The Association Between Bone Mineral Density And Disc Degeneration In The Lumbar Spine In Chinese

It is well documented that osteoarthritis is associated with greater bone mineral density(BMD)in peripheral extremities.Yet the relationship between BMD and disc degeneration remains controversial in the lumbar spine.Many studies reported that greater BMD was associated with greater degree of disc degeneration,though some others did not observe such a relation.Factors underlying the inconsistency mainly include differences in study populations,measures of BMD and disc degeneration,and adjustment for vertebral hypertrophic changes such as facet joint degeneration,osteophytes,and endplate sclerosis.Clarifying the relation between the vertebral BMD and disc degeneration will contribute to a better understanding of the local interaction between bone and disc and corresponding pathologies in the lumbar spine.Aims:The current paper aims to determine the association between bone mineral density(BMD)and disc degeneration in the lumbar spine in Chinese.Methods:Subjects were recruited from January of 2012 to September of 2015 in Hangzhou,a city in Eastern China,through three approaches.There were 165 patients with various degenerative lumbar spine disorders,161 customers of health assessment,and 186 randomly selected community volunteers.All subjects had lumbar spine magnetic resonance(MR)imaging and dual-energy X-ray absorptiometry(DXA)spine BMD studies,and community volunteers had additional hip BMD measurements.On T2-weighted MR images,Pfirrmann score was used to evaluate the degree of lumbar disc degeneration and facet joint osteoarthritis was assessed as none(?),slight-moderate(?),and severe(?).Regression analyses were used to examine the associations between lumbar and hip BMD and disc degeneration,adjusting for age,gender,body mass index(BMI),lumbar region,and facet joint osteoarthritis.Results:In total,512 subjects were recruited in the current study.There are 165 patients of various degenerative lumbar spine disorders(30 men,135 women,age 69.9±8.7 years,range 47-102 years),161 customers who underwent health assessment(117 men,44 women,age 48.8±8.6 years,range 31-76 years),and 186 randomly selected community volunteers(109 men,77 women,age 50.8±15.5 years,range 24-87 years).There was nodifference in demographic features between those customers who underwent health assessment and community volunteers thus,data were merged for analysis.For all subjects,greater age was associated with severe disc degeneration and severe facet joint osteoarthritis(P<0.01 for both).Greater disc degeneration was associated with greater facet joint osteoarthritis(P<0.01).For both patients and general subjects,greater age(P<0.01 for both)and less BMI(P<0.01 for both)were associated with less lumbar spine and femoral neck BMDs.For general subjects,greater spine BMD was associated with severe disc degeneration(Pfirrmann=5,P<0.05),controlling for age,gender,BMI,and lumbar region.When facet joint osteoarthritis entered the regression model,however,greater spine BMD was associated with greater facet joint osteoarthritis(P<0.01)but not greater disc degeneration(P>0.05).No statistical association was observed between spine BMD and lumbar disc degeneration in patients with back disorders(P>0.05),and between hip BMD and disc degeneration in general subjects(P>0.05).Conclusion:BMD may not be a risk factor for lumbar disc degeneration in Chinese.Facet joint osteoarthritis inflates DXA spine BMD measurements and therefore,may confound the association between spine BMD and disc degeneration.