SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
their convergence. The MDSL branches measure 12 - 20 mm in a lateral to medial
direction in the proximal pastern, decreasing to 9 - 17 mm just prior to their
convergence and measuring 0 - 9 mm (one side only) at the insertion of the ligament
onto P1. The palmar - to - dorsal thickness of the MDSL branches is 5 - 12 mm in the
proximal pastern, decreasing to 2 - 6 mm just proximal to their convergence and to 0 -
3 cm at their insertion onto P1.
Discrete core lesions are often seen in the medial and lateral branches of the MDSL,
although diffuse areas of fiber damage and splits also occur. Injuries to the insertion of
the MDSL are usually diffuse.
Acute desmitis of medial MDSL branch
Periligamentous soft tissue thickening is often detected surrounding the area of injury.
The origin and insertion of the MDSL should be carefully evaluated for avulsion
fractures. Avulsion fractures usually occur in association with fiber tearing in the distal
sesamoidean ligaments and occur both from the base of the sesamoids and the
insertion on mid P1 with seemingly equal frequency. Avulsion fractures remain visible
for years after the original injury, long after the associated desmitis in the distal
sesamoidean ligament has resolved. As the injury heals, the ligament's cross-sectional
area usually decreases, the echogenicity of the lesion increases and linear echoes are
imaged in the area of previous fiber tearing.
Straight distal sesamoidean ligament: Injuries to the SDSL occur less frequently. These
injuries are usually associated with lameness but focal heat, swelling and sensitivity are
not always detected. Horses with these injuries if severe, also must be given a guarded
prognosis.
The SDSL originates as a single trapezoid structure from the base of both sesamoid
bones with a large concave palmar border. The SDSL becomes a more oval shaped
structure and is palmar or plantar to the MDSL in the mid pastern region and remains
dorsal to the DDFT as it inserts on the proximal portion of the second phalanx. The
dorsal to palmar thickness of the SDSL gradually increases as the medial to lateral
width decreases. The SDSL measures 5 - 9 mm in palmar - to - dorsal thickness
proximally, increasing slightly over distal P1 to 6 - 12 mm and to 8 - 14 mm at the
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