In early December, San Diego-based Scripps Health earned funding from the National Institutes of Health to develop the world's first "smart" shoulder replacement implant.
The $317,000 NIH grant aims to support initial research on the implant, which could provide surgeons and researchers with new information regarding patient movement and implant integrity.
This research could prove gamechanging for upper-extremity replacement patients, the initiative's co-lead investigators Darryl D'Lima, MD, PhD, director of orthopedic research at Scripps Health, and Heinz Hoenecke, MD, orthopedic surgeon and researcher at Scripps Clinic, told Becker's.
The two surgeons discussed potential benefits of the implant and its research, as well as the development process and even more technologies in the pipeline.
Question: What benefits will the smart shoulder implant offer patients?
Dr. Darryl D'Lima: Dr. Hoenecke does shoulder replacements in patients that have arthritis of the shoulder with metal and plastic components. What we are doing is we are using the insides of the implants to house electronics, including sensors, for example, a sensor that can feel force that the patient is exerting on the shoulder joint, motion, the angle at which the arm is being held and the activity. What are they doing after a smart shoulder is implanted? A part of it is because we don't know what patients do in the field.
We have a lot of data from hip and knee replacements, because walking is the most common activity, followed by stair climbing, getting in and out of a chair, all common activities. For the upper extremity, there is no single common activity that dominates. Every person is different. From combing hair, tucking in shirts to driving and eating. So, we don't know what we don't know. So that's one thing we'll be monitoring.
The second is we've been designing based on, we design and then we look at anything that goes wrong and fix it in the design period. That's a long cycle for us to know if something will work or not. So this will hopefully shorten the cycle.
Dr. Heinz Hoenecke: Patients want to know, "How much motion will I have in my arm? How much strength will I have? What activities can I do? What activities are safe and which ones aren't?" They want to know, "Can I reach behind my back? Can I do pushups? Should I do pushups? How much weight can I lift?" Well, we don't know exactly how much motion each implant allows because it's obscured by the muscles.
We don't really know when implants are contacting each other such that they'll limit motion. We don't know how much force is on implant connections to the body, such that we worry about it either dislocating or coming loose. For those reasons, we often recommend against things like pushups or heavy weight lifting. But if we had the information that Dr. D'Lima is talking about from the implant, we'd have a much better idea which activities are safer and overtime we would know when we are exceeding a threshold of force within the implant that's risky. That will drive not only recommendations to the patient, but allow us to maximize their activities by choosing the optimal implant and placing it in the best position within the shoulder to keep forces safe. The goal is to get patients the most active shoulder we can. There could be activities we've been restricting that we don't need to restrict. Perhaps it's fine to do pushups on your knees or lift, but we don't know right now.
DD: Now we will be able to design implants based on actual evidence.
Q: Where are you in the development process for these new smart shoulders?
DD: We usually start with an implant design that's already been used in patients, because we know it's reasonably successful. The last thing we want is an implant to fail. Then we modify the design without changing the outside or weakening it so it's still structurally safe. The reason we have to modify it is because now we have to put electronics in the implant itself. These include sensors, microprocessors that collect the data, a rechargeable battery to power the implant, data chips for storing the data and there's a telemetry system which communicates wirelessly between the implant and a mobile device or lab computer that can query the information. So that's the technical aspect.
Then we test it, so we have to seal the implant completely because we can't expose the patient's body to the electronics, so it's sealed completely. Then, it's tested to the FDA requirements for safety and then we test in addition to any known risk because we have now changed and modified the design. Then we implant it in cadaver specimens for performance and look for integrity of data, is data accurate, can it be transmitted through bone and metal and skin. Then the next step is Dr. Hoenecke gets involved. We collect data and place this as a trial implant, not a final implant. The final implantation is the challenge because we have to get FDA approval, it takes a lot of testing, regulatory paperwork and approval from Scripps Health, who have to approve the research study. The FDA has to approve it and the manufacturer has to approve it because they are providing the implants.
HH: So once we have something that we can test just in surgery, not necessarily even implanting, then run through the tests that Dr. D'Lima requires, the next goal is to place one in a few research subjects to get the most basic data. It remains to be seen whether this is ever a commercially available product, but we are confident we will achieve most of the benefits and goals just through research subjects. We are getting data that would have otherwise never been available. That's where the excitement is. With Dr. D'Lima's knee project, he demonstrated significant info gain without any product ever sold.
Editor's note: In 2004, Scripps made history through the implantation of the world's first "smart" e-knee implant. Research on the knee was led by Dr. D'Lima.
Q: What other technology advancements are you keeping an eye on right now?
HH: From my perspective, we're working on shoulder reconstruction techniques. Dr. D'Lima has several other projects in the works.
DD: On the shoulder, we're also working on rotator cuff repair. In older patients with big tears, they don't heal. We are using stem cells, in a project, funded by the state of California, to grow a bio tendon. We're still in the lab testing them, so we're still a way from clinical application. These bio tendons we hope will improve the success rate of rotator cuff repairs. It's associated with arthritis but a separate problem.
For knee arthritis, we're also growing bone and cartilage in the lab. We have a robust tissue engineering research portfolio where we're growing bone, cartilage, even the meniscus, and rotator cuff tendons have unmet medical needs. There's no successful treatment for lost meniscus tissue, so having placement for this lost tissue would be valuable because those patients tend to get arthritis after 10 to 15 years. So this would reduce the burden of joint replacement.
Some work that's exciting but still over the horizon is bio printing. We can print living cells and tissue and keep them alive. The hope is to be able to print the tissue directly inside the joint. Right now, if you do a joint replacement, you have to cut out a lot of bone and cartilage to fit the implant if you want to put in an off the self implant. So arthritic patients are not eligible for full joint replacements. But if we can repair or replace or regenerate a partial arthritic legion before it expands, it would be a huge benefit to patients, especially younger patients. Joint replacements are successful but we tend not to put them in younger patients because they have to last decades.
Q: Is there anything else you want to expand on?
HH: At Scripps, we have an internal registry, so all patients are entered and tracked so that way we get very clear metrics of how well the patients are doing. We try to collect info post-operatively and every year to follow and see what long term changes are for patients muscles, tendons or interactions between the implant and bone. We're studying the relationship between studies for bone density like osteoporosis studies to see if they can predict success or failure or modification of shoulder arthroplasty techniques.
DD: Every patient Dr. Hoenecke operates on for a shoulder replacement undergoes a CT scan. We do a quantitative CT so that we can use info to calibrate and measure bone density of patients shoulder, so that gives us a unique source of information for identifying how good the quality of the bone is. Now we're tracking these patients to see if bone density impacts future outcomes. Some of these registries go back to the 1980s; we've been following these patients for over four decades.