Reverse shoulder arthroplasty (RSA) and arthroscopic-assisted lower trapezius tendon (aLTT) transfer are both treatment options for massive irreparable rotator cuff tears (MIRCTs) without glenohumeral arthritis; however, the indications for each remain controversial. Although RSA is an excellent reconstructive option, preserving the joint, recentering the humeral head, and restoring in-line active external rotation with an aLTT transfer may be preferred in certain patients to better restore more normal shoulder biomechanics. In-vivo kinematics, however, have been historically difficult to evaluate. Dynamic digital radiography (DDR) provides a novel way to examine shoulder function following surgical intervention by estimating the scapulohumeral rhythm (SHR)-the ratio of humerothoracic and scapulothoracic motion. The purpose of this study was to compare SHR between aLTT transfer and RSA in the setting of nonarthritic MIRCTs with the use of DDR. We hypothesized that aLTT transfer would restore SHR to values more typical of native shoulders compared to RSA. DDR > 6 months postoperatively was performed on 48 shoulders, comprised of 30 RSA and 18 aLTT transfer shoulders, secondary to nonarthritic MIRCT-the diagnosis for which was validated on radiographs and magnetic resonance imaging. Manual measurements of the angle between the humerus and the midline and the lateral border of the scapula and midline were taken by 2 readers at rest, 30°, 60°, and 90° of shoulder abduction. The ratio of these measurements formed the SHR. A paired subgroup analysis was performed on 7 RSA and 7 aLTT transfer shoulders with both preoperative and postoperative DDR to evaluate for precise changes in SHR. Data were compared using descriptive statistics, and inter-rater reliability of the manual measurements was assessed with intraclass correlations. The aLTT transfer cohort had a higher median rest-90° range of motion SHR of 2.30, compared to 1.83 for the RSA cohort. Subgroup analysis of the RSA cohort demonstrated a nonsignificant improvement in median rest-90° range of motion SHR from 1.84 to 2.23 following surgical intervention. The aLTT transfer subgroup's median rest-90° SHR improved significantly from 2.20 to 2.46 following surgical intervention. The inter-rater reliability was 0.99. aLTT transfer is associated with an increased SHR compared to RSA in patients with nonarthritic MIRCTs by establishing a higher glenohumeral contribution compared to scapulothoracic contribution. Further work is needed to understand scapular motion in multiple planes after these surgeries and correlate SHR changes with clinical outcomes.
Copyright remains with the authors and publisher.
Reverse shoulder arthroplasty (RSA) and arthroscopic-assisted lower trapezius tendon (aLTT) transfer are both treatment options for massive irreparable rotator cuff tears (MIRCTs) without glenohumeral arthritis; however, the indications for each remain controversial. Although RSA is an excellent reconstructive option, preserving the joint, recentering the humeral head, and restoring in-line active external rotation with an aLTT transfer may be preferred in certain patients to better restore more normal shoulder biomechanics. In-vivo kinematics, however, have been historically difficult to evaluate. Dynamic digital radiography (DDR) provides a novel way to examine shoulder function following surgical intervention by estimating the scapulohumeral rhythm (SHR)-the ratio of humerothoracic and scapulothoracic motion. The purpose of this study was to compare SHR between aLTT transfer and RSA in the setting of nonarthritic MIRCTs with the use of DDR. We hypothesized that aLTT transfer would restore SHR to values more typical of native shoulders compared to RSA. DDR > 6 months postoperatively was performed on 48 shoulders, comprised of 30 RSA and 18 aLTT transfer shoulders, secondary to nonarthritic MIRCT-the diagnosis for which was validated on radiographs and magnetic resonance imaging. Manual measurements of the angle between the humerus and the midline and the lateral border of the scapula and midline were taken by 2 readers at rest, 30°, 60°, and 90° of shoulder abduction. The ratio of these measurements formed the SHR. A paired subgroup analysis was performed on 7 RSA and 7 aLTT transfer shoulders with both preoperative and postoperative DDR to evaluate for precise changes in SHR. Data were compared using descriptive statistics, and inter-rater reliability of the manual measurements was assessed with intraclass correlations. The aLTT transfer cohort had a higher median rest-90° range of motion SHR of 2.30, compared to 1.83 for the RSA cohort. Subgroup analysis of the RSA cohort demonstrated a nonsignificant improvement in median rest-90° range of motion SHR from 1.84 to 2.23 following surgical intervention. The aLTT transfer subgroup's median rest-90° SHR improved significantly from 2.20 to 2.46 following surgical intervention. The inter-rater reliability was 0.99. aLTT transfer is associated with an increased SHR compared to RSA in patients with nonarthritic MIRCTs by establishing a higher glenohumeral contribution compared to scapulothoracic contribution. Further work is needed to understand scapular motion in multiple planes after these surgeries and correlate SHR changes with clinical outcomes.
Copyright remains with the authors and publisher.