Evidence-based recommendations for the treatment of mechanical outlet impingement

The benefits of the various therapeutic options for the treatment of subacromial impingement syndrome are a topic of ongoing debate. Several studies on the subject are insufficiently evidence-based, with many other studies being considered controversial by members of the field. Nevertheless, a general opinion against surgical interventions is developing in the media in reference to these systematic reviews and meta-analyses based on insufficiently differentiated literature. This article provides an overview of the literature and examines the outcome after arthroscopic subacromial decompression compared with conservative therapy or diagnostic arthroscopy and bursectomy. The outcome for patients treated with conservative therapy or subacromial decompression who explicitly suffered from mechanical outlet impingement (MOI) or mechanical non-outlet impingement (MNOI) has not yet been studied. The main problem concerning almost all published studies is that they are based on a mixture of pathologies. It seems likely that especially patients with a mechanical, and therefore structural, narrowing of the subacromial space can profit more from surgical management than patients with unspecific subacromial pain. Differentiation between the pathologies is crucial for the correct treatment decision, not only for the reduction of symptoms, but most importantly for the preservation of the supraspinatus tendon.