Page 184 - Canine Lameness

156 12 Distal Limb Region (I)

DISTAL LIMB REGION

(A) (C) (E) (G)

(B) (D) (F) (H)
Figure 12.7 Sesamoid disease (white circles are used to outline the affected sesamoid bones in all
images): (A) radiograph and (B) CT of traumatic sesamoid fracture of the fourth proximal sesamoid; note
that establishing a diagnosis on radiographs is difficult, but fracture is clearly revealed on CT. (C–F)
Sesamoid disease of sesamoids 3 and 7; note that radiographs (C, E) permitted to establish the diagnosis in
this case, but (D, F) CT was used to determine the extent of the disease. (G, H) Radiographs of bipartite
sesamoid (sesamoid 7, white arrow) permitted to establish the diagnosis. (I) Typical location for palpation of
thoracic limb sesamoid 7.

Sesamoid fragmentation is a condition mainly occurring in young Rottweilers. It is not associated
with trauma or specific athletic pursuits but, like traumatic fractures, usually also involves sesamoids
II and VII of either of the thoracic limbs (Read et al. 1992; Mathews et al. 2001). Fragmentation has
been reported in other breeds such as Labrador Retrievers and Cattle Dogs (Mathews et al. 2001), and
clinical signs may vary greatly. Traumatic fractures are generally associated with an acute, severe
lameness; whereas chronic conditions may present with mild or no lameness. Pain on deep, direct
palpation and during flexion may be elicited, and local swelling may be palpable. Sesamoids II and
VII are easily palpable adjacent to the metacarpal pad, while sesamoids III–VI may be covered by the
pad (however, as noted above, these are rarely affected). Over time, a thickening of the area may
develop and a reduction of flexion of the adjacent metacarpophalangeal joints may also occur. In
normal animals, this joint should be able to flex to at least 90°.
Diagnosis is generally confirmed with dorsopalmar and oblique radiographs (Figure 12.7) but
CT can also be used and simplifies the diagnosis. Tape traction and/or separation of the digits with
cotton wool may allow better radiographic visualization. Imaging may reveal fragmentation (clus-
ter of ossicles with sharp or rounded margins depending on chronicity) of the affected sesamoids.
Enthesophytosis, soft tissue swelling, or calcification (Cake and Read 1995) and other secondary
arthritic changes may also be observed. Since radiographic evidence of sesamoid disease can be an
incidental finding (Vaughan and France 1986), it is imperative to rule out other causes of thoracic
limb lameness. Further complicating the diagnosis is the fact that bipartite or multipartite sesa-
moids, a congenital abnormality where the sesamoid presents as multiple instead of a single bony
structure, may be present. These are minimally displaced, usually have rounded margins, and are
not accompanied by soft tissue swelling. Scintigraphy or CT can be used to differentiate this