The Use of Silver-Coated Orthopaedic Implants

Are All Silvers the Same?

Guy V. Morris, BSc, MBChB, FRCS (Tr & Orth); Jakub Kozdryk, MBChB, FRCS (Tr & Orth); Jonathan Gregory, FRCS BSc, MBChB, (Tr & Orth); Lee Jeys, MBChB, MSc (Orth Engin), FRCS (Tr & Orth)

Disclosures

Curr Orthop Pract. 2017;28(6):532-536. 

In This Article

Should Different Silver Technologies Be Used for Different Clinical Scenarios?

It is known that the Agluna® process deposits relatively low levels of silver onto an implant surface compared with electroplating. This allows high levels of silver to passively elute from the surface within hours of surgical implantation, providing high concentrations within the early perioperative period to reduce contamination or infection while reducing the risks of argyria (Figure 4). The senior author has undertaken studies (unpublished) to measure the silver ion concentrations in 40 samples of joint fluid from around silver-coated endoprosthetic replacement of 21 patients; these were analyzed for silver ion levels and correlated with time and volume of joint fluid. An average of 22 μg of silver was eluted 90 hr after implantation of the silver-coated prosthesis, achieving levels of up to 170 ppb at 96 hr. Assuming a linear trend, a prosthesis with a maximum 6 mg inventory of silver coating would exhaust this within 28 mo, and joint fluid silver ion levels were extrapolated to be below 10 ppb by 18 mo from initial implantation. The electroplating technique from Implantcast® (Implantcast GmbH, Buxtehude, Germany) has higher concentrations of silver and a drop in pH is required for this silver to elute into the joint cavity. This may help to prevent early contamination and biofilm formation on the implant. If an infection occurs, high concentrations of silver are eluted.

Figure 4.

A graphical extrapolation of the elution of silver ions from Agluna®-treated implants. Ionic silver levels were measured in postoperative drains, suggesting that the elution of silver ions from implants in vivo is high postoperatively giving the levels in the periprosthetic cavity. However, if extrapolated the silver reservoir in the implant will be quickly reduced in the first few weeks or months from implantation given the low silver levels on the implant.

The authors postulate that the difference in these technologies may be used in different clinical scenarios and suggest an algorithm in which the Agluna® technology, which has a low inventory and shorter term release of silver ions, is employed for short-term infection prophylaxis in standard primary implantation of a tumor prosthesis. In potentially highly contaminated situations (acute infection or staged revision) or in patients with compromised immunity, a higher concentration of silver may be more beneficial and give longer-term protection against recurrent infection.

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