TY - JOUR
T1 - Bone fragility after spinal cord injury
T2 - reductions in stiffness and bone mineral at the distal femur and proximal tibia as a function of time
AU - Haider, I. T.
AU - Lobos, S. M.
AU - Simonian, N.
AU - Schnitzer, T. J.
AU - Edwards, W. B.
N1 - Funding Information:
Funding information This research was supported by Department of Defense U.S. Army Medical Research and Materiel Command (Grant Numbers SC090010 and SC130125). REDCap is supported at FSM by the Northwestern University Clinical and Translational Science (NUCATS) Institute. Research reported in this publication was also supported, in part, by the National Institutes of Health’s National Center for Advancing Translational Sciences (Grant Numbers UL1TR001422 and UL1TR000150). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
PY - 2018/12/1
Y1 - 2018/12/1
N2 - Summary: Computed tomography and finite element modeling were used to assess bone structure at the knee as a function of time after spinal cord injury. Analyzed regions experienced degradation in stiffness, mineral density, and content. Changes were well described as an exponential decay over time, reaching a steady state 3.5 years after injury. Introduction: Spinal cord injury (SCI) is associated with bone fragility and an increased risk of fracture around the knee. The purpose of this study was to investigate bone stiffness and mineral content at the distal femur and proximal tibia, using finite element (FE) and computed tomography (CT) measures. A cross-sectional design was used to compare differences between non-ambulatory individuals with SCI as a function of time after injury (0–50 years). Methods: CT scans of the knee were obtained from 101 individuals who experienced an SCI 30 days to 50 years prior to participation. Subject-specific FE models were used to estimate stiffness under axial compression and torsional loading, and CT data was analyzed to assess volumetric bone mineral density (vBMD) and bone mineral content (BMC) for integral, cortical, and trabecular compartments of the epiphyseal, metaphyseal, and diaphyseal regions of the distal femur and proximal tibia. Results: Bone degradation was well described as an exponential decay over time (R2 = 0.33–0.83), reaching steady-state levels within 3.6 years of SCI. Individuals at a steady state had 40 to 85% lower FE-derived bone stiffness and robust decreases in CT mineral measures, compared to individuals who were recently injured (t ≤ 47 days). Temporal and spatial patterns of bone loss were similar between the distal femur and proximal tibia. Conclusions: After SCI, individuals experienced rapid and profound reductions in bone stiffness and bone mineral at the knee. FE models predicted similar reductions to axial and torsional stiffness, suggesting that both failure modes may be clinically relevant. Importantly, CT-derived measures of bone mineral alone underpredicted the impacts of SCI, compared to FE-derived measures of stiffness. Trial registration: ClinicalTrials.gov (NCT01225055, NCT02325414).
AB - Summary: Computed tomography and finite element modeling were used to assess bone structure at the knee as a function of time after spinal cord injury. Analyzed regions experienced degradation in stiffness, mineral density, and content. Changes were well described as an exponential decay over time, reaching a steady state 3.5 years after injury. Introduction: Spinal cord injury (SCI) is associated with bone fragility and an increased risk of fracture around the knee. The purpose of this study was to investigate bone stiffness and mineral content at the distal femur and proximal tibia, using finite element (FE) and computed tomography (CT) measures. A cross-sectional design was used to compare differences between non-ambulatory individuals with SCI as a function of time after injury (0–50 years). Methods: CT scans of the knee were obtained from 101 individuals who experienced an SCI 30 days to 50 years prior to participation. Subject-specific FE models were used to estimate stiffness under axial compression and torsional loading, and CT data was analyzed to assess volumetric bone mineral density (vBMD) and bone mineral content (BMC) for integral, cortical, and trabecular compartments of the epiphyseal, metaphyseal, and diaphyseal regions of the distal femur and proximal tibia. Results: Bone degradation was well described as an exponential decay over time (R2 = 0.33–0.83), reaching steady-state levels within 3.6 years of SCI. Individuals at a steady state had 40 to 85% lower FE-derived bone stiffness and robust decreases in CT mineral measures, compared to individuals who were recently injured (t ≤ 47 days). Temporal and spatial patterns of bone loss were similar between the distal femur and proximal tibia. Conclusions: After SCI, individuals experienced rapid and profound reductions in bone stiffness and bone mineral at the knee. FE models predicted similar reductions to axial and torsional stiffness, suggesting that both failure modes may be clinically relevant. Importantly, CT-derived measures of bone mineral alone underpredicted the impacts of SCI, compared to FE-derived measures of stiffness. Trial registration: ClinicalTrials.gov (NCT01225055, NCT02325414).
KW - CT imaging
KW - Finite element modeling
KW - Osteoporosis
KW - Spinal cord injury
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U2 - 10.1007/s00198-018-4733-0
DO - 10.1007/s00198-018-4733-0
M3 - Article
C2 - 30334093
AN - SCOPUS:85055450418
VL - 29
SP - 2703
EP - 2715
JO - Osteoporosis International
JF - Osteoporosis International
SN - 0937-941X
IS - 12
ER -