Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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More Than One Way to Mend a Broken Bone

Pet Column for the week of February 27, 2006

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Kim Marie Labak
Information Specialist

"The most common cause of broken bones in pets is 'hit by car,' known as HBC among small animal veterinarians," says Dr. Ann L. Johnson, interim hospital director and veterinary orthopedic surgeon at the University of Illinois Veterinary Medicine Teaching Hospital in Urbana. "Other causes include falling from a table, being bounced out of the back of a pick-up truck, bone disease, or repeated stress in active athletes."

A veterinarian's goals for repairing a broken bone are to align and reunite the pieces of bone, restore full function of the bone, and restore the normal appearance of the animal. The method used to achieve these goals depends on several factors, such as the severity and location of the fracture, the age of the animal, and anticipated patient and owner cooperation during post-operative healing.

Casts are a good method of stabilizing a fracture because their application doesn't require surgical invasion of the skin, muscle, or bone surrounding the fracture. However, the use of casts is limited to specific cases. The joints above and below the fractured bone must be immobilized, which eliminates use of casts on bones of the hip or shoulder. The fracture must be closed, meaning that there is no accompanying skin or muscle wound. Finally, the fracture must be relatively simple and easily realigned.

Some of the disadvantages of casts include the need to keep them clean and dry, the need for frequent changes and re-evaluations, and the possibility of developing cast sores, which would mean discontinued use of the cast. However, Dr. Johnson points out that in some cases the advantage of cast use, no surgical invasion of the tissue surrounding the fracture, outweighs these disadvantages.

Fractures too complicated to meet the requirements for a cast can be stabilized with surgically applied external fixators, intramedullary pins, orthopedic wire, bone plates, or any combination of these.

An external fixator consists of a rigid metal or acrylic frame outside the broken limb and long metal pins that go through the broken bone pieces and attach to the external frame. External fixation requires intensive postoperative care by the pet's owner, including daily cleaning and water massage, by whirlpool or hose, of the limb and limited postoperative activity of the pet. External fixators are removed once the fracture is bridged with new bone and is capable of supporting the animal's activity on its own.

Intramedullary pins (IM pins) are stainless steel rods inserted inside the broken bone. IM pins hold the pieces of bone together like beads on a string. Their use requires limiting the pet's post-operative exercise to prevent the rods from being dislodged, but they do not require intensive postoperative care by the owner. Like external fixators, IM pins are removed once the fracture is bridged with bone.

Orthopedic wire is used to connect fragments of bone or to anchor bone around IM pins, providing additional stability. One drawback is that orthopedic wire, if used improperly, may cut off the blood supply to the bone, which will prevent the fracture from healing. An advantage of using IM pins together with orthopedic wire is that the animal is able to use the fractured limb fairly well early in the post-operative period. Orthopedic wire may be left on the bone when the IM pins are surgically removed.

Another way to surgically stabilize broken bones is through the use of bone plates and screws. Stainless steel plates that span the length of a fractured bone are screwed directly to the bone to securely hold bone fragments together and promote healing. Plates and screws can be used for fractures of joints or for fractures of odd-shaped bones, like the pelvis, as well as long bones of the limbs. The advantages of bone plates are early post-operative pain-free use of the limb and minimal aftercare. Bone plates are usually left in place after the fracture has healed.

For more information on bone fractures in pets, consult your veterinarian.

[For a print-quality diagram illustrating external fixators, intramedullary pins, orthopedic wire, and bone plates, e-mail Mandy Barth at