What is atlantoaxial instability?
In the neck of the dog, the first vertebrae (called the atlas) articulates with the second vertebrae in the spine (called the axis). Instability of these two vertebrae allows excessive flexion (downward bending) of the joint which can lead to problems with the spinal cord.
What causes atlantoaxial subluxation?
Atlantoaxial subluxation results from an abnormality of the ligaments or bone between the atlas and axis. Several congenital and developmental abnormalities of the atlantoaxial joint can cause instability of the vertebral column, which leads to atlantoaxial subluxation. These abnormalities include dysplasia (abnormal growth), hypoplasia (decreased growth) or aplasia (absent growth), dorsal angulation, separation of the dens (part of the axis that attaches to the atlas), absence of the transverse ligament, block vertebrae or incomplete ossification of the atlas. All these conditions can result in instability between the two vertebrae that can result in damage to the spinal cord.
Traumatic subluxation can also occur in any breed or age of dog. This results from trauma causing excessive flexion (downward bending) of the head, which can cause a fracture of the atlas and axis or tear the supporting ligaments.
Are there certain breeds at risk?
Small breeds of dog, such as Chihuahua’s, Miniature Poodles, Yorkshire Terriers, Pomeranians and Pekingese are most often affected by atlantoaxial subluxation. This is because part of the axis is prone to abnormal development in miniature breeds.
Atlantoaxial subluxation has also been reported in large breed dogs, but this is much less common.
What clinical signs will my dog have?
Neck pain is the most common sign associated with atlantoaxial subluxation. Associated neurological signs depend on the degree of damage present in the spinal cord. These can range from wobbliness or ‘ataxia’ in all four limbs to being unable to walk at all.
How is atlantoaxial subluxation diagnosed?
Atlantoaxial subluxation is strongly suspected based on clinical signs; however diagnostic imaging is required to confirm the diagnosis.
Survey radiographs of the cervical spine can reveal an increased space between the atlas and axis, or malalignment of the two vertebrae. The presence and size of the dens can be seen on radiographs.
CT and MRI can help with diagnosis and planning treatment options for individual patients. CT is more useful for assessing the conformation of the dens or fracture of the vertebrae. MRI can determine if the spinal cord has been damaged, which helps with advising owners of the prognosis.
How is atlantoaxial subluxation treated?
There are multiples options for treating atlantoaxial subluxation and the best option will depend on the degree of clinical signs and whether the condition is getting worse. Your surgeon will discuss these and let you know which is best for your dog.
Conservative management: Conservative treatment may be useful in cases where atlantoaxial subluxation is due to ligament tears and is used to stabilise the atlantoaxial joint whilst the ligaments are healing. This includes strict cage confinement for 6 weeks, pain relief and a rigid neck brace. The neck brace is placed on the neck, holding the neck in extension, from the jawbone to the chest.
Conservative treatment is not often recommended for atlantoaxial subluxation as it may be more likely to result in recurrent or worsening of clinical signs.
Surgical management: The goal of surgery is to stabilise the atlantoaxial joint to prevent further spinal cord damage. Surgery should be considered in all dogs as it fuses the joint and prevents the chance of catastrophic recurrence.
There are various surgical techniques for stabilising atlantoaxial subluxations and the decision will be based on the information from diagnostic imaging and examination of your dog to give them the best chance for full recovery.
What happens to my dog after surgery?
After surgical repair, post-operative radiographs will be obtained to confirm correct implant placement and alignment of the joint.
Immediately after surgery your pet will be recovered from anaesthetic and remain in hospital for at least 24hrs post operatively. Post-operative analgesia and intensive care will be provided in our designated ICU where your patient will be monitored and nursed by a dedicated team of nurses and vets that are present 24/7. Your pets breathing will also be monitored closely to ensure that there are no problems.
In some cases, a neck splint will be applied after surgery to support the patient in the immediate post-operative period. This will be decided on a case-by-case basis.
The following day your pet will be reassessed by the surgeon and an initial physiotherapy assessment will be performed, with a physiotherapy programme being designed to cater individually for your pet. Physiotherapy plays a vital role in the recovery of animals, with inactivity resulting in decreased joint movement, stiffness, muscle weakness and contracture.
Strict cage restriction will be advised for up to 8 weeks after surgery. Post-operative radiographs will be performed at 6 weeks after surgery to ensure that the implants have remained secure. You will be advised that a collar or neck lead should not be used when walking your pet, instead a harness is suitable to avoid pressure on the neck.
When can my dog go home after surgery?
The length of stay in hospital following atlantoaxial stabilisation varies from patient to patient and is determined by their comfort levels and their recovery following surgery. We ensure that your pet can urinate normally before being discharged.
At the time of discharge, you will also have an appointment with our physiotherapist where you will be taught how to perform the necessary physiotherapy techniques to ensure your pet continues to improve and that their muscles remain active and functional. At this time, we also recommend you make additional appointments for physiotherapy through our very own in-house rehabilitation service at North Coast Veterinary Specialists and Referral Service.
What is the prognosis?
The prognosis for this condition varies greatly depending on the severity of clinical and neurological signs prior to surgery. Your surgeon will discuss the prognosis in greater detail when they have performed an assessment and full neurological examination.
What complications can occur?
While we always do our best to avoid any complications, with surgery it is inevitable in some cases. We will discuss these with you in more detail, but the most common complications seen are listed below.
Complications with conservative management include recurrence of disease, migration of the splint, moist dermatitis, pressure sores, hyperthermia, respiratory compromise, anorexia, ear infections, and accumulation of food between the splint and the jaw.
Complications associated with surgical management include neurologic deterioration, respiratory compromise, implant failure, fracture of the vertebrae, and recurrent pain. The likelihood of these will change depending on the neurological grade prior to surgery.
If you have any questions regarding this condition or the right treatment for your dog, please contact us at the clinic either by phone or email and we can discuss it further.