Aims

The Mathys Affinis Short is the most frequently used stemless total shoulder prosthesis in the UK. The purpose of this prospective cohort study is to report the survivorship, clinical, and radiological outcomes of the first independent series of the Affinis Short prosthesis.

Introduction. In rheumatoid patients the use of a long intramedullary stem in ipsilateral shoulder and elbow replacement carries the risk of humeral fracture of the small area of unviolated bone between the implants. Healing may be compromised. Because of this a short stemmed humeral head prosthesis was designed which rests on the bone surface after resection of the humeral head instead to be fixed in the shaft of the humerus. Since 1994 this prosthesis, specially designed for the rheumatoid patients has been in use in our clinic. The design rationale and the clinical results will be presented. Result. Since 1994 the short stemmed shoulder prosthesis has been inserted by the author in 54 shoulders. 8 Patients had osteoarthritis, 42 patients rheumatoid arthritis, 3 patients osteonecrosis and 1 patient a post-traumatic osteoarthritis. The average age was 65 years (range 32–83). In 19 shoulders a total shoulder arthroplasty was performed and the 36 shoulders a hemiarthroplasty. 32 Patients had a follow-up of more than 1 year and the average follow-up in this group is 2. 5 years (range 1-5. 5). All patients were scored clinically with the HSS score and the Constant score and radiographically before the operation, 1 year after the operation and after that at regular intervals. At follow-up pain decreased in all patients but more than 50% of the shoulders still had some mild or moderate pain during daily activities. Pre-operatively active forward flexion averaged 61°, external rotation 10° and abduction 50°. Postoperatively the active forward flexion increased to 75°, the external rotation to 19° and the abduction to 67°. The gain in ROM is similar to a group of patients operated in the same time period with another shoulder prosthesis. Discussion. The short stem shoulder prosthesis is a good alternative for a shoulder prosthesis with a long intra medullary stem. The clinical results with regards to pain reflief and gain in ROM are similar. The long term fixation of short sem humeral prosthesis remains good, without signs of radiolucency or migration. The advantage of a short stem prosthesis are:. easy technique to reconstruct the anatomical position of the humeral head. bone sparing. no stress shielding of the shaft. no surgical problems when a long stemmed elbow prosthesis is used. possibility for revision