Quantification of the osmotic expansion in implants filled with polyethylene glycol.

High reoperation rates continue to agonize the field of breast augmentation surgery. Patient dissatisfaction is a contributing factor for reoperations. This is often attributable to patients' desire to be larger after the augmentation. Polyethylene glycol (PEG) is a potential alternative breast implant filler under investigation. It has been shown to swell secondary to osmotic expansion when it is placed in vivo. We hypothesize that there is a finite expansion in this process. An experimental study was designed utilizing an in vitro model to quantify the rate and volume of the osmotic expansion of PEG-filled implants. Seventeen silicone elastomer shells were filled with various percent concentration and molecular weight PEG/saline solutions. These implants were kept in saline baths at varying temperatures to assess the effect of temperature on osmotic expansion. Daily weights were recorded to quantify the expansion and determine if a plateau was reached. Implant expansion was observed to plateau in all groups tested. Implants filled with 85% concentration PEG solutions demonstrated a uniform expansion at a rate of 0.032 to 0.037 g/d. Implants filled with 85% concentration PEG stored at human core temperature (37 degrees C) gained on average 6.2% to 7.6% of their original weight. Implants stored at 4 degrees C expanded to a higher volume than implants stored at 37 degrees C (P < 0.01). Implants filled with 50% concentration PEG solution gained only 2.7% of their original weight (P < 0.01). PEG-filled implants undergo controlled osmotic expansion to a final predictable weight in vitro. Higher concentration PEG induces greater volume expansion. A colder environment also induces greater volume expansion. PEG is biologically inert and may be an alternative filler for breast implants. The predictable expansion process may be beneficial in breast augmentation that may alleviate patient dissatisfaction about breast size once postoperative edema resolves.