Narrative Review Subacromial impingement syndrome: a musculoskeletal condition or a clinical illusion?

Background: Subacromial impingement syndrome is considered by many to be the most common of the musculoskeletal conditions affecting the shoulder. It is based on a hypothesis that acromial irritation leads to external abrasion of the bursa and rotator cuff. Objectives: The aim of this paper is to review the evidence for the acromial irritation theory and in doing so challenge the rationale for subacromial decompression. Major findings: There is a body of evidence that suggests there is a lack of concordance regarding (i) the area of tendon pathology and acromial irritation, (ii) the shape of the acromion and symptoms, (iii) the proposal that irritation leads to the development of tendinitis and bursitis, and (iv) imaging changes and symptoms and the development of the condition. In addition, there is no certainty that the benefit derived from the surgery is due to the removal of the acromion as research suggests that a bursectomy in isolation may confer equivalent benefit. It is also possible that the benefit of surgery is due to placebo or simply enforces a sustained period of relative rest which may allow the involved tissues to achieve relative homeostasis. It is possible that pathology originates in the tendon and as such surgery does not address the primary pathoaetiology. This view is strengthened by the findings of studies that have demonstrated no increased clinical benefit from surgery when compared with exercise. Additionally, exercise therapy is associated with a substantially reduced economic burden and less sick leave. Conclusion: As there is little evidence for an acromial impingement model, a more appropriate name may be ‘subacromial pain syndrome’. Moreover, surgery should only be considered after an appropriate period of appropriately structured rehabilitation.