TY - JOUR
T1 - Finite element modeling of temporal bone graft changes in XLIF
T2 - quantifying biomechanical effects at adjacent levels
AU - Ramakrishna, Vivek A. S.
AU - Chamoli, Uphar
AU - Larosa, Alessandro G.
AU - Mukhopadhyay, Subhas C.
AU - Prusty, B. Gangadhara
AU - Diwan, Ashish D.
PY - 2022/6
Y1 - 2022/6
N2 - Extreme lateral interbody fusion allows for the insertion of a large-footprint interbody cage while maintaining the presence of natural stabilizing ligaments and the facets. It is unclear how the load-distribution mechanisms through these structures alter with temporal changes in the bone graft. The aim of this study was to examine the effects of temporal bone graft changes on load distribution among the cage, graft, and surrounding spinal structures using finite element analysis. Thoracolumbosacral spine computed tomography data from an asymptomatic male subject were segmented into anatomical regions of interest and digitally stitched to generate a surface mesh of the lumbar spine (L1-S1). The interbody cage was inserted into the L4-L5 region during surface meshing. A volumetric mesh was generated and imported into finite element software for pre-processing, running nonlinear static solves, and post-processing. Temporal stiffening was simulated in the graft region with unbonded (Soft Callus, Temporal Stages 1–3, Solid Graft) and bonded (Partial Fusion, Full Fusion) contact. In flexion and extension, cage stress reduced by 20% from the soft callus to solid graft state. Force on the graft was directly related to its stiffness, and load-share between the cage and graft improved with increasing graft stiffness, regardless of whether contact was fused with the endplates. Fused contact between the cage-graft complex and the adjacent endplates shifted load-distribution pathways from the ligaments and facets to the implant, however, these changes did not extend to adjacent levels. These results suggest that once complete fusion is achieved, the existing load paths are seemingly diminished.
AB - Extreme lateral interbody fusion allows for the insertion of a large-footprint interbody cage while maintaining the presence of natural stabilizing ligaments and the facets. It is unclear how the load-distribution mechanisms through these structures alter with temporal changes in the bone graft. The aim of this study was to examine the effects of temporal bone graft changes on load distribution among the cage, graft, and surrounding spinal structures using finite element analysis. Thoracolumbosacral spine computed tomography data from an asymptomatic male subject were segmented into anatomical regions of interest and digitally stitched to generate a surface mesh of the lumbar spine (L1-S1). The interbody cage was inserted into the L4-L5 region during surface meshing. A volumetric mesh was generated and imported into finite element software for pre-processing, running nonlinear static solves, and post-processing. Temporal stiffening was simulated in the graft region with unbonded (Soft Callus, Temporal Stages 1–3, Solid Graft) and bonded (Partial Fusion, Full Fusion) contact. In flexion and extension, cage stress reduced by 20% from the soft callus to solid graft state. Force on the graft was directly related to its stiffness, and load-share between the cage and graft improved with increasing graft stiffness, regardless of whether contact was fused with the endplates. Fused contact between the cage-graft complex and the adjacent endplates shifted load-distribution pathways from the ligaments and facets to the implant, however, these changes did not extend to adjacent levels. These results suggest that once complete fusion is achieved, the existing load paths are seemingly diminished.
KW - degeneration
KW - finite element analysis
KW - fusion
KW - interbody cage
KW - lumbar
UR - http://www.scopus.com/inward/record.url?scp=85114194839&partnerID=8YFLogxK
U2 - 10.1002/jor.25166
DO - 10.1002/jor.25166
M3 - Article
C2 - 34432322
AN - SCOPUS:85114194839
SN - 1554-527X
VL - 40
SP - 1420
EP - 1435
JO - Journal of Orthopaedic Research
JF - Journal of Orthopaedic Research
IS - 6
ER -