Resection interposition arthroplasty of the shoulder affected by inflammatory arthritis.

To determine the therapeutic value of resection-interposition arthroplasty (RIAP) of shoulders in rheumatoid or other inflammatory arthritis, 53 patients were reviewed clinically and radiographically after a mean follow-up period of 8.2 +/- 4.3 years (3.5 to 17.5 years). The Constant Score averaged 42.33 +/- 16.2 (12 to 76). Patients with a follow-up period of more than 10 years performed significantly worse than those with shorter follow-up periods. In most cases, radiographs showed a progressive medial displacement and loss of size of the humeral head as well as a decrease of the joint space with time. Abduction proved to be highly dependent on the degree of medial displacement of the humeral head, whereas the Constant Scores correlated with the width of the joint space. Despite initially acceptable postoperative results, outcome at longer follow-up periods worsened as the result of wear of the glenoidal cartilage and osseous resorption of the humeral head, resulting in a progressive medialization of the center of rotation.