Replication of the rotational center of the humeral head with second-generation stemmed prostheses

Objective: Reconstruction of the anatomy of the proximal humerus is an indispensible prerequisite to achieve good clinical results and long-term prosthesis stability. Modern, adjustable prostheses have greater flexibility of inclination, retrotorsion, as well as medial and dorsal offset, in comparison to older prostheses. Such improvements are expected to allow for more accurate reconstruction of the anatomical condition, such as targeted reconstruction of the primary and the secondary rotational centers. Methods: The reconstruction of the humeral rotational center was assessed in 48 second-generation prostheses. All reconstructions were compared by radiographic parameters with the preoperative state and the operated opposite side. Results: The positions of the new rotational centers after arthroplasty were not close to those of pre-operative and healthy opposite side s radiographs. No characteristic change in the position of the humeral head, or of its rotational center was detected. Conclusion: Second-generation prostheses can only provide a limited reconstruction of the original anatomy in shoulder hemiarthroplasty. In contrast, the modern third- and fourth-generation modular prostheses with variable inclination are more potent in replicating the original shoulder anatomy with its primary and secondary rotational centers.