| Objective In this study,quantitative computed tomography(QCT)was used as a tool to study the relationship between musculoskeletal system and adipose tissue.We measured the bone mineral density(BMD),fat content of liver and paravertebral muscles in subjects to investigate the correlation among them and the correlation with age and BMI.The purpose is to understand the trend of lumbar BMD and fat infiltration of paravertebral muscles in different liver fat content,in order to use QCT to monitor physical composition,find high-risk groups as soon as possible,improve people’s attention to chronic metabolic diseases,prevent and delay the occurrence of adverse events such as osteoporotic fractures.Methods A total of 646 subjects who underwent non-contrast abdominal CT examination in Qingdao Municipal Hospital affiliated to Qingdao University from December 2020 to January 2022.GE 256-row Revolution CT scanner was used for abdominal CT scanning.Subjects were placed in supine position and head advanced,the scanning range was from the top of the diaphragm to the lower margin of the lumbar 3 level.The CT reconstructed images with thickness of 1.25 mm were transmitted to Mindways QCT workstation,on which fat content of liver,lumbar vertebrae and paravertebral muscles(psoas,multifidus and erector spinae)were measured.Measurement method of fat content in liver: in the hepatic hilar region,the largest layer of the liver cross-section,we placed three interest areas of similar size in the right anterior lobe,right posterior lobe and left inner lobe respectively,avoiding intrahepatic bile ducts,blood vessels and gallbladder fossa as far as possible.Measurement method of lumbar BMD: adjusted the position of lumbar 1-3 and placed the region of interest in the bone cancellous area in the center of each vertebral body,avoiding the bone cortex and bone hyperplasia area.Measurement method of fat content in paravertebral muscles: in lumbar 3 level with clear muscle profile,placed six interest areas at bilateral psoas,multifidus and erector spinae,avoiding subcutaneous adipose tissue and muscle edges.The average of each position was taken as the final measurement value.In the classified variable data,two independent sample T-test was used for the normally distributed data,and Wilcoxon rank sum test was used for the non-normally distributed data.When comparing multiple data,one-way ANOVA was used for the data with normal distribution and homogeneity of variance,the data that did not obey normal distribution or homogeneity of variance were tested by Kruskal-Wallis H.Pearson correlation analysis was used between the data that followed normal distribution,Spearman correlation analysis was used between data that did not follow normal distribution,and we used partial correlation analysis to correct the age and BMI.Multiple stepwise regression was used to analyze the correlation between age,BMI,fat content of liver and paravertebral muscles and lumbar BMD.Results The group of non-alcoholic fatty liver disease had lower lumbar BMD and higher fat content of paravertebral muscles than normal group.People were divided into 4groups according to the fat content of liver,there were statistical significances in lumbar BMD and the fat content of psoas and erector spinae(P<0.05).People with higher liver fat content had lower BMD,and the fat content of paravertebral muscles showed an upward trend.After that,people were divided into 3 groups(normal bone mass group,bone mass reduction group and osteoporosis group)according to BMD,there were statistical significances in the fat content of psoas,multifidus and erector spinae(P<0.05).The fat content of paravertebral muscles was higher in the group with significantly decreased BMD of lumbar vertebrae.There were statistically significant differences in lumbar BMD,fat content of liver and paravertebral muscles among different age groups(P<0.05).With the increase of age,BMD of vertebral body decreased,while the fat content of liver and paravertebral muscles increased.The BMD of lumbar vertebrae was negatively correlated with fat content of liver(r=-0.101),psoas,multifidus and erector spinae(r=-0.332,-0.410,-0.430,P<0.05),and had the highest correlation with age(r=-0.720).After adjusting for age and BMI by partial correlation analysis,lumbar BMD was negatively correlated with fat content of liver(r=-0.104,P=0.008).The results of multiple stepwise regression analysis showed that fat content of liver was an independent impact factor of lumbar BMD after adjusting for age and BMI(P=0.008).And the regression equation was: Lumbar BMD=213.969-2.035× Age +1.159×BMI-0.608× Liver fat content.Conclusion 1.QCT can accuratel y evaluate the bone mass and fat content in different tissues and organs,and it is an important tool for clinical measurement of liver fat content and lumbar BMD.2.Lumbar BMD was different among groups with different liver fat content.A little fat deposited in liver had little effect on lumbar BMD,while lumbar BMD was significantl y decreased when a lot of fat was deposited in liver excessively.3.The fat content of paravertebral muscles was increased with lumbar BMD decreased,and the fat infiltration of multifidus muscle was the most significant.4.There was a weak negative correlation between lumbar BMD and liver fat content,and the negative correlation between lumbar BMD and fat content of paravertebral muscles were mainl y affected by age.5.There was no significant correlation between fat content of liver and paravertebral muscles,but liver fat content was positivel y correlated with BM I.6.Age,BMI and live r fat content were independent influencing factors of lumbar bone mineral densit y,which could explain 50.4% of changes in lumbar BMD. |
