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° 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° 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.