What are Focal Bone Reaction and Avulsion Fractures?
This specific type of injury is often found in dressage and jumping horses, but is most common in racehorses where the risk of trauma is higher. It can be a solitary injury, or can be associated with other leg issues, such as proximal suspensory ligament desmitis (PSD). PSD is a common injury in the limbs of horses, and can occur in one or more legs at a time. When all three conditions are present, the bone reaction, avulsion fracture and PSD, it can be termed high suspensory syndrome.
Avulsion fracture in horses refers to an injury to the third metatarsal bone in the leg where the suspensory ligament attaches. This injury also causes a focal bone reaction, meaning the periosteum membrane that surrounds the bone is torn and becomes inflamed, causing a reaction to form new bone to repair the injury. Such a condition causes varying degrees of pain, and can lead to lameness, which can affect your horse’s performance.
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Symptoms of Focal Bone Reaction and Avulsion Fractures in Horses
Horses afflicted with focal bone reaction and avulsion fractures, and the associated PSD, can show very little evidence of signs, or can have varying degrees of discomfort and lameness depending on the severity of the injury. Symptoms to look for are:
- Mild swelling
- Sudden lameness that may improve with rest
- Intermittent lameness
- Lameness that worsens with exercise
- Chronic mild to moderate lameness
- Loss of action
- Poor performance
- Drift into or away from the rail
- Break stride while racing
- Change in gait
Causes of Focal Bone Reaction and Avulsion Fractures in Horses
Causes of this condition can include:
- Repeated fetlock joint hyperextensions, often during exercise
- Repeated carpal hyperextensions
- Long toe and low heel conformation
Diagnosis of Focal Bone Reaction and Avulsion Fractures in Horses
After an examination, your veterinarian will need to know any history of trauma and of symptoms, such as the type of lameness observed, and how long or often it affects your horse. A lameness exam may be performed, applying firm pressure over the suspensory ligament origin. Diagnostic analgesia can be given to localize the pain. An X-ray may be used to see evidence of the fracture, but more often, an MRI, ultrasound, CT scan, or horse scintigraphy is needed to confirm the diagnosis. Thermography may be used to look for signs of inflammation. Your veterinarian will also be looking for signs of PSD.
Treatment of Focal Bone Reaction and Avulsion Fractures in Horses
The goal of treatment is to relieve stress to the area to allow the bone to heal. This can be accomplished with rest, controlled exercise and the use of anti-inflammatory medications, and will depend on the severity of your horse’s condition, as well as performance demands.
Typically, therapy lasts 2 to 6 months, beginning with rest through stall confinement for the first month of treatment. This is generally followed by 1 to 2 months of added daily exercise in the form of hand walking. Then, it is recommended to give your horse 1 to 2 months of limited time of turnouts in a small paddock. X-rays or scintigraphy are recommended at the 3 to 4 month mark to assess your horse’s healing, and allow for further exercise recommendations.
For horses who are not allowed sufficient rest due to schedules, systemic and local anti-inflammatories, along with concurrent corticosteroid injections, can help to relieve lameness.
Other therapies can include extracorporeal shockwave therapy, or corrective trimming to shorten the toes in cases of a long toe and low heel conformation.
If PSD is involved, the lameness may recur, especially if the horse returns to work or performance demands prematurely. Chronic cases of PSD may require long term therapies that can include pain relievers, shockwave therapy, and regenerative therapies. In severe cases, a neurectomy may be needed to remove the lateral plantar nerve, thus allowing a return to continuous athletic performance.
Recovery of Focal Bone Reaction and Avulsion Fractures in Horses
Be sure to give your horse adequate rest and exercise following the treatment plan given by your veterinarian. A follow-up visit for imaging tests will help to monitor your horse’s healing, and can help your vet to adjust the exercise regimen. You may be given medications to give at home.
Recovery is good for avulsion fractures, as long as the fracture has had enough time to heal. This typically happens within 3 to 4 months, but each case may have other conditions involved which can alter healing time. Cases with concurrent PSD may be more complex, and will need further diagnostic work and treatments with the suspensory ligament. In these cases, a recurrence of the lameness is possible.