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April 10, 2021  

Charles Ray, MD: Taking Spine Surgery to a Higher Level

September 11, 2001

Charles Ray, MD, is a trained neurosurgeon with a background in mechanical engineering and business. He is the Medical Director and Chairman Emeritus of RayMedica, Inc., a medical device company that aims to treat patients with debilitating low back pain. Dr. Ray is also the president of the American College of Spine Surgery and a spinal neurosurgeon at the Institute for Low Back and Neck Care in Minneapolis.

Dr. Ray earned his medical degree at the Medical College of Georgia and completed his neurosurgery residency and straight surgery internship at the Baptist Memorial Hospital in Memphis, Tennessee.

MedTech1: You are a trained neurosurgeon who started a back device company. Can you tell me a bit about how you got started with RayMedica, Inc.?

Dr. Ray: In addition to being a neurosurgeon, I am also an engineer and a businessman and I have almost equally divided my career into those three different compartments. I taught medical engineering to the staffs at the Mayo Clinic, Johns Hopkins, and the University of Basel in Switzerland. The department of which I was the chief when I was in Switzerland was a division of Hoffman LaRoche, one of the biggest pharmaceutical companies in Switzerland. A friend of mine [Earl Bakken, founder of Medtronic] persuaded me at the time to come back to the United States and start a diversification with Medtronic. I became a vice president of Medtronic and started a new diversification of theirs in neurologic and rehabilitation devices.

While I was with Medtronic, I realized it was more important for me to develop applications than it was to develop hardware alone. So I began to go back more and more into practice. I opened a department in Minneapolis and got a former resident of mine from Hopkins who was on the faculty in Philadelphia at the time to head up that department. We built one of the largest spine practice groups there.

At that time, I realized there were a lot of instruments needed for spine surgery that did not exist. So I started a company and began to design, develop, manufacture, and sell medical equipment primarily for spine use. I sold that company to a California company, which then expanded it. That company was, in turn, acquired by US Surgical and became part of their Surgical Dynamics division. The company now manufactures my fusion cages, which have been used in over 200,000 people around the world.

One of the projects I did not sell to US Surgical was my prosthetic disk nucleus (PDN). So I started yet another company and began to work on the device. With venture capital, I further developed my work into what is now known as RayMedica.

I was doing surgery just last week in three hospitals in Egypt. For both my fusion cages and the prosthetic nucleus, I have operated in 25 countries and well over 100 hospitals in the past 14 years.

MedTech1: Are your products for patients with severe back problems?

Dr. Ray: Many neurosurgeons do not believe in disabling back pain, believe it or not. They have been a difficult group of people to deal with. When I was president of the North American Spine Society, I made it a point to try to attract more neurosurgeons into spine work, and now it is becoming the fastest growing part of neurosurgery.

Many neurosurgeons are surprised I do fusion for back pain. I say to them, do you do surgery for cancer? They say, it depends upon the cancer. I reply, you just answered my question. It depends upon the kind of back pain. The kind of pain that requires surgery changes the life of the patient. This is not something that happens after a weekend of football. We perform surgery when a patient is beginning to lose his job, his family, his self-respect, his avocation, basically when his back pain is destroying his lifestyle.

What we do in these cases is obliterate part of the disk. I have spent the past 15 years trying to understand the chemistry involved inside the disk that leads to degeneration and severe pain. That is one topic I lecture on because so little is known about it. There is a chemical basis for the degenerative changes in the disk, which is part of the reason there is such severe, disabling back pain. For many years it was known that, to stop the pain, you had to obliterate the disk or make a fusion. It occurred to me early on that there was something wrong with a disk that was doing all that damage. It was not just a flat tire that had gone bad or a cushion that had lost its oomph. Instead, it had the ability to provoke damage to nerve endings and to carry on destructive changes in the mechanics of the spine. It turns out the cause is chemical. The center of the disk has no circulation and accumulates catabolytes, or metabolic byproducts, without the presence of oxygen. These byproducts are toxic to other tissues and if some of them leak out of the disk and make their way to the surrounding nerve endings, the patient will have a severe pain. For many years, surgeons would stop disk movement by fusing the spine but never really knew where the pain came from and why it needed to be stopped.

I worked for several years on a method of simplifying the fusion procedure and developed the fusion cages, which have now become a world standard, though not without some controversy. The procedure looks so simple that many surgeons do not watch the details and mess it up. So I am working on a booklet on how to do it wrong.

The PDN does not fuse the disk. Instead, it allows the disk to maintain essentially normal motion and activity and obliterates the source of all that horrible pain. It changes the chemistry of the disk and alters what the disk does from a metabolic point of view, but it does not change it from a mechanical structure point of view like a fusion would do. There will always be a place for a fusion though.

There are other kinds of artificial disks but most of these are mechanical devices, such as hinges and springs, which allow the disk to move but prevent normal motion. The PDN restores the function of the disk by restoring part of the natural anatomy. The inside of the disk contains a gel material that swells. The swelling pressure is enough to lift the disk space by tightening the fibers around the outside of the disk, where the stability comes from. It’s like an automobile tire, where the air is really the thing that keeps the tires tight. If the air goes out, the tire does not work. In the disk, when the nucleus goes bad, the pressure to keep the annulus tight goes away and they start to break down. For the past 15 years I have been working on how to replicate that nucleus. The result is the PDN. It is implanted in a dehydrated state and then swells vertically to lift the disk space and tighten the fibers again.

We now have about 400 patients around the world and are awaiting approval from the FDA to start doing a large study in the United States.

MedTech1: Does the PDN last the lifetime of the patient?

Dr. Ray: The natural disk does not move like other joints in the body. There is no sliding, rotating, or grinding motion. Instead, it’s like sitting on a cushion. We took prototypes of the PDN and put them into a testing machine to simulate the normal wear and tear of a person’s back for over 50 million cycles. We saw no degenerative change whatsoever to the constituents. We have also tested the polymer we use and it has stood up very well. The body does not attack it, and it does not attack the body.

MedTech1: What types of patients receive the PDN implant? Are they older? Active? Inactive?

Dr. Ray: as a general rule, degenerative conditions of the spine that change the patient’s life occur principally during the working years of life. It has been said that disorders of the back are products of the modern age because we do not walk like we used to. Sitting at a computer terminal is just not natural. Fairly stressful motion is important to make the disk pump and to exchange its metabolites. If you lead the life of a couch potato, that does not happen.

Around the world, 80 percent of the population will have a significant back problem. But only a small percentage of those will actually get to the point where they have to do something surgical. These people are mostly of working age. We say we do not do cases younger than 18 or older than 65. The average age is about 41.

MedTech1: Can the patients return to a normal lifestyle after surgery?

Dr. Ray: Yes. In the earliest cases done with the PDN in Germany, most patients went back to work between six weeks and three months after surgery. Some of these patients are now five years after implant and are continuing to do well and get even better slowly. Some have returned to hard labor, which confirms what I thought about the construction of the disk several years ago.

When I first started looking at the disk several years ago, it was a lonely field because so little data was available. Being an engineer, I looked at the disk space not only as a physiological and chemical structure but also as a mechanical structure. Asking questions about the origins of the mechanics has also led to a better understanding of how to imitate the nucleus. I think I’ve arrived at that because of my peculiar background in medicine, chemistry, and mechanical engineering.

MedTech1: Are you still involved with RayMedica?

Dr. Ray: Absolutely. Just last week when I was doing some cases in Egypt I got excited because I figured out a way to simplify a part of the PDN implant procedure. I really felt good about that. Now I am working with an illustrator who does great pen and ink work and can convert my findings into teaching materials. I am going to focus on my booklet on how to do the procedure wrong.

For more information about the PDN, visit the RayMedica Web site.

Last updated: 11-Sep-01

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