The chronically foundered horse
Central to the chronic rehabilitation research underway at the HDRC is a herd of horses with chronic laminitis that has been
donated to the Hoof Project Foundation in College Station, Texas, the organization that funds the HDRC. The foundation funds
help maintain the horses, and investigators from other institutions are also using these animals for their research.
"The overall goal of the rehabilitation research is optimizing the clinical management of the difficult cases," says Hood.
Given the central role that lameness plays in chronic laminitis, a force plate system has been developed and tested that allows
an objective assessment of lameness severity in the standing horse. While the system's data analysis package is still being
studied, this system is already a key component of the rehabilitation project.
"One of the primary goals of the project is to obtain a clearer picture of what pathologies are present in the foot and to
define how the presence (and severity) of a pathology impacts the severity of lameness shown by the horse," Hood explains.
In addition to standard diagnostic tests (e.g., radiographs, venograms) special diagnostic approaches are being developed.
One of these is a laminar biopsy—full thickness down into the dermis, below the laminar interface. It's a fairly simple surgical
procedure done under a local anesthetic, Hood says. In addition to tissue from necropsied horses, tissues from biopsies are
examined and used to index the healing response that is present in the laminar interface. The endpoint that they are working
toward is to develop a treatment regimen for the chronically foundered horse. Diagnostic nerve blocking is also being used
to define the regional location of lameness.
As more is learned, data are being organized into diagnostic, prognostic paradigms that allow specific rehabilitation approaches
for affected horses to be developed. "For example, once we index the lameness and define what pathological lesions are present
in the foot, we have a better focus on what an individual horse needs to optimize its rehabilitation," Hood says. "We are
developing a diagnostic battery of tests and logic paradigms to establish data about the foundered horse, other than just
noting that the horse has sore feet. With our nerve blocking diagnostic tool, we can assess where the pain is coming from—it
may be coming from the sole surface, from the laminar interface, from the heel or from above the foot, the fetlock."
Much has already been learned about the hoof of the foundered horse, says Hood. "We have also learned that a significant number
of chronically foundered horses in this age group have acquired injuries to the back, hock or stifle that impact the lameness
diagnosis. At this time we are attributing this to some arthritic or traumatic-type injury induced by the horse getting up
and down without using the front feet."
Another component of the project is assessing treatments to see if they are impacting lameness severity. "We need to know
if the type of shoe used actually does what we think it does. Does it make the horse more comfortable?" says Hood. "Consider
that in clinical practice, trimming, shoeing and maybe bute [phenylbutazone] are administered nearly simultaneously. Even
with the same treatment protocol, some horses will show a decreased lameness where others demonstrate an increased lameness.
In this component of the work, we are separating the specific trimming, shoeing and pain management protocols and evaluating
the effect of each on lameness severity. We are also looking at the short- and long-term effect of treatments on the pathologies
present in the foot."