Background: To evaluate the per-operative process of shoulder joint replacement, time-action analysis can be used. Material/Methods: Forty procedures performed by 7 surgeons with different experience using 5 different prostheses and 3 different surgical approaches were analyzed. Results: The surgical procedures showed a large variation in, for example, duration, tasks of team members, and protocol used. The surgical procedure was infl uenced by several factors, such as the prosthesis used, the surgical approach, the patient’s condition, and the experience of the surgeon. Exposure of the glenoid was diffi cult and several retractors were needed, which were held by an extra assistant or clamped to the table or the surgeon. Two main limitations were seen in all procedures: repeated actions and waiting. Also, fi ve errors could be identifi ed. None of the alignment instruments was completely reliable and they allowed the surgeon to make major errors. Conclusions: Better alignment instruments, pre-operative planning techniques, and operation protocols are needed for shoulder prostheses. The training of resident surgeons should be focused on the exposure phase, the alignme nt of the humeral head, the exposure of the glenoid, and the alignment of the glenoid. Evaluating the surgical process using time-action analysis can be used to etermine the limitations during surgical procedures. Furthermore, it shows the large variation in factors affecting surgical performance, indicating that a system approach is needed to improve surgical outcome.

Keywords: Arthroplasty, Replacement - methods, Arthroplasty, Replacement - methods, Clinical Competence, Equipment Failure Analysis, Joint Prosthesis, Medical Errors, Postoperative Complications - etiology, Shoulder Joint - surgery