Bony Increased-Offset Reverse Shoulder Arthroplasty (BIO-RSA) for Cuff Tear Arthropathy

Abstract

Given the disappointing results of hemiarthoplasty and the unacceptably high failure rates of total shoulder protheses, reverse shoulder arthroplasty (RSA) has become an attractive treatment option for patients with painful cuff tear arthropathy. Grammont's original medialized design represented a major advance in the restoration of shoulder function for these patients. Scapular notching, prosthetic instability, limited shoulder rotation, and loss of shoulder contour are all problems resulting from the medialization of the center of rotation, stimulating others, in turn, to develop lateralized RSA designs. Rather than changing the geometry of the glenoid prosthesis, our approach to achieving lateralization has been to increase the bony offset of the glenoid. In this article, we present the surgical technique of bony increase-offset reverse shoulder arthroplasty (BIO-RSA). By using a modified base-plate with a lengthened central peg, we place a cancellous bone graft harvested from the humeral head beneath the baseplate of the RSA, effectively creating a long-necked scapula. At a minimum of 2 years after surgery, in a prospective cohort of 42 patients receiving BIO-RSA, there were no cases of glenoid loosening or prosthetic instability. Computed tomography and plain radiographic review demonstrated healing of all glenoid bone grafts. Scapular notches were observed in only 9 cases. Significant improvements were observed when disease-specific outcome measures were used and in all planes of shoulder mobility. BIO-RSA appears as a biological solution to minimize inferior scapular notching and to maximize shoulder stability and mobility without increasing the risk of glenoid component failure. Healing of the humeral bone graft on the native glenoid is consistently observed, allowing the creation of a scapula with a long neck. In contrast to metallic increased-offset, BIO-RSA offers the advantage of maintaining the center of rotation of the joint at the prosthesis-glenoid interface and therefore minimizing torque on the glenoid component.