Oxidation of silicone elastomer finger joints

We analyzed the oxygen content of 19 retrieved implants and 6 packaged implants to further understand the mechanism of degradation of silicone elastomer finger joints while in vivo.

Nineteen Swanson (Wright Medical Technology, Arlington, TN) silicone elastomer finger joints were retrieved at revision surgery at an average of 7 years of use. Six packaged and expired implants (5 years after the expiration date) along with the retrieved implants were studied with an elemental analyzer for the total percentage (by weight) of oxygen content.

The retrieved implants showed a mean total oxygen content of 0.41% +/- 0.35%, whereas each of the packaged specimens showed less than 0.1% total oxygen content. Eight of the 19 retrieved implants remained unoxidized. There was no correlation between implant fracture and the oxygen content of the retrieved implants.

Our results suggest that silicone elastomers are oxidized in vivo. Although such oxygen embrittlement may have implications in compromising silicone elastomer material mechanics during in vivo use, our data indirectly suggests that mechanical factors also have an important role in the final fracture of the silicone elastomer implant.