This retrieval study documents taper damage at modular interfaces in retrieved MOM THA systems and investigates if increased modularity is associated with increased fretting and corrosion. One hundred thirty-four (134) heads and 60 stems (41 modular necks) of 8 different bearing designs (5 manufacturers) were analyzed. Damage at the shell–liner interface of 18 modular CoCr acetabular liners and the corresponding 11 acetabular shells was also evaluated. The results of this study support the hypothesis that fretting and corrosion damage occurs at a variety of modular component interfaces in contemporary MOM THAs. We also found that modularity of the femoral stem was associated with increased damage at the head. An analysis of component and patient variables revealed that dissimilar alloy pairing, larger head sizes, increased medio-lateral offsets and longer neck moment arms were all associated with increased taper damage at the modular interfaces.

Background Gross trunnion failure (GTF) is a rare complication in total hip arthroplasty reported across a range of manufacturers. Specific lots of the Stryker LFIT Anatomic cobalt chromium alloy (CoCr) V40 femoral head were recalled in August of 2016. In part, the recall was based out of concerns for disassociation of the femoral head from the stem and GTF. Methods We report on 28 patients (30 implants) with either GTF (n=18) or head-neck taper corrosion (n=12) of the LFIT CoCr femoral head and the Accolade TMZF femoral stems. All of these cases were associated with adverse local tissue reaction (ALTR) requiring revision of the THA. Results In our series, a conservative estimate of the incidence of failure was 4.7% (n = 636 total implanted) at 8.0±1.4 years from the index procedure. Failures were associated with a high offset 127° femoral stem nec k angle and increased neck lengths. 43.3% (13/30) of the observed failures included implant sizes outside of the voluntary recall (27.8% (5/18) of the GTF and 75.0% (8/12) of the taper corrosion cases). Serum cobalt and chromium levels were elevated (Cobalt: 8.4±7.0μg/mL; Chromium: 3.4±3.3μ/L; Cobalt/Chromium ratio: 3.7). MARS MRI demonstrated large cystic fluid collections typical with ALTR. During revision, a pseudotumor was observed in all cases. Pathology suggested a chronic inflammatory response. Impending GTF could be diagnosed based on aspiration of black synovial fluid and an oblique femoral head as compared to the neck taper on radiographs. Conclusion In our series of the recalled LFIT CoCr femoral head, the risk of impending GTF or head-neck taper corrosion should be considered as a potential diagnosis in a painful Accolade TMZF THA with unknown etiology. Almost half of the failures we observed included sizes outside of the voluntary recall.

These results suggest that fretting and corrosion damage is insensitive to differences in taper size. The final model derived explains almost half of the fretting corrosion damage observed and identifies contributing factors that are consistent with other in vitro and retrieval studies.

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This study documents the surface changes and tissue reactions for retrieved PEEK rod stabilization systems. Permanent indentations by the set screws and pedicle screws were the most prevalent observations on the surface of explanted PEEK rods.

We observed evidence of in vivo oxidation in both HXLPE and control tibial inserts. We found no association between the levels of oxidation and the clinical performance of the HXLPE tibial components. The findings of this study document the revision reasons, surface damage modes, and oxidative behavior of sequentially annealed HXLPE for TKA.

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