UHBMES

Hello again! This is me testing out, you guessed it, another blog post. This time instead of including random stuff in the post, I will now test out the “featured image” option on this post. As always, random text will follow. Observe.

There are limitations to the accuracy of any analysis of motion by indirect surface methods, even when the accuracy of three-dimensional marker tracking is assumed. Our model describes movement of the humerus relative to the trunk, which is not an accurate representation of true shoulder anatomy or function. We do not know how much elbow flexion is necessary for accurate determination of humeral rotation, although use of a posterior olecranon marker and the presence of physiologic elbow flexion posture minimizes this problem in most circumstances. Skin movement is a constant problem with all markerbased motion measurements, and the degree to which it affects accuracy is unknown. There is little statistical information to support the displacements between markers and joint centers that were used in this study, but we have attempted to address this issue by examining the effect of inaccuracies on joint center estimation, and we feel that the described offsets produce acceptable measurement accuracy for practical analysis. There is no available data on joint center location in children, and we are forced to use extrapolations from modest adult measurements to perform movement analysis in immature subjects. Gimbal lock can be an unrecognized problem, leading to angular measurements whose interpretation is difficult and nonintuitive. Despite the multiple limitations, we believe that investigators who take these issues into account can achieve reliable, reproducible results of appropriate accuracy and practical utility.