Abstract
INTRODUCTION
The aim of this retrospective study is to evaluate clinically and radiographically the effectiveness of implanting an eccentric glenosphere and if a correct glenosphere positioning would avoid the occurrence of notching.
METHODS
since 2006 40 patients with shoulder eccentric osteoarthritis were treated with reverse shoulder arthroplasty with a 36 mm eccentric glenosphere. We have selected 25 patients, with a minimum follow up of 24 months. The patients were clinically evaluated with the Constant score and SST and with X-ray, MRI and/or CT before and after surgery. At the follow up we evaluated the presence or absence of notch, and we measured the PSNA (prosthesis-scapular neck angle), the DBSNG (distance between the scapular neck angle and glenosphere), the PGRD distance (peg glenoid distance). Stastistical analysis was performed with a paired t test.
RESULTS
In every patient the range of motion was improved. The AP X-ray did not show inferior scapular notching. The mean DBSNG, was found to be 4.3 mm. The mean PSNA was 92 ° and the mean PGRD was 21.2. The Constant score improved from 30 to 74 points and the SST from 1.7 to 8.4 points.
DISCUSSION and CONCLUSION
The scapular notching is shown as the most frequent complication in reverse shoulder replacement. In our study the results indicate that proper positioning of the glenosphere with the inferior part of the metal back that overlaps the lower glenoid rim without overhang and the implantation of an eccentric glenosfere, lowers the center of rotation of 4 mm and avoid contact between the humeral component and the scapular neck during the adduction. Thus, all the patients increased the total joint range of motion.
