What are Exostosis and Osteochondroma of the Distal Radius?
Exostosis is the formation of new bone on the surface of existing bone, and when it is accompanied by a cap of cartilage, it is known as an osteochondroma. These benign tumors are uncommon and are usually caused by a dominant, autosomal gene which can be passed down from either parent, although repetitive damage can also produce these deformities as well. When located on the distal radius they may interfere with the joints of the leg and cause damage and swelling to key tendons.
Distal radial exostosis or osteochondroma of the distal radius is the formation of new bone over existing bone and can cause acute pain and deformity.
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Symptoms of Exostosis and Osteochondroma of the Distal Radius in Horses
Initial symptoms are similar to other conditions of the radial bone of the horse, and a definitive diagnosis of the disorder often requires x-rays.
- Bony lump
- Increased warmth of affected limb
- Reduced ability to bend joints
- Sensitivity to touch in affected area
- Swelling of the carpal sheath
- Swinging leg syndrome
This is the formation of new bone on the surface of existing bone. Usually, the bone growth starts around a joint and moves upward. When the new bone develops on the long radial bone in horses, it can cause chronic pain and lameness in the affected leg.
A benign tumor of the bone that presents as an exostosis with a cap formed of cartilage. When examined microscopically, hyaline cartilage is found in osteochondroma, but not in exostosis formations that are not osteochondroma.
Carpal sheath tenosynovitis
A common result of exostosis or osteochondroma on the distal portion of the radial bone is an irritation to the deep digital flexor tendon that runs down the leg, which can cause an inflammation of the sheath around the flexor tendons is known as carpal sheath tenosynovitis.
Causes of Exostosis and Osteochondroma of the Distal Radius in Horses
- Hereditary multiple exostoses - A dominant, autosomal gene is a common cause of exostosis and osteochondroma in horses; this condition is not reversible, but in some cases, the exostosis needs to be removed to allow the horse full range of motion and to protect the flexor tendons
- Repeated trauma - Exostosis can sometimes be caused by repeated or chronic damage to the bone; a common human exostosis often caused by repeated trauma is the bunion
Diagnosis of Exostosis and Osteochondroma of the Distal Radius in Horses
An initial diagnosis of this condition can be made by a physical and visual examination. The bumps and protrusions on the bone often give the leg a bumpy appearance and can be acutely painful. Bone growths on the distal radius of horses can also press against the flexor tendons that run down the back of the leg. This can cause additional pain and swelling that may be evident when your veterinarian palpates the affected leg.
Radiography is usually employed to get a better look at the skeletal structure of the leg and is generally quite effective at visualizing this kind of growth. Ultrasound technology is generally more successful at imaging soft tissues such as the ligaments, tendons, and joints so are more commonly used for determining the status of the tendons and carpal sheath as well as ensuring that there is no swelling or fluid located in the joints themselves.
Treatment of Exostosis and Osteochondroma of the Distal Radius in Horses
When exostosis or osteochondroma causes lameness, as is common when it is located on the distal radius, the growth will need to be removed in order to return the animal to proper athletic function. This type of surgery will require that the patient be fully anesthetized and supportive care, such as the administration of replacement fluids and oxygen, will also be required. In rare cases, either superficial or the deep flexor tendon may be severely stretched or torn, which will require additional tenoscopic surgery.
A procedure known as an arthroscopy is often utilized in removing intrusive growths from the surface of the bone. During an arthroscopic procedure, a small incision is made a tiny camera with surgical instruments is inserted into the joint itself in order to get a clearer image of any growths. The technician is often able to remove exostosis and osteochondroma growths using a curette, and then debride any remaining fibers.
Recovery of Exostosis and Osteochondroma of the Distal Radius in Horses
After any sort of equine surgery, you will be given specific instructions from your veterinarian regarding post surgery care. In most cases restricted exercise will be required for full healing, particularly with bone, tendon, or joint surgery. In some cases, stall confinement may be necessary to facilitate healing and regrowth, particularly if the tendons are involved. This can be difficult for many horses, and depending on the temperament of the horse, sedation may be required to keep the patient calm during this healing period. Once they are allowed out of their stall for exercise, they may require close supervision or hand-walking until they are suitably restored.