**8.1 Glenoid wear and erosion**

As has been previously discussed, overzealous reaming or the need for excessive glenoid version correction can result in penetration of the subchondral plate and exposure of cancellous bone in the glenoid vault. It can also result in narrowing of the anterior-posterior dimensions of the glenoid concavity, which reduces the overall surface area for contact stress distribution and predisposes to instability. In these situations, patients will continue to experience pain following humeral hemiarthroplasty and may demonstrate recurrent glenoid erosion both medially and posteriorly. Thus patient selection and work-up are critical to predicting who is the ideal candidate likely to have a good outcome and all patients must be counseled about the potential need for glenoid replacement if the principles and goals of non-prosthetic glenoid arthroplasty cannot be met intraoperatively. Rhee and colleagues have shown that the results of salvage glenoid replacement after failed hemiarthroplasty are inferior to primary total shoulder arthroplasty.48 This highlights the importance of doing the right operation the first time around.
