Department of Mechanical and Aerospace Engineering, University of California-Davis, Davis, CA, USA.
Department of Surgical and Radiological Sciences, University of California-Davis, Davis, CA, USA.
Equine Vet J. 2021 Mar;53(2):294-305. doi: 10.1111/evj.13291. Epub 2020 Jul 23.
Proximal sesamoid bone (PSB) fracture is the most common fatal injury in Thoroughbred (TB) racehorses in the United States. Epidemiological and pathological evidence indicates PSB fracture is likely the acute culmination of a chronic stress-related process. However, the aetiopathogenesis of PSB fracture is poorly understood.
To characterise bone abnormalities that precede PSB fracture.
Two retrospective case-control groups of PSBs from TB racehorses with, and without, unilateral biaxial PSB fracture.
Proximal sesamoid bones were harvested post-mortem from TB racehorses subjected to euthanasia for unilateral biaxial PSB fracture (cases) or causes unrelated to PSB fracture (controls) while racing or training. The fractured medial PSB (FX-PSB) and contralateral intact medial PSB (CLI-PSB) from racehorses that sustained PSB fracture, and an intact medial PSB (CTRL-PSB) from racehorses that did not have a PSB fracture were collected as case and control specimens. Study 1 distributions of morphological features were compared among case and control groups using visual examination, photographs, radiographs and histology of whole PSBs and serial sagittal sections (10 FX-PSB, 10 CLI-PSB and 10 CTRL-PSB). Study 2 local bone volume fraction and mineral densities were compared among case and control PSBs using microcomputed tomography (9 FX-PSB, 9 CLI-PSB and 9 CTRL-PSB).
A focal subchondral lesion characterised by colocalised focal discoloration, radiolucency, osteopenia, low tissue mineral density and a surrounding region of dense cancellous bone was identified in most case horses but not in controls. This subchondral lesion was found in a slightly abaxial mid-body location and was bilaterally present in most case horses.
The post-mortem samples may not represent the spectrum of abnormalities that occur throughout the development of the subchondral lesion. Lateral PSBs were not examined, so their contribution to biaxial PSB fracture pathogenesis is unknown.
Abaxial subchondral lesions are consistent with pre-existing injury and likely associated with PSB fracture.
在美国，赛马的近籽骨（PSB）骨折是最常见的致命伤。流行病学和病理学证据表明，PSB 骨折可能是慢性应激相关过程的急性结果。然而，PSB 骨折的病因发病机制尚不清楚。
描述 PSB 骨折前的骨骼异常。
对双侧 PSB 骨折的赛马和未发生单侧 PSB 骨折的赛马的 PSB 进行了回顾性病例对照研究。
从因双侧 PSB 骨折（病例）或与 PSB 骨折无关的原因（对照组）而被安乐死的赛马中取出死后的近籽骨。从发生 PSB 骨折的赛马中采集了骨折的内侧 PSB（FX-PSB）和对侧完整的内侧 PSB（CLI-PSB），以及未发生 PSB 骨折的赛马的完整内侧 PSB（CTRL-PSB）作为病例和对照组标本。研究 1 通过对整个 PSB 及矢状位连续切片（10 个 FX-PSB、10 个 CLI-PSB 和 10 个 CTRL-PSB）的肉眼检查、拍照、X 线和组织学比较病例组和对照组的形态特征分布。研究 2 通过 microCT 比较病例组和对照组 PSB 的局部骨体积分数和矿密度（9 个 FX-PSB、9 个 CLI-PSB 和 9 个 CTRL-PSB）。
在大多数病例马中发现了一个特征为局灶性软骨下病变，其特征为局灶性颜色变深、放射性透光、骨质疏松、组织矿密度低和周围密集的松质骨区域。这种软骨下病变位于稍远轴的中体位置，在大多数病例马中双侧存在。
死后样本可能无法代表整个软骨下病变发展过程中出现的异常谱。未检查外侧 PSB，因此其对双侧 PSB 骨折发病机制的贡献尚不清楚。
远轴软骨下病变与先前存在的损伤一致，可能与 PSB 骨折有关。
