Prevalence, radiographic resolution and outcomes of slab fractures of the third and central tarsal bones in juvenile Thoroughbred horses

Abstract

Background Veterinarians are required to interpret the significance of radiographic findings for sale, soundness and future racing performance of weanling and yearling Thoroughbreds. We investigated the prevalence and radiographic appearance of slab fractures of the third (T3) and central tarsal (Tc) bones.Methods Weanling and yearling horses with complete or incomplete T3 or Tc fracture were identified by searching a database of radiographs. The prevalence and radiographic appearance at initial diagnosis and after continued pasture turnout, as well as prognosis for racing, of fractures of T3 and Tc were determined. ResultsFractures were identified in 186 tarsi (184 T3 fracture only, 1 Tc fracture only, 1 Tc and T3 fracture) of 157 horses (126 unilateral T3, 29 bilateral T3, 1 contralateral Tc and T3, 1 unilateral Tc and T3) from 7676 examinations. The prevalence of T3 and Tc fractures was 2.40 (95% CI 2.07, 2.76) and 0.04 (95% CI 0.01, 0.11) per 100 radiographic examinations respectively. Fractures were identified on the D556-65 MPlLO view and occurred by survey examination at 11.1 AE 1.3 months in 85.7% horses. At initial diagnosis, 84.3% of T3 fractures appeared incomplete and involved the distal articular surface. Fracture score improved (P < 0.001), and dorsal modelling (P < 0.001) and osteoarthritis score increased in the distal intertarsal joint (P < 0.001), but not the tarsometatarsal joint, between survey and repository examinations. Fractures healed by repository examination in 71.9% of tarsi if there was > 6 months between examinations. There was no difference in sale price, and horses with T3 fractures had fewer trials when 2 and 3 years old (P = 0.023), yet no difference in other parameters of racing success when 2 or 3 years old compared with controls.Conclusion Tarsal slab fractures can occur in juvenile Thoroughbreds and most heal with continued pasture turnout of > 6 months. Further investigation is required to determine risk factors and before making firm conclusions regarding the optimal management, prognosis for racing and long-term soundness. Figure 2. Radiographic views (D55-65 MPlLO) of the tarsus of weanling or yearling Thoroughbred horses with dorsal modelling of the third (T3) or central (Tc) tarsal bones described as (a) grade 0 (nil), (b) grade 1 (mild), (c) grade 2 (moderate) and (d) grade 3 (severe). Additional changes include: (c) a slab fracture of T3 with marked blurring of the fracture line (stage 3 healing) and (d) a complete Tc fracture. D55-65 MPlLO, dorso-55-65 medial-plantarolateral oblique.

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

“…Bilateral fractures occurred in one horse in this study (complete and incomplete) and have not been previously reported in the central tarsal bone in sports horses, unlike in racehorses (Steel et al, 2019). Bilateral stress related bone injuries are common in other anatomical sites in sports horses, such as the sagittal groove of the proximal phalanx (Dyson et al, 2011; Gold et al, 2017) and have been described in the proximomedial aspect of the palmar cortex of the third metacarpal bone (Morgan & Dyson, 2012).…”

“…Incomplete partial‐thickness vertical fractures of the central tarsal bone have not previously been reported in non‐racehorses, even though the images of one horse in a report on bone marrow lesions of the distal tarsal bones (Biggi et al, 2012) strongly resemble the appearance of such a fracture. Incomplete partial‐thickness fractures of the central tarsal bone occur in racehorses but with a different configuration (Steel et al, 2019). The partial‐thickness fractures in our study demonstrated the same consistent configuration as the full‐thickness slab fractures, affecting the dorsomedial proximal part of the central tarsal bone and the proximal subchondral bone plate, with a short hyperintense line coursing in a dorsomedial to plantarolateral orientation, associated with marked sclerosis surrounding the fracture line in all cases.…”

Highlights of recent clinically relevant papers

“…This study by Cate Steel and colleagues in Australia and the USA examined the prevalence, radiographic resolution and outcomes of slab fractures of the third (T3) and central tarsal (Tc) bones in juvenile Thoroughbred horses .…”