What is Cervical Disc Arthroplasty (CDA)?

Cervical Disc Arthroplasty (CDA) is a relatively new procedure that is used to treat Disc Associated Wobbler's Syndrome (DAWS).  It was developed by Dr. Filippo Adamo ECVN, the inventor of the artificial disc implant that we use in the procedure (The Adamo Spinal Disc).  Dr. Adamo created the technique based on disc replacement surgeries that are done in people because of the tendency for DAWS patients to develop a 'domino lesion' of DAWS in the adjacent discs shortly after surgical correction of the first lesion.

This is a picture of the instrument table and set-up before placing the disc implant in a patient.

The disc implant serves two purposes in treating DAWS.  First, it distracts the intervertebral space to relieve the compression on the spinal cord.  This is similar to the stated goal-of-therapy of several of the older procedures as well.  But where the CDA procedure differs, is in it's ability to maintain movement and range-of-motion at the surgical site.  By maintaining the dynamic nature of the intervertebral disc space, the CDA technique seeks to minimize the effects on the adjacent discs and prevent the dreaded 'domino lesion'.

We can place more than one disc implant in a patient when indicated.

The Adamo Spinal Disc is currently in it's 5th iteration.  The current design uses state-of-the-art manufacturing techniques and materials to improve the device and the surgical outcome for our patients.  

This is the complete Adamo Spinal Disc implant.  The white material on the back of the implants promotes bony fusion between the vertebrae and the implant.

First, the device is made of surgical grade titanium.  This lightweight and durable metal is also MRI safe.  Which means that we can safely repeat MRI studies of the patients if needed after the surgery.  In fact, repeat MRI studies are part of our post-operative evaluation for this procedure.  Because the technique is so new and cutting edge,  LOVN performs these post-operative MRI studies for these patients at no cost in exchange for using their outcomes and data for future studies and scientific papers.  That's how much we believe in this procedure!

Second, the device uses a small thermoplastic articular surface to maintain the movement at the site.  It works just like a 'ball and socket' to allow the two parts of the implant to move relative to one another.  If the contact surfaces were made of metal, small microparticles would be produced from the friction and could lead to worsened inflammation or other problems.

Here you can see the two parts of the Adamo Spinal Disc and the 'ball and socket' articulation between the two.  You can also see the screw threads that allow us to remove the positioning pins once the implant is in place.

Finally, the surface where the implant contacts the end plate bone of the vertebrae is specially treated in two ways to help in the healing process.  First, the surface is treated in a very special way to create titanium 'pores' or tunnels that encourage bone growth into the implant.  Once the bone grows into these 'tunnels' the interface between the bone and the implant becomes incredibly strong and durable.  Secondly, the titanium porosities are coated with hydroxyapatite crystals.  This is the same material that your body produces to create bone.  It serves as a substrate to speed up the bone growth into the pores and the ultimate incorporation into the vertebrae.

What is Caudal Cervical Spondylomyelopathy (CCSM)?

This blog post is going to discuss the second form of "Wobbler's Disease" in dogs, Caudal Cervical Spondylomyelopathy or CCSM.

The breeds most commonly affected with CCSM include the Mastiffs and the Great Dane, but almost any large breed dog can be affected.  Typically, this condition is seen in younger dogs as it is a developmental problem (contrasted with the degenerative problem that causes Disc Associated Wobbler's Disease or DAWS).  

Again, to contrast with DAWS, the compression of the spinal cord is due to bony changes rather than discs, tendons, ligaments, or soft tissues.  The parts of the vertebrae that form the bony tunnel of the vertebral canal develop abnormally and are thickened towards the tail-end of the vertebrae.  This bony thickening is most noticable along the lateral (side) walls of the tunnel called the pedicles.  So, the compression is from the side in CCSM, whereas it's mostly top-to-bottom with DAWS.

Once again, there are two different options for therapy, medical management vs surgery.

With medical management, the goal is to control the dog's clinical signs.  But the drugs don't do anything to stop the disease progression.  And, sometimes, the disease can progress very suddenly due to vascular or 'bruising' injuries to the spinal cord!  Othertimes, the progression is slow and due to progressive bony changes at the true joints in the vertebrae, the facets.

Thickening of the facets can often cause progressive signs in CCSM due to worsening spinal cord compression...

Surgery attempts to alleviate the compression and works with medical management to control the clinical signs but also to halt the progression of the disease.  In the ideal situation, surgical decompression even allows us to stop the medications.  

Unlike DAWS which can suffer a 'domino effect' following surgery, this isn't common with CCSM decompression.  But, just like DAWS, there are several surgical options for pets with CCSM.  Some include decompression by removing bone from the top and sides of the vertebral canal.  Others involve a distraction-fusion technique to allow the bone to resorb on its own and alleviate the compression.

Diagnosis of this disease often requires an MRI or a CT scan combined with a myelogram.  In the end, the diagnosis will play an integral role in deciding which medical or surgical option is right for each individual patient.

What is Wobbler's Disease?

Wobbler's disease is a term used to describe two different pathological processes in the neck of dogs.  One form happens in younger large breed dogs, and the Great Dane and Mastiff are the most common breeds.  The other form happens in older dogs, and the Doberman Pinscher is the most common breed.  It also occurs in horses, but we'll save that for another blog post on another day!  

The medical term for the condition in younger dogs is Caudal Cervical Spondylomyelopathy.  In this disease, the spinal cord is compressed by increased thickness of the bones in the vertebrae themselves.  Typically, this is towards the base of the neck, and it is slowly progressive.  While low doses of steroids can help control the disease; this type of medical management does not address the underlying cause and the signs often progress in spite of the drugs.  Surgery to remove the compressive bone is often curative but is a complicated procedure and carries some degree of risk.

In older dogs, Wobbler's disease is more aptly termed Disc Associated Wobbler's Syndrome, or DAWS.  In these patients the spinal cord compression is caused by bulging of the intervertebral disc and thickening of other supportive ligaments in the vertebrae at the base of the neck.  Medical management for this condition also makes use of low-dose steroids.  Just like the condition in younger dogs though, medications do not treat the underlying cause and the clinical signs often progress.  Surgical options exist for these pets as well, but have often been plagued with complications.  Particularly, a problem known as the 'Domino Effect'.  We'll discuss this condition and the surgical options in more detail in a later post.

Because both of these conditions occur in the neck and are progressive, dogs can become completely paralyzed if not treated.  Classically, these pets have a 'two-engine' gait where the forelimbs take short and choppy strides and the hindlimbs have a longer, loping gait.  

If you think your pet might have Wobbler's disease, contact your veterinarian.  Oftentimes an MRI is necessary to make the diagnosis, but there are treatment options and help is out there!

This is a video illustrating the gait disturbance we typically see and outlining the story of a dog with Wobbler's Disease that had a disc replacement surgery!  If you're interested in learning more about disc replacement therapy and the Adamo Spinal Disc click here.