Understanding Failure Mechanisms for Two Colorectal Anastomosis Techniques

Colorectal Surgery continues to be one of the most common gastrointestinal surgeries performed in the US. A common complication known as Anastomotic Leakage (AL) that threatens up to 30% of patients with this surgery. Many cases of AL can decrease the quality of life for patients or extensively extend hospital stays, and in many cases, lead to death. Researchers have studied this complication in clinical trials, yet few studied the mechanics of stapled anastomosis in controlled environments. The purpose of this research was to understand the mechanical interaction between the staples and the tissue, and to eventually apply it in a Finite Element Model (FEM). In doing so, the aim is to develop a resource “playground” for staple manufacturers to test and enhance current designs of staples and different anastomosis techniques before going to clinical trials. Firstly, to understand the colon tissue, an anisotropic -hyperelastic material model was introduced and calibrated to tensile testing data collected from freshly harvest porcine colon tissue. An initial FEM was developed to show the effectiveness of the model in predicting the stress and strain properties that were experimentally verified. Next, colon specimens were harvested from porcine tracts to compare two types of anastomosis techniques, End to End (EE) and End to Side (ES). Additionally, a control section of the tract was harvested to be used as a benchmark of a healthy colon tract. These specimens were subjected to burst testing to simulate the inflation of the colon, and burst pressures were recorded when AL occurred. The results showed no difference in the burst pressures of the EE and ES techniques, however showing more similar behavior of time to failure and expansion of ES and Control vs EE. Using this data, three FEM were developed to compare to the three specimens subjected to burst testing. The results showed a clear correlation to the experimental data.