|ECR 2018 / C-1456|
|Subacromial “Biodegradable Spacer” in the Management Irreparable Rotator Cuff Tears: Radiological Findings|
Findings and procedure details
The massive irreparable tears of rotator cuff (IRCT) represents a debilitating condition for the patient as well as it is still a hard challenge to an orthopedic surgeon.
It is important to differentiate between massive and irreparable rotator cuff tears. By definition, massive tears have been described as > 5 cm and tears involving two or more tendons. An IRCT, as the name suggests, is any RCT which cannot be repaired back to the rotator cuff footprint on the greater tuberosity of the humerus or as Gerber et al suggested, any repair that is successful but will almost certainly be associated with structural failure.
Although the final decision on reparability of the rotator cuff is made intraoperatively, various symptoms, signs and radiologic findings may suggest irreparability prior to surgery allowing for appropriate preoperative planning.
Once a rotator cuff is deemed irreparable, a variety of arthroscopic treatment options have been proposed to reduce pain and improve function in patients with IRCT, including subacromial decompression or debridement, various techniques for partial tendon repair, tendon transfer, muscle-tendon slide procedures, the use of rotator cuff allograft and synthetic graft materials, arthrodesis, hemiarthroplasty, and reverse total shoulder arthroplasty.
The most recent treatment modality proposed for an irreparable rotator cuff tear is the InSpace system. This device is a biodegradable spacer (balloon shape), which is implanted between the acromion and the humeral head in an attempt to restore the shoulder biomechanics by reducing subacromial friction through lowering the humeral head during abduction. The InSpace system contains an introducer and a preshaped spacer made of poly(L-lactide-co-E-caprolactone), a biodegradable and widely used material that biodegrades over a period of 12 months.
Contraindications include arthritis, allergies to the device materials and active infections. Potential complications include foreign body response, local irritation or inflammation, tissue necrosis and device displacement.
Knowing the radiological findings of the subacromial spacer, including its main complications, may be useful in the clinical management of the patient.
Under normal conditions, the subacromial spacer may be visualized during the first year after insertion, since after 12 months it tends to spontaneously reabsorb itself.
It is an oval-shaped structure with smooth margins located in the subacromial space. In MRI studies, its signal intensity is homogenously hyperintense in the T2-weighted and Proton Density sequences, unlike synovial fluid, which is usually not as homogeneous. It is common to observe some hypointense lines in its interior in relation to the folding of the ball. This sign can also be observed in ultrasound images and is very useful to recognize it (Figures 1,2).
The main complications that can be radiologically identified are the following: migration of the balloon outside the subacromial space (anterior, posterior or cranial) (Figures 2,5,6,7,8) and inflammatory changes secondary to spacer micro-rupture (Figures 3,4). In this last scenario, alterations in signal intensity in muscle tendon structures and subcutaneous tissue (especially manifest in STIR sequences or enhancement after administration of contrast), may be a relatively expected finding in the first days after the intervention, so it can not be differentiated from postoperative changes.
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