title: Lumbar disc degeneration was not related to spine and hip bone mineral densities in Chinese: facet joint osteoarthritis may confound the association.
abstract: A sample of 512 Chinese was studied and we observed that greater disc degeneration on MRI was associated with greater spine DXA BMD. Yet, this association may be confounded by facet joint osteoarthritis. BMD may not be a risk factor for lumbar disc degeneration in Chinese.
  
  
  OBJECTIVE
  Evidence suggested that lumbar vertebral bone and intervertebral disc interact with each other in multiple ways. The current paper aims to determine the association between bone mineral density (BMD) and lumbar disc degeneration using a sample of Chinese.
  
  
  METHODS
  We studied 165 patients with back disorders and 347 general subjects from China. All subjects had lumbar spine magnetic resonance (MR) imaging and dual- energy X-ray absorptiometry (DXA) spine BMD studies, and a subset of general subjects 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
  Greater facet joint osteoarthritis was associated with greater spine BMD (P < 0.01) in both patients and general subjects. For general subjects, greater spine BMD was associated with severe disc degeneration, 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Spine lab, Department of Orthopedic Surgery, The First Affiliated Hospital of Zhejiang University, 79# Qingchun Road, Hangzhou, 310003, China.
authors.forename: Jianjiang
authors.initials: J
authors.lastname: Pan
authors.affiliation: Spine lab, Department of Orthopedic Surgery, The First Affiliated Hospital of Zhejiang University, 79# Qingchun Road, Hangzhou, 310003, China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Lu
authors.affiliation: Spine lab, Department of Orthopedic Surgery, The First Affiliated Hospital of Zhejiang University, 79# Qingchun Road, Hangzhou, 310003, China.
authors.forename: Ge
authors.initials: G
authors.lastname: Yang
authors.affiliation: Healthcare center, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, 310020, China.
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Han
authors.affiliation: Spine lab, Department of Orthopedic Surgery, The First Affiliated Hospital of Zhejiang University, 79# Qingchun Road, Hangzhou, 310003, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Tong
authors.affiliation: Spine lab, Department of Orthopedic Surgery, The First Affiliated Hospital of Zhejiang University, 79# Qingchun Road, Hangzhou, 310003, China. wangyuespine@gmail.com.
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D000368:Aged; D015519:Bone Density; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000473:pathology; D055959:Intervertebral Disc Degeneration / Q000175:diagnosis / Q000453:epidemiology / Q000473:pathology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000175:diagnosis / Q000453:epidemiology / Q000473:pathology; D010384:Pelvic Bones / Q000000981:diagnostic imaging / Q000473:pathology; D011859:Radiography / Q000379:methods; D012044:Regression Analysis; D021801:Zygapophyseal Joint / Q000000981:diagnostic imaging / Q000473:pathology
keywords: Bone mineral density; Disc degeneration; Facet joint osteoarthritis; Lumbar spine