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Definition

A break in the continuity of bone.

Clinical Signs

May observe any of the following:

• Manifestations of pain: limping, guarding limb from movement, squeaking when touched.
• Local swelling, skin discoloration from bleeding in tissue (which may occur sometime following fracture).
• Loss of function in limb, and possible deformity in appearance at site.
• Bone may be exposed in open fractures.

Etiology

Fractures may result from trauma, disease, or indirect leverage on bone. In rats, fractures are generally the result of a household accident (trauma) such as: being stepped on while free ranging, being caught in a closing cage or room door; as a result of falling from heights, getting limbs caught in wire exercise wheels, or inappropriate-sized cage floorings. Of these types of accidents, the latter is the most common causing the fracture to occur below the patella (knee) of the hind limb. Because this area has little soft tissue, the bone is not well protected.

Fractures to bone occurs when the outside force is greater than the bone is able to “bend” in order to accommodate that force. How severe the fracture is will depend on the type and how great the force applied is. Less force may only cause the bone to crack, but not completely break through.

Types of fractures that can occur: a complete fracture, where a break is across the entire bone and is often displaced, and, the incomplete fracture, where the break is only through part of the bone.

Fractures can also be classified as an open fracture or a closed fracture. In an open fracture, also referred to as a compound fracture, bone breaks through the skin and is exposed. A fracture of this type is of more concern due to the increased chance of infection not only to the soft tissue, but the chance of infection penetrating the bone. In the closed fracture, bone does not break through the skin. With fractures, an open or closed reduction (a procedure to place the bone in alignment often done under anesthetic) may be required for the bone to heal correctly. The ends of fractured bone must be in close proximity since healing occurs by a “knitting” of the bone with new bone being formed around the fractured area.

Though bone is directly affected, the severity of the injury may cause additional trauma to surrounding tissues, muscles, and joints. Swelling may be seen if there is bleeding into the soft tissue. There may be a rupture of tendons, severed nerves, and damaged blood vessels as well as trauma to body organs from the force that caused the fracture, or from actual fracture fragments penetrating the organs themselves.

Complications to be aware of primarily associated with open/compound fractures and or comminuted fractures (bone that is broken, splintered, or crushed into a number of pieces) are:

• Compartment syndrome: a condition that occurs when the pressure inside muscles continues to build. This can sometimes be seen in the fractured limb as swelling that is hard and cool to touch. This constitutes as an emergency and the animal should be taken to the vet as soon as possible.
• Osteomyelitis: development of an acute or chronic inflammatory process of the bone and structures secondary to infection with pyogenic organisms, sometimes seen in the fractured limb as increased warmth, redness, swelling, and possible abscess development. Since organisms present in osteomyelitis may often be Gram-negative, or anaerobic, an antiinfective such as Flagyl should be considered in the treatment regimen.

Although a rat’s small size can make it difficult to immobilize the injured area, helping to keep the rat calm and confined to a small one-level cage, slowing any bleeding that is present, and reducing pain (until seen by a veterinarian) will greatly help in the rat’s recovery.

Note that all the signs and symptoms listed above do not always occur with every fracture. When it is a linear or fissure fracture, or when the fracture impacts, then a majority of these symptoms may not be seen.

Figures

Case Histories and Photos of Fractures

• Fig. 1: Closed fracture of right foot
• Fig. 2: X-ray showing pelvic and femur fracture
• Fig. 3: Picture of open (compound) fracture of the right tibia (warning— graphic!)

Diagnostics

Assess for shock, hemorrhage, respiratory compromise and treat accordingly.

When stable obtain history.

Do orthopedic and neurovascular assessment.

Radiography to detect type and extent of fracture.

Treatment

For simple closed fractures apply cold pack to site. If swelling appears and cold packs do not resolve it, an injection of dexamethasone may be required to reduce swelling. May give Tylenol for discomfort if there is no hepatic impairment. Avoid, if possible, the use of NSAIDS such as ibuprofen or meloxicam as some studies have indicated they may possibly delay bone healing in rats.

If a simple fracture is in the hind limb or foot, a splint with wrap may be applied by the veterinarian for immobilization during initial healing if the rat will tolerate.

If signs of shock and bleeding are present, use a clean cloth to cover wound and control bleeding, keep rat warm and get to a veterinarian quickly, as these symptoms are life threatening! The veterinarian will want to start fluid replacement of warmed SQ fluids, oxygen therapy, and possibly a glucocorticoid such as prednisone or dexamethasone.

For open fractures, provide analgesic for pain, such as butorphanol (Torbugesic).

Antibiotics should be initiated, such as cephalexin, or enrofloxacin, or cefadroxil. If infection presents, Flagyl should be considered in the treatment regimen.

Once the rat is stabilized, x-rays are taken to determine type and severity of the fracture. The vet, after sedating the rat, may surgically debride and flush the area with sterile saline, reduce the fracture (meaning to place the bone in proper alignment), and immobilize the limb in a normal position.
If the area of soft tissue damage is small and the fracture does not require internal fixation to keep the broken ends of the bone in alignment, such as with the use of pins, the veterinarian may then choose to continue treatment like that of a closed fracture.
If damage is too severe , or if infection can not be controlled with antimicrobials and threatens the rat’s life, as in the case of some compound fractures, amputation of a limb may be required. Where fractures of the spine or crush injuries are involved quality of life must be determined and euthanasia may have to be considered.

For information pertaining to the medications listed above see the Rat Medication Guide:

*Note: It is not uncommon for a weanling rat to get a hind foot caught in cage wire while playing. Fractures are often simple fractures that heal well. Healing is usually complete in under six weeks.

Nursing Care

• Provide hospital or one-level cage during healing.
• If surgery is required, provide the following post-op care:
  A hospital cage (small individual cage), non-litter bedding such as clean cloths or ink-free paper towels. Clean and change bedding daily. Avoid litter-type bedding to prevent the chance of wound contamination or infection.
• Provide additional warmth using a hot water bottle or heating pad, if needed, in order to maintain body temperature within normal limits. Use low heat settings and place under one half of cage to ensure rat does not become overheated or dehydrated.
• Medicate for post-op pain as needed.
  Remember not to over-medicate for pain in simple closed fracture. Allowing the rat to feel slight discomfort will help to alert the rat that the injury is not yet healed, and prevent further injury or delayed healing.
• If required give antibiotics as prescribed.
• Provide extra fluids in the post-op recovery period. *Note: A juicy type of fruit also provides an additional fluid source in the diet.
• During bone healing, increase protein, carbohydrates, vitamins, and minerals in existing diet, or provide additional food supplements such as, Nutri-Cal Paste, canned Ensure, soy or soy formula.
• Monitor for neurovascular changes, and report to veterinarian if limb becomes cooler, pale or cyanotic, or if signs of infection are present, or condition worsens.
• Whether surgery was required or not, proper bone healing can require several weeks (although rats, especially very young rats, can heal in a shorter amount of time), be sure to provide a cage that is one level to prevent further injury from climbing or jumping during time of healing.

Outcome

• Return of mobility.
• Free of deformity.
• No signs of infection.

Prevention

• Check rat’s environment frequently for hazards.
• Supervise free ranging time and alert other members in home when rats are free ranging.
• Put other pets in another room if rat is in danger of injury.
• Be observant when closing cage doors.
• Think Rat Safety!

Posted on June 30, 2003, 10:28, Last updated on April 28, 2009, 12:54 | Musculoskeletal