The Use of A Biodegradable Subacromial Balloon Spacer in the Setting of Irreparable Superior Rotator Cuff Tears
Recently a subacromial balloon spacer (InSpace, Orthospace, Israel) has been introduced as an option to treat irreparable rotator cuff tears. The purpose of this study was to investigate the effects of this device on shoulder biomechanics, with the hypothesis that the balloon would restore glenohumeral contact pressure, acromion-humeral interval, and deltoid load after an irreparable supraspinatus tear.
Fourteen cadaveric shoulders were tested using a custom shoulder test frame. Glenohumeral contact pressure, acromion-humeral interval, and deltoid load were measured using a digital sensor, a microscribe, and a spring scale, respectively. Various conditions simulating clinical relevance were utilized for this study for biomechanical comparison including the intact shoulder, supraspinatus tear, supraspinatus repair, repair plus balloon, irreparable supraspinatus tear, and irreparable tear plus balloon, in balanced and unbalanced loading conditions.
When the balloon was inflated over the irreparable supraspinatus tear in balanced condition, glenohumeral contact pressure increased by 121% (P=0.006) at 0º (increase from 70.5 ±10.5 kPa [mean ± SEM] to 156.5±26.1 kPa) and 94% (P=0.046) at 60º. In the unbalanced condition, there was a decrease in glenohumeral contact pressure after the balloon was inflated, restoring pressures to close to intact state. The irreparable tear displaced the humeral head superiorly 4.8±1.2 mm at 0º (P<0.001) and 2.7±1.3 mm at 30º (P= 0.046) in the unbalanced condition, decreasing the acromion-humeral interval. The balloon inferiorized the head 6.2±1.3mm (P<0.001) at 0º, 4.4±1.3 mm (P<0.001) at 30º, and 3.0±0.8 mm (P<0.001) at 60º. The balloon increased the deltoid load after an irreparable tear by 8.2% (P=0.025) at 0º, 12.6% (P=0.004) at 30º, and 11.1% (P=0.010) at 60º.
The balloon demonstrated favorable biomechanical properties when inserted in the setting of an irreparable supraspinatus tear model, restoring intact state glenohumeral contact pressures, lowering the humeral head, and increasing the deltoid load.