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Problem Fractures in Cat and Dogs

March 14, 2014

This piece briefly looks at problem factures in cats and dogs and the types of treatments available. 

Problem Fractures in Cat and Dogs

The healing time for a fractures in cats and dogs varies depending on aspects such breed, age, general health, the bone involved, severity of the fracture, soft tissue damage and type of fixation.

A delayed union can be diagnosed when no or minimal union of the bone is observed in what would be considered this ‘normal' time frame, for a fracture in a similar breed, age and general health, which has been repaired in the same way, and heals without complication.

Typically a delayed union can be caused by one or more of: poor immobilisation, distraction, excessive compression, restricted blood supply, infection, or excessive fracture gap.

An excessive fracture gap is frequently a prime cause of delayed union and often leads to other issues such as excessive motion at the site, which can then lead to soft tissue disruption, affecting vascular supply and ultimately callus formation. With internal fixation, external fixation and external coaptation, adequate stability is the key to the progress of healing.

Stability can be achieved using different methods; cast immobilisation allows relatively large amounts of movement between fracture ends during the progression through hematoma, fibrin clot, cartilage and finally bone.  Each stage of repair will tolerate varying degrees of movement within the limits of each tissue.

Following internal fixation, bone ends are fixed relative to each other and the gap between them is maintained. This may delay healing if lack of stimulation prevents effective in-growth of granulation tissue.

What is a Non Union?

The standard definition of non-union fracture is the complete cessation of the repair process without bony union. However, in practice the diagnosis of non-union is often subjective and can depend on a range of factors.

There may be non-use of the limb that leads to muscle atrophy, stiffness, reduced range of motion in joints and misalignment of the bone. If fixation is too stiff the animal may bear weight comfortably, and ends up to all intents and purposes ‘walking on implants'. This can be problematic in the radius and ulna of small dogs, where resorption of bone can occur if there is minimal weight bearing, or internal fixation is too rigid.  These changes can be difficult to reverse and often require further surgery.

Radiographically, a radiolucent line will remain at the fracture site. The medullary cavity can become sealed with sclerosis at the edge of the bone and resorption of the bone may be evident. The fracture fragments may develop a hypertrophic "elephant's foot" callus or exhibit "rounded ends"

Once non-union is diagnosed, a full examination is required to identify any associated pathology such as nerve damage, soft tissue injury and reduced joint function. Even if bone union itself can be achieved through additional intervention, it is possible that adequate function cannot be restored due to ongoing problems.

Case Study:

One year old Labrador Retriever with non union fracture treated after referral.

History: A 10 week fracture to proximal calcaneus prior to referral which had been conservatively managed with a cast. Radiographs revealed a non union with further proximal displacement of the tuber calcanei.

Treatment: Initially, fibrous tissue was debrided from the fracture site and the proximal fragment stabilised with k-wires and tension band wire. A combination of allogeneic cancellous chips and demineralised bone matrix was applied to promote healing. However, after 6 weeks follow up the radiographs showed no evidence of healing and resorption of the proximal fragment, was evident leaving a large gap and loosening of the k-wire.

Due to poor bone quality in the proximal fragment, revision surgery to improve fixation and apply further graft was undesirable.  LIPUS (using the Sonivet device) was employed to accelerate the  healing process. A splinted dressing was also applied whilst daily 20 minute treatments were performed at home for three weeks. A small window was left in the dressing so treatment could be applied.

Results: Three weeks after treatment radiographs revealed bone density and quantity had increased significantly enabling the supportive dressing to be removed and exercise levels gradually increased. Normal function was achieved. Radiographs performed following an unrelated tibial fracture four months later showed almost complete healing of the calcaneus.

The author wishes to thank Mark Morton of Davies Veterinary Specialists for his assistance and contribution to this article.

Further details on this and other case studies are available upon request. Contact us at or call 0191 375 9083

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