Artificial Disc Replacement (ADR)

An Overview of Artificial Disc Replacement (ADR) for Cervical Spine

The artificial disc replacement (ADR) for cervical spine procedure could theoretically be used in any case where an anterior cervical decompression and fusion (ACDF) is used. There are mechanical advantages, disadvantages and limitations associated with this procedure.

The reason the artificial disc was invented initially was because degenerative disc disease can occasionally progress above and below the level of a cervical fusion. If some motion could be preserved, the levels adjacent might be spared further degeneration. Movement sparing devices can take some of the stress off of the levels above and below by preventing some increased forces that could cause degeneration.

Disc arthroplasty is designed to replace the motion of the damaged segment. It does so by restoring the height of the disc space and implanting bearing surfaces in place of the disc itself. Most disc replacements use titanium or chrome-cobalt alloys. The metal is designed to press fit into the disc space and the bone will either grow into the metal or attach to it by scar formation. The problem with this metal is it is not very MRI compatible. This does not mean that an MRI cannot be performed but the metal obscures the signal of the MRI around the area of the artificial disc replacement. Titanium is more ‘friendly” to MRI than chrome-cobalt is.

The replacement disc shares some of the characteristics of the biological disc but not all of them. The articulation or joint itself is a type of elongated ball and cup design. This design allows bending forward and backwards, side to side bending and some rotation. These designs will not allow shock absorption- an important component of a normal biological disc.

It turns out that genetics plays a big role in the determination of the health of a disc. There have been reports of degenerative changes above and below implanted artificial discs so the additional motion may not solve the dilemma of continuing degenerative changes.

Limitations of Artificial Disc Replacement

The artificial disc replacement (ADR) for cervical spine will not work in certain situations. The artificial disc replacement depends upon the vertebral segment other than the native disc to be intact to function properly. That is, the facets and the ligamentous connections have to be “normal”.

If the facets (the joints in the rear of the spine) exhibit degenerative changes such as wear of the cartilage surface, this could create pain with motion which is what the surgery is trying to avoid. If the facets have worn down enough to create a condition called a degenerative spondylolysthesis (where the vertebra above has shifted forward on the vertebra below) this instability would preclude using an artificial disc arthroplasty. If the disc space is diminished greater than 50%, the disc replacement has less chance of working as designed.

The long-term viability of the disc is not yet determined as these devices have not been around for more than 10 years. For artificial joints like a hip or knee, we know these joints will last 10 -15 years before they need to be replaced. Because of that wear pattern, artificial hip and knee joints tend to be implanted in individuals older than 60 years of age.

Disc replacements are being surgically implanted in younger adults and we do not know the life expectancy of the ADR at this point. Replacement procedures will have to be planned. The artificial disc in the cervical spine is generally easy to revise to a fusion if necessary.

Finally, some individuals, especially women, will develop osteoporosis as they age. The interface between the metal of the disc replacement and the bone of the vertebra may fail with advancing osteoporosis and the metal disc may subside into the bone.

Types of Artificial Disc Replacements

There are 2 main types of cervical disc implants- Medtronics Prestige LP, and Synthes Prodisc C.

The Prestige LP total disk replacement is made of titanium-ceramic composite which makes it somewhat better for MRI imaging. It has a ball-and-socket design. The entire disc is made of metal with the bearing surfaces entirely metal on metal. It attaches through a “fin and channel” into the endplate of the vertebra for initial stability and ingrowth surfaces for long-term stability. This is the only disc that is approved for a two adjacent-level procedure.

The ProDisc-C consists of two chrome cobalt alloy endplates (similar to stainless steel) with a plastic bearing surface fixed to the lower plate. The edges of the implant are attached to the vertebra by a central keel with an in-growth surface. The keel stabilizes the implant until bone growth occurs into the endplate.

(Click to Enlarge Image) Prestige LP artificial disc replacement-note the two keels on each half of the ADR and the “rough” flat surface on the top (and bottom) of this disc. This allows bony ingrowth from the vertebral body into the disc.

(Click to Enlarge Image) These are two Prestige LP artificial discs implanted in the front of the neck. You can see the “keels” imbedded in the bone and the small “rings” on either side of the disc that stabilizes these implants

(Click to Enlarge Image) This is a lateral X-ray of a Synthes artificial disc replacement.

(Click to Enlarge Image) This is a Synthes artificial disc replacement at C6-7. The arrow points to the disc.

(Click to Enlarge Image) AP X-ray of a cervical artificial disc.

(Click to Enlarge Image) Lateral X-ray of cervical artificial disc in extension (bending backwards).

(Click to Enlarge Image) Lateral X-ray of cervical artificial disc in flexion (bending forwards). Note the motion in the disc from flexion to extension.

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The differences in the two discs are not significant for a one level surgery (except for MRI compatibility) but do become significant with more than one level disease. The only approval currently for 2 ADRs in a row in a cervical spine is the Prestige LP disc. If a fusion (an ACDF) is needed in conjunction with an ADR for more than one level of disease, the Prestige LP and ProDisc-C will allow fixation of the ACDF level with a plate. This would allow a better chance of healing for the fusion level. Using a Prestige disc will not allow a plate to be used in an adjacent vertebra.

If two ProDisc-C ADRs are used next to each other (such as at C5-6 and C6-7), the keels that attach the disc to the vertebra can act as a wedge and possibly split the vertebral body in-between with significant impact.

Dr. Donald Corenman, spine surgeon and neck specialist, welcomes new patients at his practice. To learn more about the artificial disc replacement (ADR) for cervical spine procedure as a treatment option for spine related conditions, please contact Dr. Corenman at his Vail, Aspen, Denver and Grand Junction, Colorado area office.

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Donald Corenman, MD, DC

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81 reviews

Eric S

Sep 26, 2021

by Eric S on Donald Corenman, MD, DC

Successful pars repair at 46 years old

Back in November of 2018 (at 46 years old) I came from Vancouver BC to have a pars repair done with Dr. Donald Corenman at the Steadman Clinic in Vail Colorado. I'm finally posting this review nearly three years later in late 2021. The reason I waited so long was I wanted to know the final result before I posted my review. Unfortunately in that time Dr. Corenman has retired. Nevertheless, I want to post this review of Dr. Corenman and his staff at the Steadman Clinic in their excellent treatment of my L5 pars interarticularis.

I fractured my pars at age 42 back in 2014 when rolling on the gym floor, and was denied treatment by the Canadian healthcare system, probably due to my age. First my GP told me there was no surgical option for a pars defect, which was quite incorrect! I tried to live with it, but the symptoms worsened (periodic random spine slippage and weeks of resultant pain after just bending over to tie my shoe, so I eventually learned to mostly squat and hardly bend). When I finally consulted with Canadian spine surgeons, I was told they believed my pars defect had been congenital (since birth). This was absurd, considering I had done extreme martial arts (including jiu jitsu) for years prior, as well as 5 years of reinforcing steel full time in my 20s, probably the hardest job on the back you can find. No pars defect like mine would possibly have allowed this--ergo it was impossible that I had had the defect since birth. I did however have an asymptomatic congenital spina bifida occulta that made me more susceptible to a pars fracture. In 2014 in one instant, I went from having the strongest back people I knew said they'd ever seen, to being unable to safely bend over and tie my shoe without a non-negligible risk of my spine slipping randomly (which would lead to weeks of pain after each occurrence). This was due to the unilateral L5 pars defect, otherwise known as spondylolysis. It was when lying in pain on the floor 4 years later after maybe the 6th spine slippage event post injury, that I had had enough, and resolved to have surgery. If Canada's "universal health care" said no, I would make lemonade from lemons, and find the very best surgeon in the world at pars repairs. That was Dr. Donald Corenman. Dr. Corenman back in 2018 ran a website https://neckandback.com/ that dedicated many pages to the science of every aspect of pars repairs, from eligibility (good discs on MRI), to best surgical techniques (minimal open compared to minimally invasive), best imaging to use (i.e., O-Arm with Stealth imaging vs. older fluoroscopy), the ideal amount of BMP to use and why not use too much or too little, and much more, all to do with pars repairs, pages upon pages of his site just on the pars, with scientific references and his own extensive expert opinion. As a health research statistician, I was very impressed with this. It was in stark contrast to the websites of other spine surgeons which barely gave the pars a word or two, focusing almost exclusively on fusions. I had found the best surgeon in the world for pars repairs, and so after Dr. Corenman personally screened my MRI to ensure my discs were healthy, I booked the surgery.

Being 46 years old at the time of surgery in 2018, with a 4-year-old pars fracture from 2014 combined with a congenital SBO meant my pars fragment was somewhat atrophied, but it was "very solid", said Dr. Corenman in the operative report. Nevertheless, it was challenging with two things to fix, the pars and SBO, and OR time was around 4 hours. Recovery over the following months was guided by a very clear "Spine binder" from the Steadman Clinic with strict rules of "no BLT" (no bending, lifting or twisting), and illustrated physiotherapy guidelines. They even warned patients to avoid fish oil supplements, which could excessively dampen inflammation and hence slow bone healing. They answered many questions I had during months of recovery, with responses coming from the very supportive Lori Fugate (then director of Dr. Corenman's practice), and Ehrich Bean (then physician's assistant at the practice), as well as a couple calls with Dr. Corenman himself after two of the CT scans. Ehrich Bean offered great advice for taking the spine binder conservatively due to the nature of pars repairs vs. fusions. The final post-op CT scan I had was a couple weeks ago at 34 months post-op, and Dr. Corenman had retired, but I got a very positive and informative call from Eric Strauch (current PA at the Steadman Clinic under Dr. Corenman's replacement there, and who had also worked with Dr. Corenman previously). The staff at the Steadman Clinic were extremely supportive all the way through the process. I should mention, the local Canadian spine surgeon did offer me very good post-operative support including antibiotics as needed to deal with a mild surface incision-site infection early on, booking numerous x-rays when I felt something was amiss, as well as booking all four of my post-op CT scans. I am very grateful for that support also.

My final result shows plenty of solid bone across the pars and a healed SBO, with my vertebral body now a solid bone ring instead of being broken at two places as it was pre-op. Does my spine hold up in the real world? You bet! I have recently dug and moved several yards of dirt and sand and gravel by myself (shovel and wheelbarrow!) to fix our water main, pulled roots from the yard, moved several "portable" (these are HUGE) air conditioners up several flights of stairs my myself, and lifted weights. I now run 2 miles (3.2 KM) several times weekly with a hard 100 meter dash in the middle. I bend deeply before each run I go on, with no spine slippage. My spine feels amazing. I can bend over to do exercise, or real word tasks, with no risk of spine slippage.

My sincere thanks to God, Dr. Donald Corenman, Lori Fugate, Ehrich Bean, Eric Strauch, and the Steadman Clinic, as well as the Canadian spine surgeon who offered me excellent post-operative care back in Canada. You have all given me a new lease on life.

Sincerely,
Eric S

Robert S

May 11, 2021

by Robert S on Donald Corenman, MD, DC

Back Fusion Surgery

I had my entire lumbar spine fused in November of 2018. I had scoliosis , with pinched nerves that were so painful I could hardly walk - and standing for more than a few minutes was impossible. Even sitting was painful.
The fusion surgery produced immediate relief! And the recovery was much easier than I expected.
To this day I can do all the activities I love from hiking, to standing in a stream fly fishing to riding my bike long distances - or just walking down the street with my wife.
Kudos to Dr. Corenman and his staff, (including the two Erics) for taking such good care of me!

Leslie R

Jul 9, 2020

by Leslie R on Donald Corenman, MD, DC

TLIF

I had my TLIF surgery on 6/24/2020 by Dr. Corenman, I can not say enough good things about the Dr or his staff. I was always treated with respect and explained everything throughly, that made it easy for everyone to understand. I highly recommend Dr. Corenman and the Steadman Clinic.

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Artificial Disc Replacement (ADR) for Cervical Spine

An Overview of Artificial Disc Replacement (ADR) for Cervical Spine

Limitations of Artificial Disc Replacement

Types of Artificial Disc Replacements

Are you a candidate for artificial disc replacement (ADR)?

Related Content

About the Author: Donald Corenman, MD, DC