脊髓损伤后的骨脆弱性：远端股骨和近端胫骨的刚度和骨矿物质减少与时间的关系。
Bone fragility after spinal cord injury: reductions in stiffness and bone mineral at the distal femur and proximal tibia as a function of time.
机构信息
Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, T2N 1N4, USA.
McCaig Institute for Bone and Joint Health, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 1N4, USA.
出版信息
Osteoporos Int. 2018 Dec;29(12):2703-2715. doi: 10.1007/s00198-018-4733-0. Epub 2018 Oct 17.
UNLABELLED
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 (R = 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).
目的
使用计算机断层扫描和有限元建模来评估脊髓损伤后膝关节的骨结构随时间的变化。分析区域的刚度、矿物质密度和含量均出现下降。这些变化可以很好地描述为随时间的指数衰减，在损伤后 3.5 年达到稳定状态。
简介
脊髓损伤（SCI）与膝关节周围的骨脆弱和骨折风险增加有关。本研究的目的是使用有限元（FE）和计算机断层扫描（CT）测量来研究股骨远端和胫骨近端的骨刚度和矿物质含量。采用横截面设计比较了非卧床 SCI 患者随损伤后时间（0-50 年）的差异。
方法
从 101 名 SCI 患者中获得膝关节 CT 扫描，这些患者在参与研究前 30 天至 50 年内发生了 SCI。使用个体特定的 FE 模型来估计轴向压缩和扭转加载下的刚度，并对 CT 数据进行分析，以评估股骨远端和胫骨近端骨骺、骨干和干骺端区域的整体、皮质和小梁容积骨矿物质密度（vBMD）和骨矿物质含量（BMC）。
结果
骨降解可以很好地描述为随时间的指数衰减（R=0.33-0.83），在 SCI 后 3.6 年内达到稳定水平。与近期受伤的患者（t≤47 天）相比，处于稳定状态的患者的 FE 衍生骨刚度降低 40%至 85%，CT 矿物质测量值也大幅下降。股骨远端和胫骨近端的骨丢失的时空模式相似。
结论
SCI 后，膝关节的骨刚度和骨矿物质迅速而显著地降低。FE 模型预测轴向和扭转刚度相似的降低，表明这两种失效模式可能具有临床相关性。重要的是，与 FE 衍生的刚度测量值相比，CT 衍生的骨矿物质测量值单独预测 SCI 的影响不足。
试验注册
ClinicalTrials.gov（NCT01225055，NCT02325414）。
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