Posterosuperior Irreparable Tears: Arthroscopic Subacromial Balloon

Mohamad Y. Fares

Peter Boufadel

Adam Z. Khan

Joseph A. Abboud

Abstract

Treating massive irreparable rotator cuff tears is a challenging feat in the world of shoulder surgery. Different treatment options exist, each with their own strengths and limitations. One treatment option that has recently emerged is the subacromial balloon spacer, a simple procedure that helps alleviate pain and improve function in the appropriate patient with rotator cuff tear. Indications include massive posterosuperior irreparable rotator cuff tears with intact subscapularis and teres minor muscles, adequate forward elevation, and absence of severe osteoarthritis. The purpose of the subacromial balloon spacer is to depress the superiorly migrating humeral head in patients with rotator cuff tears, thereby relieving acromiohumeral impingement and decreasing pain. In addition, the balloon alters the kinematics and biomechanics of the glenohumeral joint and redistributes stress on nearby musculature to offset the deficient rotator cuff. As such, the subacromial balloon can be considered a salvage procedure and a rehabilitation accelerator that improves patient symptoms for several years prior to resorting to a total shoulder arthroplasty. The literature on the subacromial balloon has generally reported positive outcomes, with a few studies demonstrating conflicting results that challenge its therapeutic potential. Additional research that properly adheres to the indications and contraindications of this novel treatment is needed in order to equivocally comment on its efficacy and determine its place in treatment guidelines. Moreover, proper understanding of the capabilities and utility of this procedure should be established in order to ensure its appropriate use in the right setting.

INTRODUCTION

Massive rotator cuff tears, many of which are judged irreparable,¹ in patients without significant glenohumeral osteoarthritis pose a momentous challenge for orthopedic surgeons and result in significant shoulder pain and dysfunction for patients. A wide variety of treatment options are described in the orthopedic literature²^, ³ ^and ⁴ as there is no “home run” surgical option. For this reason, prior to discussion of any surgical treatment, appropriate patient counseling and preoperative expectation management is paramount.

The implantable, biodegradable (polymer of polylactic acid and epsilon-caprolactone) subacromial balloon spacer (InSpace, Stryker, Kalamazoo, MI) is a novel technology, recently approved by the US Food and Drug Administration (FDA) (July 2021) for use in the United States. This novel technology has a track record of effective and safe use in Europe since 2010. Its surgical technique and application was first described in the literature in 2012.⁵ The theory behind its effectiveness and the proposed mechanism of action is to temporarily (dissolves at 12 months postoperatively) depress the humeral head in an attempt to restore or closely replicate native glenohumeral biomechanics and facilitate shoulder rehabilitation.⁵ By reducing subacromial friction between the humeral head and acromion during elevation and abduction, it can provide pain relief.⁵^, ⁶ ^and ⁷

Insertion of the subacromial balloon is comparatively efficient, can reduce time under anesthesia for the patient, has potentially lower procedure-associated risk, and can be cost-effective when compared with other available treatment options.⁸^,⁹ Implantation and total procedural time varies but has been reported to be between 2 and 20 minutes.¹⁰ A recent multicenter study of 20 surgeons demonstrated a mean implantation time of 3.8 minutes.¹¹ This chapter will provide an overview of the clinical pathology, patient indications, surgical considerations, and implantation technique for the subacromial balloon spacer.

INDICATIONS AND CONTRAINDICATIONS

Achieving satisfactory results following subacromial balloon spacer implantation is highly reliant on proper adherence and commitment to the procedure’s indications and contraindications.⁷^,¹² One of the most important notions to take into consideration is the reparability of the massive rotator cuff tear.⁷^,¹² Restoring the anatomy should take precedence over placement of the subacromial balloon, and as such, all patients should be thoroughly evaluated in order to rule out a rotator cuff tear capable of being repaired arthroscopically.⁷^,¹² This can be done preoperatively through clinical and radiographic examination and intraoperatively through arthroscopic exploration. In addition, it is very important to have preserved function in the subscapularis and teres minor muscle tendons of the rotator cuff, as that is necessary to maintain and preserve the coupling between external rotation and internal rotation.⁷^,¹²^, ¹³ ^and ¹⁴ Similarly, having a functional deltoid is necessary as the deltoid will become the major elevator of the arm, compensating for the deficient rotator cuff, in setting of subacromial balloon placement.⁷^,¹²^, ¹³ ^and ¹⁴ The balloon is also contraindicated in patients with pseudoparalysis, as these patients are less likely to benefit from the procedure and are more likely to have persistently diminished function following it.⁷^,¹²^, ¹³ ^and ¹⁴ As such, it is recommended for patients to have at least 90° of active forward elevation prior to the surgery, in order to attain favorable outcomes post procedure.⁷^,¹²^,¹³ The balloon is also contraindicated in the case of severe glenohumeral arthritis, as these cases are predicted to have persistent pain and diminished function following the procedure, relating to the arthritic joint and the existent osteophytes.⁷^,¹²^,¹³ And finally, as with other orthopedic procedures, a concurrent infection can lead to the propagation of a septic joint and, as such, is a strict contraindication for the placement of a subacromial balloon.⁷^,¹²^,¹³

PREOPERATIVE PREPARATION

When considering a patient for a subacromial balloon placement procedure, a comprehensive clinical and diagnostic investigation should take place. This involves holistic history taking to understand the mechanisms and background of the shoulder injury presented and meticulous examination to make sure the patient falls into the right indications for the procedure. Physical examination should usually reveal positive signs for a posterosuperior rotator cuff tear with pronounced pain and weakness on shoulder abduction and flexion.¹⁵^,¹⁶ The subscapularis should have intact function and mobility, with no pain or weakness, and negative provocative testing. However, for patients to be considered for the subacromial balloon, they should have relatively preserved forward elevation of the shoulder, with a minimum of 90° of active forward flexion.¹⁵^,¹⁶ Clinical investigation should also take into account patient’s demographics, medical history, concurrent expectations, and goals.

Obtaining the appropriate diagnostic imaging is imperative for the preoperative preparation for a subacromial balloon spacer. Initially, a radiograph of the affected shoulder can be taken to check for any signs of moderate to severe osteoarthritis and for any concomitant bone deformities. The radiograph should show absent to minimal osteoarthritis, with possible superior migration of the humeral head as a result of the present tear in the rotator cuff.¹⁵^,¹⁶ Afterward, magnetic resonance imaging (MRI) is necessary to evaluate the soft tissues of the affected shoulder. The coronal cut of the MRI should show a massive posterosuperior rotator cuff tear, usually with retraction to the level of the glenoid. Sagittal cut can show significant atrophy of the supraspinatus and/or infraspinatus tendon and healthy subscapularis and teres minor muscle bellies.¹⁵^,¹⁶ The axial cut should show an intact subscapularis tendon.¹⁵^,¹⁶ The imaging modalities used help in confirming the diagnosis at hand and the suitability of the patient undergoing the procedure. Patient education remains key when deciding on a subacromial balloon placement procedure. Patients should understand the mechanism by which the subacromial balloon works and learn about the rehabilitation protocols and trends following the procedure. This assures patients during the management process and optimizes their comfort, both prior to and after undergoing the procedure.

TECHNIQUE