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Metal on Metal Metal on Metal Local Tissue Reaction is Associated with Corrosion of Head Taper Junction

Discussion in 'Allergies and MoM articles' started by Josephine, May 4, 2016.

  1. Josephine

    Josephine FORUM ADMIN, NURSE DIRECTOR Administrator
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    Metal on Metal Local Tissue Reaction is Associated with Corrosion of Head Taper Junction
    POSTER NO. P068
    C. A. Engh, Jr, MD, Alexandria, VA
    Henry Ho, MSc, Alexandria, VA
    Kevin B. Fricka, MD, Alexandria, VA
    William J. Peace, MD, Denver, CO


    INTRODUCTION: Corrosion at the head/neck taper interface has been associated with elevated ion levels and revision total hip arthroplasty (THA). Elevated ion levels, tissue masses, and osteolysis have been reported in failed metal-on-metal (MOM) hips. These failures are not completely understood at this time. It is possible that taper junction corrosion could be a contributor to MOM THA failure. We evaluated the extent of taper corrosion in large diameter MOM femoral heads retrieved for various reasons. Our hypothesis was that corrosion would be associated with the occurrence of MOM adverse local tissue reaction (ALTR).

    METHODS: Twenty-nine retrieved MOM bearing CoCr heads from a single manufacturer were analyzed. There were 19 (65%) 36mm and 10 (35%) 40mm diameter heads in this study. All retrieved heads had a 12/14 taper and were mated with a CoCr stem. Mean age at revision was 56.7 years (range 36-79). Mean implantation time was 2.5 years (range 0.04 to 8.03). Eleven of the heads came from patients who were diagnosed with ALTR. Taper corrosion was visually graded with a 5 point scale by three reviewers who were blinded to the revision diagnosis. The grading scale is a modification of a previously published scale. In addition corrosion products seen outside of the taper zone were recorded. Grading score of taper corrosion: 1 (NONE) - No visual corrosion observed; 2 (MILD) <30% of engaged taper surface discolored/dull; 3 (MODERATE)- >30% of engaged taper surface discolored/dull OR <10% of engaged taper surface has black/dull gray debris, pits or etch mAK; 4 (SEVERE) - >10% but <50% of engaged taper surface has black/dull gray debris, pits or etch mAK; 5 (EXTREME)- >50% of engaged taper surface has black/dull gray debris, pits or etch mAK.

    RESULTS: Of the 29 retrieved heads, 14% had no visible corrosion, 41% had mild, 3% moderate, 21% severe and 21% had an extreme degree of corrosion. The length of implantation time was correlated with corrosion score (p=0.012 spearman’s rho correlation test). Nine heads had corrosion that extended beyond the taper junction. Eight of those nine had a MOM adverse tissue reaction. Corrosion extending beyond the taper junction area correlated with ALTR (p<0.01 spearman’s rho correlation test). The mean corrosion score was 4.36 for cases with ALTR and 2.06 for other cases (p<0.01, Kruskal wallis test ).

    DISCUSSION AND CONCLUSION: A total of 42% of our retrieved MOM heads had severe to extreme taper corrosion. Patients that had an adverse local tissue reaction to a MOM bearing had more corrosion and were more likely to have corrosion products outside of the taper junction. Since we found that corrosion worsens with time we are concerned that MOM ALTR failures will also increase with longer follow up.

    Image 1: Example of taper corrosion score 1
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    Image 2: Example of taper corrosion score 5 with corrosion extended outside of taper
    Image18259_opt.jpeg
     

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