Wrist Bone Motion during Flexion-Extension and Radial-Ulnar Deviation: An MRI Study

Area of Science:

• Biomechanics
• Orthopedics
• Medical Imaging

Background:

• Wrist joint function is crucial for daily activities, but detailed kinematic analysis is limited by a lack of soft tissue and comprehensive carpal bone motion data.
• Understanding wrist biomechanics is essential for therapeutic planning, prosthesis design, and clinical assessments.

Purpose of the Study:

• To establish detailed 3D models of carpal bones with cartilage.
• To determine the helical axes (HA) of all eight carpal bones during wrist motion.
• To advance the understanding of wrist kinematics for clinical applications.

Main Methods:

• 3D modeling of carpal bones and cartilage using in-vivo magnetic resonance imaging (MRI) from five subjects.
• Segmentation of all wrist bones and cartilage.
• Analysis of carpal bone kinematics using the helical axis (HA) method during flexion-extension (FE) and radial-ulnar deviation (RUD).

Main Results:

• The helical axes for all carpal bones during FE were tightly bounded and located superior to the radius.
• During RUD, distal carpal row bones rotated, while the scaphoid, lunate, and triquetrum primarily flexed and extended.
• Carpal bones exhibited greater translation during RUD compared to FE.

Conclusions:

• This study provides the first comprehensive analysis of helical axes for all eight carpal bones.
• The generated detailed wrist models and kinematic data enhance the understanding of wrist biomechanics.
• Improved knowledge of wrist kinematics supports better pathologic assessment and surgical treatment strategies.