Eccentric reaming in total shoulder arthroplasty: a cadaveric study.

Posterior glenoid bone loss often is seen in association with glenohumeral osteoarthritis. Many different techniques have been proposed to account for this bone loss during total shoulder arthroplasty, the most popular being eccentric anterior reaming. However, the amount of correction that can be achieved has not been been well quantified. The purpose of this study was to define the amount of eccentric posterior glenoid wear that can be corrected by anterior glenoid reaming. Eight cadaveric scapulae were studied. Simulations of posterior glenoid wear in 5 degrees increments were performed on each scapula. The specimens were then eccentrically reamed to correct the deformity. Anteroposterior width, superior-inferior height, and the best-fit pegged glenoid prosthesis size were measured. Anterior reaming to correct a 10 degrees posterior defect resulted in a decrease in anteroposterior glenoid diameter from 26.7+/-2.5 mm to 23.8+/-3.1 mm (P=.006). In 4 of 8 specimens, placing a glenoid prosthesis was not possible after correcting a 15 degrees deformity because of inadequate bony support (N=2), peg penetration (N=1) or both (N=1). A 20 degrees deformity was correctable in 2 of 8 specimens and only after downsizing the glenoid component. Anterior glenoid reaming to correct eccentric posterior wear of >10 degrees results in significant narrowing of the anteroposterior glenoid width. A 15 degrees deformity has only a 50% chance of successful correction by anterior, eccentric reaming. Orthopedic surgeons need to be cognizant of this in their preoperative planning for total shoulder arthroplasty.