Background-Distraction enterogenesis is a novel method for increasing small bowel length by the application of linearly directed forces. However, the magnitude of distractive forces that human and animal small bowel can safely withstand is unknown.
Purpose Previous methods of distraction enterogenesis have relied upon blind-ending intestinal segments or transmural device fixation, requiring multiple operations and potential bowel injury. We hypothesized that using a novel attachment would allow reversible device coupling to the luminal bowel surface, achieving effective endoluminal distraction. Methods A telescopic hydraulic device was designed with latex balloon attachments covered with high-friction mesh and a dilating fenestrated elastic mask (DFM attachment), allowing mesh-to-mucosa contact only with inflation. Yorkshire pigs underwent jejunal Roux-en-Y limb creation and device placement via jejunostomy. Devices underwent 3 cycles of balloon inflation and hydraulic extension/retraction per day for 7 days and then explanted and studied for efficacy. Results DFM attachment allowed reversible, high-strength endoluminal coupling without tissue injury or reduction in bowel perfusion. After 7 day implant, distracted bowel achieved a 44±2% increase in length vs. fed, non-distracted bowel, corresponding to a gain of 7.1±0.3 cm. Distracted bowel demonstrated increased epithelial cell proliferation vs. control bowel. Attachment sites demonstrated villus flattening, increased crypt depth, thicker muscularis mucosa, and unchanged muscularis propria thickness vs. control. Conclusion Novel high-strength, reversible attachments enabled fully endoluminal distraction enterogenesis, achieving length gains comparable to open surgical techniques. This approach may allow development of clinically applicable technology for SBS treatment.
Background Distraction-induced intestinal growth may be a novel treatment for short bowel syndrome. Longitudinal, distractive tension created by the application of force creates a significant challenge: to produce adequate force, yet not cause perforation at the fixation points. This paper describes our development of a coupling strategy to allow for successful bowel lengthening. Methods A curvilinear hydraulic device was implanted in an isolated Roux limb of small bowel in young Yorkshire pigs. Bowel was lengthened over a 2 week period. Study groups included: Group 1: Twelve silk transmural anchoring sutures into an engineered-coupling ring at each device end. Group 2: Addition of felt pledgets to the coupling rings on the serosal surface of the small bowel. Group 3: Extraluminal use of either thin AlloDerm®, thick AlloDerm®, or Strattice™ mesh to anchor the device. Results Group 1 (suture-only) resulted in a gradual pulling through of the suture with increasing tension and no lengthening. Felt pledgets eroded in a similar fashion, causing abdominal sepsis. Thin AlloDerm® failed to prevent erosion, however it protected against gross contamination. Animals in which either thick AlloDerm® or Strattice™ mesh was used survived complication-free to the study endpoint. Both thick AlloDerm® and Strattice™ prevented erosion and perforation allowing for an average of 10.85-cm expansion. Conclusion This study demonstrates use of either thick AlloDerm® or Strattice™ reconstructive tissue matrix allows for safe and effective coupling. Further, we suggest this approach could be an adjunct to esophageal lengthening procedures.
The Shape Memory Alloy (SMA) helical actuation architecture overcomes the typical strain limitations of straight wire SMA actuators by producing larger stroke in a small package size. SMA Helical actuators also provide design tailorability where the tightness of the coil can be used to make tradeoffs between force and displacement, along with the coupled tradeoff between package length and diameter. These are very attractive for industrial settings such as the automotive industry, but require models and design processes to support the needs of the quick, early design cycles typically required. This paper presents an experimentally-based parameter study from which a streamlined design process is extracted. SMA helical actuators with a range of wire diameters and coil diameters were fabricated and experimentally characterized. The functional dependence of performance metrics such as austenite stiffness, force level of the martensite plateau, and recoverable strain were evaluated. A two-step decoupled design procedure is presented based on the resulting empirical model where the kinematic design is first undertaken to select the spring index which provides the required strain within the available package space, and then the non-dimensionalized force is used to scale the design such that the required actuation force is achieved. The streamlined, systematic design framework presented in this paper provides the means for the design of compact, large stroke helical actuators in industrial settings.
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