Low‐field MRI findings and follow‐up of central tarsal bone fractures in four non‐racehorses

Abstract

Background: Central tarsal bone fractures in non-racehorses are uncommon and their MRI appearance and follow-up have not been described. Objectives:To describe the clinical and MRI characteristics and follow-up of central tarsal bone fractures in non-racehorses. Study design:Retrospective descriptive case series. Methods:The low-field MRI appearance of central tarsal bone fractures in sports horses identified over a 9-year period, was reviewed. Follow-up MRI examinations, treatment and clinical outcome were included.Results: Four horses with five vertical fractures of the central tarsal bone were included.There were three Warmbloods, of which two were showjumpers and one a dressage horse, and one Quarter Horse used for western performance. All fractures could consistently be visualised on low-field standing MRI and were associated with marked sclerosis in the surrounding bone, with little to no associated bone marrow lesion of the central tarsal bone. One horse had bilateral fractures. Three fractures were complete (full-thickness) slab fractures and two were incomplete (partial-thickness) slab fractures.Fractures occurred in a consistent dorsomedial to plantarolateral oblique orientation and were non-displaced. Incomplete fractures occurred at the dorsomedial proximal aspect of the central tarsal bone. All horses were treated conservatively initially. The dressage horse with bilateral fractures and the Quarter Horse remained lame after conservative treatment and were subsequently treated surgically. Three horses returned to their previous level of performance, one horse in spite of persistent MRI evidence of a fracture line (non-union), while the Quarter Horse returned to a lower level of reining.Main limitations: Small number of horses. Conclusions:Standing low-field MRI is helpful in the diagnosis of central tarsal bone fractures. Central tarsal bone fractures occur in a dorsomedial to plantarolateral orientation in sports horses, can be complete or incomplete, unilateral or bilateral and remain nondisplaced. The prognosis is good for return to performance.

Computed tomography and fluoroscopy versus radiographic guidance for internal fixation of simulated dorsomedial‐plantarolateral central tarsal bone fractures in nonracehorses

“…Despite problems with screw placement due to CTB curvature, clinical experience at this institution and in published literature 2,4,6,9 has shown that these fractures heal well with internal fixation. CTB fractures are unique in that screw placement often requires the violation of several basic principles of internal fixation that are considered clinically acceptable in these cases.…”

“…Also, in most fractures the drill tract should be continued through the far cortex to achieve maximal screw purchase and compression of the fracture fragment 14 ; however, the ideal amount of bone engagement beyond the fracture is unknown for CTB fractures. Compared to other fracture locations in horses, it is likely that less of the screw needs to extend beyond the fracture due to the degree of sclerosis that is often present 4–6 . Small tarsal bone fractures are also provided additional stability by a tight fibrous joint capsule and the surrounding tendons and ligaments in the distal tarsus 3 .…”

“…Small tarsal bone fractures are also provided additional stability by a tight fibrous joint capsule and the surrounding tendons and ligaments in the distal tarsus 3 . This added stability may explain why conservative management can be successful in some cases 1,3,6 …”

“…Compared to other fracture locations in horses, it is likely that less of the screw needs to extend beyond the fracture due to the degree of sclerosis that is often present. [4][5][6] Small tarsal bone fractures are also provided additional stability by a tight fibrous joint capsule and the surrounding tendons and ligaments in the distal tarsus. 3 This added stability may explain why conservative management can be successful in some cases.…”

“…Fractures of the central tarsal bone (CTB) are an uncommon but well‐described cause of lameness in horses, occurring predominantly in performance horses after strenuous exercise 1–4 . In nonracehorses, these fractures commonly extend from dorsomedial to plantarolateral with involvement of the articulation between the central and fourth tarsal bones 4–6 …”