On effective movement in CPM for shoulder joint

Continuous passive motion (CPM) is an orthopedic treatment or physiotherapy method that promotes recovery of impaired joints, and is tried to apply for treatment of the shoulder joint disorders. The shoulder joint has a complex structure, where the inner/outer rotation torque of the shoulder joint varies due to ad-/abduction angle. Wrong ad-/abduction angle causes the excessive inner/outer rotation torque of the shoulder joint, and aggravates joint disorders. So, it is required to adjust suitably the ad-/abduction angle to suppress the inner/outer rotation torque. In this paper, the ad-/abduction motion that suppresses the inner/outer rotation torque is clarified. The variation of the inner/outer rotation torque due to ad-/abduction angle is analyzed in experiments with fixed ad-/abduction. From the experiments, we clarify the ad-/abduction motion suppressing the inner/outer rotation torque. To realize the clarified ad-/abduction motion, we developed the CPM device that has two d.o.f with the inner/outer rotation and the ad-/abduction. Finally, the experiment with the CPM device is performed in order to confirm that this motion is effective to suppress the excessive inner/outer rotation torque of the shoulder joint.