The forelimb has two bones between the wrist, or carpus, and the elbow joint, the radius and ulna. The radius is the main weight-supporting bone of the forelimb; whereas, the ulna supports only 20% of the weight. Puppies have much softer bones than adults; therefore, more fractures occur in younger dogs. In addition, small breed dogs have a poor blood supply to the lower fourth of the radius, which increases the risk for fracture. Due to the impaired blood supply to the lower fourth of the radius, healing of the fracture can take longer than in other bones in the body. Large breed dogs have a much better blood supply to this region; therefore, a very substantial force needs to be applied to the bone before a fracture develops. If the radius fractures, the ulna usually fractures too.
Cause of fracture
In small breed dogs, landing on the front limbs from a fall is the most common cause of fracture of the radius. Examples of such trauma commonly include the pet falling out of the owner’s arms or the pet jumping off a bed. In large breed dogs, usually substantial trauma is needed, such as being hit by a car, to cause the bone to fracture. Gun shot injuries not only can fracture the bone, but will result in an open wound over the fracture through which dirt and hair usually are driven into the tissues. This could potentially result in infection and delayed healing of the bone.
For most fractures of the radius and ulna, a bone plate and series of screws are used to stabilize the fracture. This treatment requires the least amount of care for the client and has the best chance for a successful outcome. If the fracture is caused by a gunshot or other trauma that results in an open wound over the fracture site, an external fixator may be the treatment of choice. Also, if the radius is fractured in multiple small pieces, the best treatment may be an external skeletal fixator. This apparatus consists of multiple pins that penetrate the skin and bone and are connected to external bars that run parallel to the bone.
An older technique to repair a radius fracture involves placement of a single pin into the marrow cavity of the bone. This method of repair is considered less than ideal, as it does not provide adequate stability for predictable bone healing. Similarly, the use of a cast as the sole treatment commonly results in a non-healing fracture.
Repairing a fractured radius with a plate and screws offers multiple benefits in comparison to older techniques. These include a faster recovery, earlier use of the limb after surgery, better chance to return to athletic activity, less risk of a second surgery being required, and better range of motion of the joints above and below the fracture. Uncommon complications include infection, non-healing of the fractures, breakage of the metal plate, osteoporosis of the bone, bone cancer, cold sensitivity and re-fracture of the bone. In general, about 90 to 95% of the patients that have surgical planting of a fractured radius heal uneventfully.
For more information on this subject, speak to the veterinarian who is treating your pet.