Fracture of the Humerus in Cats

Overview of Humeral Fractures in Cats

Fractures of the humerus (upper arm bone in front leg) are not frequently seen in veterinary medicine. These fractures are usually the result of major trauma, but can be caused by disease of the bone itself.

Generally, humeral fractures cause acute, non-weight bearing lameness of affected fore leg. These fractures can occur in an immature bone (one that has not finished growing) or in a mature one, can be “open” (skin wound with bone exposed) or “closed” fractures, and can be “simple” or “comminuted” (multiple bone fragments).

Depending on the nature of the fracture and the age of the animal, different methods of repair may be indicated for each situation.

Humeral fractures can have serious complications if not repaired or if the repair fails.

What to Watch For

Diagnosis of Fractured Humerus in Cats

A thorough physical examination and medical history are important in any illness or injury. Based on the results of the physical examination, additional tests may be recommended. No laboratory tests are required to make the diagnosis.

Treatment of Fractured Humerus in Cats

Treatment will vary depending on the severity of the trauma. Treatment recommendations may include:

Home Care and Prevention

Bring the animal to the veterinarian as soon as possible after any trauma for immediate attention. Try to prevent your pet from walking or moving too much. Prompt veterinary treatment is recommended. Do not attempt to place a splint or bandage on the leg unless profuse bleeding is occurring.

After surgical repair of the fracture, the animal will be kept restricted from activity for several weeks and the skin incision will be monitored while healing. A recheck with your veterinarian will occur in several weeks to evaluate how the bone is healing (with new radiographs), to monitor the animal’s progress, and to make sure it is safe to increase the animal’s activity level.

Many traumatic events are true accidents and thus unavoidable. Avoid the chance for motor vehicle trauma by keeping your cat indoors.

In-depth Information on Humeral Fractures in Cats

Of all of the long bone fractures (humerus, femur, radius, ulna and tibia), humeral fractures are the least common.

Motor vehicle trauma is the most frequent cause of humeral fractures in cats. These injured animals tend to be young, non-neutered males who roam away from home and get hit by a car. Animals of both sexes and of any age are susceptible to this type of trauma if not kept restrained. Cats can develop non-traumatic fractures of the humerus when certain disease conditions exist. These fractures, also known as “pathologic fractures,” can occur if the animal is malnourished, has a systemic illness such as kidney disease, has an endocrine disorder such as hyperparathyroidism, has a bone infection (osteomyelitis), or has cancer of the bone.

Immature bones have growth plates (physes) that are still “open” and growing. These regions of the young bone are generally weaker than the bone that has already been created. The energy of a trauma often results in fracture at these parts of the immature bone and can lead to premature “closure” of the physes resulting in abnormal growth of either end of the humerus. Frequently encountered fractures of the immature femur include physeal fracture at the end of the bone near the shoulder joint, fracture of the part of the humerus that forms the elbow joint, and fractures of the middle of the bone.

Mature bones have more uniform strength along their entire length and the energy of each particular trauma may lead to fractures in various portions of the bone. Frequently encountered fractures of the mature humerus include shaft fractures and joint fractures involving the elbow.

A very common injury to the humerus is fracture of the lateral condyle as the animal jumps down from a height. In this fracture, the end of the humerus splits in the middle disrupting the smooth contour of the inside of the elbow joint. The surface of the elbow must be surgically reconstructed or the animal will suffer severe arthritis in the future.

Fractures of the midshaft (diaphysis) of the humerus can be classified as “open” or “closed” depending on whether the skin surface has been damaged during the injury. Open fractures have a greater chance of getting infected may have more complications than closed fractures.

As with all fractures, fractures of the humerus can also be classified as “simple,” if the bone breaks into two pieces, or “comminuted,” if there are multiple pieces.

Each case of humeral fracture needs to be evaluated in its entirety (age of animal, severity of the fracture, experience of the surgeon, and financial concerns of the owner) to determine the most appropriate and best form of treatment.

Inappropriate case management, inadequate surgical stabilization, or poor aftercare can lead to complications such as non-unions (fractures that will not heal), malunions (fractures that heal in an abnormal direction or orientation), osteomyelitis (bone infection), arthritis of the shoulder or elbow, or a non-functional leg.

Diagnosis In-depth

A thorough physical examination is very important to make sure your pet is not showing signs of hypovolemic shock secondary to the trauma or blood loss. It is also important to make certain that there are no other injuries present. No laboratory tests are required to make the diagnosis, but additional tests may include:

The radial nerve is extremely important in allowing the animal to use the leg properly. The nerve courses alongside of the humerus and can easily become damaged during the original trauma or during surgical repair. In most cases the damage is only temporary, but permanent damage can occur leaving the leg non-functional or requiring more operations to help the animal use the leg. The thorough orthopedic examination is especially important for an animal that is unable or unwilling to get up and move on the other three legs. Specific palpation of the upper arm and finding swelling, bruising, and crepitation (abnormal “crunchy” feeling with motion) can be highly suggestive of fracture of the humerus.

Treatment In-depth

Emergency care for concurrent problems is paramount. Shock is a frequent result of major trauma and must be treated quickly. Treatment for shock involves intravenous fluid administration to maintain blood pressure and adequate oxygen delivery to the body. Injury to the lungs and chest cavity are also commonly seen after major trauma and may require supplemental oxygenation or removal of free air (pneumothorax) from around the lungs. After stabilization, additional treatment may include:

Home Care of Cats with Humeral Fractures

After surgery and discharge from the hospital, the cat must be restricted from activity to allow the fracture to heal. Activity must be restricted for several weeks after surgery. The duration will vary depending on the severity of the injury, the type of fixation that was used, and the age of the animal. Restricted activity means that the cat should be kept confined to a carrier, crate, or small room whenever he cannot be supervised, the animal cannot play or rough-house, even if he appears to be feeling well, and the use of stairs should be limited and outdoor walks should be just long enough for the cat to relieve himself and then should be returned indoors for more rest.

Cats whose fracture was repaired with an external fixation device will have pins exiting the skin. The “pin tracts” should be monitored daily for excessive swelling or discharge. Some discharge is normal and any crusty build-up that occurs at these sites can be gently cleaned with warm water.

Analgesics (pain medications) or anti-inflammatories should be given as directed by the veterinarian. Analgesics, such as butorphanol (Torbugesic®) can cause sedation, and anti-inflammatories, such as aspirin, can cause upset stomach. Your veterinarian should be informed if any adverse side effects do occur.

The skin incision needs to be monitored daily for signs of excessive swelling or discharge. These can indicate problems with the incision or possibly infection. If at any point prior to the recheck radiographs being taken the animal stops using the leg again after some improvement following surgery, there could be a problem.

Several weeks after surgery, the humerus will need to be radiographed again to make sure the bone is healing properly. If the healing has occurred as expected, the external fixator, if present, will be removed and the cat’s activity level will be allowed to increase slowly back up to normal over the next few weeks.
In general, any other implants that were used in the repair will be left in place unless they cause a problem at some point in the future. Potential problems can include migration (movement) or infection of the implant.