The official reason for the recall was the higher-than-normal risk of corrosion and fretting at the neck juncture of the implant, however since that time many more issues have come to light. The four small metal trunnions located at either end of the neck portion of the Rejuvenate were found to suffer corrosion when body fluids become trapped underneath. Further, higher levels of cobalt were found to be coming from the Morse taper which is a slightly angular junction between the stem and the neck.

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.