Biomechanical Analysis of Joint Movement

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1. A personal computer system using magnetic sources and sensors has been developed to measure three-dimensional translations and rotations of joint movement. Eight-channel electromyograph has been combined with the system to examine relationships between joint movement and the muscle activities involved in the movement. Analysis of the motion of the upper limb by the combined system has shown that (1) activities in the anterior, middle and posterior deltoids gradually increase as the upper limb is elevated in abduction in the frontal plane and in elevation in the sagittal plane and that (2) activities in the middle and posterior deltoid, the biceps brach and the supraspinatus increase as the upper limb is extended from the maximally flexed position in horizontal extension.2. In the field of joint kinematics, clinical terms such as internal-external, or medial-lateral, rotations are commonly used to express the rotation of a body segment about its own long axis. However, these terms ar … More e not defined in a strict mechanical sense. A new mathematical definition of axial rotation has been proposed to avoid vagueness, and methods to calculate it from the measured Euler angles have been given. The definition is based on the integration of the component of the angular velocity vector projected onto the long axis of the body segment. The well-known Codman's paradox can be solved using the definition. This definition has been generalized to give the relative axial rotation of one body segment with respect to another body segment when the two segments are moving in the 3-dimensional space.3. The instantaneous center of rotation (ICR) is a basic quantity for describing planar motion of rigid bodies and useful for analysis of anatomical joint motion. The conventional methods for calculating ICR have been sensitive to measurement error in position so that few reliable ICR data have been reported. We have reduced the overall error in ICR to <plus-minus> 3 mm by employing photo-sensitive semiconductor sensors and smoothing technique and improving experimental conditions. ICR of temporomandibular joint motion has been measure Less