Diagnosis and management of traumatic equine fractures

There are a number of equine fractures that may be encountered in practice and equine practitioners should be able to diagnose and manage with confidence in the field. These can largely be divided into three categories; traumatic fractures, pathological fractures and those that occur as a result of repetitive stress-related pathology. Donati et al (2018) studied a population of 499 equids with fractures resulting from known kick injuries. The 2nd and 4th metacarpal/tarsal (splint) bones were affected most frequently (15%), followed by the radius and ulna (13.8% each), the tibia (12.2%) and the head (12%). Other commonly encountered sites of traumatic fractures include the distal phalanx. Sites of repetitive stress fractures include the pelvis, the condyles of the 3rd metacarpal bone and proximal phalanx. Pathological fractures may occur secondary to neoplasia or osteomyelitis. This article will focus on the diagnosis and management of traumatic fractures.

Fractures of the distal phalanx (pedal bone) usually occur as a result of trauma such as kicking a solid object, standing on a stone or fast exercise on hard ground. Horses may present with similar signs to those seen in a subsolar abscess; acute severe lameness, heat in the foot, increased digital pulses and focal pain on hooftesters. Horses with an articular fracture may have an effusion of the distal interphalangeal joint. Forelimbs are more commonly affected than hindlimbs (Honnas et al, 1988). Horses may be unwilling to place their heels or toes on the ground. Once an abscess has been ruled out radiography can be used to diagnose most distal phalanx fractures. The foot should be carefully pared and packed to avoid air artefacts and care taken to differentiate between normal vascular channels and fracture lines. Images must include a lateromedial, dorsoproximal-palmarodistal 65° oblique (upright pedal) and dorsal 45° proximal 45° lateral-palmarodistal oblique (pedal bone wing) views (Figures 1a,b and 2a). A 50° palmaroproximal-palmarodistal (navicular skyline) view should also be used to identify abaxial (wing) fractures. In some cases hairline fracture lines may be very difficult to diagnose initially and repeat radiography at ~7 days may be required. In a minority of cases pedal bone fractures cannot be diagnosed on radiographs but can be identified on magnetic resonance imaging (MRI) (Figure 2b). In the author's experience horses in which a distal phalanx fracture is diagnosed on MRI alone are likely to have a history of lameness localised to the foot which has shown an initial improvement to non-steroidal anti-inflammatory drugs and rest. There is recurrence of lameness once exercise resumes, although this is not pathognomonic for fractures. Distal phalanx fractures are categorised into seven types: type I) abaxial non-articular; II) abaxial articular; III) mid-sagittal articular; IV) extensor process; V) multifragment (comminuted); VI) Solar margin; VII) solar margin fractures in foals (Honnas et al, 1988).