I am somewhat confused on the metal allergy tests. On the one hand, the consensus (on this site at least) seems to be that a) deep tissue (as opposed to skin) metal allergy is very rare, and b) that in any case there is little /no correlation between metal allergies and a bad resurfacing outcome. This seems confirmed by fact that neither Mr Treacy, nor dr Su require a metal allergy test as a pre-condition to an HR preop. On the other hand, I reda somewhere on this site of someone who was in fact refused a resurfacing by Dr Su after a reported skin reaction to metal (green finger). I also heard of a patient being turned down for HR by Mr McMinn when tested positive for metal allergy (on the basis of a blood test called the LTT?). So i would appreciate any feedback on the following:
1) has anyone who tested positive for metal allergy had gone ahead and done an HR anyway/
2) does the LTT test actually test for deep tissue metal allergies, ie those that are very rare and might cause problems, or only for skin allergies?
3) do other experienced HR doctors (dr gross, de smet etc) perform an LTT blood test or similar to deterimine who qualifies for an HR?
4) is the whole metal allergy a red herring, since it's never come up in THR's and one would think it would given that millions of THRs have been performed and 10-20% of general population has a metal allegrgy.
The adverse reaction that causes elevated Co and Cr ions in the blood/serum (metallosis) has generally been tied to poor placement of the components (usually acetabular cup), causing more degradation of the component. Poorly placed componets have higher wear and thus generate more metal debris, which in turn causes adverse tissue reactions around the joint. The reaction may or may not be related to someone's sensitivity to a metal.
Keep in mind there are about 10 to 15 fairly common metals (heavy metals) in our world that have various levels of toxicity and cause a variety of reactions. Basically, a skin sensitivity to something like silver or gold (which seems odd), has very little to do with joint tissue reacting to excessive CoCr debris (which is uncommon). I suppose that someone who has a skin sensitivity to a metal, might be more sensitive to metal debris in the joint, but I don't think the studies are conclusively showing that.
I haven't heard of the LTT and some, actually a lot of THRs have a poly cup, so that would dilute the metal on metal failure data if you were to assume all THRs were MoM.