Page 133 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

108 CHAPTER 1

VetBooks.ir centres of ossification and these may occur unilat- Diagnosis
The history of an acute-onset, moderate to severe
erally, bilaterally or, occasionally, in three or four
lameness, withdrawal response to hoof testers placed
limbs.
across the heels or on the frog and an absence of
Aetiology/pathophysiology swelling or other physical findings is compatible
The fracture is caused by trauma such as kicking at with a distal sesamoid fracture, although other more
a wall or landing hard on an uneven surface. The common problems are often considered initially.
fractures are slow to heal and usually heal with a In horses with lameness associated with chronic
fibrous union if untreated. OA of the DIP joint usu- fractures, regional analgesia, usually a palmar
ally occurs as a sequela. digital nerve block, is needed to localise the pain.
Radiography is essential to achieve a definitive diag-
Clinical presentation nosis (Figs. 1.188, 1.189). The most useful projec-
Horses with an acute distal sesamoid bone fracture tions are 60° dorsoproximal/palmarodistal oblique
present with a moderate to severe lameness. Horses and the palmaroproximal/palmarodistal oblique
with a chronic fracture of the distal sesamoid pres- views. Superimposition of a paracuneal (collateral)
ent with a mild to moderate lameness. Instability sulcus on the navicular bone in the 60° dorsoproxi-
between separate centers of ossification can cause mal/palmarodistal oblique projection can mimic
mild to moderate lameness. a fracture and must be carefully distinguished by
examining the palmaroproximal/palmarodistal
Differential diagnosis oblique and standing dorsopalmar projections or
Any disease of the palmar aspect of the foot that by packing the sulcus and repeating the radiograph.
causes acute severe lameness or chronic moderate CT and MRI are useful to determine the true frac-
lameness: navicular disease; sheared heels; bruis- ture configuration and the presence of comminu-
ing; puncture wound; abscess; soft-tissue injuries tion. MRI can also be useful to determine whether
of the foot. The radiographic appearance must there is any concurrent damage to the dorsal surface
be differentiated from a bi-partite distal sesamoid of the DDFT caused by abrasion of the sharp frac-
bone. ture margins. Laceration of a tendon lobe is a poor

1.188 1.189

Figs. 1.188, 1.189 Navicular bone fracture.
Dorsoproximal/palmarodistal (1.188) and
palmaroproximal/palmarodistal oblique (1.189)
radiographs showing a fracture through the body of
the navicular bone.