By Ruth-Anne Richter BSc (Hon), DVM, MS
Once a diagnosis of a specific tendon or ligament injury is
made, a therapeutic plan must be formulated. Discussion about treatment options
should include the regenerative therapies, shockwave therapy, surgery or
conservative methods. For the treatment to have a successful outcome, a team
approach and dedication to the case is extremely important.
The goals of therapy for tendon or ligament injury are: (1)
To reduce acute pain and inflammation; (2) Optimize repair of the injured
structure; (3) Reduce any adverse biomechanical forces; and (4) Rehabilitation
and return to athletic performance.
The third goal: “Reduction of adverse biomechanical forces” is
the key to a successful outcome.
This is where teamwork between the veterinarian and the farrier is crucial, and
can significantly affect the outcome of the case. Open communication is
critical and knowledge of the potential negative and positive effects of
certain types of shoes or trimming techniques is necessary. The goal is to
reduce any adverse forces that might contribute to stressing or overloading the
injured structure by altering the ground reaction forces on that structure, and
is accomplished through therapeutic shoeing.
Biomechanically, the superficial digital flexor tendon
(SDFT) and the suspensory ligament do not respond well to being wedged up.
Whereas the deep digital flexor tendon (DDFT) and distal check ligament (DSL)
prefer to be wedged up when they are injured. That is with injuries to those
structures related to the SDFT or suspensory ligament, the goal is to reduce
stresses on those structures during the rehabilitation phase so the heels are
actually lowered, thus reducing ground reaction forces at the heel and
increasing them at the toe. Conversely, elevating or protecting the heel with
injury to structures that are biomechanically related to the DDFT and DSL
increases the ground reaction forces and reduces stress on those structures.
Using this information, shoes can be made to alter those
forces that cause stresses on some of these structures in the distal limb,
thereby unloading and protecting the injury.
Severe injury to the DDFT, can be treated in the acute phase
with a shoe with an elevated heel. A shoe with removable bars is useful
initially, removing bars intermittently to gradually return the affected limb
to the normal alignment. When there is injury to the distal aspect of the DDFT,
particularly at the insertion onto the coffin bone, additional support is often
necessary. A heart bar shoe is very useful for many of these horses. However,
some horses that have injury at or near the insertion of the DDFT onto the
solar surface of the coffin bone, do not tolerate the focal pressure placed by
the heart bar shoe. In these cases, a modified plate with dental impression has
been very useful. The bar of this shoe is very wide covering the caudal 1/3 of
the foot, and can be placed either between the branches of the shoe if the
hoof-pastern axis is normal, or on the ground surface of the shoe to add a
little height to the heel as needed. Caution must be used with this type of
shoe; it is best when the horse is confined. In work, the horse gets little
traction, and can slip causing secondary injury. The goal is to gradually
reduce the width of the bar and the amount of dental impression until the horse
is finally in a straight bar shoe for a short period of time, or permanently.
This type of shoe is also very useful for horses with injury to the small
ligaments associated with the navicular region such as the distal sesamoidean
impar ligament of the navicular bone.
Shoes useful for horses that have desmitis of the suspensory
ligament (SL) include those that encourage the heel to sink into the ground a
little. Beveled or penciled branches fit short/to the perimeter with a wide toe
are used for these cases. The increase in toe width ‘elevates’ the toe, the
heel drops slightly and there is less stress applied to the SDFT and SL.
The challenge comes with horses that have asymmetric
lesions, such as those with a medial or lateral collateral/suspensory ligament
injury. In general, an asymmetric shoe is used with the width applied to the
branch of the shoe on the injured side. The opposite branch is then beveled to
permit that side of the foot to sink into the ground.
Additional challenges arise when there is more than one
injury in the same limb. The more significant of the problems should be
addressed first, but listen to the horse; communication between owner, farrier
and veterinarian will help determine how the horse is tolerating a particular
shoe.
None of these shoes will be successful in facilitating
repair if the foot has not been trimmed and balanced appropriately. While this
may be something that should go without mention, it often contributes to
reinjury and loss of usefulness of the horse.
The ultimate goal of therapeutic shoes is to facilitate
rehabilitation of the injury and to eventually return the horse to functional
use, and to be back in ‘regular shoes’.
For more information
contact Dr. Richter at: rrichter@surgi-carecenter.com
This article originally appeared in Horse & Pony
magazine in August, 2011 and is reprinted with their permission.