Investigation of silicone oil and fumed silica in an adjuvant animal model.

Human adjuvant disease is the label given to a syndrome that resembles a connective tissue disease such as scleroderma and that has been hypothesized to follow augmentation mammoplasty with silicone gel implants or silicone with adulerants. To date, there is no proof that pure silicone is the cause of these symptoms. The cases presented in the literature suggest a comparison to the events seen in the rat adjuvant arthritis model. Male Lew/SsN rats (n = 65) were used. To evaluate both the adjuvant and antigenic properties of the gel implant, variations of the standard Freund's complete adjuvant inoculum were prepared. Tested were the abilities of low molecular weight silicone to act as an adjuvant and for fumed silica to act as an antigen by modifying a rat adjuvant arthritis model to include silicone and fumed silica. On day 0, 0.25 ml of each inoculum was injected intradermally into the plantar aspect of the hindfoot of each rat. The foot diameter was recorded at each time period, compared with the contralateral hindfoot, and normalized to controls at regular time periods over the course of 120 days. Silicone oil did not act as an adjuvant. Furthermore, fumed silica alone did not act as an antigen; however, it is capable of eliciting a reaction that is both delayed and uncharacteristic of the rat adjuvant arthritis model. These results indicate that "human adjuvant disease" may be inappropriate and misleading.