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J Orthop Res. 2015 Dec;33(12):1868-74. doi: 10.1002/jor.22970. Epub 2015 Jul 25.

Shorter, rough trunnion surfaces are associated with higher taper wear rates than longer, smooth trunnion surfaces in a contemporary large head metal-on-metal total hip arthroplasty system.

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Newcastle University, Newcastle, United Kingdom.
Department of Orthopaedics, University Hospital of North Tees, North Tees, United Kingdom.
FDA, Silver Spring, Maryland.
Biomedical and General Engineering, California Polytechnic State University, San Luis Obispo, California.
North Tees Explant Centre (NTEC), University Hospital of North Tees, North Tees, United Kingdom.


Taper wear at the head-neck junction is a possible cause of early failure in large head metal-on-metal (LH-MoM) hip replacements. We hypothesized that: (i) taper wear may be more pronounced in certain product designs; and (ii) an increased abductor moment arm may be protective. The tapers of 104 explanted LH-MoM hip replacements revised for adverse reaction to metal debris (ARMD) from a single manufacturer were analyzed for linear and volumetric wear using a co-ordinate measuring machine. The mated stem was a shorter 12/14, threaded trunnion (n=72) or a longer, smooth 11/13 trunnion (n=32). The abductor moment arm was calculated from pre-revision radiographs. Independent predictors of linear and volumetric wear included taper angle, stem type, and the horizontal moment arm. Tapers mated with the threaded 12/14 trunnion had significantly higher rates of volumetric wear (0.402 mm3/yr vs. 0.123 mm3/yr [t=-2.145, p=0.035]). There was a trend to larger abductor moment arms being protective (p=0.055). Design variation appears to play an important role in taper-trunnion junction failure. We recommend that surgeons bear these findings in mind when considering the use of a short, threaded trunnion with a cobalt-chromium head.


arthroplasty; explant analysis; metal-on-metal; taper-junction

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