Patients with Stryker ABGII or Rejuvenate hip implants could see a wide variance between the cobalt and chromium levels with the cobalt levels being considerably more elevated. The probable reason for the difference in these numbers is that the wear in the Rejuvenate and ABGII hip implants does not come from the cup and ball portion of the joint rather it comes from the stem and neck. The design of these Stryker devices implements a Morse taper between the stem and the neck.  The Morse taper is a slightly angular junction which the physician hammers into the stem until it is snug, then hammers again so it will lock tightly.