Page 570 - Adams and Stashak's Lameness in Horses, 7th Edition
P. 570

536   Chapter 4


            Treatment
              Surgical transection of the PDAL and DDAL is the
  VetBooks.ir  treatment of choice. In one report, five of seven horses
            with DDAL injury that had surgical transection of the
            DDAL were able to return to performance, two of which
            had failed to respond to rest and medical therapy. 7

            Prognosis
              The prognosis for return to work after surgical tran-
            section of the DDAL appears to be good, although only
            one report is currently available. 7


            SDFT AND DDFT ABNORMALITIES
              In general, injuries in the pastern region to the SDFT
            occur most frequently in the forelimbs. Chronic DFTS
            effusion  seems  to be  more  common  in the  hindlimbs,
            and injuries to the DDFT within the DFTS occur most
            frequently  in  the  hindlimbs;  however,  in  horses  that
            jump, DDFT injury within the DFTS was more common
            in the forelimbs. 2,64  Injuries to the DDFT that are associ-
            ated with navicular syndrome are covered under the
            foot section. Injuries involving the SDFT most com-
            monly involve the branches of the SDFT located outside
            the DFTS.  The SDFT branches at the level of the MCP/
                     13
            MTP joint, giving rise to medial and lateral branches
                                                           75
            that insert on the palmar/plantar eminences of P2.
            Abnormal conformation such as a long pastern or an
            underrun heel may predispose the horse to injury of the
            SDFT branch. Injuries to the DDFT within the pastern
            are nearly always within the DFTS, often cause effusion   Figure 4.116.  This horse was 4/5 lame in the left hindlimb and
            of the sheath, and may contribute to chronic tenosyno-  had severe effusion of the digital flexor tendon sheath and chronic
            vitis of the DFTS (Figure 4.116). In two different studies   DDFT injury. Arrows demonstrate the largest outpouchings of
            of horses with DFTS tenosynovitis, injuries to the DDFT   synovial effusion proximolateral and medial (black) and
                                                                 plantarodistal (white). Lesions of the DDFT within the tendon sheath
                                      64
            were found in 44 of 76 horses  and 101/130 horses. 2  appear to be more common in the hindlimbs than the forelimbs.
            Etiology
                                                               appears to be more frequently injured than the lateral
              Injuries to the SDFT in the forelimbs are usually asso-  branch, and avulsion fractures of P1 at the insertion of
            ciated with hyperextension of the MCP joint, resulting   the SDFT branch occur infrequently. Some SDFT injuries
                                                           54
            in nonphysiologic stretching and overload of the SDFT.    and damage to the manica flexoria may occur within the
            These injuries occur commonly in racehorses, but why   DFTS and result in tendon sheath effusion. 14,64
            some horses get SDFT injuries in the pastern compared
            to the metacarpal region is unknown.  The cause of
            DDFT injuries  within the tendon sheath is  unknown,   DDFT
            but hyperextension of the MCP/MTP joint and over-     Deep digital flexor tendinitis occurs in a variety of
            stretching  of  the  tendon  are  also  likely.   It  seems  as   horses and typically presents as an acute‐onset, unilateral
                                                2
            though  both  SDFT  and  DDFT  injuries  in  the  pastern   moderate to severe lameness that is persistent.  Heat,
                                                                                                         54
            region occurs more frequently as a result from a single   pain, and swelling of the DDFT itself are usually not pal-
            traumatic event as compared to flexor tendon injuries at   pable because the damage is often located within the
            the level of the metacarpus (tarsus).
                                                               DFTS, which can  be quite effusive (Figure  4.116).
                                                               Lameness is often worse on a soft surface and generally
            Clinical Signs                                     improves with perineural anesthesia of the palmar/plantar
            SDFT Branch Injuries                               nerves at the level of the proximal sesamoid bones.
                                                               Distension of the DFTS often occurs in conjunction with
              Lameness usually occurs at the onset of injury with   the injury, and many horses present with chronic teno-
            focal heat, swelling, and sensitivity noted on palpation.   synovitis of the DFTS of undetermined cause. The use of
            However, careful palpation and comparison of the medial   MRI and/or diagnostic tenoscopy in addition to ultra-
            to lateral branches are important to detect differences in   sound has increased the frequency of a definitive diagnosis
            size, heat, and pain because these injuries can be easily   of DDFT injury 2,64,78  (Figure 4.117). If the DFTS is dis-
            missed. Generally, swelling develops within 3–4 days and   tended, intrasynovial anesthesia of the sheath is the pre-
            is usually uniaxial on the limb. The medial SDFT branch   ferred method to confirm the location of the lameness.
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