients with normal pelvic incidence into moderate disc degeneration group(with modified Pfirrmann grade 4 or grade 5,group A)、lowly severe disc degeneration group(with modified Pfirrmann grade 6,group B)and highly severe disc degeneration group(with modified Pfirrmann grade 7 or grade 8,group C)and compared and analyzed the difference of lumbar lordosis and slipping rate among these three groups(in this classification,there were no patients with highly normal or lowly degenerated disc,so we did not compare these patients to other two groups).Ultimately there are no significant difference on the weight and age among group A、group B and group C(p>0.05).In terms of the slipping rate,there is an significant difference between group C and group A,and the slipping rate of group C is greater than that of group A(p<0.05).The average slipping rate of group B is slightly greater than that of group A but there is no significant between group A and B(p>0.05).The lumbar lordosis of group C is significantly smaller than both group B and group A(p<0.05),and after comparison we found there is no significant difference on the lumbar lordosis between group B and group A(p>0.05).4.Differences based on the sliping rate.Finally we divided all the patients with normal pelvic incidence into low slipping rate group(with slipping rate<25%,group A)and moderate slipping rate group(with 25%<slipping rate<50%,group B)and compared and analyzed the difference of lumbar lordosis between these two groups(in this classification,there were not patients with severe slipping rates,so we did not compare severe slipping rate group to other two groups).Through one way ANOVA,we found ultimately there are no significant difference on the weight and age among group A and group(p>0.05).Through independent t test,we found the average lumbar lordosis of group B is slightly greater than that of group A but there is no significant difference between these two group.ConclusionIn case of L5 isthmic spondylolisthesis,pelvic incidence is closely associated with the morphology of lumbar segment、the degree of L5/S1 intervertebral disc degeneration and the slipping rate of L5 vertebrae respectively.In detail,pelvic incidence has an impact on the progress of L5 isthmic spondylolisthesis,which can not be neglected,and the degeneration of L5/S1 intervertebral disc in patients with L5 isthmic spondylolisthesis may be another risk factor that accelerating the progress of L5 isthmic spondylolisthesis.When it comes to the influence of severe degenerated L5/S1 intervertebral disc on the lumbar segment,we found that the severe degenerated L5/S1 intervertebral disc may transform the morphology of the lumbar segment and lead to back rotation of pelvis,which presents on the loss of lumbar lordosis angle and the horizontal tendency of S1 endplate.In addition,there may be no significant difference of L5 vertebrae slipping rate on the lumbar lordosis in the patients with slight or moderate L5 isthmic spondylolisthesis. |
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