Page 543 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Distal Limb 509

tinued drainage. In the severely underrun subsolar
abscess, one author (JKB) lavages the foot with satu-
VetBooks.ir cannula through small portals either in the distal hoof
rated Epsom salts delivered through a catheter or teat
wall (preferred) or sole. If there is moderate to severe
capsular rotation also present in the affected foot, a
deep digital flexor tenotomy with “derotation” of the
distal phalanx is also indicated to improve healing and
decrease the chance of recurrence by decreasing the
pressure on the affected dorsodistal aspect of the distal
phalanx and the adjacent subsolar/solar tissue.

HOOF WALL RESECTIONS
Full dorsal hoof wall resections were at one time
widely advocated to decrease the pressure of the wall on
the coronary band, debride necrotic material, and
12
encourage the realignment of the distal phalanx. They Figure 4.84. Grooving of the proximal dorsal hoof wall immedi-
accomplish these goals to some degree, including ately distal to the coronary band to encourage dorsal hoof wall
enhancing growth of new wall at the coronary band and growth and mechanically dissociate new hoof wall growth from the
increasing the likelihood that the newly formed wall will older distal wall.
conform to the parietal surface of the distal phalanx.
However, resecting the dorsal wall removes any support
that the dorsal wall supplied to the distal phalanx, enhance drainage of exudate that has accumulated
increases the vertical stresses in the wall at the margins under the separated tissues. It is advisable to bevel the
of the resection, and causes further instability by remov- proximal margin of the remaining hoof wall so that it is
ing circumferential tension that spans the dorsal hoof thinnest proximally (immediately distal to the coronary
capsule connecting quarter to quarter. Consequently, the band) to minimize the pressure ridge that develops and
remaining dorsal quarters are more likely to become dis- impinges the underlying dermis of the coronary band
tracted from the underlying tissues. Therefore, more lim- and proximal lamellae. The indications and optimal tim-
ited/partial hoof wall resections are more commonly ing for this procedure have not been determined.
performed than total dorsal hoof wall resections to min-
imize the loss of support to the distal phalanx and sta- Prognosis
bility of the adjacent wall observed in more extensive
resections. They are currently most commonly per- There are numerous reasons why treatment of horses
formed to debride necrotic tissues and remove the lamel- with laminitis is unsuccessful, but the three most impor-
lar “wedge” to encourage new hoof wall growth to tant reasons are the severity of the original pathology,
follow the contour of the distal phalanx. type of displacement, and severity of the clinical signs. 5,38,55,56
These factors are likely to determine the continued
course of the disease and the development of complica-
CORONARY BAND GROOVING AND RESECTION tions. The prognosis following displacement is always
considered guarded to poor.
Coronary band grooving is designed to take pressure Regarding the different types of displacement, rota-
off the coronary band to increase the rate of new hoof tion is considered to have a more favorable prognosis
wall growth (Figure 4.84). It also creates a discontinu- than either symmetrical or asymmetrical distal displace-
64
ity between older, more distal hoof wall and the newer ment. Increased experience with the treatment of asym-
proximal wall so that the distal wall is less likely to dis- metrical distal displacement suggests that the prognosis
tract the new hoof away from the distal phalanx. The for this condition is better than that with symmetrical
groove is created in the dorsal hoof wall at the level of displacement so long as separation at the coronary band
the base of the extensor process and extends through the has not occurred. Two radiographic criteria have been
full thickness of the stratum medium of the wall from documented to determine prognosis: the degree of rota-
one toe–quarter junction to the other. A modification of tion and the distance from the proximal margin of the
this technique involves creation of the groove as extensor process of the distal phalanx to the firm proxi-
described above and then removing all of the stratum mal margin of the hoof capsule (immediately distal to the
medium proximal to the groove to the level of the coro- coronet, distance also termed the “founder distance”). 14,68
net. In the authors’ experience, results with this tech- Capsular rotation greater than 11.5° predicted poor sur-
nique are highly variable. vival and capsular rotation less than 5.5° predicted
Resection of the cornified layer of hoof at the coro- return to performance. A coronet‐to‐extensor‐process
nary band is probably most frequently performed when distance of greater than 15.2 mm is indicative of poor
the hoof wall has separated from the coronary band. In survival. Both of these reports are dated, and with recent
these circumstances, it is done to decrease the chafing by advances in the treatment of this disease, their prognostic
the separated—and therefore somewhat mobile—hoof value should be reassessed. Additionally, the thickness of
wall that damages underlying viable germinal tissue and the sole and the angle that the solar margin of the distal