Albert Carolyne, Jameson John, Smith Peter, Harris Gerald
Shriners Hospitals for Children-Chicago, Chicago, IL, USA; Department of Biomedical Engineering, Marquette University, Orthopaedic and Rehabilitation Engineering Center (OREC), Milwaukee, WI, USA.
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA; Department of Biomedical Engineering, Marquette University, Orthopaedic and Rehabilitation Engineering Center (OREC), Milwaukee, WI, USA.
Bone. 2014 Sep;66:121-30. doi: 10.1016/j.bone.2014.05.022. Epub 2014 Jun 11.
Osteogenesis imperfecta is a genetic disorder resulting in bone fragility. The mechanisms behind this fragility are not well understood. In addition to characteristic bone mass deficiencies, research suggests that bone material properties are compromised in individuals with this disorder. However, little data exists regarding bone properties beyond the microstructural scale in individuals with this disorder. Specimens were obtained from long bone diaphyses of nine children with osteogenesis imperfecta during routine osteotomy procedures. Small rectangular beams, oriented longitudinally and transversely to the diaphyseal axis, were machined from these specimens and elastic modulus, yield strength, and maximum strength were measured in three-point bending. Intracortical vascular porosity, bone volume fraction, osteocyte lacuna density, and volumetric tissue mineral density were determined by synchrotron micro-computed tomography, and relationships among these mechanical properties and structural parameters were explored. Modulus and strength were on average 64-68% lower in the transverse vs. longitudinal beams (P<0.001, linear mixed model). Vascular porosity ranged between 3 and 42% of total bone volume. Longitudinal properties were associated negatively with porosity (P≤0.006, linear regressions). Mechanical properties, however, were not associated with osteocyte lacuna density or volumetric tissue mineral density (P≥0.167). Bone properties and structural parameters were not associated significantly with donor age (P≥0.225, linear mixed models). This study presents novel data regarding bone material strength in children with osteogenesis imperfecta. Results confirm that these properties are anisotropic. Elevated vascular porosity was observed in most specimens, and this parameter was associated with reduced bone material strength. These results offer insight toward understanding bone fragility and the role of intracortical porosity on the strength of bone tissue in children with osteogenesis imperfecta.
成骨不全症是一种导致骨骼脆弱的遗传性疾病。这种脆弱背后的机制尚未完全了解。除了典型的骨量不足外，研究表明患有这种疾病的个体的骨材料特性也受到损害。然而，关于患有这种疾病的个体在微观结构尺度之外的骨特性的数据很少。在常规截骨手术过程中，从9名成骨不全症儿童的长骨干骺端获取标本。从这些标本中加工出纵向和横向于骨干轴的小矩形梁，并在三点弯曲中测量弹性模量、屈服强度和最大强度。通过同步加速器微计算机断层扫描确定皮质内血管孔隙率、骨体积分数、骨细胞陷窝密度和体积组织矿物质密度，并探索这些力学性能与结构参数之间的关系。横向梁的模量和强度平均比纵向梁低64 - 68%（P<0.001，线性混合模型）。血管孔隙率占总骨体积的3%至42%。纵向性能与孔隙率呈负相关（P≤0.006，线性回归）。然而，力学性能与骨细胞陷窝密度或体积组织矿物质密度无关（P≥0.167）。骨特性和结构参数与供体年龄无显著相关性（P≥0.225，线性混合模型）。本研究提供了关于成骨不全症儿童骨材料强度的新数据。结果证实这些特性是各向异性的。在大多数标本中观察到血管孔隙率升高，并且该参数与骨材料强度降低有关。这些结果有助于理解骨脆弱性以及皮质内孔隙率对成骨不全症儿童骨组织强度的作用。
