[Shoulder replacement in arthritis of the shoulder joint]

Primary arthritis of the shoulder is one of the main indications for implantation of a shoulder endoprosthesis. The shoulder endoprostheses currently preferred have developed through four generations from the original monobloc prostheses to modular prostheses. Fourth-generation models allow the implant to be adjusted to suit the anatomical situation of the shoulder joint, so that physiological tensions and the centre of rotation can be restored. Conventional X-ray exposures in a-p and axial projections and an MRI investigation are considered standard parts of the surgical planning, and a CT examination is also performed when bony defects are present. The deltoid-pectoral approach is recommended for implantation of the prosthesis. In most cases the cup has also undergone arthritic alterations, which means that a total prosthesis is indicated. Results with total prostheses are superior to those obtained with hemi-endoprostheses. In the older patient the stem of the prosthesis is mostly cemented in, while cement-free fixation is also possible in the younger patient with good bone quality. The rates of loosening found in some 10-year follow-up studies of patients with cemented prostheses are well under 1%. The weak point of a shoulder endoprosthesis is still the replacement of the glenoid. The implantation is technically challenging. Cemented glenoid replacement is regarded as standard. Clinically significant loosening has been found to occur in up to 10% of cases in 10-year follow-up studies, and in up to 80% of cases in which there are radiologically demonstrable lytic borders. The newest development is that of humeral head implants that are anchored in the metaphysis without cement. These implants can be expected to be implanted in increasing numbers of patients with good bone quality in the future.