Scientific Publications by FDA Staff

J Orthop Res 2015 Dec;33(12):1868-74

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.

Brock TM, Sidaginamale R, Rushton S, Nargol AV, Bowsher JG, Savisaar C, Joyce TJ, Deehan DJ, Lord JK, Langton DJ

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 ([0.123 mm3 /yr vs. 0.402 mm3 /yr] [t = -2.145, p = 0.035]). There was a trend to larger abductor moment arms being protective (p = 0.055). Volumetric wear rate was significantly higher in the tapers mated to the shorter, threaded 12/14 trunnions. 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.