Editorial Commentary: Subacromial Bursa-Friend or Foe Within The Shoulder? An Old Debate With New Insights.

There is an ongoing debate about whether to resect or preserve the subacromial bursa during surgical treatment of rotator cuff tears. Neer was the first to systematically describe bursitis as a component of subacromial impingement syndrome that may extend to rotator cuff disease, often discussed as a point of controversy with Uhthoff who first identified the bursa as a contributor to rotator cuff healing, both experimentally and clinically. Because the subacromial bursa provides the gliding mechanism of the shoulder and regenerates itself after surgical removal, interest evolved on the role of the bursa in the healing of rotator cuff tears for evolution of regenerative therapies as a support of arthroscopic repair techniques. In vitro work could identify human subacromial bursa as a source of mesenchymal stem cells, which revealed lineage-specific differentiation capacity, including the tendon and a marker profile that was highly similar to, although in some aspects distinct from, marrow-derived mesenchymal stem cells. Only recently, this knowledge was used in controlled experimental work in vivo to demonstrate superior engraftment of bursal cells within tendon tissue. These findings shed new light on the biology of the subacromial space and provides novel prospects for the clinical use of local stem cells in rotator cuff repair.