Page 382 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.8 Soft-tissue injuries 357

VetBooks.ir 1.707 and should technically not be termed ‘tenosynovitis’.
The cause is unclear but may relate to a previous
inflammatory episode or to a discrepancy between
synovial fluid production and elimination.
Primary traumatic tenosynovitis is due to
direct trauma to the area of the sheath. There is,
reportedly, contusion of the synovial tissues and
intrathecal haemorrhage, which induces an acute
inflammation. The trauma may be spontaneous and
of unknown cause, but these cases are likely to be
due to tearing of the synovial membrane through
overextension or overuse. When no known cause
is identified, the term idiopathic tenosynovitis is
often used.
Secondary traumatic tenosynovitis relates to
inflammation caused by a lesion of a structure
within the sheath or sheath wall. Causes include
digital flexor tendinopathy and manica flexoria
Fig. 1.707 Transverse sonogram of the distal dorsal tears, fractures of the bones associated with the
radius just proximal to the carpus showing a severely sheath (phalanges, PSBs) and injury to the annular
damaged ECR within a distended sheath dorsal to the ligaments. Lesions in structures outside, but in close
radius. Note the subcutaneous fibrosis and thickening. vicinity to, the sheath wall (PSBs, distal sesamoidean
(Photo courtesy Graham Munroe) ligaments, SDFT insertion branches, palmar foot
area) can also lead to active tenosynovitis.
effective, although the gait abnormality and sheath Sympathetic tenosynovitis refers to non-
distension usually persist. Tenoscopic debride- inflammatory, transitory synovial fluid distension
ment of the sheath and frayed tendon ends has been due to inflammation elsewhere in the distal limb.
reported to benefit some horses, particularly those Inflammatory conditions lead to hyperaemia
with partial tears. Repair of the ruptured tendon is and oedema within the synovial membrane, which
not effective in most cases. thickens. If the inflammation persists, synovial cells
will proliferate, leading to permanent thickening
Prognosis of the membrane and eventual fibrosis in chronic
The prognosis for soundness is fair, but it is poor cases. Fibrous adhesions may also develop between
for return to athletic activities. Partial tears may heal the parietal and visceral sheath layers. In addition,
adequately after tenoscopic debridement. some types of pony and horse (native breeds, cobs
and draught types) are particularly prone to second-
DIGITAL FLEXOR TENDON ary subcutaneous and perisheath fibrosis, subsequent
SHEATH TENOSYNOVITIS to chronic tenosynovitis of the digital sheath. All of
these anomalies can severely compromise the func-
Definition/overview tion of the sheath, causing partial to total restriction
Inflammation of the synovial tissues of the DFT of lower limb mobility.
sheath (DFTS), usually but not necessarily associated
with distension of the sheath (tendinous windgalls). Clinical presentation
Cold sheath distension is characterised by moder-
Aetiology/pathophysiology ate to marked fluid accumulation within the sheath
There may be many causes. Spontaneous fluid dis- lumen, often bilaterally. The proximal pouch pro-
tension of the sheath without lameness or overt trudes laterally and medially to the digital flexor ten-
signs of inflammation (‘cold windgalls) is common dons and proximally to the palmar annular ligament