title: Bone microarchitecture in ankylosing spondylitis and the association with bone mineral density, fractures, and syndesmophytes.
abstract: BACKGROUND
  Osteoporosis of the axial skeleton is a known complication of ankylosing spondylitis (AS), but bone loss affecting the peripheral skeleton is less studied. This study on volumetric bone mineral density (vBMD) and bone microarchitecture in AS was conducted to compare peripheral vBMD in AS patients with that in healthy controls, to study vBMD in axial compared with peripheral bone, and to explore the relation between vertebral fractures, spinal osteoproliferation, and peripheral bone microarchitecture and density.
  
  
  METHODS
  High-resolution peripheral quantitative computed tomography (HRpQCT) of ultradistal radius and tibia and QCT and dual-energy x-ray absorptiometry (DXA) of lumbar spine were performed in 69 male AS patients (NY criteria). Spinal radiographs were assessed for vertebral fractures and syndesmophyte formation (mSASSS). The HRpQCT measurements were compared with the measurements of healthy controls.
  
  
  RESULTS
  The AS patients had lower cortical vBMD in radius (P = 0.004) and lower trabecular vBMD in tibia (P = 0.033), than did the controls. Strong correlations were found between trabecular vBMD in lumbar spine, radius (rS = 0.762; P < 0.001), and tibia (rS = 0.712; P < 0.001). When compared with age-matched AS controls, patients with vertebral fractures had lower lumbar cortical vBMD (-22%; P = 0.019), lower cortical cross-sectional area in radius (-28.3%; P = 0.001) and tibia (-24.0%; P = 0.013), and thinner cortical bone in radius (-28.3%; P = 0.001) and tibia (-26.9%; P = 0.016). mSASSS correlated negatively with trabecular vBMD in lumbar spine (rS = -0.620; P < 0.001), radius (rS = -0.400; p = 0.001) and tibia (rS = -0.475; p < 0.001) and also with trabecular thickness in radius (rS = -0.528; P < 0.001) and tibia (rS = -0.488; P < 0.001). Adjusted for age, syndesmophytes were significantly associated with decreasing trabecular vBMD, but increasing cortical vBMD in lumbar spine, but not with increasing cortical thickness or density in peripheral bone. Estimated lumbar vBMD by DXA correlated with trabecular vBMD measured by QCT (rS = 0.636; P < 0.001).
  
  
  CONCLUSIONS
  Lumbar osteoporosis, syndesmophytes, and vertebral fractures were associated with both lower vBMD and deteriorated microarchitecture in peripheral bone. The results indicate that trabecular bone loss is general, whereas osteoproliferation is local in AS.
authors: Eva
authors: E
authors: Klingberg
authors: Mattias
authors: M
authors: Lorentzon
authors: Jan
authors: J
authors: Göthlin
authors: Dan
authors: D
authors: Mellström
authors: Mats
authors: M
authors: Geijer
authors: Claes
authors: C
authors: Ohlsson
authors: Elizabeth J
authors: EJ
authors: Atkinson
authors: Sundeep
authors: S
authors: Khosla
authors: Hans
authors: H
authors: Carlsten
authors: Helena
authors: H
authors: Forsblad-d'Elia
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D000368:Aged; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011884:Radius / Q000000981:diagnostic imaging; D016103:Spinal Fractures / Q000000981:diagnostic imaging*; D013167:Spondylitis, Ankylosing / Q000150:complications / Q000000981:diagnostic imaging*; D013977:Tibia / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D055815:Young Adult