Coffin Bone Fracture

Most of us equate fractures in the horse’s leg to a grave prognosis, but surprisingly, this isn’t necessarily the case. One such example is with fractures of the third phalanx bone (PIII.) This bone is better known as the coffin bone because it is encased completely inside the hoof capsule just as a body is in a coffin. It serves a vital role in the horse’s physiology. The lamina that adhere the hoof capsule to the skeleton attach on the dorsal surface of the coffin bone, and the digital extensor and flexor tendons that facilitate limb movement anchor to it. Without a functional coffin bone, one may conclude that the horse has no chance for survival. However, in the case of coffin bone fracture, horses can have a shot at recovery.

Radiograph of a coffin bone fracture.

Coffin bone fractures are classified by type. Each of the 7 types has a distinct fracture pattern and prognosis.

Fracture management techniques vary tremendously depending on the type of fracture, owner capabilities (including finances, time commitment, and facilities,) and other factors such as the age of the horse and additional physical problems. In most cases, the veterinarian will institute the following basic fracture management strategies:

1. Characterize the fracture by having your veterinarian take radiographs and make an accurate diagnosis as to the type and severity of the fracture. Your vet can then outline a treatment program and also talk with your farrier about trimming and shoeing the horse to reduce forces on the fractured bone (see #2).

2. Stabilize the fracture by working with a farrier to apply a bar shoe to the hoof. This protects the rim of the hoof, can alleviate pain, and will prevent instability by creating a solid support structure which limits expansion of the hoof capsule.

3. Limit mobility of the horse by confining the horse to a stall.

4. Provide deep bedding not only to pad the hoof but also to promote laying down by providing a comfortable environment.

5. Give non-steroidal anti-inflammatory (NSAID) medications such as bute or Previcox to limit inflammation and subsequently reduce pain. *Remember- using pain as a way to limit your horses movement is not a good strategy for humane reasons. In addition, pain itself has been shown to involve chemical mediators which will prohibit healing. Don’t make your horse stand on a broken bone for months in excruciating pain- curb it with medication!

6. Tincture of time is a cornerstone in coffin fracture management. Expect resolution to take at least 6 months- assuming that other aspects of fracture management listed above are being effectively implemented.

Although not among the more common therapies, the following are also possible options to treat a fractured coffin bone:

· Surgery involving the placement of a permanent screw in the bone can be useful for types 2, 3, 4 and sometimes 5 fractures. Types 1,6 and 7 fractures can be treated by surgical removal of the chip. The healing time for any surgery is extensive as the entire hoof capsule needs to regrow after the procedure. This can take upwards of one year. Complications such as infection are also possible with surgery.

· The use of bisphosphonate medications such as OsPhos and Tildren for the treatment of coffin bone fractures may be beneficial since these medications enhance calcium resorption in bone. Bisphosphonates should not be used during the first month of the fracture since they inhibit cells that are actually instrumental in cleaning up the area before new bone can be formed. Their efficacy to assist in fracture repair in horses has not been proven, so the addition of bisphosphonates to fracture treatment would be purely empirical.

Waiting for 6 months can drive horse owners (and the horses for that matter) crazy! It is a long and difficult haul- but there can be a light at the end of the tunnel! Don’t give up too soon on coffin bone fractures- they are not necessarily terminal.

To learn more about coffin bone fractures, we recommend an excellent guide published by the American Farrier’s Journal called Anatomy and Fractures of the Coffin Bone.

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