ABSTRACT
BACKGROUND: Sagittal imbalance makes significant effect on spinal biomechanics, and choosing osteotomy for ankylosing spondylitis depends on its biomechanics characteristics. OBJECTIVE: To establish a three-dimensional (3D) finite element model of kyphosis in ankylosing spondylitis treated by osteotomy on software, and to analyze its biomechanical properties, thus providing theoretical basis for clinical practice. METHODS: A 3D finite element model of kyphosis in ankylosing spondylitis was established based on CT data, and the predetermined angle of the osteotomy at L2was measured. Afterwards, vertebral column decancellation and vertebral column resection were stimulated, and then the biomechanical parameters were analyzed. RESULTS AND CONCLUSION: (1) The 3D finite element models of kyphosis in ankylosing spondylitis treated by vertebral column decancellation or vertebral column resection at L2were established successfully. (2) Finite element analysis on Ansys workbench 15.0 showed that the vertebral column decancellation (948 874, 1 564 477 nodes) and vertebral column resection (931 969, 1 548 812 nodes) were meshed and analyzed by 10-node tetrahedron solid element. (3) After loaded, the stress values of the vertebral column decancellation were higher than those of vertebral column resection; the equivalent stress on the screw was 40.946, 67.26, 493.64, 304.05, 75.359, and 146.31 MPa; the equivalent stress on the titanium rob was 391.01 MPa. (4) These results suggest that both two methods can reconstruct the sagittal balance, but vertebral column decancellation exhibits significantly higher stress values. Indeed, the incidence of internal fixation failure and complications in vertebral column decancellation is higher than that in vertebral column resection at the same segment and angle.
ABSTRACT
BACKGROUND: Kyphosis in ankylosing spondylitis is a kind of spinal sagittal imbalance; due to center of gravity displaced and complicated biomechanical properties of the spine, the spinal biomechanics after kyphosis correction is little reported. OBJECTIVE: To establish a three-dimensional finite element model of the spine after osteotomy for kyphosis. METHODS: A three-dimensional finite element model of kyphosis in ankylosing spondylitis was established, simulating three kinds of osteotomy orthopedic programs (osteotomy angle in 20°, 30° and 40°), and the orthopedic effect and biomechanics were analyzed.RESULTS AND CONCLUSION: (1) The three-dimensional finite element model of finite element model of kyphosis in ankylosing spondylitis was established successfully, and simulated three kinds of osteotomy orthopedic programs at the angles of 20°, 30°, and 40°. (2) The best osteotomy angle was 30°, the stress distribution was less, and the stress on the T12, L1, L2, L4, L5, S1and rod was 7.346 1, 11.952, 72.783, 81.368, 28.144, 41.114, and 109.69 MPa, respectively. (3) Under 30°osteotomy angle, the postoperative Cobb angle is 1.4°, which not only obtains better orthopedic effect, but also reduces the incidence of complications caused by stress concentration.