Fracture of the Femur in Cats

Overview of Femoral Fractures in Cats

Fractures of the femur (thigh bone) are some of the most common fractures seen in cats. These fractures are usually the result of major trauma, but they can be caused by disease of the bone itself.

Generally, femoral fractures cause acute, non-weight bearing lameness of the affected hind leg. These fractures can occur in an immature bone (one that has not finished growing) or in a mature one; they 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 cat, different methods of repair may be indicated for each situation. Femoral fractures can have serious complications if not repaired or if the repair fails.

What to Watch For

• Lameness
• Abnormally positioned leg
• Pain or inability to move

Diagnosis of Femoral Fractures 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.

• Chest radiographs
• Complete orthopedic examination
• Radiographs of the affected leg

Treatment of Femoral Fractures in Cats

Treatment will vary depending on the severity of the trauma. In general, anesthesia and surgical stabilization of the bone fragments are indicated for most femoral fractures because the femur cannot be adequately immobilized in a cast or splint to allow proper healing. Other treatment recommendations may include:

• Emergency care for concurrent problems caused by the trauma
• Treatment of concurrent soft-tissue injuries
• Injectable analgesics (pain medications) are given to the animal while being treated in the hospital and may be continued orally once discharged from the hospital.

Home Care and Prevention

Take your cat to your veterinarian as soon as possible after any trauma for immediate attention. Try to prevent your cat from walking or moving too much. Do not attempt to place a splint or bandage on the leg unless there is profuse bleeding.

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

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

In-depth Information on Femoral Fractures in Cats

Of all of the long bone fractures (humerus, femur, radius/ulna and tibia), femoral fractures are the most common, comprising approximately 20 to 25 percent of all fractures in small animal practices.

Motor vehicle trauma is the most frequent cause of femoral fractures, and the victims tend to be young, non-neutered males cats who roam away from home and get hit by a car. Cats 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 femur when certain disease conditions exist. These fractures, also known as “pathologic fractures” are commonly caused by:

• Malnourishment
• Systemic illness such as kidney disease
• Endocrine disorder such as hyperparathyroidism
• Bone infection (osteomyelitis)
• Cancer (neoplasia) 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 femur. Frequently encountered fractures of the immature femur include:

• Physeal fractures at the end of the bone near the hip joint
• At the distal physis near the knee
• 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 femur include femoral neck fractures, femoral shaft fractures, and joint fractures involving the stifle or hip.

Fractures of the midshaft (diaphysis) of the femur 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 and may have more complications than closed fractures.

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

Each case of femoral fracture needs to be evaluated in its entirety, including the age of your pet, the severity of the fracture, the experience of the surgeon and financial concerns of the owner, to determine the most appropriate 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) or a non-functional leg.

Diagnosis In-depth

A thorough physical examination is 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. Additional tests may include:

• Chest X-rays (thoracic radiographs). Chest trauma, in the form of pulmonary contusions (bruising) or pneumothorax (collapsed lung secondary to free air within the chest cavity), must be ruled out with chest radiographs prior to anesthesia to repair the leg fracture.
• Complete orthopedic examination. A complete orthopedic examination must be performed to look for the cause of the non-weight bearing lameness as well as possible injuries in other bones or joints. Examination involves palpation of all of the bones and joints of each leg for signs of pain or abnormal motion within a bone or joint as well as an assessment of the neurological status of each 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 thigh finding swelling, bruising, and crepitation (abnormal “crunchy” feeling with motion) can be highly suggestive of fracture of the femur.
• Radiographs of the leg. Two radiographic views of the cat’s thigh are used to confirm the diagnosis of femoral fracture and may also show pelvic fractures or hip dislocation if they are present. Based on the location and severity of the fracture, a more informed discussion with the owner can occur regarding potential treatments, prognosis and costs.
• No laboratory tests are required to make the diagnosis.

Treatment In-depth

Treatment will vary depending on the severity of the injuries and may include:

• Emergency care for concurrent problems. 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.
• Soft-tissue injuries must be addressed in order to minimize the chance for the development of wound infections. Lacerations and other open wounds or open fractures must be cleaned of debris and covered or closed to minimize infections.
• In the interim between treating the emergency patient and surgical repair of the femoral fracture, all of the orthopedic injuries that have been found should be addressed with splints and/or pain medications to keep the animal comfortable until the fracture can be treated.
• Depending on the specific fracture type, location, and age of the animal, femoral fractures may be repaired in many different ways. Pins alone, pins and wires, bone plates and screws, and external fixators (pins holding the bone fragments stable through holes in the skin, like a scaffolding) are used separately or in combinations to provide stability to the bone fragments while they heal.
• Femoral fractures are not adequately stabilized with a cast or splint.
• Femoral fractures, as well as any other traumatic injuries that the animal might have, are painful and the animal will be given analgesics before and after surgery.

Follow-up Care for Cats with Femoral Fractures

After surgery and discharge from the hospital, the cat must be restricted from activity to allow the fracture to heal properly. 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 animal should be kept confined to a carrier, crate or small room whenever he cannot be supervised. He cannot play or rough-house, even if he appears to be feeling well; the use of stairs should be limited; and outdoor walks should be just long enough for him to relieve himself and then return indoors for more rest.

Animals 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-inflammatory medication should be given as directed by the veterinarian. Analgesics, such as butorphanol (Torbugesic®) can cause sedation, and anti-inflammatory drugs, such as aspirin or carprofen (Rimadyl®), can cause an upset stomach. Your veterinarian should be informed if any adverse side effects occur.

The skin incision needs to be monitored daily for signs of excessive swelling or discharge. These can indicate problems with the incision or possible infection. Contact your veterinarian if these occur.

If at any point your cat stops using the leg again after some improvement following surgery, there could be a problem. Again, call your veterinarian.

Several weeks after surgery, the femur will need to be X-rayed 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.