The effect of glenoid component size on the stability of total shoulder arthroplasty

Frequently, during the course of total shoulder arthroplasty, the measurement of the patient's native glenoid is between the available prosthetic glenoid sizes. Technically, it may be easier for the surgeon to implant a smaller glenoid component. Currently, there is no information regarding the difference in joint stability by use of glenoid components of different sizes. Stability ratio measurements were performed by use of a multiaxis testing machine with 3 different glenoid sizes (small, medium, and large) and compared by use of analysis of variance and the Tukey HSD test. Changes in the size of the glenoid component were found to have a significant effect on the stability ratio. At a load of 50 N, the stability ratio increased by 18% from the small to the medium glenoid component and by 15% from the medium to the large glenoid in the superoinferior axis. In the anteroposterior axis, the stability ratio increased by 17% from small to medium and by 10% from medium to large. The results from this study indicate a modest increase in stability when one chooses the larger of the 2 glenoid components.