The absorbable subacromial spacer for irreparable posterosuperior cuff tears has inconsistent results

Purpose To evaluate the 2-year results of an absorbable subacromial spacer in patients with irreparable posterosuperior rotator cuff tears. Methods Prospective longitudinal study of a consecutive case series of 16 subjects with irreparable tears of the posterosuperior rotator cuff in which the InSpace (R) subacromial spacer was arthroscopically implanted. A full clinical evaluation that included the Constant test, Simple Shoulder Test (SST) and the QuickDash questionnaire was performed preoperatively and at 12 and 24 months follow-up. The primary outcome for assessing the success of the procedure was a variable composed of a clinically relevant variation of the Constant (established in an improvement greater than 10 points) and the absence of surgical reintervention. Results Fifteen subjects (11 women/4 men, median age=69.4years [interquartile range 7.50], range 60-80 years) completed the 2-year of follow-up. According to the main evaluation criteria, only 6 patients (40%) had a successful outcome. Five subjects required reconversion to a reverse shoulder arthroplasty (at a median of 9.8months postoperatively) due to absence of clinical improvement or worsening of symptoms. Of the ten remaining subjects, only 6 had improvements greater than 10 points in the Constant score. Despite of this, these 10 subjects had, on average, some improvement in the Constant test (preoperative Constant: median 35.0 [27.0-52.5] vs Constant at 24 months: 53.5 [55.0-84.0], significant differences p=0.02), in the SST (3.0 [2.0-4.0] vs 6.0 [3.25-7.75], p=0.039) and in the QuickDASH test (37.0 [33.25-40.0] vs 27.5 [20.5-32.75], p=0.012). Conclusions The outcomes of the implantation of the subacromial biodegradable spacer at 2-year follow-up are not satisfactory. In this small case series only 40% of patients seem to clearly benefit from surgery. One in three required revision to a reverse shoulder arthroplasty. The described technique does not seem a reasonable alternative for the management of the majority of patients with irreparable ruptures of the rotator cuff. The indications of this device should be more clearly defined.