Page 399 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

374 CHAPTER 1

VetBooks.ir Differential diagnosis Diagnosis
Traumatic or septic bursitis of the calcaneal bursa, Clinical examination
capped hock (acquired subcutaneous bursa), septic
calcis under the skin. The instability is easily pal-
osteitis of the calcaneus and tendonitis of the deep The tendon may be seen to flick on and off the tuber
tarsal tendons should be considered. pated during passive hock flexion. If the luxation is
permanent, a tense band is palpable or even visible
on the affected side of the calcaneus. The luxation is
most commonly lateral.
1.740
Ultrasonography
Ultrasonography will confirm the luxation, calca-
neal bursitis and rupture of the medial (or lateral)
calcaneal branch of the SDFT. The ruptured branch
is usually not visible and replaced by hypoecho-
genic tissue (haematoma, oedema and frayed liga-
ment initially, echogenic fibrous scar tissue later on)
(Figs. 1.741, 1.742). The intact, opposite branch is
often visible as a hypoechogenic, mass-like struc-
ture, the loss of tension causing it to retract like an
accordion. There may occasionally be damage to the
SDFT and the author has encountered a case where
the SDFT was partially split longitudinally, causing
each portion of the tendon to luxate abaxially.

Fig. 1.740 Permanent lateral luxation of the SDFT Management
off the tuber calcis. The tendon is visible under the Surgical repair is difficult, and a variety of tech-
skin, following a straight path over the lateral aspect niques have been described to reattach the tendon
of the calcaneus. in position. However, breakdown and recurrence are

1.741 1.742 Figs. 1.741, 1.742
Transverse sonograms of
the calcaneal region of the
plantar hock of a horse with
an acute lateral subluxation
of the SDFT. (1.741) This
scan shows the damaged
medial retinaculum (+) and
the slight lateral position of
the SDFT. (1.742) A slightly
more medially obliqued scan
showing the damaged ligament
adjacent to an area of calcaneal
bone roughening caused by the
avulsion of the ligament from
its insertion. (Photos courtesy
Graham Munroe)