Page 723 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 689

assess with standard imaging techniques. These types of must be distinguished from TC joint distension. If the
injuries usually present with moderate effusion of the TC joint is distended, fluid can be moved from the plan-
VetBooks.ir may require arthroscopic exploration. Arthroscopy per- compression. Unilateral benign distension associated
tar synovial pouches to the dorsal pouches by manual
TC joint, and confirmation of the structure(s) involved
with idiopathic tenosynovitis often decreases with exer-
mits direct visualization and debridement of torn fibers
of the sCL. In a recent report of 20 horses with intra- cise and worsens with shipping or stall confinement.
synovial CL, all injuries involved the sCL with four also Effusion will often resolve spontaneously. Treatment is
5
involving the lCL. Medial sCLs were torn in 14 cases unnecessary if no lameness is present. Horses with effu-
and lateral sCLs in 11 (including five cases with medial sion combined with lameness and/or a positive response
and lateral tears). No arthroscopic evidence of joint to tarsal flexion most likely have an underlying cause.
instability was found when the tarsus was manipulated An accurate diagnosis and directed treatment provide
in any case. All horses recovered uneventfully from the best chance for a return to soundness.
general anesthesia, and there were no significant postop- Intrathecal analgesia of the TS can be performed to
erative complications. confirm the TS as a source of lameness particularly if
nothing is found with diagnostic imaging. However,
Nonseptic Tenosynovitis of the Tarsal Sheath intrasynovial diagnostic analgesia of the TS is not often
performed and does have limitations. It is not uncom-
In the normal horse the TS is not often apparent on mon for analgesia of the TS to manifest significant
clinical or ultrasonographic examination of the plantar improvement but not alleviate lameness. However, more
aspect of the tarsus. 34,35,116,146 Thoroughpin is a morpho- improvement is often seen following a tibial and pero-
logic description of swellings of the TS that occur from neal nerve block. Intrathecal analgesia of the TS can be
a variety of problems and with varying degrees of difficult when there is minimal effusion. A good land-
inflammation (Figure 5.91). Often the causes of effusion mark for injection is a site dorsal to the LDFT, 2 mm
within the TS are unknown and called idiopathic as plantar to the middle of the palpable plantar edge of the
nothing is found on radiographic and ultrasonographic flexor groove of the ST. However, without recovery of
examination. Many of these cases can be reclassified if synovial fluid, it can be difficult to determine if the nee-
endoscopy of the sheath is performed because LDFT dle is actually in the TS. Therefore, synoviocentesis of
tendinitis or injuries to the ST are often found as the the TS should be performed either directly with US guid-
cause. True idiopathic tenosynovitis of the TS can occur ance or after seeing fluid pockets with US examination
and is often bilateral and most likely related to limb in one of the several recesses of the sheath.
conformation. A 10‐ to 14‐MHz sector‐scanner transducer with a
Clinically, moderate effusion of the TS typically pre- standoff pad at a display depth of 5–6 cm should be used
sents as two swellings cranial to the calcaneal tendon on to evaluate the character of the synovial fluid and detect
both the medial and lateral aspects of the distal crus. In fibrin deposition, adhesion development, and lesions
more pronounced effusions of the TS, a swelling may be within the LDFT. This technique can be used to assess
seen distal to the tarsus on the medial aspect of the DT the integrity of the fibrocartilaginous groove, flexor reti-
joints just proximal to the chestnut. Distension of the TS naculum, and edge of the ST. The course of the LDFT

A B C
Figure 5.91. Clinical (A; arrows) and DP radiographic observations (B; arrows) of a horse with thoroughpin presenting with swelling
primarily on the lateral aspect of the tarsus. Thoroughpin may also be observed on the medial aspect of the tarsus (C; arrows).