Delayed union or nonunion are a bone disease characterized by prolonged or absent fracture healing.
The rate of nonunion fracture is reported to be 3.4% of the total bone fractures in dogs. Nonunion is defined as the cessation of all reparative processes of healing without bony union. These fractures show movement at the fracture site and will not heal without surgical intervention.
There are a number of causes:
- Excessive fracture movement, instability
- Systemic disease resulting in delayed osteoclastic activity - e.g bacteremia, neoplasia, chronic fever
Clinically affected dogs usually present with chronic lameness associated with orthopedic repair of a fracture. Joint stiffness, lethargy, regional swelling and fever may be apparent with secondary osteomyelitis.
Diagnosis is usually based on clinical evidence of poor fracture healing and definitive confirmation is usually obtained on radiographic analysis of fracture site.
Treatment usually requires improving fracture stability, and removing underlying metabolic or inflammatory disease.
Nonunion fractures often require the addition of cancellous bone autograft at the fracture site to stabilize the bone fracture.
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