Wrist rhythm during wrist joint motion evaluated by dynamic radiography

Area of Science:

• Orthopedics
• Biomechanics
• Radiology

Background:

• The scapulohumeral rhythm describes coordinated shoulder and scapular motion.
• A similar coordinated motion, or
• wrist rhythm,
• is hypothesized for the wrist joint.

Purpose of the Study:

• To investigate the existence and characteristics of a
• wrist rhythm.
• Specifically, to evaluate the ratio of radiolunate and capitolunate joint motions during wrist movement.

Main Methods:

• Dynamic radiography using a flat-panel detector was employed.
• Twenty healthy male subjects underwent active wrist exercise for ten seconds.
• Radiocarpal (RL angle) and midcarpal joint angles (CL angle) were measured from dynamic images.

Main Results:

• Regression lines were calculated from average curves of RL and CL angle variations.
• The ratio of RL to CL angle motion was determined from the slopes of these regression lines.
• A motion ratio of approximately 1:4 was observed during palmar flexion, and 2:1 during dorsiflexion.

Conclusions:

• The wrist joint exhibits a coordinated rhythm analogous to the scapulohumeral rhythm.
• Distinct ratios of radiocarpal and midcarpal motion occur during palmar flexion and dorsiflexion, defining the wrist rhythm.