Glenoid loosening in response to dynamic multi-axis eccentric loading: a comparison between keeled and pegged designs with an equivalent radial mismatch.

Glenoid loosening is a common failure mode observed in total shoulder arthroplasty. In an effort to isolate the affect of differing fixation techniques on loosening, an edge displacement test was conducted using two, pear-shaped, UHMWPE glenoid designs: one keel and one peg, each having a glenohumeral radial mismatch of 4.3 mm. The susceptibility of each design to loosening was established by quantifiably comparing the maximum glenoid edge displacement before and after 100,000 cycles of eccentric loading by the humeral head along both the superoinferior (SI) and anteroposterior (AP) glenoid axes. Regardless of the axes tested, the results of this study indicate that no discernable difference in edge displacement (distraction and compression) occurred before or after cyclic, eccentric loading for either the keeled or pegged glenoid designs. Additionally, each keel andpeg glenoid remained firmly fixed after testing, suggesting that either fixation technique provides sufficient resistance to edge displacement.