Page 701 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Proximal Limb 667

that was eliminated by proximal plantar analgesia that felt that the presence of the corticosteroids within the
underwent MRI of the region, some of the horses had joint would have a significant detrimental effect on
VetBooks.ir of the CT and 3T bones, intertarsal ligament pathology, compromised cartilage would lead to the advancement
chondrocyte metabolism and the continued work on
OA of the DT joints, subchondral cystic lesions (SCLs)
of the cartilage damage in these joints. However, clini-
and bone edema of the third and fourth tarsal bones
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without evidence of proximal suspensory disease. cally this does not seem to be effective, and there has
Many of these horses had diagnostic analgesia of the been little evidence that ankyloses can be promoted by
TMT and DIT performed without significant response. consistent intra‐articular injection of corticosteroids.
The findings in this study continue to fuel questions The current approach to managing bone spavin espe-
about causes of tarsal pain and the accuracy of analgesia cially in a younger horse is to preserve the articular car-
of the proximal metatarsal region. tilage whenever possible.
Many factors may play a part in determining the spe-
cific treatment and management of horses with bone
Treatment of DT OA
64
spavin. These may include the degree of lameness,
OA of the DT joints commonly affects athletic horses extent of radiological abnormalities, use of the horse,
during the most productive years of their lives and can competition regulations, response to previous treatment,
limit their career potential. The goal of treatment is to and financial constraints. Clinically horses with exten-
provide significant, long‐lasting pain relief that will per- sive radiological abnormalities or with scintigraphic
mit the horse to remain comfortably in work. Horses abnormalities in the absence of radiological change
with minimal radiographic changes of the DT joints seem to have a more limited response to intra‐articular
may respond favorably to a short period of reduced injections. Resting horses with bone spavin is usually
activity, corrective shoeing, systemic medications (like not beneficial. Anti‐inflammatory medications are indi-
nonsteroidal anti‐inflammatory drugs [NSAIDs]), and a cated to reduce inflammation and pain in affected
change in the work program. Intra‐articular treatment horses. Phenylbutazone (2.2 mg/kg, BID) can be contin-
options have included the use of corticosteroids, hyalu- ued for an extended period of time in most horses or
ronan, or polysulfated glycosaminoglycans (PSGAGs). given only when the horse is worked. Treatment with
A common strategy in the management of horses dis- NSAIDs (particularly phenylbutazone) can be quite
playing mild bilateral hindlimb lameness (particularly effective in some horses, and attempts should be made
those breeds and disciplines that are predisposed to DT to find the lowest dose possible that will alleviate lame-
lameness) is to medicate the DT joints with corticoster- ness. Long‐term use of oral phenylbutazone at 1gram
oids and evaluate for a response. A short‐term response twice daily for a 500‐kg horse is generally well tolerated.
(less than 2–3 months) should be a concern that the pri- Any treatment should be combined with corrective trim-
mary source of pain was not effectively addressed and ming and shoeing. The inclusion of systemic treatment
should be an indication to more carefully evaluate the such as PSGAGs, pentosan, oral nutraceuticals, or any
tarsal region for other sources of lameness. The deposi- combination may also be chosen in certain cases.
tion of steroids into the TMT joint can have a local
effect on the soft tissue structures in proximal plantar
region and may suppress inflammatory changes in the Intra‐articular Medications
proximal SL. Corticosteroids can also suppress healing Intra‐articular medications such as corticosteroids,
by inhibiting the production of collagen, which may hyaluronan, and more recently IRAP can be utilized in
lead to a perpetuation/exacerbation of any injury of the joint inflammation. 43,53,81,90,130 Corticosteroids are potent
proximal SL in this area. A short duration of effect for anti‐inflammatory agents and inhibit the inflammatory
intrarticular (IA) corticosteroids could also be indicative process at all levels and have been the mainstay of treat-
of more advanced changes within the DT joints. Further ment for many years. Many horses with DT joint pain
clinical and imaging examination (potentially including have been successfully managed throughout their ath-
MRI) of the tarsal region should be recommended. letic career with consistent (biannual to annual) intra‐
Most clinicians recommend some form of intra‐artic- articular injections of corticosteroids. There are quite
ular medication (see below) to help subdue the inflam- varying opinions about which drugs are most effective
matory changes within the DT joints. The response to in the DT joints and for how long the clinical effects
therapy can often be predicted based on the extent of from these different drugs might last. It is not univer-
radiographic signs and to a certain degree on the dura- sally accepted which drug is most efficacious, what dose
tion of clinical signs. One study demonstrated a positive of any drug should be given, how frequently these injec-
outcome following intra‐articular medication in only tions need to occur, or if intra‐articular antibiotics
81
38% of cases with OA of the DT joints. However, in should be given in conjunction with the drug. The corti-
that study only the TMT joint was treated in the major- costeroids that are most frequently used include methyl-
ity of the horses, which may explain their low success prednisolone acetate (MPA), betamethasone, and
rate. Another study reported that 52% of horses were triamcinolone (TA) either alone or in combination with
able to return to their previous level of exercise, with an some form of hyaluronan products. Rest has been rec-
improvement in 70% of horses that had both the TMT ommended after injection, but there is little evidence to
and DIT joints injected. 24 support any prolongation of effect by doing so. In
Historically it had been suggested that injection of humans rest postinjection has been advocated after
corticosteroids (with or without hyaluronic acid [HA]) intra‐articular medications in the belief that restriction
into the DT joints while maintaining the horse in work of activity might reduce clearance of the medication and
would eventually lead to ankylosis of these joints. It was enable better penetration of intra‐articular tissues.