Most of titanium alloys are considered biocompatible such as Ti64, but there are degrees to biocompatibility. The Ti64 material is considered toxic for the long term due to Al and V ions emission within body fluids. In addition to that CoCr alloy was also recently banned from medical use du to the high toxicity of Co.  The alternative solution is to look for an alloy that fits the need of the human body such as a long life.