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EQUINE VETERINARY EDUCATION / AE / SEPTEMBER 2017


stable in an extended (weightbearing) position and horses usually then will load the limb. Open luxations are catastrophic, carry a poor prospect for survival and the large majority justify immediate humane destruction. If an animal is of sufficient value to justify perseverance then the exposed tissues should be cleansed before the joint is reduced. Optimal temporary support is provided in the form of a


bandage cast or cast that extends from the bearing surface to the proximal metacarpus. However, once the joint is reduced and placed in an extended position, it usually is stable and therefore maintenance of this position with a Robert Jones or splinted Robert Jones bandage extending to proximal metacarpus or use of a compression boot may suffice.


Transverse or oblique fractures of the metacarpal diaphysis Complete transverse or oblique fractures of the metacarpal diaphysis are inherently unstable, displace immediately and invariably are catastrophic in racehorses. Comminution is common and, due to the paucity of overlying soft tissue they frequently are, or become, open (McClure et al. 1998; Beinlich and Bramlage 2002; Hill 2003a; Bischofberger et al. 2009). Unrecognised or inappropriately managed incomplete fractures of the dorsal cortex are thought to be a major predisposing factor (Hill 2003a). The distal limb is uncontrollable and when moving at speed afflicted horses may fall; if possible the horse should be restrained (physically and chemically) in this position until subjected to euthanasia. Standing horses are markedly anxious and sometimes panic. Immediate sedation and sometimes physical restraint is necessary in order to effect control long enough for euthanasia to be organised. Any necessary dialogue with connections should be swift and opinions, including if necessary colleague support, forthright.


Carpal subluxation Carpal subluxation is an uncommon racing or training injury. Most angular deviations result from displaced/collapsing cuboidal bone fractures which usually are comminuted and frequently involve bones in both proximal and distal rows with consequential collapse on the affected side. Radial with third and/or second carpal bones are most common, resulting in varus deformity (Ruggles 2006; Ross 2011). It is not known whether such fractures occur concomitantly or from sequential overload. Lameness is marked and usually is sufficient to prevent the horse from continuing to run. Angulation generally is visible and accompanied by crepitus with an abnormal range of mediolateral motion. Joint distension (haemorrhage) is quickly evident together with periarticular swelling over the affected bones as joint integrity commonly is compromised. In the absence of collapsing cuboidal bone fractures,


mediolateral instability requires complete disarmament of one collateral ligament and usually is accompanied also by fracture at its origin or insertion. In the author’s practice, the most frequently encountered of these is fracture of the proximal second metacarpal bone. The author has encountered dorsopalmar subluxation only


in the presence of multiple palmar cuboidal bone fractures. Emergency immobilisation of choice is a tube/sleeve cast


extending from proximal antebrachium to distal metacarpus with the limb in a loaded/weightbearing position (Fig 10).


© 2016 EVJ Ltd


a)


b)


Fig 10: a) and b) Carpus immobilised in an extended position with a sleeve cast applied from proximal antebrachium to distal metacarpus.


Under sedation, the affected limb should be placed perpendicular to the ground so that the horse ‘stands square’. Five-cm squares of adhesive cast felt with central 2 cm diameter circles removed (doughnut like) should be placed over medial and lateral styloid processes of the radius and accessory carpal bone. Three to 4-cm wide bands of the same can then be stuck to the skin at the proximal and distal margins of the cast. A single layer of conforming bandage such as Soffban2 then covers the cast area. Eight to 10 rolls of 10 cm plaster of Paris are layered over this, varying the thickness of the plaster of Paris to reduce protuberances in


the limb and thus to create a smooth surface for the rigid fibreglass tape. Three rolls of 7.5 cm followed by four rolls of 12.5 cm polyurethane impregnated fibreglass tape follow immediately while the plaster of Paris is wet. This promotes interdigitation of the materials creating a secure bond and eliminating independent movement. At the ends of the cast, a small amount of foam/felt should protrude adjacent to the skin and a small amount of plaster of Paris should protrude from the fibreglass. Cast materials all are applied in accord with


manufacturers’ recommendations. Useful tips include keeping the fibreglass wet for several minutes while rubbing the surface to encourage the polyurethane to run between the layers of fibreglass to promote bonding. Once frothing of the polyurethane subsides then wrapping loosely a water soaked gauze bandage over the cast surface also promotes this activity.


Moving horses from the racetrack to the racecourse


clinical facility is optimally achieved with a splinted full limb Robert Jones bandage or bandage cast in order to limit damage caused by the collapse and to permit the animal a degree of control of the limb which assists significantly in reducing accompanying anxiety.


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