Midbody fractures of the proximal sesamoid bones occur infrequently in the Thoroughbred and Standardbred racehorse and are rarely seen in all other horse breeds. This type of fracture typically is diagnosed in a forelimb and is considered to be career-ending without surgical intervention.
Dorsopalmar and lateromedial radiographic views of a horizontal midbody fracture of the medial proximal sesamoid bone in a forelimb. For an exact diagnosis multiple views including oblique views are necessary.
Fractures of the proximal sesamoid bones - all fracture types
Fractures of the proximal sesamoid bone occur primarily in racing breeds. Occurrence of the fracture is usually associated with fast strenuous exercise, but has been reported in horses on paddock exercise and in young foals running on large pastures.
Fractures of the proximal sesamoid bone are more commonly diagnosed in the forelimb and the medial proximal sesamoid bone is the most frequently affected structure.
Typically the patient is presented with an acute non-weight-bearing lameness and minimal soft-tissue swelling associated with or without joint effusion.
Overview of fracture types
The following fracture types are diagnosed:
I. Apex fractures II. Midbody fractures III. Base fractures IV. Abaxial fractures V. Axial fractures VI. Comminuted fractures
In this chapter the management of the different fracture types will be discussed in sequence as they are listed here, which corresponds with ascending severity and descending prognosis as listed in the human fracture classification. Axial fractures almost exclusively occur in conjunction with break-down injuries, or a displaced condylar fracture, which will be discussed under Metacarpo-/metatarsophalangeal arthrodesis.
Example of an abaxial fracture
Example of an axial fracture combined with a lateral condylar fracture.
Standard radiographic views of the metacarpo/metatarsophalangeal (fetlock) region including dorsopalmar/plantar, lateromedial and two oblique views commonly reveal the fracture on more than one view. In selected cases additional radiographic views may be needed to confirm the diagnosis.
Scintigraphy, computed tomography (CT) (see image), and magnetic resonance (MR) imaging are valuable aids for the diagnosis, especially in the assessment of associated soft tissues. CT and MRI are especially useful to assess articular fractures and to identify displacement of the fragments.