Participation of the intestinal layers in supplying of the mechanical strength of the intact and sutured gut

The tensile properties of the intact and sutured human intestine were examined using Instron 1122 tensimeter on 471 cadaveric and 98 surgically removed specimens. By a constant strain rate method two maxima curves were received, which permit examination of the intestinal wall as a multi-layered structure. Repeatable results were generated for cadaveric and surgically removed intestines, whose mechanical properties were similar under certain storage conditions. The mechanical properties of intact intestine in axial and transversal directions were different. The mechanical strength of the intact intestinal wall was conditioned by the submucosa and muscularis, while the serosa and mucosa showed no significant strength. Comparison of axial specimens' mechanical properties of the intact intestinal wall and intestinal wall with all layers sutured through determined that only the submucosa supplies mechanical strength to anastomosis. Other layers contribute no significant force to anastomotic strength. The strength applied to thread during knot tying does not change the participation of the intestinal layers in supplying suture-holding capacity for 8 and 12 mm stitch depth. It was shown graphically why sutures that don't stitch onto the submucosa are unreliable.