Observations on retrieved glenoid components.

To obtain more information on the pattern of damage of prosthetic glenoid components, we analyzed 7 retrieved glenoid components. The consecutive series included 2 standard polyethylene components and 5 highly crystalline polyethylene glenoids (Hylamer; DePuy Dupont Orthopaedics, Warsaw, IN) retrieved 3 to 12 years after implantation. At revision, 4 of 5 Hylamer components were fractured. Common wear patterns were i) deformation and crumbling of the rim, particularly at the inferior hemicircumference, probably caused by direct contact of the humerus with the prosthetic component; ii) roughening (abrasion and scratching) of the adjacent articulating surface; and iii) concentric and congruous wear centered posteriorly. Available glenoid components may cover an excessive sector of the head. This can result in mechanical restriction of glenohumeral motion and abutment of the humerus against the glenoid rim. Abutment may cause major shear forces and therefore cause glenoid loosening. The value of articular surface mismatch is questionable because retrieved glenoids were worn to a conforming joint.