Can Distalisation and Lateralisation Shoulder Angles in Reverse Arthroplasty Interfere with the Functional Results in Patients with Rotator Cuff Arthropathy?

 To evaluate the influence of radiographic values on clinical and functional results in patients treated with reverse arthroplasty for rotator cuff arthropathy (RCA) using a lateralized design.  A retrospective analysis was performed. Patient demographics were recorded, as well as preoperative and postoperative range of motion. Function was calculated using the Constant-Murley score both before and after the procedure. Pre and postoperative anteroposterior and axial radiographs of the affected shoulder were analysed. In the preoperative images, the following was calculated: acromiohumeral distance (AHD) and lateral humeral offset (LHO). Postoperative measurements included: AHD, LHO, distalization shoulder angle (DSA) and lateralisation shoulder angle (LSA). Linear regression and quadratic regression analysis was performed to determine their degree of association with final functional outcomes. By applying a quadratic regression analysis and ROC curves, the cut-off values were determined with respect to the above-mentioned angles and the positive predictive value was calculated.  The greater anterior elevation (AE) ranges were found with DSA between 40-45° and LSA among 80°- 90°, while better ABD was observed with LSA of 90-100°. Preoperative AHD was correlated to RE (r :0.47; p:0.049). Postoperative AHD was found to be in a directly proportional relationship with AE (r :0.49; p:0.03). Postoperative ABD showed an inverse linear regression with preoperative AHD (r : -0.44, p:0.047). LSA and DSA were inversely related.  We found that a DSA between 40-45° and a LSA of 80-100° could lead to better range of motion regarding AE and ABD in patients with rotator cuff arthropathy treated with RSA.