Page 120 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.3 The foot 95

VetBooks.ir Diagnosis 1.165
The classical radiographic image of pedal osteitis
shows variable demineralisation and an irregular con-
tour of the dorsal margin of the distal phalanx, with
vascular channels that fan out as they approach the
periphery of the bone. These are best seen on a 45°
dorsoproximal/palmarodistal oblique radiographic
projection (Fig. 1.165). Additional changes, including
lipping of the dorsal margin and mineralisation on the
parietal surface of the distal phalanx, may be seen on
lateromedial radiographic projections. These can also
identify pedal osteitis of the palmar processes, seen
as scalloping of the solar margin and bony remodel-
ling of the palmar process. This may also be observed
on the 45° dorsoproximal/palmarodistal oblique but
is best interpreted in conjunction with the laterome- Fig. 1.165 Pedal osteitis. Radiograph demonstrating
dial radiographs. Horses with persistent lameness demineralisation and irregularity of the solar margin
following treatment of penetrating injuries to the of the distal phalanx and widening of the vascular
foot, subsolar bruising, abscesses, laminitis, kerato- channels.
mas and implant surgery should be evaluated radio-
graphically to determine if the distal phalanx shows 1.166
remodelling changes suggestive of osteitis.
As pedal osteitis is a symptom that appears to
reflect either ongoing or past inflammation in the
tissues adjacent to the distal phalanx, and is found
in sound and lame horses, it is not always possible
to determine the clinical significance of the radio-
graphic findings, especially as considerable individ-
ual variation exists in the number and size of vascular
channels of the distal phalanx. Therefore, it should
be interpreted in the light of clinical findings and
other diagnostic tests. Particular emphasis should
be placed on the thickness and degree of convexity
of the sole, as well as the response to application of Fig. 1.166 Dorsal fat-suppressed MR image of the
hoof testers. The lameness in most horses in which foot. There is marked generalised hyperintense signal
pedal osteitis is significant will improve with palmar in the spongiosa of the distal phalanx indicative of
digital regional analgesia. Intra-articular analge- bone oedema associated with severe pedal osteitis.
sia of the DIP joint and navicular bursa analgesia
must be interpreted cautiously. If undertaken with
appropriate volumes of local anaesthetic and the clinical and radiographic findings. MRI may show
response can be observed within 5–10 minutes, they the presence of abnormal osseous fluid and roughen-
are unlikely to improve the lameness, but if larger ing of the cortical surface of the distal phalanx to
volumes are used, or too long a time is allowed to support the diagnosis, especially in one or both of
lapse before the lameness is re-evaluated, a false- the palmar processes (Fig. 1.166). An association
positive response is common. Scintigraphic exami- has been observed between osseous injury of a pal-
nation may indicate increased radiopharmaceutical mar process of the distal phalanx and the presence of
uptake in the solar margin area that corroborates the either extensive ossification of the ipsilateral ungual