"The development and clinical adoption of more effective fixation devices for re-approximating and immobilizing the sternum after open-heart surgery to enable bony healing has been limited, in part, by the lack of in vitro test methods used to evaluate these devices which precisely emulate in vivo loading of the sternum. The present study is an initial effort to determine the loading parameters necessary to improve current in vitro and numerical test methods by characterizing the direction, magnitude, and distribution of loading along the sternotomy midline in vivo using a porcine model. Changes in forces incurred by death and embalming were also investigated to estimate the applicability of cadavers as chest models for sternal fixation. Two instrumented plating systems were used to measure the magnitude, direction, and distribution of forces across the bisected sternum in four pigs during spontaneous breathing, ventilated breathing, and coughing for four treatments; live, dead, embalmed, and refrigerated. Forces were highest in the lateral direction and highest at the xiphoid. An important finding was that the magnitude of the respiratory forces in all directions was smaller than anticipated from previous estimations, ranging from 0.37 N to 43.8 N. No significant differences in force were found between the four treatments, most likely due to the very small magnitude of the forces and high variability between animals. These results provide a first approximation of in vivo sternal forces and indicate that small cyclic fatigue loads should be applied for long periods of time, rather than large quasistatic loads, to best evaluate the next generation of sternal fixation devices. "

Colonoscopy is the current standard for colorectal cancer screening. This procedure requires improvement since it causes patient pain and can even result in injury. Novel colonoscopy devices have to be evaluated to gain information about their performance. At the preclinical stage of the device development the evaluation is typically performed in laboratory experiments. For these experiments an artificial environment is required which can recreate the anatomical and biomechanical features of the colon. A colonoscopy simulator for the evaluation of colonoscopy devices was developed within the ERC funded CoDIR project (Colonic Disease Investigation by Robotic Hydrocolonoscopy). The here developed simulator had to provide a colon phantom with realistic biomechanical properties as well as a sensor setup to measure signals which can be used to quantify the performance of devices which are tested within the simulator. Related literature was reviewed and possible tissue mimicking materials were selected. The suitability of the selected materials was evaluated by testing the frictional and elastic properties of the materials and subsequently comparing the results to those of colon tissue. PVA cryogel was selected as the most suitable material as it exhibits comparable elasticity and coefficients of friction. The tissue mimicking materials were mould casted into phantoms which were designed to represent the anatomical features of the colon. A simulator environment was developed which integrates the phantom as well as force and pressure sensors into a functional system. The sensors measure mesenteric forces and intraluminal pressures which can be related to the performance of tested devices. The simulator allows the arrangement of the sensors and the phantoms in an adjustable, modular approach. The simulator environment was successfully applied in the evaluation of a novel colonoscopy device. The results indicate that PVA cryogels exhibit unique mechanical properties which can be compared to those of colon tissue. The developed colonoscopy simulator provides a promising tool which can aid the development of novel colonoscopy devices.