Home Forums Other Specialities Orthopaedics Should We Stop Using Metal on Metal Total Hip Replacement

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    Kan Badrinath
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    Orthopaedic Surgeons have been arguing about the merits of using metal on metal versus metal on polyethylene total hip jointsfor many years without reaching any consensus. Having worked with Mr Watson Farrar who was involved with the design of the original Mckee-Farrar MOM hip joint I have seen many patients with MOM hips coming back a few years later with adverse tissue reaction attributed to the metal particles. I have therefore never been keen on using any MOM total hip joint. However over the years following a lot of research manufacturers have been introducing a variety of new MOM joints which are supposed to last longer with fewer untoward reactions.

    In a 2014 issue of Bone and joint journal (July 2014, 96-B) a paper titled “A comparative assessment of small-head metal-on-metal and ceramic-on-polyethylene total hip replacement” by A.Lübbeke, MD, et al from Switzerland was published. They compared the incidence of complications such as infection, dislocation, revision, adverse local tissue reactions, mortality and radiological and clinical outcomes in small-head (28 mm) MoM and ceramic-on-polyethylene (CoP) THRs up to 12 years post-operatively.

    The prospective study included 3341 THRs in 2714 patients. The mean age was 69.1 years (range 24 to 98) and 1848 (55.3%) were performed in women, with a mean follow-up of 115 months (18 to 201). There were 883 MoM and 2458 CoP bearings. The occurrence of infection, dislocation and all-cause mortality remained similar over the whole period of study. The incidence of femoral osteolysis and clinical outcomes were also comparable after five and ten years. However after 10 years a significantly lower survival of the Metal on Metal group than of the Ceramic on Polyethylene group (91.7% vs 97.7%) was noted in their study.

    They found a higher rate of infection in the MoM group, although the difference was not statistically significant. Many think the metal debris predisposes to infection. There have been many reports of Adverse Reaction to Metal Debris (ARMD) and Pseudo tumors around the implant following use of large head MOM hips. These again have been attributed to excessive metal wear and/or metal hypersensitivity reaction. In this present study, the authors found ARMD in 1.1% and pseudo tumour formation in 0.5% respectively (38.5% and 15.4%) of the revision cases in this group. All pseudo tumours occurred in MOM THRs revised 12 years post-operatively or later.

    They conclude that the presence of an adverse response to metal debris seen in the small-head MOM group at revision is a cause for concern and close follow-up, even after ten years, is strongly recommended.

    Would you still consider using a Metal on Metal Total Hip Replacement for your patient? In spite of all the improvements, I am sure there are many like me who will be reluctant to use a MOM joint.

    Badri
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