How to Apply a (Plaster) Cast in Cases of Acute Laminitis.

1. Introduction

Laminitis is a medical emergency; however, it also requires urgent mechanical measures aimed at diminishing tension on the inflamed laminae, reducing pressure on the anterior sole under the distal margin of the coffin bone and finally, minimizing the asymmetrical tensions on the hoof capsule produced when the horse turns.

These mechanical measures can be obtained in many ways.

• Duct taping polystyrene foam pads under the hoof/hooves.
• Wrapping of the foot/feet with a role of gauze under the frog.
• Fitting the horse with raised heel hoof boots with frog-support material.
• Wearing dental silicone supports that are held in place under the palmar/plantar region of the foot/feet with bandaging.
• Wrapping with plaster casting that is molded adequately around and under the hoof.

The advantages of this last procedure can be summarized as follows: quick, cheap, clean, simple to apply, easy to change, and moldable to the required shape.

2. Materials and Methods

Materials needed include a bucket of water (warm water will speed up the process) and three to four rolls of plaster (CaSO4 x 2H2O) that are 10 cm wide for small/medium feet and 15 cm high for large feet. Start by unrolling the first drenched roll in one’s hands, and after squeezing out the excess water, molding it into a rounded mass to be applied to the caudal part of the foot. Then, with the other two to three (wetted) rolls, the clinician wraps the hoof, holding the initial "ball" in place and leaving the sole (anterior to the frog) free (Fig. 1).

Figure 1. Palmar aspect of the right fore with plaster cast.

The hoof should be preferably unshod and trimmed moderately; most importantly, the toe should be trimmed if it is too long. The “ball” of plaster should protrude from under the distal margin of the hoof at the heels. The wrapping should be performed in the usual, diagonally alternated way: medial bulb-lateral toe first and lateral bulbmedial toe next.

Care should be taken to round off the proximal part of the cast around the coronary band and the bulbs before the plaster sets. This will prevent pressure sores (do not use synthetic casting material) (Fig. 2). The final result should distantiate the sensitive anterior sole from the ground and transfer weight to the caudal part of the sole, bars, and frog.

Figure 2. Lateral view of the applied cast.

The quick setting time of plaster usually permits the application of the cast without regional anesthesia to the weight-bearing limb if the following items are available: fresh plaster bandages, warm water, and an efficient helper to hold up the leg. Additionally, the contra-lateral limb should be placed on a soft padding material, and the clinician should always start with the most painful foot first.

3. Results

Weight is transferred in a stable manner to the frog, bars, and palmar/plantar sole, which unloads the dorsal wall and laminae. The dorsal sole is raised away from the ground, and lateral medial breakover is enhanced to make turning less painful. After removing the plaster cast with a cast cutter or a toeing knife, the underlying structures, including the frog grooves, have a clean aspect without excessive build up of humidity (Fig. 3).

Figure 3. Inside view of a removed cast.

In the acute phase, horses usually show a marked degree of instant relief, probably because the weight is redistributed away from the most painful structures (dorsal laminae) to the palmar/plantar areas of the hoof. This is also the reason that the most painful foot should be treated first, because it will be better able to bear weight after it is in a cast and able to support the horse during casting of another foot.

Plaster casts allow for horses to be walked for clinical examination purposes, which is often a problem with alternative methods. The casts do not interfere greatly with X-rays.

This is a common method used in some European countries (e.g., Germany) [1]. It has been used for >10 yr by the author as an emergency care measure with an average of 28 patients/yr.

4. Discussion

With a bit of practice, the procedure is quite easy and effective in the acute stage of laminitis. It diminishes laminar tension in the dorsal part of the hoof because of the raised heels, which reduces deep digital flexor tendon pull. Additionally, it stabilizes the hoof capsule relative to its laminar suspension apparatus.

The malleability of plaster is useful in customizing the emergency support system (e.g., heel support can be adjusted higher, lower, more lateral, more medial, etc. as needed), and it seems more stable than some of the other emergency mechanical methods.

It is important to use plaster cast and not synthetic casting material. Although the latter is much lighter and stronger, it is also sharper at the edges. Because horses do not always stand perfectly still because of the discomfort on the weightbearing limb, it is hard to keep the proximal edge of the cast below the coronary band. Additionally, the cast wrapping usually goes over the bulbs. With plaster casts, the author has not encountered any skin, bulb, or coronary band ulcerations; however, these complications often arise with the use of synthetic casts. However, if the horse is doing well and moving about, it can be useful to cover the dorsal sole with a rigid, synthetic pad (there should remain space between the pad and the sole) fixed to the lower part of the original plaster cast, because this renders the arrangement a lot more wear resistant.

A plaster cast of the hoof, thus applied, should be seen as a mechanical emergency measure to be used until the acute problem has been stabilized (1 - 3 wk). After that time, a more durable shoeing solution should be found.