3-D motion analysis tool used to diagnose wrist disorders

New MRI-based system may be effective at studying the in vivo 3-D kinematics of the wrist joint.

Issue: December 2004

Using a newly developed MRI-based markerless bone registration algorithm, a Japanese researcher reported early success in being able to study the in vivo 3-D kinematics of the wrist joint.

Hisao Moritomo, MD, an orthopedic surgeon at Osaka University Graduate School of Medicine, said in vivo 3-D motion analysis enables surgeons to view any in vivo motion of one bone relative to another bone. It also allows surgeons to calculate the axis of rotation associated with joint motion.

Moritomo and his colleagues studied the in vivo kinematics of the wrist during wrist flexion-extension motion (FEM) and radioulnar deviation (RUD) in 12 normal wrists and 26 wrists with a disorder, including scaphoid nonunion, scapholunate dissociation or triangular fibrocartilage complex injury.

The investigators acquired MRIs in five positions, including a neutral position and four extreme positions of FEM and RUD. They also created 3-D animations of the carpal motions and investigated accurate estimates of the relative positions and orientations of the bones.

“In the study of scaphoid nonunions, we specifically tested the hypothesis that the fracture location relates to the kinematic pattern,” Moritomo said in his abstract.

Distal and proximal types

The pattern of the relative motions among the distal and proximal segments of the scaphoid and lunate was separated into two types, based on the fracture location.

The distal type, he said, included cases where the fracture was located distal to the dorsoulnar apex of the scaphoid ridge, where the dorsal scapholunate interosseous ligament and the dorsal intercarpal (DIC) ligament attach, and where the distal scaphoid was unstable relative to the proximal scaphoid and the lunate. The distal scaphoid movement was similar to the motion of the distal row, while the proximal scaphoid movement was similar to the lunate, resulting in a “book-open” motion of the fragments, Moritomo wrote.

In the proximal type, the fracture was proximal to the apex, the relative motion between the segments of the scaphoid was less, and the relative motion between the scaphoid and the lunate was nearly normal.

Regarding carpal instability following scaphoid nonunion, Moritomo said it may be critical to determine whether the fracture line passes distally or proximally to the dorsoulnar apex of the scaphoid ridge.

“The 3-D ‘movie’ of the carpus afforded more information than I expected. 3-D visual information not only facilitates an understanding of 3-D motion, but it also validates the existing 2-D data,” he told Orthopedics Today.

In addition, a combination of motion analysis and 3-D reconstruction of MRIs “affords an in vivo 3-D analysis of kinematics without radioactive exposure.”

Although, there are time constraints with using MRI with these patients,

Moritomo said MRI shows a lot of promise as a diagnostic tool for wrist disorders.

“We anticipate that this MRI-based 3-D motion analysis system will be helpful for gaining a clinical understanding of the kinematics of the normal wrist joint as well as of the pathological wrist joint,” he said. “We are also using the movie right now to explain the condition of the disease to the patient.”

For more information:

Moritomo H. In vivo, 3-D motion analysis using MRI as a new diagnostic tool for wrist disorders. #2-D-7. Presented at the 77th Annual Congress of the Japanese Orthopaedic Association. May 20-23, 2004. Kobe, Japan.