Page 176 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.4 The forelimb 151

VetBooks.ir 1.276 FRACTURES OF THE SECOND/FOURTH
METACARPAL/METATARSAL BONES

Definition/overview
Fractures of the second/fourth metacarpal/meta-
tarsal bones are commonly known as ‘splint bone’
fractures.

Aetiology/pathophysiology
These fractures are common in equine practice
and many cases are due to external trauma (e.g.
kick injury). As such, the most common splint bone
fracture is of the lateral or fourth metatarsal bone.
Fractures can occur proximally, mid-body or distally.
Involvement of the carpometacarpal/tarsometatarsal
joint in horses with proximal splint bone fractures
can occur and be important both in the management
as well as the prognosis of the case. Fractures can be
open or closed, simple or comminuted and may be
associated with a wound/contamination. Fractures
Fig. 1.276 Dorsopalmar radiograph of the carpus and involving the distal part of the splint bone may occur
proximal cannon of a horse with a lameness localised without overt trauma. In horses with concurrent
to the proximal cannon region by perineural analgesia. suspensory desmitis and reduced fetlock support,
Note the longitudinal palmar cortical fracture chronic stress remodelling on the distal aspect of the
(arrowhead) and surrounding subchondral bone bone may lead to failure of the bone and fracture.
sclerosis (arrow). (Photo courtesy Graham Munroe)
Clinical presentation
Horses with splint bone fractures due to external
not discriminate between this and other causes of trauma usually present with acute lameness, initially
pain in the area. Radiography may show a linear with swelling centred over the affected region. In
radiolucency in the proximal metacarpal region open fractures a wound may be present (Fig. 1.277)
medial to midline with sclerosis adjacent to the line and if the proximal part of the splint bone is frac-
(Fig. 1.276). Ultrasonography may show periosteal tured, involvement of the carpometacarpal/tar-
changes at or near the origin of the suspensory liga- sometatarsal joint will require early clarification
ment, often with no abnormalities in the ligament (Fig. 1.278).
itself. MRI may provide further evidence for a pal-
mar cortical injury as well as evaluating the suspen- Differential diagnosis
sory ligament and other structures (e.g. interosseous Third metacarpal/metatarsal fracture; synovial sep-
ligament). sis; exostosis of second/fourth metacarpal/metatar-
sal bone.
Management
Most cases respond well to conservative manage- Diagnosis
ment (rest/NSAIDs). Diagnosis of a splint bone fracture is usually through
clinical examination and radiography. Digital palpa-
Prognosis tion may reveal fracture fragments, but confirma-
Prognosis is generally good, although concurrent tion of the fracture and its configuration is made
suspensory ligament injury will reduce outcome. through radiographic examination. Standard views