Introduction and Aims: Modular acetabular designs are widely used in THA procedures and now accommodate highly cross-linked polyethylene liners. However, polymer processing influences material properties, including a decrease in resistance to crack propagation. This study comparatively evaluated locking mechanism integrity of three modular acetabular designs, which employ conventional and highly cross-linked polyethylene liners.

Method: Locking mechanism integrity was established for both conventional and highly cross-linked polymers through push-out (n=3) and lever-out (n=3) testing of fully seated liners. When possible, liners were reinserted and forcibly disassembled.

Results: The push out and lever out strengths measured for the highly cross-linked polyethylene acetabular liners in this study indicated that short-term disassociation of these components is no more likely than that for the conventional polyethylene liners of each design. Student t-tests confirmed the null hypothesis. In addition, when compared to the strengths of clinically successful modular designs none of the systems evaluated presents any great risk of short-term disassociation. Significant reductions in locking mechanism strength after liner reinsertion were also noted for both polymers.

Conclusion: Short-term static disassociation failure of highly cross-linked polyethylene liners were found to be equivalent to conventional polyethylene liners. Given their touted improvement in wear reduction, they would appear to be a reasonable alternative in the young patient requiring THA. Secondarily, neither conventional nor highly cross-linked polymers should be re-inserted for any reason at the time of surgery.