Abstract:
Axial sesamoiditis or osteitis of the proximal sesamoid bones (PSBs) in the horse is described
as a rare condition. The cause remains unknown and speculative, with vascular, infectious
and traumatic aetiologies implicated. It is specifically associated with injury of the palmar or
plantar ligament (PL), also known as the intersesamoidean ligament. Imaging findings are
generally rewarding, and radiological changes are typical, if not pathognomonic, for the
condition. Lesions consist of bone lysis at the apical to mid-body axial margins of the PSBs,
with variable degrees of joint effusion. Radiographic technique warrants careful attention to
make a diagnosis, and exposure factors may need to be adjusted. Perineural, intra-articular
and intra-thecal anaesthesia does not seem to provide consistent improvement of lameness
in these cases, with literature reporting inconsistent findings. Ultrasonographic findings
include digital flexor sheath effusion, loss of the normal fibre structure of the PL at its
attachment to the PSBs, abnormal echogenicity or change in thickness of the PL, and irregular
hyperechoic cortical margins of the axial margins of the PSBs. Scintigraphy, computed
tomography and magnetic resonance imaging, although not necessary to make a diagnosis,
may add valuable information regarding the location and extent of lesions. The prognosis
remains guarded to poor for return to athletic function. The focus of this article is a
comprehensive review of the proposed aetiopathogenesis of the condition, the prognosis and
a summary of the literature findings with focus on the notable diagnostic imaging features,
including radiography, ultrasonography, scintigraphy, computed tomography and magnetic
resonance imaging.
