Page 485 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Distal Limb 451

any of these shoes enhances break‐over, thus reducing meglumine, phenylbutazone, and firocoxib are used
the stress on the DDFT. The goals of any of these shoes most commonly, and all should be effective in reducing
VetBooks.ir reduce the forces acting on the navicular bone by the ease that were treated with 1.1 mg/kg of flunixin meglu-
inflammation and lameness. Horses with navicular dis-
should be to ease break‐over, support the heels, and
mine or 4.4 mg/kg phenylbutazone once daily for 4 days
DDFT.
Heel elevation has been shown to decrease tension in showed significant reduction in lameness scores for
the DDFT, reduce pressure applied to the navicular 24 hours after the last dose compared with baseline
bone, reduce the load to the forelimbs, and reduce the and horses treated with saline. The clinical responses
52
stresses on the hoof capsule (Figure 4.16). 96,98,102,132 The between flunixin meglumine and phenylbutazone were
heels are supported for a greater proportion of the stride, similar and suggest that once‐daily dosing of NSAIDs
and the wedge tends to increase the weight transferred should be effective to control pain in the majority of
through the heels. A recent study that quantified the these horses.
pressure distribution across the palmar surface of the NSAIDs are often used for pain relief if the horse is
navicular bone documented that the maximum pres- severely lame or if the horse needs to continue working
sures exerted by the DDFT corresponded to the areas of through the initial treatment period. Phenylbutazone is
128
known navicular pathology. However, raising the usually used most frequently because it is less expensive
heels by 5° and 10° only redistributed the pressures on than flunixin meglumine. It is usually given at a dose of
the navicular bone, suggesting that raising the heels may 4.4 mg/kg PO once daily for 7–10 days as the initial
not be that beneficial in horses with navicular syn- treatment. This appears to effectively break the pain
128
drome. Some clinicians feel that elevated heel shoes cycle and allows for adjustment to corrective trimming
offer mixed results and should only be used temporarily and shoeing. NSAIDs may be used intermittently
96
106
especially in horses with DDF tendinopathy. However, thereafter if they are permitted for the athletic activity of
heel elevation alone or when combined with phenylb- the horse.
utazone has been shown quantitatively (using a force
plate) to improve lameness in clinical cases of horses
with navicular syndrome. The disadvantages of rais- Intrasynovial Medication
102
ing the heels with the use of pads in horses with under- Injecting medications into the DIP joint or navicular
run heels may cause further collapse of the poorly bursa is often used as an adjunctive treatment for horses
supported heels, and heel growth appears to be reduced with navicular disease/syndrome. 3,25,27,75,102,127 Injection
with wedge pads. 25 of medications into the digital flexor tendon sheath
Egg‐bar shoes and natural balance shoes have not (DFTS) may also benefit some horses with more proxi-
been shown to reduce the forces on the navicular bone mal lesions of the DDFT that are documented with
as effectively as heel elevation. However, egg‐bar shoes MRI. Deciding when to treat horses with navicular
96
106
increase the length of the toe–heel axis causing the center disease/syndrome intrasynovially and with what
of pressure to shift caudally. Egg‐bar shoes are usually medication(s) to use is strictly empirical based on many
98
recommended in cases where the hoof capsule is unsta- clinical and diagnostic findings. The types of medications
ble due to shearing or in horses with severely underrun used are similar to those used to treat OA/synovitis/cap-
or collapsed heels. The egg‐bar shoe increases the sur- sulitis in joints at other locations, such as corticosteroids
face area of contact and the stability of the hoof. The alone, corticosteroids combined with hyaluronan (HA),
shoe should be applied so it is clearly visible at the quar- polysulfated glycosaminoglycans (PSGAGs), or other
ters and extends far enough palmarly to cover the biologic therapies.
heels. 115,120,121 Natural balance shoes, by their design, Horses with navicular disease are thought to benefit
reduce break‐over and if combined with heel elevation from intra‐articular treatment of the DIP joint by reduc-
also reduce the forces acting on the navicular bone. See ing the inflammatory response both within the joint and
Chapters 8 and 11 for more information on corrective within the navicular region. 18,85 Studies have demon-
trimming and shoeing. strated that methylprednisolone acetate (MPA) or triam-
A minimum 2‐ to 3‐week adaptation period is often cinolone (TA) can diffuse between the DIP joint and
necessary to achieve pain relief with any type of shoe- navicular bursa after intra‐articular or intrabursal injec-
ing. 96,102 In most cases improvement in clinical signs tion. 18,85 Other studies have documented the benefit of
after corrective trimming and shoeing should be evident intrabursal injections in providing substantial but tem-
within 6 weeks but may depend on the severity of the porary relief of pain in many horses with navicular dis-
initial lameness and the specific structures affected. ease. 27,75,127 The benefit of DIP joint injections is less well
Severe hoof imbalances may require several shoeing documented, but anecdotally it is considered effective in
intervals to achieve a normal hoof conformation, and, in many horses. 4,25 One study did not find a significant
some cases, the underrun heels may persist indefinitely. reduction in lameness after treating the DIP joint with
Additionally, not all horses respond in the same manner TA compared to corrective shoeing alone although the
to a particular shoeing type, and we as veterinarians overall severity of lameness was further reduced follow-
should remain flexible in using a different type of shoe if ing treatment. However, many clinicians use intrasyn-
102
a clinical response is not obtained. ovial treatment of the DIP joint as part of the initial
treatment regimen, together with corrective trimming
and shoeing and phenylbutazone for most horses with
Nonsteroidal Anti‐inflammatory Drugs
navicular disease/syndrome.
The use of NSAIDs is a common adjunctive treatment In many horses, especially if advanced imaging can-
for horses with navicular disease/syndrome. Flunixin not be performed, there is a stepwise progression of