Editorial Commentary: Subacromial Balloon Spacer for Irreparable Rotator Cuff Tears Produces Clinical Improvement, Yet the Mechanism of Action Is Unclear.

Subacromial balloon spacers, a treatment option for massive irreparable rotator cuff tears, have been available in the United States since 2021 and much longer in Europe. The device has been described as a humeral head depressor that increases the subacromial space, centers the humeral head preventing superior migration, and improves deltoid mechanical advantage. This is not convincing. Balloon deflation occurs 3 months after implantation, eliminating the head-depressing effect, and the balloon fully degrades within 15 months. Some propose scarring in the subacromial space smoothes the acromial-humeral articulation; this is also unconvincing. The scar is not thick. Clinical studies largely report unchanged or worsened acromiohumeral interval after surgery. Short-term case series show improvement in pain and function, but comparative studies show mixed results. There may be some advantages over partial rotator cuff repair, but debridement alone may be sufficient treatment, and the generally positive short-term results do not determine whether symptom relief persists over the long term after balloon degradation. A recent clinical study does show mid-term improvement, but the mechanism remains unclear, and, if it is a result of smooth subacromial scarring, tuberoplasty may be an alternative.