Shoeing for Palmar Hoof Pain

Introduction

Palmar hoof pain (PHP) is usually defined as a positive reaction (absence or decrease of lameness) after a distal palmar digital nerve block ( DPDN block near the margin of the ungular cartilages). Although sometimes defined as a “heel block”, it anesthetizes the DIP joint, the entire sole, the distal phalanx (PIII) and the navicular apparatus ( 1/ Schumacher 2006)

Besides podotrocleosis, which in itself is a condition which encompasses more than just “naviculitis “or “navicular syndrome “, PHP may therefore be due to:

• Heel or solar bruises and / or abscesses.
• Severe thrush or canker.
• Trauma to the bulbs ( over reaching injuries ).
• Osteitis of P III.
• (wing) fractures of P III.
• Quarter cracks.
• Quittor.
• Artrosis-arthritis of the DIP joint.

The last is not always easy to differentiate from podotrocleosis) as DIP joint anesthesia ( especially when more than 6 ml of local anesthetic is used ), might, by distending the palmar pouches, anesthetizes the DPD nerves.( 1/ Schumacher 2006).

Clinical examination

Careful clinical examination, including inspection, palpation, pulse taking and judicious use of hoof testers ( before anesthesia of course ), remains the most valuable tool in differentiating among the different conditions mentioned above. This examination requires patience and more clinical skills than is often assumed, but can , together with a good history work up, often save a lot of frustration.

An especially valuable clinical test is the digital extension / elevation test. Traditionally done with a board, this test evaluates the horse’s tolerance to dorsal extension, ( 2/Desbrosse, 2002).[ fig.1.a,b,c,].

A graduated Digital Extension Device ( DED) has been developed by the author which , besides measuring the exact degrees of tolerance to the dorsal extension of each forelimb, also permits evaluation and measurement of the tolerance to lateral and medial elevation of the foot, which causes collateromotion of the DIP joint ( 3/ Chateau et al, 2002).

Tolerance to dorsal extension is variable for each limb, depending on conformation, and can vary in sound horses from around 30° ( some quarter horses with straight short pasterns and “ tighter “ deep digital flexor tendons (DDFTs), to over 45° ( e.g. some thorough bred horses with long oblique pasterns ,and lax DDFTs).

Sound horses tolerate lateral and medial elevations of the foot till the opposite side of the foot lifts off the surface of the DED. The degree of elevation at which this occurs , is much more standardized across breed- and conformation types, than dorsal elevation; typically being 19° of lateral elevation and 20-21° of medial elevation. Differences between lateral and medial degrees, are probably due to the fact that the test is performed with the opposite limb held off the ground, whereby the horse places the weight bearing , and tested , limb , closer to the midline of its body.

Intolerance to dorsal extension may indicate :

• Podotrocleosis, including bursitis, impar ligament desmitis, distal DDF tendonitis and desmitis of the collateral ligaments of the distal sesamoid.
• Proximal DDF tendonitis.
• Inferior check ligament desmitis.
• Dorsal laminar inflammation.

Intolerance to lateral or medial elevation may indicate:

• DIP, PIP or MC Phalangeal collateral ligament desmitis ( on the opposite side of the elevation)
• Laterally or medially located subcondral bone lesions of the digital joints ( on the ipsilateral side of elevation).
• Lateral or medial suspensory ligament branch desmitis ( opposite side ).
• Arthrosis of digital joints with lateral or medial bone spur formation ( ipsilateral side , generally).
• Distal DDF tendonitis located in the lateral or medial lobes of the tendon, (opposite side).
• P III fractures ( wing, ipsilateral side).
• Trimming mistakes are characterized by reduced elevation values on one side, accompanied by increased elevation values on the opposite side of the foot (trim more on the side of reduced elevation values).

Finally, there are conditions which might reduce tolerance to extension in a combination of directions: dorsal and lateral, dorsal and medial, lateral and medial, all three.

Diagnostic Imaging

In recent years diagnostic imaging has made great strides, as first ultrasound and then MRI and CAT have allowed for much more detail when “looking” into the foot. High quality, ( digital) X rays, including the use of contrast material, have also progressed, but the great difference is certainly the ability to better detect soft tissue injuries, which generally precede bony lesions.[ fig.2]

Better diagnostics though, also means finding more lesions, often in different , even adjacent structures, each of which theoretically requires different biomechanical solutions ( read shoeing strategies ) . This is another point which indicates the importance of a good, clinical work up; e.g. if a lesion in the distal DDFT, adjacent to a lesion in the straight distal sesamoidean ligament is detected, it is necessary to find out if the horse resents dorsal digital extension more than fetlock extension, before prescribing therapeutic shoeing. [ fig.3.a,b.].

Therapeutic shoeing techniques.

The following elements should be taken into account when considering shoeing prescriptions:

• Type of lesion, clinical signs.
• Type of work-performance expected from the horse.
• Surface the horse works on.

The last element is of paramount importance, because a lot of shoeing techniques which are based on changing around the ground wearing surface of the shoe, only work on penetrable ground. As far as the type of work goes, some disciplines require an enormous amount of work on ( tight) circles others do not ( e.g. standard bred racing).

Some lesions hold out hope for eventual healing ( e.g. some soft tissue injuries ), and the therapeutic shoeing will only be temporary; other lesions are permanent ( e.g. ring bone),and therapeutic shoeing techniques will be necessary for the rest of the horse’s (working) life.

General objectives of therapeutic shoeing is to spare painful structures, but this can only be done by loading other structures more: e.g.: a reverse shoe on soft ground relieves the DDFT, but loads the superficial DFT and the suspensory ligament ( S:L.) more.

Table 1 : Illustrates therapeutic shoeing techniques for Palmar Hoof Pain conditions excluding DIP-PIP artrosis and podotrocleosis

Table 2 : Illustrates therapeutic shoeing techniques for DIP-PIP artrosis and for podotrocleosis