Metal release and corrosion effects of modular neck total hip arthroplasty

Abstract

Modular neck implants are an attractive treatment tool in total hip replacement. Concerns remain about the mechanical stability and metal ion release caused by the modular connection. Five different implant designs were investigated in an experimental set-up. In vivo conditions were simulated and the long-term titanium release was measured. Finally, the modular connections were inspected for corrosion processes and signs of fretting. No mechanical failure or excessive corrosion could be identified for the implants tested. The titanium releases measured were extremely low compared to in vivo and in vitro studies and were not in a critical range.Résumé Dans les prothèses totales de hanche l'utilisation d'implants avec col modulaire est d'une utilisation fré-quente et pratique. Néanmoins, cette utilisation laisse persister des doutes sur la stabilité mécanique et sur le relargage des ions métalliques. 5 différents implants ont été étudiés en reproduisant les conditions in vivo, en mesurant le relargage de titane et en évaluant la corrosion et les lésions du col. Ce travail n'a pas permis de mettre en évidence d'échec secondaire à une corrosion excessive, et les taux de titane sont restés extrêmement bas dans les limites de l'acceptable.

Proximal Component Modularity in THA—At What Cost?: An Implant Retrieval Study

“…Third, we did not perform in vitro testing to elucidate the mechanism of fretting, micromotion, or corrosion peculiar to each of the modular designs. This type of testing is technically challenging, however, and commonly such in vitro studies have concluded modular-junction degradation is of little clinical relevance [17,18,22,25], which contrasts to the findings of this retrieval study. Finally, we could not retrospectively collate metal ion levels, which may indicate the degree of systemic metal exposure.…”

“…We found the severity was greater at the neck-stem junction than at the head-neck junction. This is not unexpected as the forces at the head-neck junction are transferred through a spherical bearing resulting in relatively low contact stresses, whereas there is eccentric loading at the neck-stem junction, and depending on the offset and length of the neck, these stresses can be high [7,17,22] (Table 6). In this regard, one case study of 5000 Ti modular-neck prostheses reported an implant neck fracture rate of 1.4% [7].…”

“…Even though the analysis of micro-CT data of representative samples showed good congruency, crevices remain that may be subject to crevice corrosion or mechanically assisted crevice corrosion in the presence of fretting. In vitro studies described an insignificant amount of corrosion and fretting at the modular head-stem junction [9,22] while a similar in vitro study of the effect of machine surface finish on fretting and corrosion showed a negative correlation with surface roughness but also concluded the degree of degradation is ''within a clinically non-critical range'' [17]. These studies are in direct contrast to our study where revision of some devices can be attributed to degradation at the neck-stem taper junction.…”

“…Determination of fretting at the junction in response to higher applied stresses Kretzer et al [17] Simulation study (n = 5)…”

Corrosion at the Head-Neck Taper as a Cause for Adverse Local Tissue Reactions After Total Hip Arthroplasty

“…Subsequent design and manufacturing improvements minimized these concerns, allowing a nearly universal adoption of modular femoral head-neck tapers in modern total hip arthroplasty. As a result of these design improvements, corrosion at this modular taper interface has received relatively little attention over the last decade 5,11,12 . Historically, a diagnosis of corrosion at this femoral head-neck interface has been made only on the basis of retrieval analysis [2][3][4][5]8,[13][14][15][16][17][18] or, rarely, in cases of catastrophic failure 2,7 .…”