Metal Ions/Metal Implants
The first is metallosis. This is when there is a manufacturing or alloy or placement problem that leads to high metal ion or particle production. This causes localised inflammation, swelling, pain and tissue necrosis, but not usually implant loosening. It is something everyone and anyone can have although the threshold level at which the 'overload' becomes a problem will vary. Some alloys are more 'toxic' than others. It is NOT an allergy! The second is a true 'allergic' reaction and this may occur at very low metal ion levels. It is called ALVAL and seems exceptionally rare.
Scientists knew for long that body tissues’ reaction to wear products of metal-metal hip joints, compared with reaction to wear products of polyethylene or ceramic total hips, is different. Microscopic examination of tissues around the failed metal-metal total hips showed that body reacts to presence of metallic wear products by strangling the small arteries in the tissues around the metal on metal hip joints. Death of these soft tissues follows. If the patient is allergic to metals contained in the metal-metal total joint the death of the tissues may be extensive.
Also let me note that the concern about metal ions in pregnancy is actually not about mutation of the sperm or egg, but the exposure to metal ions affecting the developing fetus. That is why they looked at trans-placental transfer. They saw that there were increased levels of ions in the fetal side of the placenta, but thankfully, no abnormalities have been seen in the children.