Preliminary study of the in vivo motion in the canine shoulder.

An instrumented spatial linkage was used to measure the total motion in a canine shoulder as the dog was engaged in a variety of activities, including walking on a level carousel track, as well as over a hurdle, up and down a step, and up and down a ramp placed on the same track. For each activity, the motion data were analyzed, using 2 procedures. First, the linkage data and the joint contour data were combined by computer, and the motion was represented by a series of sequential computer drawings showing the scapular and humeral articular surfaces in their proper relative positions for selected increments of time during the various activities described. As an alternate but approximate method for describing the relative humeral-scapular motion, rotations about 3 mutually perpendicular axes through the average center of the shoulder joint were determined.