Etiology

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.

Photos and case study listed below.

• 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

When stable obtain history.

Do orthopedic and neurovascular assessment.

Radiography to detect type and extent of fracture.

Treatment

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

Outcomes

Prevention

Posted on June 30, 2003, 10:28, Last updated on June 16, 2008, 21:03 | Musculoskeletal