Page 653 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 619

DESMITIS OF THE ACCESSORY LIGAMENT alteration in fiber pattern alignment. Injury to the
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AL‐SDFT can also be accompanied by abnormal find-
(RADIAL OR SUPERIOR CHECK LIGAMENT)
VetBooks.ir OF THE SUPERFICIAL DIGITAL FLEXOR TENDON ings involving one or more of the structures in the carpal
canal such as synovial effusion within the carpal sheath,
tendinitis of the SDFT, distension and thickening of the
Etiology
The accessory ligament of the superficial digital retinaculum flexorum, tenosynovitis of the sheath of the
tendon of the flexor carpi radialis muscle, and/or injury
flexor tendon (AL‐SDFT) is a strong fibrous band that to the proximal attachment of the suspensory ligament
originates from the distal caudomedial surface of the (third interosseous muscle). Characterization of this
radius and joins the SDFT at that level. Until recently additional damage is important for determining therapy
42
sprain to this structure has been poorly defined, and and prognosis.
many conditions associated with the caudal aspect of
the radius and carpus were attributed to this condition
including (1) lowering of the angulation of the accessory Treatment
carpal bone, (2) enthesophyte formation at the distal In the acute cases exhibiting carpal sheath distension,
caudomedial aspect of the radius, (3) cranial displace- needle drainage and the injection of a corticosteroid and
ment of the proximal end of the radius, and (4) altera- hyaluronic acid are recommended. 27,28 Rest in a stall for
tions in the antebrachiocarpal (radiocarpal) joint capsule 4–6 weeks is recommended with hand‐walking exercise
on its dorsal surface. 42,74 beginning at the third week. Systemic nonsteroidal anti‐
Sprain of the AL‐SDFT has been more clearly defined inflammatory drugs may be indicated for associated
with the improvements in ultrasound resolution and the problems and are administered as needed. Pressure/sup-
advent of MRI. 27,28 The condition occurs most commonly port wraps are applied and maintained for 2–3 weeks.
in young adult horses with a high level of physical activ- Following stall rest the horse should be confined to a
ity. In a report on 23 horses with abnormal ultrasono- small run for another 6 weeks. Recheck ultrasound
graphic findings in the AL‐SDFT, 11 of 23 were racehorses, examination should be done at this time to assess heal-
9 of 11 were sport horses, and the remaining were pleas- ing. Generally, affected horses can return to performance
ure or instruction horses. Presumably, extreme hyperex- in 4–6 months. Arthroscopic examination of the car-
28
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tension of the fetlock in conjunction with hyperextension pal canal can be performed to aid in characterization of
of the carpus can cause a sprain of the AL‐SDFT. 66,74 the damage and treatment if necessary, and tenoscopic
release of the carpal flexor retinaculum can be per-
Clinical Signs formed if needed.
Affected horses have a history of starting races and
workouts quite well but are reluctant to really sprint Prognosis
out. Rarely do they attain their previous performance The prognosis appears to depend on the severity of
levels. 42,74 A visible swelling of the carpal sheath is the injury, the intended use of the horse, and whether the
observed in some cases. At a walk, a gait impediment SDFT is involved. In one study, 8 of 13 sport horses were
characterized by a lateral floating placement of the foot able to return to their previous level of activity, whereas
just before it contacts the ground may be observed. The only 7 of 16 racehorses returned to racing at their previ-
toe and heel are placed on the ground at the same time, ous level. In another report, of eight horses suffering
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much like a horse walking down an incline. In a review from injury to the AL‐SDFT alone, without tendinitis of
of 30 cases, this gait alteration was most commonly the SDFT, six returned to their previous level of perfor-
observed with radiographic lesions on the caudomedial mance within 4–6 months. Tenoscopic release of the
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distal aspect of the radius associated with the origin of carpal flexor retinaculum has been useful for resolving
the AL-SDFT. In acute cases the carpal sheath is fre- lameness in two horses. 117
42
quently distended and variably painful to digital palpa-
42
tion. Simultaneous trauma to the SDFT may also
occur, resulting in a painful swelling. 54 References
1. Adams R, Poulosp A. A skeletal ossification index for neonatal
Diagnosis foals. Vet Radiol Ultrasound 1988;29(5):217–222.
2. Andren L, Eiken O. Arthrographic studies of risk ganglions. J
In acute cases, radiographs of the caudal aspect of the Bone Joint Surg Am 1971;53:299.
distal end of the radius are usually negative. However, in 3. Auer J. Diseases of the carpus. Vet Clin North Am Large Anim
Pract 1980;2:81–99.
chronic cases, radiographs of the distal radius may reveal 4. Auer JA, Martens RJ. Periosteal transection and periosteal strip-
enthesophytes associated with the attachment of the AL‐ ping for correction of angular limb deformities in foals. Am J Vet
SDFT. Interestingly, in a study in which radiographs were Res 1982;43:1530–1534.
taken on horses with abnormal ultrasonographic find- 5. Auer JA, Watkins JP, White NA, et al. Slab fractures of the fourth
ings in AL‐SDFT, only 4 of 18 had an abnormal profile at and intermediate carpal bones in five horses. J Am Vet Med Assoc
1986;188:595–601.
the caudal distal aspect of the radius, and 14 of 18 were 6. Baker WT, Sloan DE, Lynch TM, et al. Racing and sales perfor-
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considered normal. This underscores the value of ultra- mance after unilateral or bilateral single transphyseal screw inser-
sound examination in the diagnosis of desmitis of the tion for varus angular limb deformities of the carpus in 53
AL‐SDFT. thoroughbreds. Vet Surg 2011;40:124–128.
Ultrasound findings associated with injury of the 7. Baker WT, Sloan DE, Ramos JA, et al. Improvement in bilateral
carpal valgus deviation in 9 foals after unilateral distolateral radial
AL‐SDFT include thickening, hypoechoic defects, and periosteal transection and elevation. Vet Surg 2015;44:547–550.