Definition

A break in the continuity of bone.

Clinical Signs

May observe any of the following:

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

*Note: for additional information on recognizing various signs of pain or discomfort refer to: Signs of Pain In Rats.

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 (i.e., 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 anti-infective such as Flagyl (metronidazole) 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 clinical signs listed above do not always occur with every fracture. When it is a linear or fissure fracture, or when the fracture impacts, then many of these signs may not be seen.

Figures

Case Histories and Photos of Fractures

• Fig. 1: Closed fracture of right foot in adult male rat
• Fig. 2: X-ray showing pelvic and femur fracture in young female rat
• Fig. 3: Picture of open (compound) fracture of the right tibia 33-month-old male rat. *Warning– graphic!*
• Fig. 4: Case history, with X-ray, showing fracture of ulna and radius in male rat (Naboo)

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, of the extremities, a small cold pack may be applied to the site. If swelling appears and cold packs do not resolve it, an injection of dexamethasone may be required to reduce swelling. Tylenol may be given for discomfort if there is no hepatic impairment. Caution when using NSAIDs such as ibuprofen or meloxicam as some studies have indicated they may possibly delay bone healing in rats.
The veterinarian may choose to apply a splint with wrap in simple fractures involving a hind limb or foot for the purpose of immobilization if the rat will tolerate, or to leave off the splint with wrap allowing the fracture to heal by callus formation.

For fractures that have occurred to the pelvis or main portion of the body, place the rat carefully on cloth bedding in a one level carrier and transport to a veterinarian to determine severity. In many cases (depending upon the severity) pelvic fractures can and will heal.

In the event 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).

cephalexin, or enrofloxacin, or cefadroxil. If infection presents, Flagyl (metronidazole) 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 veterinarian, 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 simple closed fracture.

In the event 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

The following can be applied for both non post-op and post-op care as appropriate.

• If surgery is required, provide the following post-op care:
  • A hospital cage (small individual cage), clean non-litter bedding such as felt, soft t-shirt type material, 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 to maintain body temperature within normal limits. It is essential that the rat does not become overheated or dehydrated. The rat should also be able to move away from the heat source if it becomes uncomfortable. If the rat is unconscious or immobile extreme care must be taken to keep the heat low and stable.
  • You can use an isothermic product that is heated in the microwave such as SnuggleSafe®. Make sure to follow the product directions carefully and wrap in a towel before placing in the cage. SnuggleSafe® will provide heat for 12 hours before needing to be reheated. Other similar types of product may vary in re-heat time. Check directions for individual product.
  • If using a heating pad (good for long term use) use only the low heat setting, put a thick towel in between the pad and the cage bottom, and place beneath a corner of the cage.
  • If none of these options are available you can use a plastic bottle filled with hot water, and wrapped in a towel, in the corner of the cage.
• Medicate for pain as prescribed.
  • 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.
• Because hypovolemia (loss of fluid volume primarily due to bleeding) can occur with both open and closed fractures, it is important for the rat to stay hydrated.
  *Note: juicy types of fruit provide an additional source of fluid 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 may 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

• Signs of bleeding controlled
• Dehydration prevented
• Pain controlled
• Return of mobility
• Free of deformity
• No signs of infection

Prevention

• Check the rat’s environment frequently for hazards.
• Supervise free ranging time and alert other members in home when rats are free ranging.
• Be observant and aware of rat’s proximity when opening and closing doors to rooms or cage.
• Put other pets in another room if rat is in danger of injury.
• For tall cages or cages placed on high stands: provide carpeting, rugs, or padding around the base of the cage if the rat is permitted to climb on the outside of the cage.
• Think Rat Safety!