Is the Manica Flexoria Always Entirely Derived from the Superficial Digital Flexor Tendon? Hinnigan GJ1, Owen KR1, Ricci E2. 1Oakhill Veterinary Centre, Preston, United Kingdom; 2University of Liverpool, Liverpool, United Kingdom.
The manica flexoria (MF) is described as a thin band of tissue derived from the superficial digital flexor tendon (SDFT) which courses dorsal to the deep digital flexor tendon in the digital flexor tendon sheath (DFTS). A variation in the composition of the MF was identified during diagnostic tenoscopy, and this variation in anatomy studied. This case series describes variable anatomy in five limbs of three horses. Four hindlimbs from two horses and one forelimb. These were identified in clinical cases with naturally occurring lameness referrable to the DFTS due to palmar/plantar annular ligament (PAL) constriction syndrome. In five limbs, the MF was not comprised of tissue entirely derived from the SDFT. On the lateral aspect there was an abnormally thick MF comprised of tissue derived from the PAL in addition to a variable component of tissue from the lateral border of the SDFT. Preoperatively the variation was not definitively diagnosed on ultrasonographic examination. Two hindlimbs of one horse were submitted for gross pathological and histopathological analysis. This confirmed the tissue to be organized tendinous tissue derived from the PAL which merged with a smaller component of tissue from the lateral SDFT on midline. PAL desmotomy resolved the lameness with the abnormal tissue left in situ. The series is limited by the low numbers of cases identified with this anatomical variation. A band of organized tissue coursing from the PAL onto the MF should not necessarily be considered an injury of intra-thecal tissues and may be a normal variation.