Many advances in medicine come in the form of pharmaceuticals – drugs for Alzheimer’s, diabetes, allergies, and many other conditions. But some of the most sophisticated medical advances come in the form of medical devices and tools, including X-ray, MRI, or microsurgery. Here at the Yale School of Medicine, these advances are continuing to be pursued. John S. Reach, Jr., MSc, MD, an orthopaedic surgeon and assistant professor at the Yale School of Medicine and Yale College alumnus, JE ‘96, has pioneered many innovations in his field, advancing technology in the treatment of joint injuries, both in instrumentation as well as technique.
Orthopaedic surgeons perform surgery dedicated to bone and joint repair, including the ligaments, cartilage, and tendons. Joint and bone problems can arise from many places including sports injuries, automobile accidents, or genetics. Orthopaedic surgeons try to repair these problems by resetting broken bones, adjusting joints, and reconnecting torn ligaments and tendons. Frequently, metal implants are used to straighten and brace broken bones or misaligned joints. As Reach describes, “A lot of what we do is carpentry – we make crooked things straight.” Medical devices and tools are instrumental for the orthopaedic surgeon. For example, many times, if a joint is unable to be set correctly, the joint may need to be replaced or fused, which causes loss of motion. Reach, with the help of the Yale Office of Cooperative Research, has spent the past five years working on new ways to improve his patient function via custom cartilage transplant (Accelerated Orthopaedic Technologies), designing new biologic implants, and perfecting minimally invasive image-guided injection techniques.
The Promise of Foam Metal Implants
Reach specializes in the treatment and repair of joints in the knees, ankle, and feet. One focus area is in the application of novel materials to enhance orthopedic prosthetics, such as artificial cartilage or tendon. In particular, he used a special material composed of a sponge-like tantalum foam, called trabecular metal, that allows for the biologic ingrowth of tendons directly into orthopaedic implants. This tight bonding allows for a much more successful integration of tendon with metal and helps metal implants function better in the body.
Foam titanium or tantalum is a spongy matrix of metal that looks similar to bone. Initially developed by the military, tra-becular metal was found by Reach to have unique biologic properties. Porous metal approximates many of natural bone’s properties: it has strength, weight, microstructure and surface roughness similar to bone. This spongy foam creates a very complex and rough surface ideal for biologic tissues to ingrow and biologically heal. If put in contact with amesenchymal tissue, such as tendon or ligament, fibrous tissue will integrate into the foam. Thus, trabecular metal offers a solution to a vexing orthopaedic problem: how can surgeons biologically integrate strong metal prostheses into their patient’s bodies to improve function and to relieve pain?
From Complication to Opportunity
Reach is quick to point out that he was not the first to use porous metals in orthopaedics. Foams originally were used as bulk bone substitutes in hip and knee replacements. He was the first, however, to design and test a porous metal implant that successfully allowed true biologic tendon-metal integration. This discovery, like most inventions in medicine, was an accident. Early bone substitute studies had showed problematic soft tissue ingrowth when researches had wanted bone ingrowth. This “complication” was actually the eureka moment. Reach’s ingenuity came from his realization that this foam material could be used as a surrogate for the interface between metal and flesh. By using porous metals as a transition between hard solid metal implants and soft ductile soft tissues, orthopaedic surgeons have the opportunity to successfully integrate metal with tendon and ligament with true Sharpies fibers integration.
From Lab to Patient: Investigating Trabecular Techniques
Discovering such potential in porous metal is not enough to guarantee commercial use. Reach is currently focused on designing specific implants and device applications. Despite the rigorous FDA requirements for investigational device design, the clear opportunities afforded by these materials have not been lost on those in the orthopaedic industry. At present, three large medical devices companies, Zimmer, Biomet, and Wright Medical Technologies, have invested time and resources into exploring human use of these foam metals. Reach is optimistic that in the next few years, we will see true biologic prosthetic integration, especially in the areas of amputee, limb salvage, and tumor resection/joint replacement.
A Better Way: Ultrasound Visualization and Injection Guidance
Reach says his research is focused at the junction between the laboratory and the operating room, an area he calls transla-tional medicine. “It is not enough to have a great idea or even a great result in the lab,” says Reach. “Research should yield tangible effects for patients. I need solutions now for the arthritic ankle replacement patient or young crippled athlete I’ll see tomorrow in the Yale Physicians Building.” Given the regulatory hurdles inherent in the medical device approval process, the effects of this translational research can take more time that one might think. As an example, he points to a touch screen box with three medical ampules: a fine gauge needle, the thickness of hair, snakes out at one end, and with an ultrasound transducer and monitor at the other. This injection system, says Reach, was just approved by the FDA in November.
For the past 5 years, Reach has worked with a company called Carticeptin Atlanta, Georgia to design a better way to deliver medications to locations difficult to reach in the body. Their final product is an automated precision instrument that targets, guides, and delivers medications with the touch of a button. The key, says Reach, is in the image guidance. Previously, injections into joints were performed blindly, guided only by the experience of the doctor. This often led to inaccurate needle “mis-adventures,” causing pain to the patient and reducing the effectiveness of the drug. While CT and MRI technology can guide such injections, the radiation exposure, time loss, and expense of such imaging modalities preclude their use for common injection guidance.
Seeing this problem, Reach looked around for a solution and found none. He needed an instrument that could visualize the injection target beneath the skin. Ideally, it also needed to be cheaper and faster to use than an MRI as well as be able to capture real-time motion of the needle and medication. Ultrasound was a good candidate as it allows for incredibly detailed and fast real-time imaging of bones and tendons. By collaborating with Carticept and Sonosite, a DARPA company that developed the first military-spec portable ultrasound, Reach was able to build a device that dramatically increased the success rate and efficiency of drug delivery to joints. “Very rarely do we have a medical device which is both cheaper and better than our current offerings,” notes Reach. “Our work in collaboration with Mary Badon, MD, MBA at the Yale School of Management, has shown that we can save millions of Medicare dollars through the use of musculoskeletal ultrasound at the point of care by the orthopaedic surgeon.”
To turn Reach’s innovations into commercial realizations, these devices must be manufactured and sold. Research and development for orthopaedic devices are typically measured in tens of millions of dollars. No matter how good ideas can be, products will not be developed if an investor doubts their ability to recoup this money. Despite these difficulties, Reach continues to push the boundaries of his profession. To him, his research focuses on anything he’d find useful: “If I’m in the [operating room] and I find that I need something, if I can’t find something that’ll solve my problem, we’ll make a solution.” With this spirit, Reach has become one of the most innovative and promising orthopaedic surgeons here at Yale.
About the Author
HENRY ZHENG is a junior Molecular Biophysics and Biochemistry major in Pierson College. He currently works in a computational neuroscience lab on fluorescent modeling of calcium ion flux in the mammalian visual system.
Acknowledgements
The author would like to thank Dr. John Reach for taking time to explain his work in medical devices.
Further Reading
Reach J, Dickey I, Talac R, Zobitz M, Adams J, Minagawa H, Scully S, and Lewallen D. Direct Tendon Attachment to a Trabecular Metal Prothesis: An in-vivo Canine Study. Scientific Presentation at the American Academy of Orthopaedic Surgeons Annual Meeting. San Francisco, CA. March 2004.