How to Apply Foot Casts for Managing Distal Limb Injuries

1. Introduction

Distal limb injuries are frequently encountered emergencies in equine medicine. More specifically, heel bulb lacerations, pastern lacerations, hoof wall avulsions, collateral ligament injuries, and coffin bone fractures can be managed using a distal limb or foot cast. The most common distal limb injury is heel bulb or palmar/pastern lacerations.^1,2  Primary or delayed primary closure should be performed, when appropriate, before applying a foot cast; however, distal limb wounds may be allowed to heal by second intention under a cast. Casts that incorporate the foot and extend upward to the distal fetlock can substantially decrease the length of convalescence in horses by more completely immobilizing the distal interphalangeal and proximal interphalangeal joints than bandages or just casting the hoof wall.¹  Although the initial treatment of a distal limb injury may be performed under general anesthesia, it can be more advantageous to apply a foot cast when the horse is standing. Applying a foot cast in a standing horse has the advantage of enabling the proper hoof-pastern axis to be achieved and fixed because the horse bears full weight on the casted limb before the casting material sets, minimizing the likelihood of complications that develop with poorly conforming casts.¹  In contrast, applying a foot cast while the horse is under general anesthesia may result in an improper hoof-pastern axis as a consequence of hyper- or hypoextension of the distal portion of the limb. 

2. Materials and Methods

Precasting Considerations

A considerable number of synovial structures (distal interphalangeal joint, proximal interphalangeal joint, navicular bursa, digital flexor tendon sheath) are present in the equine distal limb; therefore, all synovial structures close to a distal limb injury should be thoroughly examined to determine whether there is communication with the wound. Arthrocentesis and synovial structure distention with sterile saline may be necessary to determine synovial structure involvement (Fig. 1); radiographs, contrast radiographs, and ultrasonography are adjunctive diagnostic modalities that may help assess the severity of the injury and whether synovial structures are involved. If a synovial structure is involved, then appropriate therapy to treat the infected synovial structure should be performed. It is important that the clinician is confident that the infected synovial structure has been eliminated before a distal limb cast is applied.
 

Patient Preparation

The most common distal limb injury is heel bulb or palmar/pastern lacerations.^1,2 Primary or delayed primary closure should be performed, when appropriate, before applying a foot cast; however, distal limb wounds may be allowed to heal by second intention under a cast. A light bandage that consists of a nonstick pad,^a elastic gauze,^b and a small length of elastic bandage material^c should be applied over the lacerations. Before a cast is applied, the shoe should be removed from the affected limb, and the foot should be trimmed to avoid focal pressure along the edges of the cast. All casting materials should be gathered in one location to expedite the cast application (Fig. 2).
 

General Casting Recommendations

General casting recommendations are as follows: 

• Wear latex or nitrile gloves.
• Casting material should not be opened until ready to use.
• Submerge casting material in water for 10 seconds to activate cast resin.
• Shake off excess water from casting material.
• Warmer water typically results in faster casting material cure times.
• Avoid wrinkles when applying casting material.

Forelimb Cast

With the horse sedated, an assistant should hold the affected limb off the ground along the distal metacarpus so the foot can position itself into a neutral position (Fig. 3). A double layer of stockinette^d (3–4 inches wide) is placed over the foot and extended to a level 2 inches above the metacarpopha-langeal joint. A premeasured length of stockinette should be cut, and each end should be rolled toward the middle; one end is rolled inward, and the other end is rolled outward (Fig. 3). 
 

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