Normal MRI features of the manica flexoria in horses and evaluation of the anatomic variability between forelimbs and hindlimbs.
Abstract: Manica flexoria tears are increasingly recognized as a cause of lameness in horses resulting in a need for improved pre-operative diagnosis. Partial tears are difficult to pre-operatively diagnose and thus research for diagnostics of manica flexoria tears has been seen in increasing frequency over the past decade, though a deficit of information exists for the features of this structure on MRI, which is best suited for evaluation of soft tissues. The goal is to perform an observational study on the morphometry of the normal manica flexoria prospectively and describe it retrospectively on MRI. Inclusion criteria includes: MRI of the metacarpophalangeal/metatarsophalangeal regions in non-lame limbs without MRI tendon abnormalities identified, and the entire manica flexoria included on transverse proton density-weighted images. The manica flexoria on MRI was measured at the proximal and distal margins, halfway between (middle), and halfway between the middle and proximal margin (proximal fourth), with measurements including dorsal, lateral/medial and dorsolateral/dorsomedial thickness. Eighteen MRI studies fit the inclusion criteria: 6 forelimbs, 12 hindlimbs. The manica flexoria on gross dissection was thicker proximally in forelimbs, and thinner proximally in hindlimbs where it blends with overlying fascia. On proton density-weighted images, the manica flexoria was hyperintense to the superficial digital flexor tendon (12/18), isointense (3/18), or hyperintense proximally and isointense distally (3/18). The proximal fourth dorsal measurements were the thickest in both forelimbs and hindlimbs on MRI images compared to other measurement sites within the same limb. The forelimb medial aspect was thicker than the lateral aspect in the proximal fourth and middle (average 17.1% thicker, p = 0.0372, 22.7% p = 0.0183, respectively), and in the hindlimb the lateral aspect was thicker in these regions (average 50.4% thicker p = 0.0099 and 23.7% p = 0.0394, respectively). This study provides an anatomical and morphometric reference for future studies evaluating abnormalities of the manica flexoria on MRI.
Copyright: © 2025 Miles et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Publication Date: 2025-07-21 PubMed ID: 40690480PubMed Central: PMC12279136DOI: 10.1371/journal.pone.0327880Google Scholar: Lookup
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Summary
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This research article discusses performing an observational study on the morphometry of the normal manica flexoria in horses and describing it on MRI. Partial tears of manica flexoria, a cause of lameness in horses, are challenging to diagnose, motivating this research to provide an anatomical reference for future studies.
Objective
The study aims for a better understanding of the features of a normal manica flexoria in horses. The researchers hope this will improve the preoperative diagnosis of partial tears in this part of the horse’s body.
Methodology
- In establishing the methodology, the research team set strict criteria for what MRI studies to include. These included imaging of non-lame limbs with no discernible tendon abnormalities, and full inclusion of the manica flexoria in the images.
- The manica flexoria was measured at various points including the proximal and distal margins, and halfway between these two points. These measurements accounted for thickness from multiple perspectives.
- Eighteen MRI studies fit the criteria, comprising six forelimbs and twelve hindlimbs.
Findings
- The results indicated variation in thickness of the manica flexoria, both in different parts of the limb and between forelimbs and hindlimbs: it was thicker proximally in forelimbs, while in hindlimbs it was thinner proximally.
- In terms of intensity on the MRI results, the manica flexoria demonstrated three primary patterns: hyperintense to the superficial digital flexor tendon, isointense, or hyperintense proximally and isointense distally.
- In both forelimbs and hindlimbs, the proximal fourth dorsal measurements were the thickest on MRI images compared to other parts within the same limb.
- Thickness also varied between the medial and lateral aspects of both forelimbs and hindlimbs. In the forelimb, the medial aspect was thicker in the proximal fourth and middle, whereas in the hindlimb, the lateral aspect was thicker in these regions.
Implications
- The findings could serve as a valuable reference for future studies evaluating abnormalities of the manica flexoria on MRI.
- With a thorough understanding of the norm, veterinarians can better diagnose pathologies or irregularities and prescribe timely treatment.
- This insight could result in better preoperative diagnosis of partial tears in manica flexoria and consequently improved welfare for affected horses.
Cite This Article
APA
Miles S, McCauley C, Carossino M, Del Piero F, Liu CC, Gaschen L.
(2025).
Normal MRI features of the manica flexoria in horses and evaluation of the anatomic variability between forelimbs and hindlimbs.
PLoS One, 20(7), e0327880.
https://doi.org/10.1371/journal.pone.0327880 Publication
Researcher Affiliations
- Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, United States of America.
- Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, United States of America.
- Department of Pathobiological Sciences and Louisiana Animal Disease Diagnostic Laboratory, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, United States of America.
- Department of Pathobiological Sciences and Louisiana Animal Disease Diagnostic Laboratory, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, United States of America.
- Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, United States of America.
- Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, United States of America.
MeSH Terms
- Animals
- Horses / anatomy & histology
- Magnetic Resonance Imaging / veterinary
- Forelimb / anatomy & histology
- Forelimb / diagnostic imaging
- Hindlimb / anatomy & histology
- Hindlimb / diagnostic imaging
- Male
- Tendons / anatomy & histology
- Tendons / diagnostic imaging
- Female
- Retrospective Studies
Conflict of Interest Statement
The authors have declared that no competing interests exist.
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