Table_1_Magnetic Resonance Imaging Findings of the Proximal Metacarpal Region in Warmblood Horses: 36 Lame and 26 Control Limbs (2015–2021).DOCX

Objectives: This study aims to evaluate the distribution and severity of bone and soft tissue lesions in the proximal metacarpal region of warmblood horses in lame and control groups. Correlation between lesions and ability to return to work was evaluated in the lame group.
Methods: This restrospective analysis evaluated 62 horses with MRI examination of the proximal metacarpal region between Sept 2015 and Feb 2021. There were 36 lame limbs and 26 control limbs. The control group included seven contralateral limbs.
Results: Proximal suspensory ligament (PSL) size was not different between the lame and control groups. Hyperintensity seen on T1W/T2*W GRE images within the dorsal collagenous part of the PSL and hyperintense Short-TI Inversion Recovery (STIR) signal within the dorsal collagenous part of the PSL or within the McIII were only present within the lame group. Palmar cortical McIII resorption and dorsal margin irregularity of the PSL and McIII sclerosis were more severe within the lame limbs, but mild gradations were also seen in control limbs. Intermediate gradings for a subset of lesions were commonly seen in the non-lame contralateral to lame limbs. Return to work in the lame group is not statistically different for any measured observation(s), and 19/33 of the lame horses returned to work at similar or higher levels.
Conclusion and clinical importance: Fifty-eight percent in this group of warmblood horses returned to work within a variable time frame. The majority (81%) of lame limbs showed bone and soft tissue abnormalities, but no enlargement of the PSL was noted in lame horses, and no correlation was seen between the severity or type of lesions and the ability to return to work. The presence of STIR hyperintensity within the proximal McIII or dorsal collagenous part of the PSL and hyperintensity within the dorsal collagenous part of the PSL on T1W GRE and T2*W GRE images, as well as significant palmar cortical McIII resorption are considered clinically relevant lesions. Contralateral limbs may not truly represent the normal condition, showing nonclinical variations and adaptive remodeling.

研究目的：本研究旨在评估跛行组与对照组温血马掌骨近端区域骨与软组织病变的分布特征及严重程度，并在跛行组中分析病变与马匹重返工作能力之间的相关性。
研究方法：本回顾性分析纳入了2015年9月至2021年2月期间接受掌骨近端区域磁共振成像（Magnetic Resonance Imaging, MRI）检查的62匹马，共纳入36个跛行肢与26个对照肢，其中对照组包含7个对侧肢。
研究结果：近端悬韧带（proximal suspensory ligament, PSL）的尺寸在跛行组与对照组间无显著差异。仅在跛行组中观察到近端悬韧带背侧胶原部分在T1加权/T2*加权梯度回波（T1W/T2*W GRE）图像上呈现高信号，且近端悬韧带背侧胶原部分或第三掌骨（metacarpal III, McIII）内可见短TI反转恢复（Short-TI Inversion Recovery, STIR）序列高信号。跛行肢的第三掌骨掌侧皮质骨吸收、近端悬韧带及第三掌骨背缘不规则，以及第三掌骨硬化程度均较对照组更为显著，但对照组中也可见轻度病变分级。在跛行肢的对侧非跛行肢中，常可见部分病变呈现中度分级。跛行组中，各项观测指标与马匹重返工作能力均无统计学相关性；33匹跛行马中有19匹能够恢复至原有或更高水平的工作强度。
结论与临床意义：本研究纳入的温血马群体中有58%能够在不同时间范围内重返工作。多数（81%）跛行肢存在骨与软组织异常，但未发现跛行马存在近端悬韧带增大的情况，且病变严重程度或类型与重返工作能力之间无相关性。在T1加权梯度回波、T2*加权梯度回波图像上，第三掌骨近端或近端悬韧带背侧胶原部分出现短TI反转恢复序列高信号，以及近端悬韧带背侧胶原部分的高信号，还有显著的第三掌骨掌侧皮质骨吸收，均被视为具有临床相关性的病变。对侧肢可能无法真正代表正常生理状态，可表现出非临床性的结构变异与适应性重塑。