Kappa Delta Lanier Award Honors Work in Wrist Kinematics and Arthroplasty

By: Terry Stanton

Researchers identified the importance of the midcarpal joint in solutions for injury and arthritis

Scott W. Wolfe, MD, and co-investigator Joseph J. Crisco, PhD, have spent close to three decades working to unravel the mysteries of wrist kinematics, with the ultimate goal of addressing the degenerative condition known as scapholunate advanced collapse (SLAC), which occurs following traumatic disruption of the proximal carpal row.

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For their work on this challenging condition, Dr. Wolfe, of the Hospital for Special Surgery/Weill Medical College of Cornell University, and Dr. Crisco, of Rhode Island Hospital/Brown University, received the 2017 Kappa Delta Elizabeth Winston Lanier Award yesterday at the Your Academy 2017 event.

In their manuscript, the authors noted, “For more than a century, researchers have sought to identify a unifying theory of wrist kinematics, but the complex mechanical behavior of the wrist has to date defied all attempts to do so.”

“At a time when the rest of the orthopaedic world was investigating the power of the MRI, I recognized the dramatic evolution of computed tomography and its application to 3D visualization of small bones and joint fractures about the upper limb,” Dr. Wolfe said. He and Dr. Crisco “set out to design and test computed tomographic algorithms that could measure the complex motion of the small and irregular-shaped carpal bones in normal subjects (in vivo 3D kinematics) for the first time. Our goal was to refine and automate that technology so that we could study the kinematic abnormalities that occur when the important scapholunate ligament is disrupted, and the inexorable progression to wrist arthritis occurs.”

His research has now reached a culmination point: a total wrist arthroplasty device recently submitted to the U.S. Food and Drug Administration.

A complex challenge
The path to development of a prosthetic solution to scapholunate instability and SLAC arthritis was one of lengthy study of wrist anatomy and the process by which injury “disrupts the finely tuned synchrony of the carpal bones and leads to SLAC.” The authors noted that “the eight carpal bones that constitute the wrist joint represent the most complex articular system in the human body—each capable of moving in different degrees or directions dependent on the position, motion, and force.”

As they embarked on their studies, two main theories of carpal kinematics prevailed. Anatomically, they noted, interosseous ligaments between neighboring bones define two rows of carpal bones (proximal and distal), separated from each other by the midcarpal joint. Proponents of the “row theory” noted that the bones of the two carpal rows move in a synchronous direction regardless of the motion of the hand, and they posited that the inherently unstable proximal carpal row is guided through flexion-extension and radioulnar deviation by mechanical signals from the midcarpal joint. Adherents of the “column theory” believed that flexion-extension occurs predominantly through the linkages of the central column of the wrist (capitate-hamate-lunate), while radioulnar deviation occurs as the lateral column (scaphoid) and medial column (triquetrum) rotate around the stable central column.

Drs. Wolfe and Crisco wrote that the 3D and live-motion capture studies they have conducted “provide evidence that neither carpal bone theory is sufficiently inclusive to explain complex and ‘coupled’ motions of the wrist joint.”

The clinical implication of this incomplete understanding of wrist kinematics is that surgical approaches are not wholly effective. The authors divided their work in exploring solutions for this situation into three stages, roughly corresponding to the three decades since 1990. Initially, they focused on development of noninvasive technology to measure normal carpal bone kinematics during normal wrist motion. In the 2000s, they sought to apply that technology to understand “functional” kinematics of the normal and injured wrist. In this decade, they have worked to conceptualize and develop improved methods for treatment of SLAC and scaphoid nonunion advanced collapse (SNAC) arthritis.

It’s all in the midcarpal joint
Among the major findings that emerged from their study of wrist motion was the importance of the midcarpal joint to hand and arm function. Specifically, they studied the previously identified “dart-thrower’s motion”—an important and uniquely human path of motion from radial wrist extension to ulnar wrist flexion. With the 3D technologies the authors developed to measure wrist kinematics, they demonstrated that surgical restriction of midcarpal motion degrades functional performance.

In their paper, Drs. Wolfe and Crisco identified the following as their top 10 discoveries in wrist kinematics:

  1. Computed tomographic analysis of in vivo motion of the carpus
  2. Markerless registration for noninvasive measurement of carpal kinematics
  3. Identification of minimal in vivo motion of the proximal carpal row during the dart thrower’s motion
  4. Recognition that midcarpal motion is necessary for most occupational, recreational, and daily activities
  5. Noninvasive 3D measurement of coupled motion of the wrist
  6. Proof that restriction of coupled motion of the wrist leads to impairment of function
  7. Recognition that the mechanical (and in essence functional) axes of the wrist are oblique to its anatomically defined axes
  8. Development of a hybrid wrist coordinate system following surgical alteration
  9. Proof that functional performance is impaired when the midcarpal joint is altered
  10. Support for the fact that midcarpal joint replacement improves range of motion and outcomes

A better prosthesis
In pointing to the need for an effective arthroplasty solution for diseased wrists, the authors noted the shortcomings of current surgical approaches. “While effective at controlling pain and providing stability, most current SLAC and SNAC reconstructive procedures do so at the expense of wrist motion, and specifically, coupled wrist motion,” they wrote. 

Through computer modeling of existing prosthetic designs, the researchers theorized that wrist arthroplasty could become a durable solution if distal component failure could be minimized and coupled wrist motion restored.

Based on their understanding of coupled dart thrower’s motion and its dependence on the full mobility of the midcarpal joint, Drs. Wolfe and Crisco designed and tested the first midcarpal TWA device. Now, following promising results in a cohort of 20 patients in the United Kingdom who have received a monobloc midcarpal cobalt-chrome hemiarthroplasty version of their device (wrist hemiarthroplasty is not FDA-approved for use in the United States), the authors seek to introduce a modular midcarpal TWA device this year.

They concluded: “The future is bright indeed; advances in diagnostic imaging will enable earlier diagnosis of ligament injury, kinematic dysfunction, and cartilage loss; while advances in our kinematic understanding and materials will enable anatomic and effective means to prevent or reverse the profound functional losses due to SLAC and SNAC arthritis.”