Metal allergies and knee replacements


Nurse Director
Jun 8, 2007
The North
United Kingdom United Kingdom
Re: Nickel allergy - there is only a small percentage of people with nickel allergy.

First, don't worry too much about this now. Good standards have not established to identify possible allergies to metals in orthopaedic implants. Rather complete your course of healing for a typical knee replacement, and if you were having significant issues after about a year (post-op) then it would be reasonable to consider issues with allergies.

If you have an allergy and need a joint replacement, don't panic - there are devices suitable for nickel sensitive patients. The metal parts are coated with ceramic.

BIOLOX® delta ceramic implants
Biolox(R) delta.jpg
ceramtec knees.JPG

Smith and Nephew Oxidized Zirconium knee replacement

oxinium verilast knee.JPG

From Smith and Nephew website

"If it is determined that an implant made with VERILAST◊ technology is right for you, the femoral - or thighbone portion - of your implant will be made from OXINIUM Oxidized Zirconium - a patented and award winning ceramicised metal alloy that Smith & Nephew spent more than a decade developing.

During manufacture, OXINIUM implants undergo a process that transforms the implant's surface into a hard, ceramicised metal - while still retaining all of the durability of the underlying metal. In addition to being more durable than a true ceramic, this metal implant's ceramicised surface is more than twice as hard and therefore twice as resistant to the kind of scratching that can cause a cobalt chrome implant to wear out before its time."

If you are having problems with an already implanted device which you think may be related to allergy, steps are:
1. find out what kind of prosthesis you have and its make up
2. either you or your surgeon need to contact the Metal Allergy Testing Laboratory. which is in Chicago
3. a blood sample has to be mailed to them overnight mail
(Thanks to Maryo for this info)

LINK Lima News
Total knee arthroplasty may fail due to multifactorial causes which, however, all relate to either biological or mechanical conditions. Biological causes include allergic reactions to metal, as documented in studies. Around 10-15% of the general population is allergic or hypersensitive to metal. However, the phenomenon is not always predictable in case of joint replacements and the link between cause and effect in implant loosening cannot always be demonstrated with any degree of certainty.

All metals in contact with biological systems corrode and consequently release ions. In predisposed individuals, these ions may activate the immune system by forming metal-proteins and eventually generate delayed hypersensitivity. Nickel, cobalt and chromium are the most common allergens found in metal knee replacement devices. Titanium and vanadium as well as certain constituents of bone cement have been reported to elicit hypersensitivity responses.

Numerous clinical trials have looked into possible correlations between allergy and implant failure, however, none have so far proven a definite link between the two events.

One of the main challenges lies in the lack of universally accepted methods of investigation. Certain in vitro tests, based on the reactivity of the cells of the immune system to metal-proteins, have been proposed as diagnostic methods for evidencing metal allergy.

These are expensive procedures that can only be performed by highly qualified centres that can analyse only certain materials. As an alternative, epidermal testing (patch tests) are cheaper and can be used to assess a larger number of elements simultaneously. Patch tests are the most commonly used method for diagnosing metal allergy.

Recently, a trial was conducted by the Rizzoli Orthopedic Institute in Bologna (Italy), to assess the frequency of skin sensitivity in patients with knee implants, and to measure any impact this might have on the survival of the implant; the patch tests used the elements present in cobalt‐chromiummolybdenum (CoCrMo) and titanium-aluminium-vanadium (TiAlV) alloys, and in bone cement.

The study included three patient populations:
- one group of candidates awaiting a total knee replacement, studied prior to the procedure,
- another group of patients with stable knee implants and
- a third group of patients with clear evidence of loosening of the prosthesis.

The frequency of metal sensitivity in the patients awaiting surgery was similar to that of the general population and the most common sensitizers were nickel, followed by cobalt, chromium and manganese. The tests were significantly more positive in the patients with knee implants, both stable and mobilized.

More specifically, there was a higher frequency of positive reactions to vanadium in the stable implants with at least one component (the tibial plateau) in titaniumaluminium-vanadium alloy.

A higher percentage of positive reactions to manganese was found in patients with loosening of the prosthesis in cobalt-chromium-molybdenum (CrCoMo). It should be noted that the percentage of manganese in this alloy is very low, around just 1%.

It was also interesting to observe that the same group of patients with loosening of the CrCoMo implant was found to have a more frequent positive patch test to vanadium than the general population. This finding could be due to cross-reactivity to vanadium and other elements such as manganese. These results could confirm the assumption that it is the individual’s genetic predisposition that is responsible for sensitisation responses, rather than a concentration of the sensitising agent. In this study, patch testing was unable to discriminate between stable and loose implants.

However, implant loosening was observed to be 4 times more frequent in patients who reported symptoms associated with allergic reaction to metal before the knee replacement surgery. In conclusion, patients with a positive history of metal allergy should be assessed for possible sensitivity to the elements present in the metal alloys of knee implants.

Patch testing is a valid rapid screening exam for all the elements contained in current total knee replacement. Nonetheless, this does not rule out the possible need for more extensive in vitro diagnostic testing in doubtful cases or to confirm reactivity to a small number of elements.

NB: With respect to metal-allergic patients, an excellent solution might be found in the use of a ceramic femoral component combined with an “all-poly” polythene tibial component. This is the only type of coupling that will rule out the risk of implant elements triggering metal allergies. The use of new ceramic materials such as Biolox(R) delta (CeramTec AG, Stuttgart) appears to solve the structural limits posed by the fragile nature of ceramics, which currently requires fixation with bone cement.

There is also more on this page on the BoneSmart website
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