Short Bowel Syndrome is a serious medical condition caused by insufficient small bowel length resulting in significantly high rates of morbidity and mortality. The limited success of current therapies has prompted the investigation of a new treatment approach based on mechanotransduction — the process through which mechanical tensile loading on the bowel induces longitudinal growth. To enable clinically relevant mechanotransduction growth studies in large animals, such as pigs, a fully implantable and instrumented bowel extender device based on a Shape Memory Alloy (SMA) ratchet was developed and validated in benchtop and ex vivo tests. These devices, however, must also be validated against the unique in vivo environment which presents challenges such as sealing, battery life, surgical implantation, signal attenuation from tissue, and isolating the measurement of tensile loading on the bowel wall. This paper extends the earlier development work to in vivo validation experiments within live pigs. A brief summary of the bowel extender architecture and operation is provided along with earlier ex vivo results that established device limits for in vivo testing. The wireless communication rate was updated to extend battery life and new surgical implantation procedures and lengthening schemes were developed. Two bowel extenders were tested in in vivo experiments ranging from 2.5 to 4.5 days with data collected to validate the wireless communication, SMA ratcheting and load/displacement measurements, confirming that the bowel extender successfully operates in vivo. More importantly, the bowel extenders successfully induced significant growth, which is promising for future studies comparing different lengthening schemes for optimal growth and the development of a clinical device for treating short bowel syndrome in humans.

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