Page 179 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

154 CHAPTER 1

VetBooks.ir EXOSTOSIS OF THE SECOND/FOURTH ligament can lead to lameness. This may worsen
METACARPAL/METATARSAL BONES
with exercise and improve with rest as the ‘splint’
Definition/overview becomes transiently active.
Exostosis or ‘splints’ of the second/fourth metacar- Differential diagnosis
pal/metatarsal bones are common in the horse. Fractures of the second/fourth metacarpal/ metatarsal
bones; suspensory ligament injury.
Aetiology/pathophysiology
Trauma to the bone leads to haemorrhage and lift- Diagnosis
ing of the periosteum, with subsequent bone forma- Clinical examination is often sufficient to diag-
tion. Horses that ‘dish’ in front may traumatise the nose a splint, although local anaesthetic infiltration
second metacarpal bone with the opposing forelimb. may be required to assess clinical relevance, espe-
Damage to the interosseous ligament because of cially in chronic cases. Radiography is important to
instability or trauma can lead to ‘splints’, particularly assess the size and potential interference with other
prevalent between the second and third metacarpal structures and to rule out fractures (Figs. 1.285,
bones. Young immature animals, especially those 1.286). Ultrasonography may be required to assess
with ‘bench-knees’ ( lateral positioning of the third the locality of the exostosis in relation to impor-
metacarpus in relation to the carpus) are particularly tant soft-tissue structures such as the suspensory
predisposed to ‘splints’. ligament.

Clinical presentation Management
In the acute phase, trauma will lead to swelling, pain Most cases of ‘splints’ resolve with rest and conser-
and lameness. In more chronic cases, the soft-tissue vative management. In acute cases or flare-ups, cold
swelling and oedema will subside leaving a firm, therapy and NSAIDs may be required. Local infil-
often non-painful, fibrous/bony mass on the bone. tration with corticosteroids may reduce soft-tissue
Occasionally, axial impingement on the suspensory inflammation in the short term. Extracorporeal
shock-wave therapy has been used in some cases. In
recurrent or severe cases where axial impingement
1.285 1.286 of the suspensory ligament is occurring, surgical
removal or partial ostectomy may be required.

Prognosis
Prognosis for horses with ‘splints’ is good. Horses
with poor conformation and recurrence carry a less-
favourable outcome.

Fig. 1.285 Dorsomedial/palmarolateral oblique
radiograph of the left forelimb metacarpus showing
smooth new bone formation in the mid-aspect of the
second metacarpal bone consistent with an exostosis.

Fig. 1.286 Dorsomedial/palmarolateral oblique
radiograph of the right fore metacarpus showing
extensive new bone formation between the dorsal
aspect of the second metacarpal bone and the palmar
aspect of the third metacarpal bone relating to
ossification of the interosseous ligament.