Tomorrow’s Medicine

Material Gain: CarboFix’s Carbon Fiber Hardware Better Than Metal Implants

Carbon fiber is more flexible than metal, so it may help fractured bones heal faster. Carbon fiber hardware may also have an application in oncology.

Thomas Morrow, MD

A few years ago, as a young relative was enjoying a motorcycle ride in the countryside of western Pennsylvania, a truck pulled out in front of him from a side road, resulting in a horrible accident. As his mother watched, the first responders stabilized his multiple fractures to prepare him for a flight to a trauma center. He had many injuries but the most severe were fractures of his arms and pelvis.

The goals of the orthopedic surgeons were to preserve his blood supply, provide anatomic reduction of the bones in his arms, and create stable fixation. Overall, they were doing everything they could to allow him to become active as soon as possible so he would heal faster, staving off all the complications of immobility. Repairs of fractures have to be strong enough to keep a person’s weight and motion from moving the bones until they had a chance to heal. To do that, surgeons can use traditional casting, place nails inside the bone’s medullary cavity, or screw plates of metal to the outside of the bones to align and stabilize the fracture.

The surgeons allowed the bones to heal in a normal alignment, and after months of physical therapy, he has normal function and range of motion. Today he’s back to work at a physically demanding job.

However, while I was visiting him last winter, he mentioned that the plates ache when it gets cold. Don’t get me wrong: He was not complaining. But his cold weather aches are real.

Metal plates, nails, and screws have been used for decades in orthopedic treatments. They are used to stabilize many of the roughly 600,000 fractures of the long bones of the legs and arms that occur in the United States each year. They are manufactured by a number of major orthopedic supply companies. Like nails and screws you buy at a hardware store, they come in common standard sizes and shapes, and the plates are not just flat pieces of material but have a concave shape to the back to conform to the cylinder shape of the bones they are designed to treat. The plates come in a variety of forms—including straight, angled, and T-shaped—to allow them to be used for dozens of different types of fractures.

But metal implants have some serious drawbacks. For one thing, imaging is problematic. Normal dose X-rays don’t penetrate metal well, and metal implants interfere with MRI images of the soft tissue near the metal.

Metal is rigid, and that is important to keep a fractured bone properly aligned. On the other hand, some motion at a fracture site is beneficial and stimulates bone tissue to heal. In fact, scientists discovered decades ago that small amounts of motion around a fracture site actually creates a small electrical current and hastens healing. Electrical stimulation devices have been used for years to try to reproduce this electrical current and, in fact, the FDA has approved numerous bone-growth stimulator devices, and CMS and commercial insurers cover the treatments.

Cold-weather problems

Another problem with metal as material for implants is that it transfers heat at a different rate than human tissue. That difference is the reason my relative and many others with metal implants have aches and pains during cold weather. Often it is tolerable, but sometimes the pain is severe enough that people ask to have plates and screws removed long after healing is complete.

For these and other reasons, researchers have been searching for years for an alternative material for orthopedic screws, pins, and plates. Carbon fiber, which is not a new discovery—early forms were first used in 19th century as a filament in light bulbs—was an early candidate. But there have been a lot of advances in how carbon fiber is made, and today’s composites are used to construct race cars, drones, sports equipment, bikes—even much of the body of the Boeing 787. Drawing on its strength and low weight, early medical applications included limb prosthetic fabrication and wound dressings.

Carbon fiber has many physical, chemical, and biological characteristics that would seem to make it an ideal material for orthopedic hardware. Besides its resistance to corrosion, it has high heat tolerance and an astounding strength-to-weight ratio. It also flexes, so it’s just as elastic as real bone and should help fractures mend.

But there were some problems early on with using carbon fiber instead of metal. Results of some studies in the 1980s of plates made of many thin sheets of carbon fiber stuck together with epoxy resin showed some promise but also high infection rates. The plates were also expensive and difficult to mold into the correct shape. Research sputtered and, for the most part, stalled.

Now a small company called CarboFix Orthopedics is helping revise hope and interest in carbon fiber orthopedic implants. Headquartered in Israel, CarboFix has come up with a new adhesive, polyether ether ketone (PEEK), and a special lamination process. In numerous clinical trials, CarboFix’s plates and nails have been shown to be better than traditional metal in several ways. They are stronger and less stiff than metal implants, including those made out of titanium, and show less wear and tear. Importantly, given the track record of earlier carbon fiber implants, the CarboFix Orthopedics products haven’t triggered inflammatory reactions.

CarboFix’s plates and nails, like the one above for the femur, are stronger and less stiff than traditional metal implants.

Benefit for cancer patients

CarboFix’s carbon fiber products may have advantages beyond traumatic orthopedic injuries, particularly for some cancer patients. For patients with malignant bone and soft tissue tumors, wide surgical resection can add to the risk of pathologic fracture (a fracture related to the tumor). Radiation, cryosurgery, and argon beam coagulation can also add to this risk and to poor healing of such fractures (termed persistent nonunion). So to prevent complications, bones are commonly treated prophylactically with intramedullary nails or plates. However, traditional stainless steel or titanium implants can obstruct imaging, making it challenging to detect recurrent disease. CarboFix’s products create significantly less MRI signal loss as well as minimized artifact on CT imaging. They also do not interfere with radiation treatment in the way that metal implants can. Physicians have dubbed the carbon fiber nails the “invisible nail” because of its benefits.

But CarboFix implants are marked with faint radio-opaque markers so they are not totally invisible to X-rays, and some of the products have predrilled holes so they can be attached with standard metal screws.

Like the metal implants, CarboFix’s plates are designed for specific regions of specific bones including the proximal humerus, distal radius (standard and narrow sizes), distal fibula, diaphyseal distal femur, and others. Similarly, nails are specifically designed for the various locations of fractures of the humerus, tibia, femur, and ankle. These devices come in numerous lengths, diameters, and with a variety of number of predrilled holes for the screws.

CarboFix is currently involved in a side-by-side study to prove that the semi-flexible nature of its devices promote better healing than traditional metal implants, something that numerous orthopedists have reported anecdotally.

In Europe, CarboFix has also brought to the market what some are calling “the ultimate in orthopedic implants”—carbon fiber pedicle screws and rods for spinal surgery. They offer a real improvement in spinal surgery because radiolucency is very important in this application. These spinal surgery products aren’t on the market yet. In the United States, they have been approved for investigational study.

CarboFix’s pricing policy is noteworthy. Virtually all device and pharmaceutical companies price a superior product higher. CarboFix has chosen to price their devices competitively to the traditional metal devices.

After several decades of development, carbon fiber has finally come to the forefront of orthopedics and could mean a huge advance in treatment of fractures from trauma and the various orthopedic challenges in oncology.

Thomas Morrow, MD, is the chief medical officer of Next IT. He has been the founding medical director of five HMOs and a disease management company, a medical director at Genentech, and president of the National Association of Managed Care Physicians. You can contact him at TMorrow@ManagedCareMag.com.

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