46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
145
Non-septic tendon sheath disease
Bruce Bladon Cert EP DESTS Dipl ECVS, Specialist in Equine Surgery, Donnington Grove
Veterinary Surgery Newbury, UK , [email protected]
There are several conditions that cause lameness associated with the digital flexor
tendon sheath. However, there are two important and one more debatable
condition, all the others are of minimal significance. These conditions are linear
tears of the deep digital flexor tendon, tears of the manica flexoria, and debatably,
constriction by the annular ligament.
The signs of lameness associated with non-septic conditions of the digital flexor
tendon sheath are fairly consistent. There is almost invariably effusion of the tendon
sheath. In the absence of effusion, it should be questioned if lameness is genuinely
associated with the tendon sheath, or if local anaesthetic has diffused out to affect
other structures. However, conditions of the tendon sheath frequently affect horses
with feathered limbs and effusion may not be obvious without careful palpation, and
possibly clipping of the hair. Lameness is usually exacerbated by flexion of the lower
limb. Unlike many of the lower limb conditions, tendon sheath lameness is more
frequent in the hindlimb, but does occur in the forelimb.
Ultrasonography is the primary tool for the investigation of tendon and ligament
injuries in the horse. However, there are marked limitations with this for
investigation of conditions of the tendon sheath. The first is the frequency of the
occurrence of these conditions in cobs and other breeds with thick and hairy skin.
This can make obtaining diagnostic ultrasonographic images challenging. It is also
difficult to image the deep digital flexor tendon in the region of the ergot, as this is
the site at which the deep digital flexor tendon curves around, making off incidence
artifact frequent.
Ultrasonography is not sensitive in the detection of linear tears of the deep digital
flexor tendon, nor of the manica flexoria. The most common finding is thickening of
the annular ligament. This is not diagnostic of constriction of the annular ligament,
but is a common non-specific finding with tendon sheath lameness. In our series of
horses with tears of the manica flexoria, ultrasonographic images were recorded in
44 horses, and were inconclusive or non diagnostic due to poor contact through
thick “cob” skin in 6 cases, revealed a thickened annular ligament in 24 cases,
irregularity of the deep digital flexor tendon in 2 cases and a thickened manic flexoria
in 10 cases. Likewise ultrasonography of tears of the deep digital flexor tendon is
relatively unrewarding. It is rare to observe hypoechoic areas extending to the
tendon margin, which are directly diagnostic of a linear tear. However, signs
suggestive of a linear tear are more frequently observed, such as a truncated tendon
margin, usually laterally, or echogenic material extending from and contiguous with
the tendon. With experience ultraonography can be helpful. Arensburg (2010)
reported 74 / 97 (76%) the flexor tendons showed ultrasonographic changes
indicative of a linear tear. Ultrasonographic prediction of the presence of a tear had
a sensitivity of 63%, a specificity of 75% (95% CI = 58.96–91.03), positive predictive
value of 90% (95% CI = 82.22–96.87) and negative predictive value of 37% (95% CI =
24.31–49.36), i.e. lack of signs suggestive of a linear tear is not strongly associated
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