1Vander Cruyssen B, Mu n oz-Gomafiz E, Font P. Hip involvement in ankylosing spondylitis: epidemiology and risk factors associated with hip replacement surgery [ J ] ." Rheumatology ( Oxford ), 2009,14 (6) : 1321-1327.
3Jun JB, Joo KB, Her MY, et al. Femoral bone mineral density is associated with vertebral fractures in patients with ankyiosing spon- dylitis : a cross-sectional study [J]. J Rheumato1,2006,33 (8) : 1637- 1641.