Carpal Hyperextension and Arthrodesis
Carpal and Tarsal Arthrodesis (joint fusion)
The carpus (wrist) and tarsus (ankle or hock) in dogs and cats are complex joints consisting of numerous small bones and several joint compartments. These small bones are held in their correct positions by a network of ligaments, tendons, and other soft tissue support structures. Damage to any of these structures can result in joint pain, inflammation, instability, and significant lameness.
Carpal and tarsal arthrodesis, or fusion of the carpus (wrist) joint and tarsus (ankle or hock) joint, are procedures designed to restore acceptable limb function and alleviate pain when other medical or surgical treatments for carpal or tarsal joint injury are not possible or have failed to provide a functional outcome. The most common condition necessitating carpal or tarsal arthrodesis is a hyperextension injury, in which the ligaments and other support structures that normally stabilize the carpal joint are torn or stretched. This can happen if a dog falls or jumps down from a height and lands hard on their front paws. High-velocity trauma, such as a vehicle impact, is another common cause of damage to the supporting structures of the carpus or tarsus. There are a few non-traumatic conditions that can also cause hyperextension or laxity of the carpus or tarsus, including diabetes and degenerative and immune-mediated disorders.
Usually a dog or cat with an injury to the support structures of the carpus or tarsus resulting in significant instability will not be willing to bear weight on the affected limb(s). Often significant swelling can be appreciated at the level of the carpal or tarsal joint, and the area is usually very painful on handling. Diagnosis is based on a thorough physical exam and x-rays. Sedation and injectable pain medication are necessary for palpation and manipulation of the joint as well as for the acquisition of stressed view x-rays of the joint. While the damaged ligaments and other soft tissue structures are not directly visible on these x-rays, when stress is placed on the joint in different directions, the position of specific bones with respect to one another reveals the location of ruptured or stretched support structures.
What is arthrodesis for dogs?
Arthrodesis means the surgical fusion of a joint. In this type of procedure, the joint surfaces are removed, the joint is stabilized in a neutral position with screws and plates, and bone grafts are placed between the bone ends to encourage new bone growth where the joint used to be. Arthrodesis is considered a salvage procedure that is typically only performed when there are no other viable options to preserve the function of the joint. Drs. Brown and Sherburne perform both complete and partial carpal and tarsal arthrodesis procedures routinely at the Animal Clinic of Billings and Animal Surgery Clinic.
What is a partial carpal arthrodesis?
When only one of the multiple joint compartments comprising the carpus or tarsus is affected by instability, a partial fusion can often be performed that preserves the undamaged portion of the joint, allowing for partial range of motion to be preserved.
What joints can be arthrodesed (fused)?
The shoulder, elbow, carpal (wrist), stifle (knee), tarsal (ankle) and phalangeal (toe) joints can be arthrodesed. Typically severe disease of the hip joint is treated with a total hip replacement or a femoral head and neck ostectomy.
Reasons for performing an arthrodesis on a dog
The principal indications for arthrodesis are:
- immune-mediated destruction of a joint
- joint instability that cannot be treated by other means
- osteoarthritis with chronic pain that cannot be medically managed
- fractures involving the joint surface that cannot be repaired
- tumors in or around joints
- infection involving the joint that fails to respond to antibiotics
- muscle/tendon rupture in which other treatments have failed
Pancarpal or Complete Carpal Arthrodesis Joint Fusions in Dogs
The pancarpal (complete carpal) arthrodesis surgery begins with an incision on the top (front) of the limb along the length of the wrist. After reaching the joint, the joint compartments are entered, and the cartilage lining the joint surfaces is removed. Bone grafts are inserted into the former joint spaces to encourage new bone formation, and an appropriately sized carpal arthrodesis plate is secured with screws to immobilize the bones in a normal standing position. After closing the incision, a splint is placed to support the limb. Typically a dog will remain hospitalized for one to two days following their surgery in order to ensure that they are comfortable on oral medications and that the surgical swelling is improving before they go home.
Risks and complications of arthrodesis
The majority of arthrodesis surgeries are not associated with complications, however, this is a major orthopedic procedure, and thus the following complications are possible:
Loosening or breakage of the implants (plates, screws, pins) may occur if too much strain or force is placed on them before the joint fully fills in with new bone. Implant failure may result in joint instability and necessitate further surgery.
Surgical incision complications, such as wound separation (dehiscence) and infection, are primarily associated with arthrodesis of the carpal (wrist) and tarsal (ankle) joints. Careful wound management within the first two weeks of surgery is of vital importance to minimize this risk.
How good is limb function on dogs after arthrodesis surgery?
Limb function after arthrodesis surgery on dogs is primarily dependent on which joint is fused. It is generally good following carpal (wrist) and tarsal (ankle) arthrodesis and fair following shoulder arthrodesis. Fusion of the elbow and stifle (knee) joints significantly compromises limb function because these are normally very high-motion joints. Dogs and cats that have had an elbow or stifle (knee) fused generally have to swing their limb outward when ambulating because they are unable to flex it as they take a step.
Is Arthrodesis surgery safe on dogs?
While all surgery involves risk, the risks are no higher for this procedure than for most other orthopedic surgeries. Prior to undergoing general anesthesia, bloodwork and a urinalysis are assessed for abnormalities that could increase a patient’s anesthetic risk. An anesthetic protocol is designed for each individual patient based on their weight, age, breed, and health status. From the moment anesthesia is induced until a patient wakes up after surgery, they are closely monitored by an anesthesia technician. Monitoring equipment allows the technician to continuously track the patient’s vital signs to ensure that they are at the right depth of anesthesia for surgery and that they are handling the anesthesia well. Should a problem arise, the technician and veterinarian immediately intervene to resolve the issue. At the Animal Clinic of Billings and Animal Surgery Clinic, we perform many orthopedic and soft tissue surgeries every week, and are very experienced at safely administering anesthesia to all types of patients.
Carpal Arthrodesis Joint Fusion Recovery in Dogs
A splint or cast is usually placed on the limb for four weeks following surgery to stabilize and protect the joint while new bone grows in the former joint spaces. The bandage is typically changed weekly, and more frequent checks may be necessary during the first two weeks to monitor the surgical incision until it is healed. The skin sutures will be removed in 10 to 14 days during a bandage change. Pain medication and an antibiotic will be dispensed when the patient goes home from surgery.
It is essential that physical activity be restricted until complete bone fusion is evident on x-rays. No off-leash activity, including running, jumping, or playing with other dogs should be allowed during this period. Follow-up exams and x-rays are performed at 4-6 and 8-10 weeks to monitor the progression of bone fusion. The veterinarian will determine when physical activity can be increased. Typically, return to full activity can be expected by 4-6 months after surgery.
Arthrodesis-Necessitating Injury Avoidance in Dogs
Hyperextension carpal injuries from incidents such as falls or motor vehicle accidents are common in dogs. Ensuring your dog’s environment is safe from hazards and maintaining close supervision will greatly reduce the risk of household accidents, motor vehicle accidents, or fights with other animals that may result in injury to the carpal joints.
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