Glenoid resurfacing: what are the limits to asymmetric reaming for posterior erosion?

Eccentric posterior glenoid erosion is a common condition in osteoarthritis. No limits have ever been placed on the degree of eccentric erosion that can be corrected while still maintaining sufficient bone stock to implant a glenoid securely. Five cadaveric scapulae were dissected. Posterior glenoid erosion was created to simulate retroversion of 15 degrees or more. A computed tomography (CT) scan confirmed the degree of glenoid retroversion. The glenoid was then reshaped to correct the glenoid retroversion to neutral, and a glenoid component with central and peripheral pegs was inserted. A second CT scan confirmed the correction to neutral and also evaluated the fit of the component into the glenoid. In all 5 experimental cases, at least 1 of the 4 pegs penetrated the glenoid vault. In 1 case, there was a fracture of the anterior rim. Glenoid retroversion of 15 degrees or more cannot be satisfactorily corrected simply by reaming to lower the anterior edge of the glenoid and restore neutral version when using a glenoid component with peripheral pegs.