Tanveer Maham, Klein Karina, von Rechenberg Brigitte, Darwiche Salim, Dailey Hannah L
Department of Mechanical Engineering & Mechanics, Lehigh University, Bethlehem, Pennsylvania, USA.
Musculoskeletal Research Unit (MSRU), Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
Bone Joint Res. 2025 Jan 1;14(1):5-15. doi: 10.1302/2046-3758.141.BJR-2024-0191.R2.
The "2 to 10% strain rule" for fracture healing has been widely interpreted to mean that interfragmentary strain greater than 10% predisposes a fracture to nonunion. This interpretation focuses on the gap-closing strain (axial micromotion divided by gap size), ignoring the region around the gap where osteogenesis typically initiates. The aim of this study was to measure gap-closing and 3D interfragmentary strains in plated ovine osteotomies and associate local strain conditions with callus mineralization.
MicroCT scans of eight female sheep with plated mid-shaft tibial osteotomies were used to create image-based finite element models. Virtual mechanical testing was used to compute postoperative gap-closing and 3D continuum strains representing compression (volumetric strain) and shear deformation (distortional strain). Callus mineralization was measured in zones in and around the osteotomy gap.
Gap-closing strains averaged 51% (mean) at the far cortex. Peak compressive volumetric strain averaged 32% and only a small tissue volume (average 0.3 cm) within the gap experienced compressive strains > 10%. Distortional strains were much higher and more widespread, peaking at a mean of 115%, with a mean of 3.3 cm of tissue in and around the osteotomy experiencing distortional strains > 10%. Callus mineralization initiated outside the high-strain gap and was significantly lower within the fracture gap compared to around it at nine weeks.
Ovine osteotomies can heal with high gap strains (> 10%) dominated by shear conditions. High gap strain appears to be a transient local limiter of osteogenesis, not a global inhibitor of secondary fracture repair.
骨折愈合的“2%至10%应变规则”被广泛解读为，骨折块间应变大于10%会使骨折易于不愈合。这种解读侧重于间隙闭合应变（轴向微动除以间隙大小），而忽略了通常启动成骨的间隙周围区域。本研究的目的是测量钢板固定的绵羊截骨术中的间隙闭合应变和三维骨折块间应变，并将局部应变情况与骨痂矿化相关联。
对八只接受钢板固定的胫骨中段截骨术的雌性绵羊进行MicroCT扫描，以创建基于图像的有限元模型。采用虚拟力学测试来计算术后的间隙闭合应变以及代表压缩（体积应变）和剪切变形（畸变应变）的三维连续体应变。在截骨间隙内及周围区域测量骨痂矿化情况。
远侧皮质处的间隙闭合应变平均为51%（均值）。峰值压缩体积应变平均为32%，间隙内仅有小部分组织体积（平均0.3 cm）经历大于10%的压缩应变。畸变应变则高得多且分布更广，峰值平均为115%，截骨处及其周围平均有3.3 cm的组织经历大于10%的畸变应变。骨痂矿化在高应变间隙之外开始，在九周时，骨折间隙内的矿化明显低于其周围。
绵羊截骨术能够在以剪切条件为主导的高间隙应变（>10%）情况下愈合。高间隙应变似乎是成骨的一个短暂局部限制因素，而非二次骨折修复的全局抑制剂。
