Page 340 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.8 Soft-tissue injuries 315

VetBooks.ir The lameness is not altered by distal metacarpal or Radiography
There may be sclerosis, with loss of the trabecular
metatarsal analgesia (lower six-point nerve block),
although proximal diffusion of the anaesthetic solu-
or plantaroproximal third metacarpal or metatarsal
tion may improve the gait. The lameness may or may pattern and thickening of the cortex, of the palmaro-
not respond to proximal metacarpal or metatarsal bone (Fig. 1.602). Cortical fissures or avulsed frag-
analgesia (higher six-point nerve block), but it should ments may be visible near the origin of the ligament
be abolished by specific anaesthesia of the palmar (Figs. 1.603, 1.604).
metacarpal or plantar metatarsal nerves 4 cm distal
to the carpometacarpal/tarsometatarsal joint or by 1.603
‘instillation’ of local anaesthetic around the origin
of the ligament. In the forelimb, specific ulnar nerve
anaesthesia may be combined with the proximal
four-point metacarpal analgesia. In the hindlimb,
specific anaesthesia of the deep branch of the lateral
plantar nerve often provides marked improvement of
the gait, although it should not be considered a spe-
cific test. Local anaesthetic may diffuse elsewhere
or leak into the tarsal sheath or tarsometatarsal
joint. False-positive and false-negative responses are
observed. The lameness may also respond to analge-
sia of the carpometacarpal or tarsometatarsal joints.

1.602

1.604

Fig. 1.602 Dorsopalmar radiograph of the proximal Figs. 1.603, 1.604 Dorsopalmar (1.603) and flexed
metacarpus of a horse presenting with proximal lateromedial (1.604) radiographs of a horse with
suspensory ligament desmitis. There is a diffuse increase avulsion of both heads of the suspensory ligament.
of mineral opacity and loss of the normal, coarse Note the two slightly displaced bony fragments
trabecular pattern in the proximal metacarpus, indicative (arrows), leaving a fracture bed visible as a lucent halo
of sclerosis (delineated by arrowheads and arrow). with a sclerotic rim (arrowheads).