The smallest distance between the acromion and the humeral head is called the acromio-humeral distance (AHD).
Past studies have found that compared to healthy individuals, patients with subacromial pathology, there is a reduction in AHD of 1.9 mm and 2.1mm with those that have rotator cuff tears and rotator cuff dysfunction, respectively.
Hence, for this study, the authors set a 2 mm change post intervention as clinically relevant.