Stability of two versus three peripheral pegs of the glenoid component in modern total shoulder arthroplasty

Purpose: In total shoulder arthroplasty (TSA), the optimum number of peripheral pegs required for stability in the glenoid component is unknown. This study compared the stability of two versus three peripheral pegs in cemented glenoid components possessing a central press-fit peg. Methods: Six unmodified glenoid components with three peripheral pegs, a large, central press-fit peg and six modified glenoid components with one inferior peripheral peg sharply removed were cemented into bone substitute polyurethane blocks. A modified rocking-horse test was completed by comparing superior- and inferior-edge displacement before and after 100,000 vertical motion cycles. Then, a torsional failure test applied 2 N axial load, followed by a rotational force to the glenoid component at 0.5 °/s until failure. Results: Modified rocking-horse testing showed no statistically significant edge displacement at the superior or inferior aspect of the glenoid component before or after testing. During torsional testing, peak torque and degrees of rotation at failure also showed no significant difference. Conclusion: Two peripheral pegs offer equivalent stability as three peripheral pegs, as assessed by cyclic rocking and rotational failure testing. Fewer peripheral pegs during glenoid component implantation may lead to less dissection, less strain on soft tissues and decreased operative time.