The force deformation characteristics of externally loaded subcutaneous tissue

Abstract

White, female, weanling pigs were anesthetized and maintained on a surgical plane of anesthesia. Wick-in-needle catheters were inserted over the point of the wings of the ilia and the dorsal spinous process of the lumbar vertebra to measure tissue fluid pressure. Interface pressures were measured using a balloon catheter which was inserted between the pressure applicator and the skin. Loads of 4 and 8 kg were applied. Recordings were made at baseline, 4 kg, 8 kg, and weight off. Ratios of interface pressure to tissue pressure were calculated and found to be approximately 3.6 for the wings of the ilia and 2.4 for the dorsal spinous process of the last lumbar vertebra. Deformation measurements were made using histological techniques and stereo photogrametry. No characteristic deformation patterns were seen for any of the load conditions. Quantitative deformation measurements were made at all load conditions. Effects on the deformation of the tissue were elucidated due to the application of load. A second factor of tissue creep was also found to have an effect on tissue deformation.