Faculty of Veterinary Medicine, Department of Companion Animal Clinical Sciences, Norwegian University of Life Sciences, Equine Teaching Hospital, Oluf Thesens Vei 24, 1432, Ås, Norway.
BMC Vet Res. 2023 Jan 23;19(1):20. doi: 10.1186/s12917-023-03579-3.
Interpretation of patellar ligament (PL) ultrasonography may be difficult, as hypoechoic or heterogenous echogenicity are common findings. Verifying suspected disease of equine PLs by histopathology is also problematic as descriptions of normal PL vascularity and histology are scarce. The current study describes the PL and infrapatellar fat pad (IFP) vascular pattern from computed tomography scans of barium perfused normal equine specimens (n = 8; age 10 days to 18 years), as well as routine histology to serve as a reference for future investigations into PL pathology and IFP disease.
The PLs received a bipolar blood supply. Vascular architecture consisted of numerous distinct longitudinal vessels with several horizontal connections, which branched into extensive latticeworks of smaller vessels throughout the ligaments. Several vascular connections between the PLs and the IFP were identified. One distinct longitudinal vessel was seen entering each of the IFP lobes at the distocranial aspect, branching extensively into lobar vascular networks which anastomosed by several horizontal branches at the mid portion of the IFP where the two lobes merge. Histologically, there were large variations in PL interfascicular endotenon thickness, vascularity and fatty infiltration; these parameters increased with age for the intermediate and medial PL. Areas of metaplastic tenocytes / chondroid metaplasia were identified in all investigated adult medial PLs; in 2/7 in the intermediate PL and in 4/7 in the lateral PL. The adult IFP consisted of white unilocular adipose tissue, organized in lobules separated by thin connective tissue septa increasing in thickness towards the periphery and the distocentral aspect.
The equine PLs and IFP are highly vascularized structures with ample vascular connections suggestive of crosstalk. This, together with the large variation in PL endotenon thickness, vascularity and fatty infiltration, should be taken into consideration when assessing potential PL histopathology as these changes increase with age and are found in horses without clinical signs of stifle disease. Metaplastic tenocytes / chondroid metaplasia should be considered a normal finding throughout the medial PL and is not age dependent. The role of the equine IFP in stifle disease has yet to be elucidated.
髌韧带（PL）的超声表现可能较难解读，因为低回声或异质性回声是常见表现。通过组织病理学来验证马的 PL 疑似疾病也存在问题，因为 PL 血管分布和组织学的描述很少。本研究通过钡灌注正常马标本的计算机断层扫描（n=8；年龄 10 天至 18 岁）描述了 PL 和髌下脂肪垫（IFP）的血管模式，并进行常规组织学检查，为未来研究 PL 病理学和 IFP 疾病提供参考。
PL 接受双极血流供应。血管结构由许多明显的纵向血管和几个水平连接组成，这些连接在韧带内分支成广泛的小血管网。在 PL 和 IFP 之间发现了几个血管连接。在每只 IFP 的远颅侧，都有一条明显的纵向血管进入每个 IFP 叶，在 IFP 的中部广泛分支成叶状血管网络，在这两个叶合并的地方，通过几个水平分支吻合。组织学上，PL 束间终末内的厚度、血管和脂肪浸润存在很大差异；这些参数随着年龄的增长而增加，在中间和内侧 PL 中更为明显。在所有研究的成年内侧 PL 中都发现了移行性腱细胞/软骨样化生的区域；在 2/7 个中间 PL 和 4/7 个外侧 PL 中也发现了这种情况。成年 IFP 由白色单房脂肪组织组成，组织成小叶，由薄的结缔组织隔分开，这些隔在向周围和远中中心方向增厚。
马的 PL 和 IFP 是高度血管化的结构，有充足的血管连接，提示有相互交流。考虑到这些变化随着年龄的增长而增加，并且在没有膝关节疾病临床症状的马中也有发现，因此在评估潜在的 PL 组织病理学时应该考虑到这一点。在整个内侧 PL 中，移行性腱细胞/软骨样化生都应被视为一种正常表现，而且与年龄无关。IFP 在膝关节疾病中的作用尚未阐明。
