Total Wrist Replacement Device Treats Painful Arthritis

A novel total wrist implant mimics the kinematics of a human wrist, enabling it to be more durable than traditional replacement options.

The Extremity Medical (Parsippany, NJ, USA) KinematX modular wrist arthoplasty system is designed to serve as a replacement for wrist joints disabled by pain, deformity, and limited motion, caused by non-inflammatory degenerative joint disease of the radiocarpal joint, such as osteoarthritis (OA), rheumatoid arthritis (RA), post-traumatic arthritis, Kienbock’s disease, revisions, and scapholunate advanced collapse (SLAC). The device is designed to create an anatomic coupling of radial extension, ulnar flexion and radio-ulnar deviation, similar to that of an intact wrist.

The system includes left and right specific radial body implants in three size options and two heights, with features that include an anatomic design to emulate the proximal row; a chrome-cobalt stem with titanium plasma spray coating; allowance for midcarpal articulation; preservation of radial length and inclination-stable radial fixation; a streamlined implantation technique that removes the risk of distal hardware loosening; and provision for future conversion to a total wrist arthroplasty. An X-ray template determines the anticipated prosthesis size, and implant trial sets are available for intraoperative trialing.

“We believe the new wrist replacement, known as the KinematX Total Wrist Implant, has advantages over traditional implants, which often constrain the wrist to move in one plane at a time, and this puts stress on surrounding joints,” said hand surgeon Scott Wolfe, MD, of the Hospital for Special Surgery (HSS; New York, NY, USA), who developed KinematX together with Joseph Crisco, III, PhD, director of the Bioengineering Laboratory at Brown University (Providence, RI, USA). “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. The human wrist is highly complex, made up of more than a dozen individual joints formed by eight small bones. Fusion of the wrist bones can alleviate pain, but patients are often limited in performing some activities. By enabling the radius and the ulna bone to move with respect to each other, the natural range of wrist rotation can be preserved, improving performance of activities of daily living and reducing compensatory movements.