Julius Wolff Institute for Biomechanics and Musculoskeletal Regeneration, Charité-Universitätsmedizin Berlin, Campus-Virchow Klinikum, Augustenburger Platz 1, Institutsgebäude Süd, 13353 Berlin, Germany.
Eur Cell Mater. 2013 Jul 8;25:366-79; discussion 378-9. doi: 10.22203/ecm.v025a26.
Non-invasive assessment of fracture healing, both in clinical and animal studies, has gained favour as surrogate measure to estimate regain of mechanical function. Micro-computed tomography (µCT) parameters such as fracture callus volume and mineralisation have been used to estimate callus mechanical competence. However, no in-depth information has been reported on microstructural parameters in estimating callus mechanical competence. The goal of this study is to use differently conditioned mice exhibiting good and impaired fracture healing outcomes and investigate the relationship between µCT imaging parameters (volume, mineralisation, and microstructure) that best estimate the callus strength and stiffness as it develops over time. A total of 99 mice with femoral fracture and intramedullary stabilisation were divided into four groups according to conditioning: wild type, NF1 knock-out, RAG1 knock-out and macrophage depleted. Animals were sacrificed at 14, 21, 28 or 35 days and µCT parameters and torsional stiffness and strength were assessed post-sacrifice. Using linear regression for all groups and time points together, torsional stiffness could be estimated with strut thickness, strut number and strut homogeneity (R² = 0.546, p < 0.0001); torsional strength could be estimated using bone mineral density, strut thickness and strut homogeneity (R² = 0.568, p < 0.0001). Differently conditioned mice that result in different fracture healing outcomes have been shown to result in varying structural, material and volumetric µCT parameters which can be used to estimate regain of bone strength. This study is the first to demonstrate that microstructure and strut homogeneity influence callus stiffness and strength.
非侵入性评估骨折愈合，无论是在临床还是动物研究中，都因其作为估计机械功能恢复的替代指标而受到青睐。微计算机断层扫描 (µCT) 参数，如骨折痂体积和矿化，已被用于估计骨痂的机械能力。然而，在估计骨痂机械能力方面，关于微观结构参数的深入信息尚未报道。本研究的目的是使用表现出良好和受损骨折愈合结果的不同条件的小鼠，并研究 µCT 成像参数（体积、矿化和微观结构）与随时间推移发展的骨痂强度和刚度之间的关系。共有 99 只股骨骨折和髓内稳定的小鼠根据条件分为四组：野生型、NF1 敲除型、RAG1 敲除型和巨噬细胞耗竭型。动物在 14、21、28 或 35 天处死，并在死后评估 µCT 参数和扭转刚度和强度。对于所有组和时间点，使用线性回归，扭转刚度可以用支柱厚度、支柱数量和支柱均匀性来估计（R² = 0.546，p < 0.0001）；扭转强度可以使用骨密度、支柱厚度和支柱均匀性来估计（R² = 0.568，p < 0.0001）。已证明，导致不同骨折愈合结果的不同条件的小鼠会导致不同的结构、材料和体积 µCT 参数，这些参数可用于估计骨强度的恢复。本研究首次证明了微观结构和支柱均匀性会影响骨痂的刚度和强度。
