Postoperative management of external fixators in dogs and cats - Veterinary Medicine
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Postoperative management of external fixators in dogs and cats
Despite the widespread use of external skeletal fixation in small-animal practice, little information is available regarding postoperative care. Here are some tips to promote optimal healing, keep patients comfortable, and avoid complications.


VETERINARY MEDICINE


PREVENTION AND TREATMENT OF COMPLICATIONS

Complications can develop after applying external fixators, including element tract drainage, element loosening, infection, and pin tract fractures. Take preventive measures to avoid these complications, including client instruction on postoperative restrictions and care.

Element tract drainage

The most common complication associated with the use of external fixation is fixation element tract drainage. Mild to moderate drainage from the fixation element tracts, typically serosanguineous in nature and without irritation of surrounding tissues or implant loosening, is to be expected in the initial postoperative period. Drainage is more likely to occur if the fixator is in a proximal location on the limb, where muscle is more prominent.5

Soft tissue motion around a fixation element prolongs the débridement phase of wound healing and incites exudation.2,5 Excessive or prolonged drainage increases the likelihood of fixation element loosening and infection.1,2,5 Prevention includes the appropriate placement of fixation elements through adequate soft tissue release incisions and the application of a compressive bandage in the early postoperative period.2

Element loosening

Loosening of fixation elements is another commonly reported complication of external fixation. The bone-fixation element interface is the weakest link of the construct.1 Bone resorption and subsequent implant loosening can occur if thermal necrosis of the bone surrounding the fixation element tract occurs during placement, the bone-fixation element interface is subjected to high stress loads from placement of pins or wires too close to the fracture site, insufficient frame stiffness is present, excessive soft tissue movement around the fixation elements occurs, or a fixation element tract infection develops.1,2,5

Loose pins or wires are a continual source of pain and can predispose the animal to fracture disease, osteomyelitis, delayed union, or nonunion.2 Thus, loose fixation elements should always be removed.2 Removal may compromise the stability of the construct and necessitate placement of additional fixation elements if osseous union has not progressed sufficiently to accommodate for the decrease in frame strength.3,5

Infection

Infection of a fixation element tract should be considered any time fixation element tract drainage appears purulent, fixation elements associated with excessive drainage are loose, radiographic evidence of bone lysis around the fixation element tract is present, or patient use of the limb declines.2,3 Treatment of fixation element tract infection includes removing the fixation element, débriding the fixation element tract and surrounding soft tissues, and administering systemic antibiotics.2 If the removal of the affected fixation element compromises the stability of the construct, an additional fixation element should be placed in the same bone segment at a different site.

Although the most commonly reported causative pathogens are Staphylococcus species, treatment based on bacterial culture and antimicrobial sensitivity testing is recommended.1-3 Culture of the external fixation element-skin interface can be misleading because of contamination by normal skin flora, so it has been advocated to obtain a culture sample from inside the fixation element tract, such as a swab of the lining of a fixation element tract, débrided bone, or the previously implanted portion of the offending fixation element after removal.2,5

Pin tract fractures

Fracture through pin tracts is also a rarely reported complication of external fixator placement and is typically a sequela of improper surgical technique. Use of fixation elements that exceed one-third the diameter of the bone; placement of a fixation pin in proximity to other fixation pins, the fracture, or the osteotomy; and inadequate postoperative exercise restriction have been implicated as causes of fractures.5 Any fixation element associated with an iatrogenic fracture should be removed and replaced in intact bone.5

Client education

Inform owners of the importance of strict activity restriction to allow for bone healing. Until there is radiographic confirmation of bone union, the animal should be confined to an area small enough to prevent running, jumping on and off furniture, or rough play with other pets. Animals should always be restrained on a leash when taken outside.

While a crate is often an ideal enclosure for animals after orthopedic procedures, open wire crates and kennels with wire mesh pose a potential risk for entrapment of protruding pieces of the fixator and damage to the construct. The same consideration applies any time that an animal is hospitalized in a clinic kennel.


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Source: VETERINARY MEDICINE,
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