Re: cobalt versus titanium in surf devices

[Guest guest]

I will try to " translate " this as best I can. Again, this is a

" test-tube " experiment, with translation to the real human body left

to one's imagination.

> Metal toxicity from sources such as orthopaedic implants was

> investigated in terms of immune system hyper-reactivity to metal

> implant alloy degradation products. Lymphocyte response to serum

> protein complexed with metal from implant alloy degradation was

> investigated in this in vitro study using primary human lymphocytes

> from healthy volunteers (n = 10).

Somehow they are measuring the response of white blood cells to

two common orthopedic alloys.

>Cobalt chromium molybdenum alloy

> (Co-Cr-Mo, ASTM F-75)

this is the common Cobalt-Chrome

and titanium alloy (Ti-6Al-4V, ASTM F-136)

This is the common titanium alloy, which includes 6% aluminum and 4%

vanadium.

> beads (70 microm) were incubated in agitated human serum at 37

> degrees Celsius to simulate naturally occurring metal implant alloy

> degradation processes. Particulate free serum samples, which were

> incubated with metal, were then separated into molecular weight

based

> fractions. The amounts of soluble Cr and Ti within each serum

> fraction were measured and correlated with lymphocyte proliferation

> response to the individual serum fractions. Lymphocytes from each

> subject were cultured with 11 autologous molecular weight based

serum

> fractions either with or without added metal. Two molecular weight

> ranges of human serum proteins were associated with the binding of

Cr

> and Ti from Co-Cr-Mo and Ti implant alloy degradation (at < 30 and

> 180-330 kDa). High molecular weight serum proteins (approximately

180

> kDa) demonstrated greater lymphocyte reactivity when complexed with

> metal released from Co-Cr-Mo alloy and Ti alloy than with low (5-30

> kDa) and midrange (30-77 kDa) serum proteins. When the amount of

> lymphocyte stimulation was normalized to both the moles of metal and

> the moles of protein within each fraction (Metal-Protein Complex

> Reactivity Index, MPCRI), Cr from Co-Cr-Mo alloy degradation

> demonstrated approximately 10 fold greater reactivity than Ti in the

> higher molecular weight serum proteins (approximately 180-250 kDa).

> This in vitro study demonstrated a lymphocyte proliferative response

> to both Co-Cr-Mo and Ti alloy metalloprotein degradation products.

> This response was greatest when the metals were complexed with high

> molecular weight proteins, and with metal-protein complexes formed

> from Co-Cr-Mo alloy degradation.

I don't understand this entirely, but it basically says the white

blood cells responded more to a fixed amount of Co-Cr than to the same

amount of Titanium, but what the implication is of that I don't know.

One thing that is not factored-in was the body's ability to remove the

" degradation products " , i.e. combinations of proteins with ions from

the metal bits. Cobalt, for example, is quite corrosion resistant and

removed quite efficiently by the kidneys, concentrations may not reach

as high as what they got in the test-tubes.

Hope that helps.

-

[Guest guest]

Hello Group members,

My name is Mark Shiffner, I am a PA for Dr. Kennedy in

Sarasota, FL. We are currently performing the surface replacement

procedure.

I found this group after corresponding with one of your members, it

looks like a great forum for surface replacements.

RE: titanium... This element is actually well recieved by bone, and

is the primary componant of ingrowth and ongrowth implant systems.

The black referred to in an earlier post pertains to the wear

particulate debris in THA implants that had a titanium femoral head,

this was a short lived implant. I have also seen this occur in

revision knee surgery when the femoral componant (CoCr) wore out the

poly bearing and began to wear on the tibial tray (Ti).

I am looking forward to following this group.

Mark Shiffner, PA-C

Sarasota, FL

GatorPA@...