Normal MRI features of the manica flexoria in horses and evaluation of the anatomic variability between forelimbs and hindlimbs.
Authors: Miles Samantha, McCauley Charles, Carossino Mariano, Del Piero Fabio, Liu Chin-Chi, Gaschen Lorrie
Journal: PloS one
Summary
# Manica Flexoria MRI Anatomy: Establishing a Normal Reference Standard Manica flexoria tears are now recognised as an important cause of equine lameness, yet partial tears remain diagnostically challenging because clinicians lack detailed baseline information on how this structure normally appears on MRI—the imaging modality best suited for soft tissue evaluation. Researchers performed gross anatomical dissection and retrospective MRI analysis on 18 sound limbs (6 forelimbs, 12 hindlimbs) with no tendon pathology, measuring manica flexoria thickness at four distinct sites in dorsal, lateral/medial, and oblique planes. Key findings revealed significant asymmetries between forelimbs and hindlimbs: the forelimb manica flexoria was thicker medially than laterally (17–23% difference), whereas the hindlimb showed the opposite pattern with lateral predominance (23–50% thicker), with maximal thickness consistently observed in the proximal fourth region of both limbs; signal intensity on proton density-weighted imaging varied from hyperintense to isointense relative to the superficial digital flexor tendon depending on location. These baseline measurements and anatomical descriptions now provide practitioners and researchers with a reference standard for identifying pathological manica flexoria on MRI, potentially improving pre-operative diagnosis of partial tears that might otherwise be missed on clinical or ultrasonographic examination and allowing more accurate case selection for surgical intervention.
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Practical Takeaways
- •Understanding normal MRI appearance of manica flexoria is essential for identifying partial tears and lameness cases, as this structure was previously poorly characterized on imaging
- •Expect asymmetrical thickness patterns between medial and lateral aspects that differ between forelimbs and hindlimbs—use proximal fourth region as reference for normal thickness comparison
- •Manica flexoria signal intensity variation (hyperintense to isointense) is normal and should not be misinterpreted as pathology when evaluating MRI for lameness diagnosis
Key Findings
- •Manica flexoria is thicker proximally in forelimbs but thinner proximally in hindlimbs where it blends with fascia
- •On MRI, manica flexoria appears hyperintense to superficial digital flexor tendon in 12/18 limbs (67%), isointense in 3/18 (17%), or hyperintense proximally with isointense distal appearance in 3/18 (17%)
- •Proximal fourth dorsal measurements represent the thickest region in both forelimbs and hindlimbs
- •Forelimb medial aspect is 17-23% thicker than lateral aspect, while hindlimb lateral aspect is 24-50% thicker than medial aspect