A comparison of the disassociation strength of modular acetabular components

Five short-term in vivo disassembly of two-piece acetabular cup designs have been reported. This study evaluates the liner retention strengths of eight contemporary cup systems. Both push-out (663 +/- 65.5 pounds force to 29 +/- 1.4 pounds force) and lever-out (684 +/- 114 inch-pounds to 43 +/- 1.5 inch-pounds) test modes show a wide variation in retention strength. Repeat liner separation testing demonstrates a 26% and 32% respective decrease in locking mechanism integrity. These findings indicate that reseating modular liners at the time of surgery or reassembling a previously separated liner should be avoided.