Clinical Burden of Rotator Cuff DiseaseThe rotator cuff comprises the set of tendons that stabilize the glenohumeral joint (Fig. 1). Rotator cuff degeneration is a common pathology that results in pain, disability, lost productivity, and limitations to recreational activities 1 . Rotator cuff pathology carries a large clinical burden: in the United States, >4.5 million individuals suffer from rotator cuff tendinopathy, and >17 million individuals have a rotator cuff injury 2 . The incidence of rotator cuff pathology is high, with approximately 50% of the population who are ‡65 years of age experiencing a rotator cuff tear [3][4][5] . These injuries result in >500,000 rotator cuff repairs annually in the U.S. 1,3,[6][7][8] . Despite being one of the most common orthopaedic shoulder procedures, outcomes after rotator cuff repair are unpredictable and depend on factors such as tendon length, bone quality, and muscle quality, with failure rates ranging from 20% to 94% [9][10][11][12] . Repairs are typically performed arthroscopically and rely on sutures that are passed through the torn cuff tendon(s) and fixed to the humerus via suture anchors 13 . This serves to reapproximate the tendon to its native footprint in order to promote healing of the tendon to the bone. When the tendon is deemed irreparable due to irreversible degeneration and/or retraction, reconstruction may be recommended 14 .Before completing either repair or reconstruction, subacromial decompression often is performed (Fig. 1). This includes broadening of the subacromial space by resecting the subacromial bursa (subsequently referred to as the "bursa"), the coracoacromial ligament, and the inferior side of the acromion to varying degrees depending on the diagnosis and clinician preference 15,16 . Decompression is indicated in shoulders with or without refractory subacromial bursitis or subacromial impingement because it also improves visualization of the rotator cuff repair site 15,17,18 . However, decompression that includes subacromial bursectomy with acromioplasty has recently been shown to have no benefit over bursectomy alone, calling into question the necessity of acromioplasty 19 . Similarly, a systematic review of subacromial impingement treatment strategies revealed that bursectomy without acromioplasty is sufficient for treating symptoms of impingement 20 . Interestingly, subacromial decompression has been shown to impart no clinically meaningful improvement in patient outcomes 21,22 . Bursectomy has even been shown to be less effective in patients with subacromial pain syndrome if they also had degeneration in the shoulder 23 . Despite the judicious use of bursectomy, the impact that this procedure has on tendon-healing has not been established. Hence, investigating the involvement of the bursa in the tendon-healing response is critical for defining best surgical repair practices.
Historical PerspectiveThe bursa was first discussed in the literature in 1906 when Codman reported its involvement in "stiff and painful shoulders." 24 The bursa...