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

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.