Thursday, June 8, 2017

Shoulder arthroplasty and metal sensitivity

Shoulder arthroplasty in the patient with metal hypersensitivity

While a number of case reports have implicated metallic implants as a source of local and systemic allergic reactions, the link between metal hypersensitivity and poorly functioning or failing implants remains uncertain.  Based on their review, these authors recommend a cautious approach to patients with a history of metal hypersensitivity. In such patients they recommend a metallic implant with low to no nickel content. The fact is that the hard cobalt chrome components (from which humeral heads and glenospheres are commonly made) have nickel and the softer titanium components (from which humeral stems are commonly made) do not.

They conclude that (1) the role of metal hypersensitivity in poorly functioning or failing implants remains uncertain, (2) there is no conclusive evidence supporting the positive or negative predictive value of dermal patch testing preoperatively, (3) there is also no consensus on the best preoperative testing modality, (4) there are multiple studies that suggest an association (but not direct causality) between metal hypersensitivity and early implant failure as well as documented dermal manifestations after implantation in patients with metal sensitivities. 

Rather than using skin patch testing (as recommended by some), these authors advocate the use of an implant system  that does not contain nickel in any patient with a history that elicits concern for cutaneous metal hypersensitivity. In patients with a failed TSA, they recommend patch testing once infection and mechanical failure have been ruled out.

The great majority of head prostheses are made of chrome cobalt for a reason. The long term effects of using titanium rather than cobalt chrome heads remains to be determined.

This review prompts consideration of a recent post:

Females with Unexplained Joint Pain Following Total Joint Arthroplasty Exhibit a Higher Rate and Severity of Hypersensitivity to Implant Metals Compared with Males Implications of Sex-Based Bioreactivity Differences 

It has been reported that the prevalence of metal hypersensitivity in 10% of the general population, in 20% of people with well-performing implants, and in 60% of those with failing implants (Metal sensitivity in patients with orthopaedic implants. J Bone Joint Surg Am. 2001 Mar;83(3):428-36.).

These authors conducted a retrospective study of the rates and levels of metal sensitization in a selected group of 1,038 male and 1,575 female subjects with idiopathic joint pain following total joint arthroplasty (TJA) who were referred for sensitivity testing for cobalt, chromium and nickel.

A “no pain” control group consisted of age-matched control subjects who were tested prior to TJA implantation and had no reported history of metal allergy (n = 318).

Females demonstrated a significantly higher rate and severity of metal sensitization compared with males (median lymphocyte stimulation index (SI) among males was 2.8 (mean, 5.4; 95% confidence interval [CI], 4.9 to 6.0) compared with 3.5 (mean, 8.2; 95% CI, 7.4 to 9.0) among females (p < 0.05). Forty-nine percent of females had an SI equal to or greater than 4 (reactive) compared with 38% of males, and the implant-related level of pain was also significantly (p < 0.0001) higher among females (mean, 6.8; 95% CI, 6.6 to 6.9) compared with males (mean, 6.1; 95% CI, 6.0 to 6.3).

Interestingly, a positive sensitivity test was much more common than a positive self-reported history.

While the patients with painful joints had higher mean simulation indices, many had values in the normal range.

Comment: The place of metal sensitivity testing in the evaluation of the painful arthroplasty, the cause/effect relationship of metal sensitivity to implant failure, and the success of revision to implants with different material compositions remain to be determined.

Here's another related post:

What Role Does Metal Hypersensitivity Play in Implant Complications?


Use the "Search" box to the right to find other topics of interest to you.