Massive irreparable rotator cuff tears (MIRCTs) represent 10% to 40% of cases of rotator cuff abnormality and are challenging to treat. When MIRCTs are unresponsive to nonoperative treatment, surgery may be considered. An arthroscopically inserted biodegradable subacromial balloon spacer (InSpace; Stryker) has grown in popularity in recent years for treatment of patients with MIRCTs. The balloon spacer is made of a copolymer of poly-L-lactide-eco-ε-caprolactone and is expected to fully resorb within 12 months after implantation. Research has suggested the balloon spacer becomes progressively compressed and is slowly replaced with fibrous tissue between the humeral head and the acromion, which may support a prolonged benefit following resorption. Clinical benefits may be achieved through reduced acromiohumeral abutment and subacromial friction during shoulder movement by lowering the humeral head and facilitating humeral gliding. The primary population indicated for use of the implant are patients older than 40 years with persistent shoulder pain and functional disability due to MIRCTs. Contraindications include irreparable subscapularis tears, moderate to severe arthritis, axillary nerve palsy, and known allergy to the implant material. There are not clear indications for use of the implant for treatment of partial-thickness tears or repairable complete rotator cuff tears. Familiari et al. reported that treatment with the balloon spacer was associated with a significant improvement in shoulder function, limited need for revision surgery, and high satisfaction at mean 3-year follow-up. More recently, a prospective multicenter randomized controlled trial was conducted to evaluate the efficacy and safety of the balloon spacer in 93 patients compared to 91 patients undergoing arthroscopic partial repair. Significant and clinically relevant improvements in the American Shoulder and Elbow Surgeons score from baseline were noted in both groups up to the 2-year follow-up.
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