Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia.
New Bolton Center, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA, USA.
Equine Vet J. 2021 Jul;53(4):834-844. doi: 10.1111/evj.13356. Epub 2020 Oct 29.
Supporting limb laminitis (SLL) is suspected to be caused by lamellar ischaemia as a consequence of increased mechanical load.
Examine the effects of prolonged preferential weight bearing (PWB) on lamellar perfusion and metabolism.
In vivo experiment.
Microdialysis probes were inserted in the lamellar and sublamellar dermis of one forelimb in 13 Standardbred horses. In six horses, a platform shoe (contralateral forelimb) was used to induce increased load on the microdialysis-instrumented forelimb (PWB). The remaining seven horses were controls (CON). All horses were housed in stocks with limb weight distribution logged continuously for 92 hours. Microdialysate was collected and analysed every 4 hours for glucose, lactate, pyruvate, and lactate to pyruvate ratio (L:P). Microdialysis urea clearance was used to estimate lamellar perfusion. Data were analysed using a mixed-effects linear regression model.
Median [IQR] load on the microdialysis-instrumented limb was equivalent to 38.7% bwt. [37.3-40.3] in PWB and 27.3% bwt. [26.6-28] in CON. Limb offloading frequency increased in CON (P < .001) but not PWB (P = .2). Lamellar microdialysate glucose decreased in PWB (P < .001) and CON (P = .004), however, the rate of decrease was higher in PWB (P = .007). Lamellar L:P increased in PWB (P < .001) and peaked at 196 [79-656], whereas L:P did not change over time in CON (P = .6) and peaked at 42 [41-49]. Lamellar urea clearance decreased in PWB (P < .001) but not in CON (P = .3). Sublamellar L:P and urea clearance did not change over time in either group (P > .05).
The PWB model may not be representative of naturally occurring SLL.
Evidence of lamellar ischaemia (increased L:P and decreased urea clearance) was detected exclusively in the lamellar dermis of PWB feet subjected to persistently increased load. Lamellar ischaemia is a consequence of increased mechanical load and likely contributes to the development of SLL.
支持性蹄叶炎（SLL）被怀疑是由于层状缺血导致的，这是由于机械负荷增加所致。
研究长期优先负重（PWB）对层状灌注和代谢的影响。
体内实验。
在 13 匹标准bred 马的一个前肢的层状和亚层状真皮中插入微透析探针。在 6 匹马中，使用平台鞋（对侧前肢）来增加微透析仪器化前肢（PWB）的负荷。其余 7 匹马作为对照（CON）。所有的马都被安置在畜栏里，肢体重分布被连续记录 92 小时。每隔 4 小时收集和分析微透析液，以分析葡萄糖、乳酸、丙酮酸和乳酸丙酮酸比（L：P）。微透析尿素清除率用于估计层状灌注。使用混合效应线性回归模型分析数据。
在 PWB 中，微透析仪器化肢的平均[IQR]负荷相当于 38.7%体重。[37.3-40.3]，在 CON 中为 27.3%体重。[26.6-28]。CON 中的肢体卸载频率增加（P < 0.001），但 PWB 中没有（P = 0.2）。PWB（P < 0.001）和 CON（P = 0.004）中，层状微透析液葡萄糖减少，但 PWB 中葡萄糖减少的速度更高（P = 0.007）。PWB（P < 0.001）中 L：P 增加，并达到 196 [79-656]，而 CON 中 L：P 随时间无变化（P = 0.6），并达到 42 [41-49]。PWB 中，层状尿素清除率降低（P < 0.001），而 CON 中没有（P = 0.3）。在两组中，亚层状 L：P 和尿素清除率随时间无变化（P > 0.05）。
PWB 模型可能不能代表自然发生的 SLL。
在持续增加负荷的 PWB 足部的层状真皮中，仅检测到层状缺血（增加的 L：P 和降低的尿素清除率）。层状缺血是机械负荷增加的结果，可能导致 SLL 的发展。
