sentences:  The third surgery implanted the polypropylene string, which has been since been abandoned as a common procedure in the United States and the European Union because of the potentially unlimited growth side effect, but has been used in breast enhancement surgery procedures in South America.More specifically, in some cases of breast augmentation via the polypropylene method, the breasts may grow at different paces and usually at sometimes dangerously accelerated rates.In her case, they have grown in unison, but their growth rate has steadily slowed over the years.