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The US Food and Drug Administration has granted 510(k) clearance for the first total wrist arthroplasty implant designed to emulate natural wrist range of motion in patients with wrist arthritis and other degenerative wrist conditions.

This new implant was designed by Scott Wolfe, MD, and Joseph J. Crisco III, PhD, and it represents the culmination of 3 decades of award-winning research by the duo. Dr. Wolfe is chief emeritus of the Hand and Upper Extremity Service at Hospital for Special Surgery (HSS), and Dr. Crisco is director of the Bioengineering Laboratory at Brown University and Rhode Island Hospital.

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The HSS Innovation Institute worked closely with Dr. Wolfe and Dr. Crisco to obtain a patent for their research and design ideas. The patent was then licensed to Extremity Medical, LLC, a privately funded medical device company headquartered in New Jersey. It is expected that the implant will be available before the end of the year.

The new KinematX Total Wrist Implant is a midcarpal implant and a significant improvement over radial implants currently available in the US. It was designed specifically to negate common risks of radial implants, including limited range of motion, subluxation, distal component failure, and osteolysis.

“We believe the new wrist replacement [implant] has advantages over traditional implants,” Dr. Wolfe, said. “Our extensive research into how the wrist moves helped us design a replacement that more closely matches the anatomy and motion of a normal wrist. This should allow for more natural motion and increased durability compared to currently available implants.”

Wrist arthritis is one of the most common and debilitating conditions treated by hand surgeons, affecting about 5 million people in the US. A fusion of the wrist bones can alleviate pain, but patients are often limited in performing some activities. Wrist joint replacement surgery was proposed 5 decades ago as an option to relieve pain and restore function.

“Most people are familiar with total joint replacement in the knee or hip, which is much more common and highly successful,” said Dr. Wolfe. “Total wrist joint replacement has not enjoyed the same degree of success. Historically, some studies demonstrate failure rates of near 50% within 5 to 10 years, mainly due to loosening of implant components.”

Dr. Wolfe and Dr. Crisco set out to design a better wrist replacement 30 years ago. The first step was to unravel the complexity of how individual bones move in a normal wrist and in one that has sustained an injury. Their research led to the design and validation of a non-invasive 3-dimensional motion analysis system to measure wrist kinematics. Armed with that information, they sat down at Dr. Wolfe’s kitchen table and started sketching out their idea for a novel wrist replacement based on their research.

Over the years, Dr. Wolfe, Dr. Crisco and their colleagues have received more than $10 million in research grants from the National Institutes of Health to study the wrist. They have published hundreds of papers in peer-reviewed journals. In 2017, they received the Kappa Delta Award from the American Academy of Orthopaedic Surgeons and the Orthopaedic Research Society, considered one of the highest honors for an orthopedic researcher.

Their research demonstrated that during many activities, such as throwing a ball, hammering a nail, or pouring a glass of water, the wrist does not move the hand in just 1 plane – up and down or side to side – as previously thought. It accomplishes the action by combining movements in both planes.

“Traditional wrist replacements often constrain the wrist to move in 1 plane at a time, and this puts stress on surrounding joints,” Dr. Wolfe said. “The increased loads on the implant-bone interface often lead to prosthesis loosening and mechanical failure. In addition, traditional implants often make it difficult or impossible to return to some activities, such as tennis or golf.”

The new implant is the only wrist replacement that is computer-designed to mimic the kinematics of a human wrist – movements that are instrumental in throwing, hammering, and other high-performance activities, according to Dr. Wolfe. The unique design should enable the implant to be more durable than traditional wrist replacements.

Surgery with the new implant, which will be performed on an outpatient basis, entails replacing the proximal carpal row bones of the wrist, which are those most severely affected by osteoarthritis. The device utilizes modular components in various sizes to replicate the complex anatomy of the wrist and allow the motion necessary for occupational, recreational and household activities.