Functional analysis of shoulder arthrodesis.

The goal of this study was to determine the optimal position of shoulder arthrodesis for functional outcome and pain. Twenty patients who had undergone shoulder arthrodesis were interviewed and examined clinically and with standard radiographs. In addition, computed tomography (CT) scans were used to determine the exact position of the humerus relative to the scapula in all three planes. The average position observed was 14 degrees of flexion (humerus to longitudinal body axis), 55 degrees of abduction (humerus to lateral scapular border), and 23 degrees of internal rotation (forearm to sagittal body plane). Clinical evaluation showed functional advantages for tasks above waist level with increasing flexion but at the cost of more pain. Increasing abduction improved upper limb function above waist level but compromised complex movements below waist level. Higher degrees of abduction tended to improve the result expressed by the overall score and furnished better pain relief. Higher degrees of internal rotation resulted in improved function below waist level but also in more pain. Our results show that there is no single optimal position but suggest that a clinically estimated position of 15 degrees to 30 degrees of flexion, 35 degrees to 45 degrees of abduction, and 30 degrees to 40 degrees of internal rotation is desirable. This corresponds to CT-measured angles of 15 degrees to 30 degrees for flexion, 55 degrees to 65 degrees for abduction, and 0 degrees of internal rotation (humeral epicondylar axis to scapular plane).