An Uncommon Proximal Third Metatarsal Bone Fracture in Racehorses
Stress-related bone injuries are an important cause of lameness in racehorses, with fractures of the third metacarpal and metatarsal bones well recognised in horses during training and racing [1–3]. However, fractures of the proximal third metatarsal bone (MT3) can occur in several different configurations and may present a diagnostic and therapeutic challenge [4,5].
In our recent case series, we described the diagnosis, surgical treatment and outcome of four racehorses with an unusual radiographically incomplete, articular fracture of the proximal MT3 bone [6]. All four horses developed acute hindlimb lameness following fast exercise. The fracture had a consistent dorsomedial–plantarolateral oblique orientation, extending distally from the tarsometatarsal joint [6].
One of the key messages from these cases was the importance of obtaining the correct radiographic projections. In all four horses, a D40–50°M-PlLO projection was important for identifying the fracture configuration [6]. In one case, the fracture was not identified during the initial radiographic examination and nuclear scintigraphy was subsequently used to localise the site of injury before further targeted radiographs demonstrated the fracture. This highlights the potential for these fractures to be missed when relying on standard radiographic projections alone.
All four fractures were treated surgically using cortical screws placed in lag fashion to achieve interfragmentary compression [6]. Three procedures were performed in the standing sedated horse, while one was performed under general anaesthesia. Standing fracture fixation can offer several advantages in appropriately selected horses, particularly by avoiding the risks associated with general anaesthesia and recovery [7,8]. However, careful case selection remains essential.
This was particularly evident in one case. Following initial lag screw fixation, the fracture became unstable and ultimately required revision surgery using double locking compression plate fixation [6]. In retrospect, the development of a dorsal fracture component meant that this fracture was not suitable for lag screw fixation alone. Fractures with more complex configurations, including dorsal or transverse components, may require more extensive stabilisation under general anaesthesia [6].
The outcomes were encouraging. Three of the four horses returned to their previous level of exercise within 7–8 months and subsequently raced between 9 and 14 months after surgery. Two of these horses went on to win races. The remaining mare was retired to stud [6].
Although this is a small case series describing an uncommon fracture configuration, there are useful clinical lessons. Accurate radiographic positioning is critical, and additional imaging should be considered when clinical suspicion remains despite apparently negative radiographs. Importantly, the configuration of the fracture must guide the choice of surgical technique.
Overall, our experience suggests that these unusual proximal MT3 fractures can have a good prognosis for return to athletic function following appropriate surgical repair, while reinforcing the importance of careful case selection when considering standing fracture fixation [6].
References
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Lischer C, Klaus C. Diaphyseal fractures of the third metacarpal and third metatarsal bones. In: Wright I, editor. Fractures in the Horse. Chichester, UK: John Wiley & Sons Ltd; 2022. p. 485–500.
Wright IM, Nixon AJ. Fractures of the condyles of the third metacarpal and metatarsal bones. In: Nixon AJ, editor. Equine Fracture Repair. 2nd ed. Hoboken, NJ: Wiley-Blackwell; 2020. p. 378–424.
Pilsworth RC. Incomplete fracture of the dorsal aspect of the proximal cortex of the third metatarsal bone as a cause of hind-limb lameness in the racing thoroughbred: a review of three cases. Equine Vet J. 1992;24:147–150.
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Findley JA, O'Neill HD, Bladon BM. Outcome following repair of 63 sagittal fractures of the proximal phalanx in UK thoroughbreds using either a triangular or linear screw configuration. Equine Vet J. 2021;53:524–529.