Displaced radial fractures in adult horses
Displaced radial fractures are easily diagnosed because of usually pathognomonic signs, such as a non-weight bearing lameness, with flexed carpus and metacarpo-phalangeal joint, toe dragging, accompanied by axial instability and crepitus in the antebrachial region (Matthews et al., 2002; Watkins et al., 2019). In case of open fractures the medial surface of the antebrachium is involved, because of minimal soft tissue coverage (Sanders-Shamis et al., 1986; Watkins et al., 2019). Stewart et al. (2015), found out that 24% of 54 cases of radial fractures were open and comminuted.
Fractures of the radius are usually due to a high‐impact blunt trauma, for example a kick from another horse (Hubert, 2020), but the radius is also particularly sensitive to side‐impact loads (Piskoty et al., 2012). Fürst et al. (2008) in an ex-vivo study, found that, after a simulated kick on the medial aspect of the radius, the majority of the bones sustained a fissure fracture (incomplete fracture) running longitudinally along the diaphysis, followed by an oblique configuration and butterfly fragment fractures. Another post-mortem study mimicking kicking injuries on radii and tibiae showed that 59% developed a complete fracture, with the presence of a butterfly fragment in 52% of the complete fractures (Schneider et al., 1982). Sander-Shamis et al. (1986) found radial comminuted fractures to be the most common (21/47), followed by oblique fractures (12/47). Butterfly fragment and and comminuted fractures are usually observed in horses older than 2 years (Sanders-Shamis et al., 1986). Comminution almost always accompanies either a spiral or an oblique fracture of the diaphysis in adult patients and it usually is more severe than in foals (Watkins et al., 2019).
To evaluate the fracture configuration, treatment options and prognosis, oblique projections should be acquired (Watkins et al., 2019; Auer, 2020).
Successful repair of radial fractures in adult horses has been described by few authors (Martin and Reef, 1987; Baxter et al., 1991; Rodgerson et al., 2001; Bolt and Burba, 2003; Stewart et al., 2015); but the prognosis in adults is generally very poor. Fracture configuration is vital in determining the possibility of repair. “If anatomic reduction of the fracture(s) and solid bone‐to‐bone contact cannot be achieved in an adult, especially in the caudal cortex, the horse should be humanely destroyed” – Auer (2020).
For simple, displaced radial fractures, surgical treatment including open reduction internal fixation (ORIF) may carry a fair outcome in young horses and in patients weighting less than 250 kg (Auer and Watkins, 1987; Barr, 1989; Baxter et al., 1991; Schneider et al., 1995; Stewart et al., 2015; Watkins et al., 2019; Auer, 2020); in adult horses ORIF is a monumental challenge with low survival rate (Auer and Watkins, 1987; Stewart et al., 2015; Auer; 2020); In Sanders-Shamis et al.,’s report (1986), internal fixation was attempted in six adult horses, none of which survived, while in another study internal fixation lead to only two horses (out of 9) discharged from the hospital (Auer and Watkins, 1987) and Stewart et al.,’s study (2015) only 3 out of 13 adult horses surgically managed, using locking compression plate (LCP) implants, survived to discharge, but 2/3 were yearlings.
With an open contaminated fracture there is a poor chances of successful plate fixation due to high risk of infection, and the use of a transfixation cast could be considered (Hubert, 2020); the application of a full‐limb cast alone for displaced fractures of the radius is not acceptable because the humeroradial joint cannot be adequately immobilized, and the cast may increase rotational forces and movement at the fracture site (Hubert, 2020). Even with fractures that can be fixed, the the bone–implant construct in adult horses can easily fail, because of biomechanical forces (Watkins et al., 2019).
Displaced diaphyseal fractures of the radius easily become open because the sharp fracture fragments penetrate the skin on the medial aspect of the antebrachium, and there is often a severe injury to the musculature covering the dorsal and lateral aspects of the antebrachium, accompanied by soft tissue swelling and haematoma, which make radial fractures at high risk of developing surgical site infection (SSI) and preclude the likelihood of success (Watkins et al., 2019). Open fractures also have a higher risk of SSI, increasing the risk of morbidity and cost associated with treatment, as well as the likelihood for catastrophic failure of the bone–implant construct (Watkins et al., 2019). Furthermore, if the fracture implant is infected there will be a high level of pain, leading to support limb laminitis in the contralateral foot (Watkins et al., 2019).
Unfortunately, the high cost associated with surgical fixation, combined with the high risk of failure, often dissuades owners from pursuing repair (Watkins et al., 2019).
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