Loosening of pedicle screws after spinal fusion surgery can prevent the desired fusion between vertebrae and may be a reason for revision surgery. Especially in osteoporotic bone, toggling of pedicle screws is a common problem that compromises the fixation strength of these screws and can lead to loosening or axial pull-out of the screw. In this study, we explore the use of an in-pedicle expandable anchor that shapes to the pedicle to increase the toggling resistance of the anchor by increasing the contact area between the anchor and the dense cortical bone of the pedicle. A scaled-up, two-dimensional prototype was designed. The prototype consists of a bolt and ten stainless steel wedges that expand by tensioning the bolt. During the expansion, the wedges are required to compress the cancellous bone. Based on the first preliminary experiment, it was found that the expansion of the wedges resulted in successful compression of 5 PCF cancellous bone phantom (Sawbones). This preliminary study shows that an expandable in-pedicle anchor could be a feasible option to increase the toggling resistance of spinal bone anchors, especially in osteoporotic bone. Clinical Relevance- Toggling of pedicle screws is a major cause of screw loosening. In this preliminary study, the use of an in-pedicle expandable anchor to increase the toggling resistance of spinal bone anchors is explored.

A major challenge during minimally invasive surgery is transfer of high forces through small, flexible instruments, such as needles and catheters, because of their low buckling resistance. In this study, we determined the feasibility of using a Newton's Cradle-inspired catheter (patented) to transfer high-force impulses. Exerting a high-force impulse on the tissue increases the critical buckling load and can prevent buckling. The system comprised an input plunger onto which the impulse is given, a (flexible) shaft filled with empty set2 mm stainless steel balls, and an output plunger to transfer the impulse to the target tissue. In the proof-of-principle experiment, the effect on efficiency of clearance (0.1, 0.2, and 0.3 mm), length (100, 200, and 300mm), shaft type (rigid vs. flexible), curve angle (0, 45, 90, 135, and 180 degrees), and curve radius (20, 40, 60, and 100mm) was determined. The catheter delivered forces of 6 N without buckling. The average impulse efficiency of the system was 35%, which can be further increased by optimizing the design. This technology is promising for high-force delivery in miniature medical devices during minimally invasive surgery. (C) 2019 IPEM. Published by Elsevier Ltd. All rights reserved.

Crossing highly calcified occlusions is technically challenging mainly due to guidewire buckling. In an effort to prevent buckling, a catheter that uses a dynamic impulse load is proposed. The proposed Wave catheter consists of an input plunger to generate an impulse at the handle, a hydraulic pressure wave confined within a empty set2 mm catheter to transfer the impulse towards the tip, and an output plunger to transfer the impulse to the occlusion. To determine the feasibility of this catheter, an experiment was performed in which the input and output impulses were recorded as a function of the catheter type, curvature, and plunger travel distance. Additionally, the system was tested on artificial CTO models to determine the clinical validity. The catheter has illustrated the ability to safely transfer high force impulses of up to 43 N (1.5 N required) with only minimum catheter type and no curvature dependency, allowing for delivering high-force impulses through tortuous vasculature and under any angle. Furthermore, the catheter was able to penetrate the artificial CTO models within 1 strike.

Background. The majority of the benign and malignant lesions in the breast arise from the ductal epithelium and terminal ductlobular unit. A minimally invasive procedure called ductoscopy is able to visualize these lesions as it inspects the ductal epithelium using a small micro-endoscope. Unfortunately, it is currently challenging to obtain a tissue sample during ductoscopy and reach the most distal duct. Methods. In this study we have, therefore, developed a novel miniature (Ø1.2 mm) biopsy needle that can be used during ductoscopy. This biopsy needle consists of two coaxial counter-rotating hollow blades with a distal cutout to resect lesions from the ductal wall. Three cutouts were manufactured resulting in a beveled, straight, and reverse-beveled blade. The blades were actuated using a novel mechanism containing two helical paths that allows for the counter-rotating motion of the blades at different velocities. In a proof-of-principle experiment, the performance of the biopsy needle was evaluated using a polymeric duct model and gelatin tissue phantom. Results. During the experiment, the straight and reverse-beveled blades were able to obtain a sufficiently large tissue sample for histopathological examination. Based on these promising results, a second experiment was performed in which the micro-endoscope was integrated in the needle and we were able to take a biopsy from a chicken breast. Conclusions. In a future clinical instrument, the biopsy needle will be miniaturized and optimized to allow for an efficient, safe, and effective intraductal biopsy procedure without the need for an invasive excisional biopsy procedure.

In current bipolar electrosurgical instruments, a high frequency electrical sinusoidal wave is passed through the patient's body from an active electrode to the return electrode to cut, coagulate, or desiccate tissues. Even though current bipolar electrosurgical instruments have proven effective in minimizing blood loss, advancement is needed to allow for improved dexterity and adaptability. With current advances in three-dimensional (3D)-print processes and its integration in the medical field, it has become possible to manufacture patient-and operation-specific instruments. In this study, we introduce the first 3D-printed steerable bipolar grasper (◻ 5 mm) for use in minimal invasive surgery. The grasper significantly improves dexterity by the addition of two planar joints allowing for ±65 deg for sideways and ±85 deg for up- and downward movement. The joints enable a significantly higher bending stiffness, 4.0 N/mm for joint 1 and 4.4 N/mm for joint 2, than that of currently available steerable instruments. The tip consists of two metallic movable jaws that can be opened and closed with angles up to 170 deg and allows for grasping and coagulating of tissues; reaching tissue temperatures of over 75 °C for an activation time of ∼5 s, respectively. In order to actuate the joint, tip, and electrosurgical system, as well as to tension the steering cables, a ring handle was designed. In summary, the 3D-printed steerable bipolar grasper provides the surgeon with electrosurgical capabilities, improved dexterity, improved stiffness, and the versatility that is needed to provide patient- and operation-specific care.

Background In nature, shooting mechanisms are used for a variety of purposes, including prey capture, defense, and reproduction. This review offers insight into the working principles of shooting mechanisms in fungi, plants, and animals in the light of the specific functional demands that these mechanisms fulfill. Methods We systematically searched the literature using Scopus and Web of Knowledge to retrieve articles about solid projectiles that either are produced in the body of the organism or belong to the body and undergo a ballistic phase. The shooting mechanisms were categorized based on the energy management prior to and during shooting. Results Shooting mechanisms were identified with projectile masses ranging from 1.10 -9 mg in spores of the fungal phyla Ascomycota and Zygomycota to approximately 10,300 mg for the ballistic tongue of the toad Bufo alvarius. The energy for shooting is generated through osmosis in fungi, plants, and animals or muscle contraction in animals. Osmosis can be induced by water condensation on the system (in fungi), or water absorption in the system (reaching critical pressures up to 15.4 atmospheres; observed in fungi, plants, and animals), or water evaporation from the system (reaching up to -197 atmospheres; observed in plants and fungi). The generated energy is stored as elastic (potential) energy in cell walls in fungi and plants and in elastic structures in animals, with two exceptions: (1) in the momentum catapult of Basidiomycota the energy is stored in a stalk (hilum) by compression of the spore and droplets and (2) in Sphagnum energy is mainly stored in compressed air. Finally, the stored energy is transformed into kinetic energy of the projectile using a catapult mechanism delivering up to 4,137 J/kg in the osmotic shooting mechanism in cnidarians and 1,269 J/kg in the muscle-powered appendage strike of the mantis shrimp Odontodactylus scyllarus. The launch accelerations range from 6.6g in the frog Rana pipiens to 5,413,000g in cnidarians, the launch velocities from 0.1 m/s in the fungal phylum Basidiomycota to 237 m/ s in the mulberry Morus alba, and the launch distances from a few thousands of a millimeter in Basidiomycota to 60 m in the rainforest tree Tetraberlinia moreliana. The mass-specific power outputs range from 0.28 W/kg in the water evaporation mechanism in Basidiomycota to 1.97.10 9 W/kg in cnidarians using water absorption as energy source. Discussion and conclusions The magnitude of accelerations involved in shooting is generally scale-dependent with the smaller the systems, discharging the microscale projectiles, generating the highest accelerations. The mass-specific power output is also scale dependent, with smaller mechanisms being able to release the energy for shooting faster than larger mechanisms, whereas the mass-specific work delivered by the shooting mechanism is mostly independent of the scale of the shooting mechanism. Higher mass-specific work-values are observed in osmosis-powered shooting mechanisms ( ≤ 4,137 J/kg) when compared to muscle-powered mechanisms (≤ 1,269 J/kg). The achieved launch parameters acceleration, velocity, and distance, as well as the associated delivered power output and work, thus depend on the working principle and scale of the shooting mechanism.

A typical mechanical failure mode observed in slender percutaneous instruments, such as needles and guidewires, is buckling. Buckling is observed when the axial compressive force that is required to penetrate certain tissue types exceeds the critical load of the instrument and manifests itself by sudden lateral deflection of the instrument. In nature, several organisms are able to penetrate substrates without buckling while using apparatuses with diameters smaller than those of off-the-shelf available percutaneous needles and guidewires. In this study we reviewed the apparatuses and buckling prevention strategies employed by biological organisms to penetrate substrates such as wood and skin. A subdivision is made between buckling prevention strategies that focus on increasing the critical load of the penetration tool and strategies that focus on decreasing the penetration load of the substrate. In total, 28 buckling prevention strategies were identified and categorized. Most organisms appear to be using a combination of buckling prevention strategies simultaneously. Integration and combination of these biological buckling prevention strategies in percutaneous instruments may contribute to increasing the success rate of percutaneous interventions.

BACKGROUND:A new paradigm of surgical treatment of equine Cushing's disease has been developed using the vascular system combined with a flexible morcellation instrument to reach the pituitary gland.OBJECTIVE:The goal was twofold: (1) to design, prototype, and test an instrument that can reach the pituitary gland using the vascular system unique to equids and (2) to test the feasibility of the endovascular approach.ANIMALS AND METHODS:The morcellator consists of a radial rotating cutting blade for tissue resection, a flexible shaft incorporating a cable drive for flexible actuation, and central morcellated tissue transportation lumen. The morcellator prototype was tested on a horse's cadaver head for the validation of the cutting blade design, actuator design, and feasibility of the endovascular approach.RESULTS:The overall assembled length of the morcellator tip was 13.9 mm, allowing for non-traumatic steering through the vascular system from the proximal end. The radially rotating cutting blade (barrel of Ø 4 and 4.4 mm width) incorporated multiple cutting edges to deliver the action force during resection and provides the necessary grasping force to draw the tissue towards the second cutting edge of the morcellator incorporated inside the blunted cuboidal static tip element (5 mm square and wall-thickness of 0.3 mm). In the tests, the morcellator was successfully guided towards the pituitary and managed to sample pituitary tissue.CONCLUSION AND CLINICAL IMPORTANCE:Continued development of the prototype and the endovascular approach may in time improve the outcome and quality of life of horses suffering from Cushing's disease.