Surface Deformation Analysis of End-to-End Stapled Intestinal Anastomosis

Background. Stapling devices for creating anastomosis in internal organs are commonly used during surgery. Despite the obvious advantages of shortened procedure duration and fewer complications to manual suturing, staple-line leakage during intestinal anastomosis likely relates to the interaction between the staples and the tissue and to the tissue mechanical properties. The authors studied the deformation pattern close to the anastomosis to learn more about the mechanism involved in leakage. Methods. End-to-end anastomosis in pig small intestine was done using 21-mm circular staplers. Distension with pressure up to 100 cm H₂O was done on the anastomosed segment. Surface markers were tracked using a microscope and a CCD camera. Circumferential and longitudinal strains were computed. Results. The staples restricted the deformation both in circumferential and longitudinal directions and induced a heterogeneous strain distribution. Circumferential strains were bigger between the staples (range 0.5-1) than inside the staples (range 0-0.3). The longitudinal strain ranged from 0 to slightly negative between the staples, indicating longitudinal compression. The negative strains turned into positive strains with increasing distance from the anastomosis. Further away from the anastomosis the longitudinal strain was in the range 0.3 to 0.5. Conclusion. The surface strain field was heterogeneously close to the stapled anastomosis. The longitudinal compression between staples in the longitudinal direction during inflation may have a beneficial effect preventing leakage, a phenomenon that needs further studies. The method may be useful in the design and validation of new staplers.