Modularity of metal-on-metal total hip Arthroplasty: a flawed concept?

Ilo, Kevin (2024) Modularity of metal-on-metal total hip Arthroplasty: a flawed concept? Doctoral thesis, University of East Anglia.

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Abstract

Modular implants have been utilised in total hip arthroplasty (THA) to replicate patient biomechanics. Metal debris and its effects are unwanted consequences. Attention has focused on modular junctions as reports of corrosion could be a source of further metal debris release. This PhD by Publication thesis presents four studies reporting analyses of retrieved modular-neck and metal-on-metal (MOM) implant and one systematic review performed recently on custom femoral stems; a better option than modular neck stems?
Study 1 reported on corrosion found on the backside of two different modular metal liners, each highlighting a different corrosion pattern, but both designs illustrate greater corrosion at the equator rather than the pole.
Study 2 reported on one design of a recalled modular metal liner, highlighting a pattern of corrosion that was as a result of anti-rotation tabs for the polyethylene liner used for the same acetabular component.
Study 3 reported on retrieval analysis of MOM implants from one manufacturer but with different modularity. There was a higher incidence of adverse local tissue reactions amongst modular implants, with low levels of bearing surface material loss but increase severity of corrosion at the neck-stem taper junction.
Study 4 reported on the effect of modularity on cobalt:chromium ratio. Implants with an additional modular junction had a significantly greater cobalt:chromium ratio.
Study 5 was a systematic review on custom femoral stems, highlighting promising implant survival and functional outcomes but a lack of direct comparative studies with standard implants and cost-effectiveness.
Although MOM and modularity have advantages, retrieval analysis shows modular neck junction susceptibility to corrosion. Mechanically assisted corrosion is likely the main contributor, but modular neck-stem junctions are susceptible to galvanic corrosion, crevice corrosion, mechanical stress, and design intolerances, making modular neck MOM implants a flawed concept. Other bearing surfaces have grown in popularity and custom-made femoral stems have been designed as a solution for modular-neck MOM implants.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Medicine and Health Sciences > School of Health Sciences
Depositing User:	Nicola Veasy
Date Deposited:	20 May 2025 08:29
Last Modified:	20 May 2025 08:29
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99308
DOI:

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