What are Fractures of the Proximal Sesamoid Bones?
Fractures of the proximal sesamoid bones can happen to any horse but they are more common in racing Thoroughbreds, Standardbreds, and Quarter horses. Fractures to the proximal sesamoid bones are classified by where the fracture is located. Apical fractures occur on the upper part of the sesamoid bone. Basilar fractures occur on the bottom third of the proximal sesamoid bone and lateral proximal sesamoid fractures are located on the side of the bone. There can also be basilar, mid-body, axial or biaxial fractures of the proximal sesamoid bones. Fractures can be minor or they may be catastrophic.
Sesamoid bones are small triangular bones found within certain tendons or muscles. Proximal sesamoid bones are located in the lower limbs of the horse and are part of the metacarpophalangeal (fetlock) hinge joint. The hyperextension of the metacarpophalangeal joint causes extreme tension across the proximal sesamoid bones, which can cause them to fracture.
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Symptoms of Fractures of the Proximal Sesamoid Bones in Horses
- Joint distension
- Skin on the fetlock rips open
Causes of Fractures of the Proximal Sesamoid Bones in Horses
- Strenuous racing or training
- Torque forces caused by trailer type shoes
Diagnosis of Fractures of the Proximal Sesamoid Bones in Horses
The veterinarian will want to go over your horse’s medical history and training routine. Let him know the symptoms you have noticed and the approximate start date. If your horse has experienced any trauma or injury, discuss the event with the veterinarian. A physical examination will follow the consultation. The physical exam may include taking the patient’s temperature, blood pressure, heart rate, and pulse, and will include a reflex test and palpation of the limbs. He may want to see the horse walk first hand. The veterinarian may also do a hoof test on your horse to look for injury, fungus, or infection. He will evaluate the overall condition of your horse.
If the veterinarian suspects a proximal sesamoid fracture he will recommend taking x-rays of the limb. The x-rays will help determine if there is a fracture and the exact position of the break. He may also suggest an ultrasound scan of the area. The ultrasound scan can show if there is any injury to the soft tissue. The veterinarian may also want to have a complete blood count (CBC) drawn on the patient. The blood will be drawn from the jugular vein on the side of the neck; if the white cell count is elevated, it is an indication of a bacterial infection or inflammation.
Treatment of Fractures of the Proximal Sesamoid Bones in Horses
The treatment of the proximal sesamoid bone depends on the specific fracture and the location of the break. If the fracture is displaced (bone fragments) surgery usually is recommended. The veterinarian will refer you to an orthopedic equine surgeon.
The equine surgeon may suggest placing a screw fixation through the sesamoid bone or he may use cerclage wire around the fractured bone. These procedures are performed to stop fracture motion.
Minor fractures may be treated with anti-inflammatory medication, oral antibiotics and stall rest. Stall rest maybe for a period of 30 to 60 days. The veterinarian may also suggest vitamins and supplements to help stimulate bone production. In some catastrophic injuries, the bone fusion is the only way to have stability in the fetlock joint.
Recovery of Fractures of the Proximal Sesamoid Bones in Horses
Horses that underwent surgery will be given postoperative instructions by the surgeon. It is very important to follow the post-operative instructions. Your will be prescribed antibiotics and nonsteroidal anti-inflammatory drugs. Nonsteroidal anti-inflammatory drugs will be given to help with pain relief. The surgeon may prescribe antibiotic ointment for the incision. The bandages may need to be changed and redressed and the incision area must be kept clean and dry. Call the surgeon without delay if the incision becomes red or inflamed.
Follow up visits will be necessary to check on the horse’s progress and to remove sutures or staples. Most patients may take 6 months to 1 year for a full recovery.
Patients that did not undergo surgery will also need follow up visits to make sure the fracture is healing correctly. Repeat x-rays will need to be taken of the limb to check on the fracture. A second ultrasound scan may also be done to ensure any injury to the soft tissue is getting better. Horses with fracture to the upper part of the proximal sesamoid bone (apical fracture) rarely return to racing.