Retrieval Analysis of Failed Metal on Metal Bearings in Total Hip Replacement

Mentor

Douglas E. Padgett, MD

Co-Investigators

Natalie Kelly, MS
Timothy Wright, PhD

Scope

The long term issues with all joint replacements are issues related to wear of the bearing and its consequences such as periprosthetic bone loss and failure of fixation. Improvements in bearings function have focused on enhancement of ultrahigh molecular weight polyethylene as well as the use of alternative bearings such as ceramics and metal on metal. The initial large scale use of metal on metal (MOM) bearings in total hip replacement in the US was with the McKee-Ferrar hip design used in the late 1960’s-1970’s. Early failures of this design lead to its abandonment in favor of polyethylene as the bearing. However, some retrieval analysis suggested that in the proper setting with the right design and material, MOM bearings can demonstrate exceedingly low wear rates. Since this observation, there has been a signifcant increase in the use of MOM as a primary bearing in total hip replacement as well as in hip resurfacing.

The purpose of this investigation will be to examine our retrieval collection and specifically evaluate a prospective series of retrieved MOM bearings. Similar to our studies with retrieved polymers which are graded with light microscopic techniques; damage mapping and damage modes unique to hard bearings will be utlized. The student will correlate the clinical and radiographic demographics wth the damage assessment of the bearing to determine what factors, if any, are associated with wear of this unique surface.

Contact

Anna Mirabal
mirabala@hss.edu