Page 383 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

358 CHAPTER 1

VetBooks.ir of the fetlock (Fig. 1.708). A more distal swelling Differential diagnosis
Oedema of the digit due to inflammation (e.g. sepsis,
is palpable in the sagittal plane in the mid-pastern
area; however, there is no obvious thickening of the
lar ligament syndrome, or fractures of P1, P2 or the
sheath tissues and no heat or pain is noticeable. The trauma, etc.) of the foot or pastern, palmar annu-
distension is usually soft. There is no associated PSBs; septic tenosynovitis, SL branch injuries and
lameness, although flexion of the fetlock may occa- fetlock joint effusion may have a similar presentation.
sionally elicit pain through increased pressure and
mechanical impairment. It is more common in the Diagnosis
hindlimbs and in larger animals. Clinical examination
In other forms of tenosynovitis, the swelling is Pain on deep palpation of the palmar or plantar pas-
similar, but there is variable heat and pain on palpa- tern and over the proximal pouch of the sheath area
tion of the area of the sheath. Diffuse oedema may is suggestive of tenosynovitis. The lameness may be
be present in acute cases. Pain is typically elicited partially or totally abolished with an abaxial sesa-
by deep palpation of the palmar aspect of the fet- moid or distal metacarpal or metatarsal nerve block
lock and pastern and distal limb flexion. Lameness is (four- or six-point). Intrathecal injection of 5–10 ml
usually severe and characterised by decreased digi- of local anaesthetic solution usually substantially
tal flexion, reduced foot flight arc and, occasionally, improves or eliminates the lameness, but this is not
reduced weight bearing. always specific for the sheath as the local anaesthetic
In chronic cases, the swelling is more diffuse and agent can diffuse outside the sheath or around the
firm, and pain may not be as obvious on palpation. palmar/plantar or palmar/plantar digital nerves.
There is markedly decreased amplitude of flexion of
the fetlock and digit and forced flexion is painful. Ultrasonography
In cold sheath distension, the sheath is distended by
1.708 anechogenic fluid, but the synovial membranes are
not thickened. Intrasynovial structures such as the
plicae, vincula, mesotenons and the manica flexoria
are visible, highlighted by surrounding fluid, but
they remain thin (less than 1 or 2 mm in thickness)
(Fig. 1.709).
In acute tenosynovitis there is accumulation of
anechogenic fluid, although bleeding will produce
strands of hypoechogenic material (fibrin strands
and pannus) and the fluid may appear echogenic
and grainy (‘cellular appearance’) very early on. The
synovium is diffusely thickened and hypoechogenic,
producing a 2–4 mm thick halo around the tendons
(Fig. 1.710). This may physically separate the ten-
dons, creating a hypoechogenic interface between
them in the fetlock area.
Chronic tenosynovitis presents as partial to com-
plete obliteration of the sheath by a thickened, echo-
genic synovium (Figs. 1.711, 1.712). Typically, the
plicae lateral and medial to the DDFT, proximal
Fig. 1.708 Swelling of the digital sheath (tendinous to the fetlock, will measure 3–10 mm in thickness.
‘windgalls’) is obvious proximal to the palmar annular Dynamic examination (i.e. while flexing and extend-
ligament of the metacarpophalangeal joint (top arrow) ing the limb) may show that the tendons and parietal
and over the palmar mid-pastern (bottom arrow). sheath are adhered.