Unusual incomplete frontal plane third metacarpal fracture in a dressage horse

Abstract

Summary: Different types and locations of fractures of the third metacarpal bone have been discussed for decades, especially in regard to treatment and prognosis. There is lack of documentation of frontal plane third metacarpal fractures diagnosed by MRI within the extensive previous literature. The present case report describes an incomplete frontal plane third metacarpal fracture in a dressage horse. The A 6 year-old Hanoverian mare was suddenly lame during side passes within a dressage contest. Physical examination revealed a grade 3/5 lameness of the left forelimb. When standing the horse showed a tendency to leg rest. A discrete oedematous swelling from the medioproximal metacarpus to the middle third of the flexor tendons was palpable. Rotation of the phalanx resulted in a mild pain response. Initially a basic set of x-ray images was carried out, which did not show an evident fractureline. To further evaluate the cause of local swelling and lameness a standing MRI examination was carried out with a 0.27 Tesla Hallmarq EQ2 dedicated equine MRI system. In consequence, an incomplete frontal plane fracture of the third metacarpal bone was confirmed. The images depict typical features of acute fractures in MR studies. Angle adapted x-ray images were taken and the fracture line initially obscured by the splint bones became visible. No diagnostic block was performed due to the risk to worsen the incomplete fracture. Conservative management was chosen. During the first four weeks immobilisation was applied and exercise was restricted to box rest for another four weeks. During that time the mare was re-evaluated regarding to lameness in the walk, by MRI and by x-ray images. In the present case conservative management led to complete recovery. The last recheck in the stable took place after 46 weeks by the referring veterinarian. Until that time no signs of secondary osteoarthritis had occurred in follow-up radiographs taken by the referring veterinarian.

Multimodal imaging and surgical repair of a dorsal‐oblique plane, proximal third metacarpal fracture and the diagnostic challenge of radiographic visualisation

“…Similarly, to the report by Paschke and Walliser (2016), the horse in this case was an older, non-Thoroughbred. However, rather than an accomplished dressage mare with an increasing workload, this case was a leisure horse used for hunting with a known history of trauma.…”

“…A moderate grade of lameness was observed in both this horse and the case by Paschke and Walliser (2016), and in both cases, radiographic evaluation was of limited benefit. In this instance, complete superimposition of the fracture plane with the head of the second metacarpus prevented radiographic diagnosis, further supporting the use of cross-sectional imaging modalities such as MRI or CT.…”

“…Fractures of the proximal third metacarpus in a sagittal plane (Beccati et al, 2019; Lloyd et al, 1988; Morgan & Dyson, 2011) and fractures of the dorsal cortex (Jalim et al, 2010) have been described. To the authors' knowledge, there is only one prior report of an incomplete, frontal/dorsal plane fracture of the proximal third metacarpus (Paschke & Walliser, 2016). The distinguishing features in the case presented here include an acute lameness following known trauma, computed tomography and CT‐guided surgical repair description and the subsequently shortened rehabilitation period resulting in a successful return to full exercise.…”

“…The oblique orientation of the fracture plane is suspected to have arisen as a consequence of supraphysiological compression and/or torsion. In previous reports, including that of Paschke and Walliser (2016), a stress‐fatigue injury was hypothesised (Beccati et al, 2019), extrapolated from stress‐related fractures identified at other sites, for example, those seen in the young Thoroughbred racehorse. Therefore, irrespective of partial similarity of location, the presenting features, and thus likely management and outcome factors are likely to be different in a known traumatic event.…”

“…In the report by Paschke and Walliser (2016), their metacarpal fracture required coaptation of 4 weeks duration and a total of 8 weeks strict box rest prior to discharge, with ridden exercise not being reinstated until 22 weeks post admission. With our fracture, stabilised by surgical repair, the horse was discharged 4 days post‐surgery, began walking exercise 2 weeks later following suture and bandage removal and remained sound at walk with no lameness seen.…”