Movement Rhythm of the Shoulder Complex

Image-based graphical modeling of the shoulder joint has been used to characterize the movement rhythm of the shoulder complex during passive humerus elevation [15,26]. Image-based models were constructed to represent cadaver shoulders that were used for experimental kinematic testing. The image-based models allowed graphical construction of local coordinate axes for all of the shoulders tested. The models also provided animation of the shoulder kinematics to aid interpretation of the experimental results. The animations also were used to quantify the distance between bony surfaces in regions of possible soft tissue impingement and nerve entrapment [22,25].

For the experimental testing of joint kinematics, intact cadaver torsos were secured to a testing stand without constraining the shoulder joint. For five shoulders, the humerus was passively elevated in abduction in the scapula plane, abduction in the coronal plane, and flexion. During elevation, electromagnetic sensors rigidly fixed to the humerus, scapula, and clavicle quantified the motion of each bone. After testing, dummy sensors filled with a CT contrast medium replaced the electromagnetic sensors. CT data were used to

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FIGURE 11 Measurement of the anisotropy of trabecular orientation in a cubic trabecular bone specimen using two-dimensional Fourier transform of the X-ray image. A distribution function f{0) in one plane (a). The distribution functions in three orthogonal planes (b).

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