Martin R B, Stover S M, Gibson V A, Gibeling J C, Griffin L V
Orthopaedic Research Laboratories, School of Medicine, University of California at Davis, USA.
J Orthop Res. 1996 Sep;14(5):794-801. doi: 10.1002/jor.1100140517.
We studied remodeling and microcrack damage in specimens of Thoroughbred racehorse third metacarpal bone that had been subjected to monotonic or fatigue failure. We asked three questions. What effects does mechanical loading have on histologically observable microcrack damage? Are there regional variations in remodeling of the equine cannon bone, and do these variations correlate with mechanical properties? To what extent are remodeling and microcrack damage age-dependent? Machined beams from the medial, lateral, and dorsal cortices were loaded to fracture in four-point bending monotonically, or cyclically at a load initially producing 10,000 microstrain. Specimens were then bulk-stained in basic fuchsin, and cross sections were prepared from loaded and load-free regions of each beam. Current and past remodeling, porosity, and microcrack density and length were determined histomorphometrically. Strained and unstained microcracks were observed. Unstained cracks were associated with regions of woven bone and appeared to be damaged Sharpey's fibers. Their density (approximately 30/mm2) did not increase after failure, but their length (approximately 25 microns) did, especially near the surfaces of the beam. Stained cracks were wider and longer than unstained cracks and were located primarily near the fracture surface and on the compressed side of the beam. Stained cracks after failure were more numerous in those beams having a higher elastic modulus, a shorter fatigue life, or greater deformation at failure. The extent of past remodeling increased with age, especially in the medial region; the rate of current remodeling generally declined with age, but not in the dorsal region, which has the best fatigue resistance. In summary, while remodeling varied with age and region, its effects on bone structure did not appear to influence microdamage. Basic fuchsin staining of damage in fractured equine bone was independent of age and region and confined to near the fracture surfaces. Distributed microdamage consisted only of what appeared to be subtle disruptions of Sharpey's fibers.
我们研究了纯种赛马第三掌骨标本在经历单调或疲劳失效后的重塑和微裂纹损伤情况。我们提出了三个问题。机械载荷对组织学上可观察到的微裂纹损伤有何影响？马炮骨的重塑是否存在区域差异，这些差异与力学性能是否相关？重塑和微裂纹损伤在多大程度上依赖于年龄？从内侧、外侧和背侧皮质加工得到的梁状样本，在四点弯曲试验中被单调加载直至断裂，或在最初产生10,000微应变的载荷下循环加载。然后将样本用碱性品红进行整体染色，并从每根梁的加载区和未加载区制备横截面。通过组织形态计量学确定当前和过去的重塑、孔隙率以及微裂纹密度和长度。观察了应变和未染色的微裂纹。未染色的裂纹与编织骨区域相关，似乎是受损的夏皮氏纤维。它们的密度（约30/mm²）在失效后没有增加，但长度（约25微米）增加了，尤其是在梁的表面附近。染色的裂纹比未染色的裂纹更宽更长，主要位于断裂表面附近和梁的受压侧。在具有较高弹性模量、较短疲劳寿命或失效时变形较大的梁中，失效后染色的裂纹更多。过去重塑的程度随年龄增加，尤其是在内侧区域；当前重塑的速率通常随年龄下降，但在具有最佳抗疲劳性的背侧区域并非如此。总之，虽然重塑随年龄和区域而变化，但其对骨结构的影响似乎并未影响微损伤。马骨折骨损伤的碱性品红染色与年龄和区域无关，且局限于断裂表面附近。分布性微损伤仅由似乎是夏皮氏纤维的细微破坏组成。
