Page 402 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.8 Soft-tissue injuries 377

VetBooks.ir may be useful to decrease the bursal inflammation. bandaged. Rarely, there may be avulsion of the ori-
gin of the tendon on the lateral femoral epicondyle.
In severe chronic bursitis, adhesions and thickening
may cause mechanical lameness or persistent pain.
In these cases, bursoscopy may be useful to perform Clinical presentation
partial synovectomy and adhesiolysis. In septic cases, Typically, the horse can stand normally. Lameness
early lavage and intrabursal antibacterial administra- is variable, but there is characteristic overextension
tion may ensure full recovery, but delayed treatment of the hock at the end of the stance phase, causing
often leads to irreversible damage to the SDFT, to the distal limb to slightly lag behind. There may be
the gliding surface of the calcaneus and to restrictive swelling and oedema in the acute phase over the cra-
adhesion formation, leading to persistent lameness. nial aspect of the crus.
Bursoscopy is always recommended, even in early
cases, to remove all debris and fibrin. Diagnosis
Clinical examination
Prognosis Diagnosis is based on the pathognomonic loss of
Prognosis is fair to good for non-inflammatory reciprocal flexion between the stifle and hock. Thus,
swelling, and for acute or recent non-infectious bur- the hock can be passively extended while the stifle is
sitis when the cause can be treated adequately. It flexed (Fig. 1.747). This also leads to a dimpling of the
is poorer in chronic cases, as there is often signifi- common calcaneal tendon (‘Achilles tendon’), which is
cant mechanical impairment. In septic cases, unless no longer kept taut by the opposing extensor system.
prompt lavage and debridement can be performed,
the prognosis is guarded. It is poor when bone ero- Ultrasonography
sions and/or damage to the SDFT are present. Ultrasonography helps to determine the level of the
rupture but is not necessary for the diagnosis. It is,
RUPTURE OF THE FIBULARIS however, useful for monitoring the healing process.
(‘PERONEUS’) TERTIUS TENDON

Definition/overview 1.747
The fibularis tertius tendon is a fibrous structure,
lacking muscle fibres, that runs from the lateral
femoral epicondyle to the dorsal proximal aspect of
the metatarsus (with a secondary branch inserting
on the lateral aspect of the third and fourth metatar-
sal bones). It is a major component of the reciprocal
apparatus as it forces the tarsus to flex passively when
the stifle flexes. Rupture is usually strain induced and
spontaneous, although the tendon may be severed in
wounds to the cranial aspect of the crus.

Aetiology/pathophysiology
This condition is a consequence of a sudden strain Fig. 1.747 Rupture of the peroneus tertius tendon.
injury, the tendon being stretched to rupture The hock is extended by pulling the limb backward
through overextension of the hock while the stifle while the stifle remains flexed. Note the slight
is still flexed. This may occur when the distal limb dimpling of the common calcaneal tendon due to
is caught over a fence, door or jump or following loss of reciprocal tension from the peroneus tertius
recovery from anaesthesia when the limb is cast or tendon. (Photo courtesy Roger Smith)