In addition to joint destruction, there is often also a loss of rotator cuff function in rheumatism patients. Thus, joint replacement alone using an anatomical prosthesis is unable to achieve satisfactory results. A half-linked inverse prosthesis, on the other hand, achieves improved function even in the presence of non-functioning rotator cuffs.
Of 157 shoulder prostheses that were followed up, 21 had been implanted in patients with rheumatoid arthritis. An anatomical endoprosthesis was implanted in 15 cases and an inversed endoprosthesis in six cases (average age 55.5/66.6 years).
The Constant score improved from 23 to 65 points for the anatomical prosthesis and from 15 to 67 points for the inversed endoprosthesis. An analogous improvement was also noted for mobility, strength and pain relief.
The results of anatomical prostheses depend substantially on the extent of damage to the rotator cuff. Implantation of a semi-constrained inversed prosthesis provides a solution for severely damaged joints since it has a fixed centre of rotation. One prerequisite of success, however, is a sufficient bone stock in the glenoid region. The indication for bipolar prostheses, in contrast, is particularly strong when implantation of an inverse prosthesis is no longer possible.