Biomechanical And Imaging Study Of Lumbar Vertebral Cancellous Bone

Objective:The lumbar vertebral body is primarily composed of cancellous bone,and its density can indicate the strength and stiffness of the bone.In this experiment,we measured the strain values before and after removing the cancellous bone from the middle layer of the vertebral body using electrical resistance strain gauges,to investigate the role of cancellous bone in bearing compression load and its effect on stress transmission.Additionally,we measured the cancellous bone mineral density and analyzed its correlation with lumbar mechanics data,establishing a link between cancellous bone density and mechanical properties.Understanding the distribution of stress within the cancellous bone in the vertebral body is crucial for guiding treatment of vertebral fractures and improving treatment outcomes.Methods:1.Biomechanical Research:Fifteen lumbar spine specimens were dissected to obtain the fifth lumbar spine specimens,and the soft tissue on the surface was removed.To measure the strain values,16 strain gauges were placed near the pedicle,the surface of the vertebral body,and the upper and lower articular processes.The bonding site was cleaned and a moisture barrier was applied using paraffin before applying the strain gauge with adhesive.The wire and lead were welded and connected with the strain gauge.The specimen was fixed on a self-made fixture,connected to a biomechanical testing machine,and loaded with a vertical force of 5N/S to 400 N from the top of the vertebral body.Strain changes were recorded by strain gauge,and the overall displacement of the lumbar spine was recorded at 50 N,100N,150 N,200N,250 N,300N,350 N,and 400 N by the biomechanical testing machine.Each sample was tested three times,and the average value was taken.The bone trabecula in the middle layer of the vertebral body was destroyed(at a height of 0.5cm),and the test steps were repeated to record the data.2.Imaging Research:All lumbar spine specimens underwent Q-CT examination.A region of interest(ROI)was selected and placed in the center of the middle layer of the vertebral body,with an area of 31 mm * 19 mm and a layer thickness of 5mm.The ROI included cancellous bone as much as possible,avoiding bone island,proliferative bone,and central vein at the back of the vertebral body.The correlation between vertebral bone density and the overall displacement data of the lumbar spine before and after the destruction of cancellous bone was analyzed.3.Statistical methodsPerform normality tests(Kolmogorov Smirnov test)and homogeneity of variance tests(Levene’s test)on strain and lumbar global displacement data at all sites,and perform paired t-tests on data that both follow normality(P>0.1)and homogeneity of variance(P>0.1).Wilcoxon signed rank test is performed on data that do not obey the normal distribution.Analyze using SPSS 26.0statistical software and plot using Graphpad Prism 8.0.2.The data with normal distribution is mean ± SD,the data with non normal distribution is median and quartile,and the test level is taken as α= 0.05,when P<0.05,it is considered that there is a significant difference before and after.Perform normality testing on BMD data,and perform Pearson correlation analysis on data that follows normality(P>0.1).The rank correlation analysis was performed on the data that did not obey the normal distribution.Analyze using SPSS 26.0 statistical software and plot using Graphpad Prism 8.0.2.When P<0.05,it is considered that BMD is correlated with the overall displacement of the lumbar spine.Results:1.After damaging the middle cancellous bone of the vertebral body,the overall displacement of the lumbar vertebrae increases.Under vertical loads of 50 N,100 N,150 N,200 N,250 N,300 N,350 N,and 400 N,the overall displacement of the lumbar vertebrae after damaging the middle cancellous bone is significantly greater than before(P<0.05).2.Under vertical compressive loads,the strain distribution on the surface of the intact lumbar vertebrae is relatively uniform.On the intact vertebral body,the strain values at positions 2,3,4,5,6,8,9,10,11,and 12 are relatively high,while positions 1,7,13,14,15,and 16 have relatively low strain values.After damaging the middle cancellous bone,the strain values at positions above the damaged layer are similar,including positions 2,3,4,5,and 6;the strain values at positions below the damaged layer are also similar,including positions 8,9,10,11,and 12.The mean strain value of positions above the damaged layer is greater than that below.3.After damaging the middle cancellous bone of the vertebral body,the strain values at some positions increase.The positions where the strain values increased significantly after damaging the middle cancellous bone are 2,3,4,5,6,and 11(P<0.05),with positions 2,3,4,5,and 6 being above the damaged layer.4.The density of the middle cancellous bone in the vertebral body is correlated with the overall displacement of the lumbar vertebrae.When the vertical load is 400 N,there is a negative correlation between the overall displacement value of the anterior lumbar spine and the BMD of the cancellous bone in the middle layer of the vertebral body(R=-0.857,P<0.05).The overall displacement of the lumbar spine after destruction of the cancellous bone in the middle layer of the vertebral body was negatively correlated with BMD of the cancellous bone in the middle layer of the vertebral body(R=-0.885,P<0.05).Conclusions:1.When an external force is applied to the vertebral body,the strain distribution on the surface of the vertebral body tends to be uniform.2.Cancellous bone is crucial in the process of resisting external forces on the vertebral body.The reduction of cancellous bone within the vertebral body can lead to a change in strain distribution within the vertebral body,with a larger strain change occurring above the destruction layer than below it.3.Loss of cancellous bone can result in an increase in overall displacement of the vertebral body under vertical load.4.Cancellous bone mineral density within the vertebral body is negatively correlated with its biomechanical properties.Greater bone density leads to greater vertebral body strength and reduced overall displacement under stress.