Capsular compliance: a measure of a "hard" prosthesis.

Capsular contracture prevents a natural "feel" to an augmented breast and is frequently a source of patient and physician dissatisfaction postoperatively. The degree of hardness of a breast is difficult to quantitate. We have developed a rodent model that measures the pressure rise in a capsule in response to increasing intraluminal volume, generating a pressure-volume curve. The curve's break point determines the volume contained within the capsule and the slope of the steep part of the curve to the right of the break point determines capsule resistance to stretch and deformation. In a group of 14 rats, resistance to distension increased progressively over a 14-week period whereas capsule surface area, break point volume, and resting intraluminal pressure remained relatively constant. This model allows the assessment of changes in capsule contracture over time without having to kill the animal.