Three-dimensional movement analysis of the shoulder: A new method for the assessment of parameters of shoulder function.

Objective: An exact assessment of shoulder movement is of special importance both in the diagnosis of and in the therapy for different shoulder diseases. Therefore, we developed a feasible method for the analysis of shoulder movement. Methods: On the basis of an ELITE system and 6 skin markers (marker positions. acromion, humerus, olecranon, proc. styloideus ulnae, cervical and throracic spine), movement analysis was performed during continuous abduction of the arm over 15 s. With the help of a purpose made software we determined the exact angle of abduction and, in addition, the acceleration ((+a)AC) and the deceleration ((-a)AC) of the acromion. We evaluated 12 normal subjects (10 male, 2 female, average age 29 yrs) without shoulder conditions and 8 patients (6 male, 2 female, average age 46 yrs,) with unilateral impingement syndrome stage II according to Neer. Results: In addition to a significantly diminished abduction ability in patients with impingement syndrome, our results also revealed significantly decreased acceleration values for the acromion in impingement patients. In contrast, deceleration values for the acromion were not altered in patients with impingement syndrome. Conclusion: The presented method allows exact measurements of shoulder movement. In addition, measurements of acromion acceleration and deceleration seem to offer two parameters for the assessment of shoulder function in pathological conditions. Further investigations are required to prove the advantages and limitations of this method.