• Shoulder/Elbow Surgery

The aim of this PhD thesis is to optimize the knowledge on the use of anatomical total shoulder arthroplasty for glenohumeral osteoarthritis. This was done by examining and comparing different types of arthroplasties and by studying approaches to analyze and interpret the postoperative outcomes of shoulder arthroplasty for glenohumeral osteoarthritis. In study I, MCID was determined for two shoulder specific questionnaires (WOOS and OSS). MCID corresponds to the improvement in a specific questionnaire that must be exceeded for being clinically relevant to the individual patient. The MCID values determined in study I were used in study II to quantify that approximately 90% of patients with osteoarthritis treated with an anatomical total shoulder arthroplasty achieved a clinically relevant improvement two years postoperatively. Study III is based on data from the Danish Shoulder Arthroplasty Registry and includes all anatomical total shoulder arthroplasties used for osteoarthritis in the period from 2012-2022. There was no difference in the risk of revision between the stemmed and the stemless shoulder arthroplasty systems, as long as the glenoid component was not metal-backed. In study IV, the population is expanded to also include patients from the Australian Shoulder Arthroplasty Registry, so that approximately 16.000 shoulder arthroplasties were analyzed. In this study, the above results were supported across the two countries. The metal-backed glenoid component was mostly used in combination with a stemmed arthroplasty in Australia and with a stemless arthroplasty in Denmark. Independent of the humeral design, the metal-backed glenoid component had a significantly increased risk of revision. Based on study III and IV, the stemmed and stemless total shoulder arthroplasties seem to have the same risk of revision. However, the stemless arthroplasty design relies on metaphyseal fixation only, which, in theory, may be associated with an increased long-term risk of loosening and revision. In study V, this concern is addressed by comparing the stemmed and stemless arthroplasties with radiostereometrical analyses. This method is able to detect micro movements of the arthroplasties, which is known to be correlated to the long-term risk of loosening.