tray fracture (5.5%), difficulty inserting the baseplate (4.8%), and difficulty inserting the glenosphere (4.2%).

In Complications in reverse shoulder arthroplasty the authors point out that the reported overall complication rate of primary RSA was approximately 15%; when RSA is used in the revision setting, the complication rate may approach 40%. The most common complication of RSA was instability, followed by infection, notching, loosening, nerve injury, acromial and scapular spine fractures, intra-operative fractures and component disengagement.

In Outcomes of instability after reverse shoulder arthroplasty: reoperation and persistent instability are common the authors evaluated the outcomes of 50 patients having instability after reverse shoulder arthroplasty (RSA). 40 (80%) required revision surgery while 10 (20%) were treated successfully with closed reduction. There were no significant differences between the revision and closed reduction groups with respect to age, sex, BMI, diagnosis, or nature or number of dislocations.

Patients requiring revision were more likely to have had surgery prior to the reverse total shoulder and had longer average times from the reverse total shoulder to dislocation than those managed by closed reduction (7.6 vs 2.2 months).

Following revision surgery, 17 patients (42.5%) reported recurrent instability, and 14 (35.0%) required additional revision surgery. Of the 14 patients who required additional procedures, 4 continued to have instability (28.6%) and 5 required even further surgery (35.7%). Ultimately, stability was never achieved in 7 of 50 patients (14%) after their index instability event. Patients who required >1 revision operation were more likely to have infections and to have undergone the index RSA as a revision procedure

Five patients had positive culture findings at the time of revision surgery, and 4 were considered to have probable or definitive infections.

Comment: Taken together, these papers point to the magnitude and difficulty presented by instability after a reverse total shoulder arthroplasty. Thus in performing a reverse total shoulder it is important to properly select and position the components, to check for unwanted contact between the humerus/humeral component and the scapula, and to vigorously examine the completed arthroplasty for instability, especially with the arm in adduction, extension and internal rotation.