Spinal Kinetics M6 - A Shock-absorbing Artificial Disc with "Graded Resistance"

[tyler]

I'm a biologist and work in the biotech industry. I'm also an active 48-year old and was really concerned about choosing the best artificial disc available for my condition (severe foraminal compromise and disc degeneration at C5-6 and C6-7). Although other discs have been used longer, after researching what I could and following up with nine different surgeons in the U.S. and Europe, I decided to go with Spinal Kinetics' M6-C (picture below).

Besides being designed to match the normal kinetics of the spine, the M6 core - which is meant to replicate the functions of the natural disc - provides what would appear to be several important attributes (all closely following features of normal discs):

- the nucleus is somewhat compressible, like the healthy nucleus, and therefore capable of absorbing and cushioning some axial load, rather than just transmitting it to the adjacent regions (but not so compressible as to allow the space to be restricted)

- there is an annulus surrounding the nucleus that facilitates freedom of motion but in a restrained fashion, as in the normal disc

- the internal structure of the annulus provides "graded resistance to motion" (i.e. more resistance to motion as the turning or bending motion increases) - this again mimics the native disc and could be important to help restrain the disc from over-extending (e.g. in an accident or other stress situation), and could help to protect the facet joints since they would otherwise be forced to prevent any over-extending motion (this contrasts with typical ball-and-socket designs since the ball is generally free to spin)

- the core is surrounded by a flexible non-load-bearing collar that should tend to keep any outside materials/cells from getting into and around the core (cell intrusion and in-growth can eventually lead to reduced rotation or auto-fusion observed with many discs); also, in the event that any microdebris eventually wore off the core as can theoretically happen with any disc, it should be held inside by the collar (this again contrasts with ball-and-socket designs and other discs in use since these generally do not have a containing collar)

There are of course other considerations and every patient's situation is in some ways unique - but I decided to go with technology that appears to be among the best available - mostly because it more closely mimics what nature has already evolved, and what the surrounding structures are 'designed' to work with.

Pictures of M6 in 'cut-away' help visualize the features referred to above:


Just as important is finding a great surgeon who's experienced with the disc. In this case it was harder because I'm in the U.S., and although M6 was in clinical trials there (and I met with one of the key docs involved), it's only available outside the States. After a lot of searching and talking to patients, I felt fairly confident about going with any of the following three leading M6-users in Europe: (1) Ritter-Lang at the Stenum in Germany; (2) Nick Boeree at Nuffield Wessex Spine Clinic in the UK; and (3) Pablo Clavel in Barcelona.

I ended up going with Nick Boeree and had an absolutely amazing surgery - and result - details here:
Relief After Cervical ADR C5-6 & C6-7 with Spinal Kinetics M6-C Artifical Disc / Nick Boeree, Nuffield Wessex

Besides thanking Spinal Kinetics' engineers and my docs, I also want to thank folks here at SPS for the very helpful contacts and info. If I can be of further help to anyone, please don't hesitate to ask!

Best,
Tyler


Note: I'm not affiliated with Spinal Kinetics and I'm not a bioengineer. I am a biologist with an acute personal interest in discs for my condition (severe disruption and formaminal compromise at C5-6 and C6-7) - and believe M6 to be among the best technology available. However, every patient's different, and these technical points and comments are not to be taken as advice but rather to help promote consideration and discussion with your doctor.

[Cindylou]

Tyler, thank-you for the detailed explanation of the discs you used and why. It just sounds like with all your homework, interviews with docs, etc., you made a very informed decision. Excellent. I am so happy for you. You went to England for it....but where are you in the states, if you don't mind my asking? I cannot recall if I have read your signature or not, or if you even have one, but it looks like from your profile pic you are either skiing or snowboarding in the mountains. If you are, are you going to try to do active winter recreational activities such as those, this coming winter? I haven't skiied in a few winters, which kills me. My favorite sport. But I am hoping maybe after my lumbar facet rhizotomy I'll be able to get my pain levels down and do it this winter. One can hope. My very best to you, Cindylou

[tyler]

....but where are you in the states, if you don't mind my asking? I cannot recall if I have read your signature or not, or if you even have one, but it looks like from your profile pic you are either skiing or snowboarding in the mountains. If you are, are you going to try to do active winter recreational activities such as those, this coming winter?

Hi Cindylou -
If I do go back to the States mid-Sept. (I wish I didn't have to), it'll be to California. And yes, the pic was skiing. I've since switched to snowboarding, which might be a good thing since on skis I'm all about speed whereas I can enjoy boarding even at less than extreme velocity.
I'm even more anxious to get back to cycling though. Before I was knocked out by a head-on 'Sunday rider' in May, I was finishing training for a benefit ride from San Francisco to LA - but I'm already signed up for the next...!
Cheers from a very sunny London,
Tyler

[trkdoc714]

Tyler,

It's great to hear the success stories. How long did it take you to figure out how to "look outside the box" for your treatment?

The M6L is an exciting disc. If I could've held out a year longer, I might have gotten them instead of the Mavericks. Since there's almost no trade-in value for new discs, I'm stuck with them.

Travel safely when you come home and congratulations!

[Cindylou]

Yes, I second that: it is great to hear and read success stories!

[Hooch]

Can anyone find any peer reviewed literature anywhere on this disc? I can't find pilot studies or anything.

The cushioning effect sounds great, but you've gotta wonder how it holds up after 50 years.

[tyler]

The cushioning effect sounds great, but you've gotta wonder how it holds up after 50 years.

Hi Hooch

Well, as a scientist I don't believe we know how any disc will hold up for 50 years - but I can tell you if that's my main problem at age 98, I'll definitely be counting my blessings!!

In the meantime, a device with kinematics that mimic native discs, and restrained motion that would tend to minimize stress on facet joints and adjacent discs, seems like a good way to go for me.

With respect to projected durability/longevity, which is apparently tested by motion studies in cadaver vertebrae and/or other lab setups as part of device applications, things can always be different in the 'goopy' body, mostly because you now add cells and other body components to the mix. That's one of the reasons I liked the idea of having a fixed but non-load-bearing collar around the moving parts (not really feasible with ball-and-socket spin). Keeping body fluids and cells out and any microdebris in would be expected to help lengthen lifespan and reduce the likelihood of microdebris causing problems.

Regarding publications, like many newer devices but especially ones from smaller companies, there are relatively few publications. But you might find the following abstracts of studies interesting, as well as kinematic studies that I believe are referred to on the company's website.

All IMHO but hope that's helpful!

With best regards,
Tyler

ps- I haven't been able to attach a pdf of abstracts but will see if I can figure it out in a separate message

[tyler]

Regarding publications, like many newer devices but especially ones from smaller companies, there are relatively few publications. But you might find the following abstracts of studies interesting, as well as kinematic studies that I believe are referred to on the company's website.

Still can't seem to attach the pdf of meeting abstracts but I'll see if I can send it to you by email and maybe you'll be able to re-post. There is also some technical information and studies on the Stenum site at the following link:
Stenum Spine Neck Surgery - Cervical Disc Replacement M6 Studies

[tyler]

I am about to get a M6L, it does sound better than most of the other options out there but I am not a professional in the field. I am traveling to Stenum hospital tomorrow. At this point I really don't see any better option out there.

Helmut - wishing you the very best of luck!


Let us know how it goes!

[jss]

Hooch,

Good luck this week. I've got a couple of M6's myself and so far have only good things to say about them. In my pre-surgical research when I was researching devices, during my correspondence with Spinal Kinetics, they claimed that their testing of the device amounted to the equivalent of "85 years in the human spine". Even with that claim, we'll still have to wait 50 years to see what condition one is in after 50 years.

Good luck, Jeff