Characterization of aortic tissue cutting process: experimental investigation using porcine ascending aorta

How Strong Can We Pull? Critical Thresholds for Traction Forces on the Aortic Annulus: Measurements on Fresh Porcine Hearts

Background and Objectives: Friable or infected tissue remains a challenge in surgical aortic valve replacement. We recently described the “Caput medusae” method, in which circumferential tourniquets temporarily secure the prosthesis and are then gently knotted. Tourniquets have been shown to develop significantly less force than knots. The current study investigates the critical threshold forces for tissue damage to the aortic annulus. Materials and Methods: In 14 fresh porcine hearts, the aortic valve leaflets were removed and several pledgeted sutures were placed along the annulus at defined locations. The hearts were mounted in a self-constructed device. Incremental traction force was applied to every suture and continuously recorded. The movement of each Teflon pledget was filmed with a high-speed camera. Forces at the moment of pledget “cut-in” as well as complete “tear-out” were determined from the recordings. Results: The average threshold force was determined 9.31 ± 6.04 N for cut-in and 20.41 ± 10.02 N for tear-out. Detailed analysis showed that the right coronary region had lower threshold forces than the other regions (4.77 ± 3.28 N (range, 1.67–12.75 N) vs. 10.67 ± 6.04 N (1.62–26.00 N) for cut-in and 10.67 ± 4.04 N (5.40–18.64 N) vs. 23.33 ± 9.42 N (9.22–51.23 N) for tear-out). The findings are discussed in conjunction with the knot and tourniquet forces from our previous study. Conclusions: Even in healthy tissue, moderate forces can reach a critical level at which a Teflon pledget will cut into the annulus, while a complete tear-out is unlikely. The right coronary portion is more susceptible to damage than the remaining regions. When compared to previous data, forces during manual knotting may exceed the critical cut-in level, while rubber tourniquets may provide a higher safety margin against tissue rupture.

Microfluidic Surgery in Single Cells and Multicellular Systems

Microscale surgery on single cells and small organisms has enabled major advances in fundamental biology and in engineering biological systems. Examples of applications range from wound healing and regeneration studies to the generation of hybridoma to produce monoclonal antibodies. Even today, these surgical operations are often performed manually, but they are labor intensive and lack reproducibility. Microfluidics has emerged as a powerful technology to control and manipulate cells and multicellular systems at the micro- and nanoscale with high precision. Here, we review the physical and chemical mechanisms of microscale surgery and the corresponding design principles, applications, and implementations in microfluidic systems. We consider four types of surgical operations: (1) sectioning, which splits a biological entity into multiple parts, (2) ablation, which destroys part of an entity, (3) biopsy, which extracts materials from within a living cell, and (4) fusion, which joins multiple entities into one. For each type of surgery, we summarize the motivating applications and the microfluidic devices developed. Throughout this review, we highlight existing challenges and opportunities. We hope that this review will inspire scientists and engineers to continue to explore and improve microfluidic surgical methods.

Investigation on puncture mechanical performance of tracheal tissue

This paper investigated the mechanical behavior of the contact between the oblique tip puncture needle and the tracheal tissue during pathological examination for the diagnosis of respiratory diseases. By analyzing the force of the oblique tip puncture needle, this paper established a theoretical model of the contact mechanics between the needle and the tracheal tissue. With the material characteristics, needle diameter and puncture angle of trachea tissue as the loading conditions, the biomechanical simulation of piercing process was carried out by using the finite element simulation method, and realistic puncture experiments on isolated porcine tracheal tissue were performed by electronic universal testing machine. The results showed that the puncture needle was mainly subjected to the combined effect of cutting force, clamping force and frictional force on the needle shaft. When the needle diameter was 22G, penetrating the tracheal tissue vertically, the force on the needle was minimal. Meanwhile, it was found that the error between the experimental and theoretical values of the puncture force did not exceed 10%, thus verifying the feasibility of the hypothetical model of the puncture force in the tracheal tissue rupture stage. It provided a theoretical basis for the intervention of surgical instruments and reduced surgical risks.

Study on cutting force of reaming porcine bone and substitute bone

Accurate mechanical feedback systems are critical to the successful implementation of virtual and robotic surgical assistant systems. Experimental measurements of reaming force could further our understanding of the cancellous bone reaming process during hip arthroplasty to help develop surgical simulators with realistic force effects and improve the protection mechanism of robot-assisted surgical systems. In this study, reaming experiments with natural bone (porcine femur) and a bone substitute (polyurethane blocks) were performed on a CNC lathe. This paper proposes using the maximum reaming force of the steady reaming stage to represent the force characteristic. The reaming force is biased to one side in the overlap direction and the maximum reaming force will vary when the reamer is not coincident with the long axis of the bone. The diameter of the reamer has the greatest influence on reaming force, which clearly increases with increasing reamer diameter. During operation, a medium rotation speed and high feed speed can reduce the reaming force. After cutting, the morphology of the cut surface is not flat, but arc-shaped, which will have a significant impact on implantation of the femoral prosthesis. In in vitro cutting experiments, polyurethane blocks can be used as a substitute for cancellous bone.

Utilization of a robotic mount to determine the force required to cut palatal tissue

Determination of the material properties of soft tissue is a growing area of interest that aids in the development of new surgical tools and surgical simulators. This study first aims to develop a robot-operated tissue testing system for determination of tissue cutting forces. Second, this system was used to ascertain the cutting properties of the hard and soft palate mucosa and soft palate musculature for the purpose of developing a robotic instrument for cleft palate surgery and a cleft-specific surgical simulator. The palate tissue was cut with a 15 blade mounted to the robot with varying angles (30°, 60°, 90°) and speeds (1.5, 2.5, 3.5 cm/s) of cutting to imitate typical operative tasks. The cutting force range for hard palate mucosa, soft palate mucosa and soft palate muscle were 0.98-3.30, 0.34-1.74 and 0.71-2.71 N, respectively. The break-in force of the cut (i.e. force required for the blade to penetrate the tissue) is significantly impacted by the angle of the blade relative to the tissue rather than the cutting speed. Furthermore, the total surface area of the tissue in contact with the blade during the cut has a significant impact on the total force expended on the tissue.

Prevalence of haptic feedback in robot-mediated surgery: a systematic review of literature

With the successful uptake and inclusion of robotic systems in minimally invasive surgery and with the increasing application of robotic surgery (RS) in numerous surgical specialities worldwide, there is now a need to develop and enhance the technology further. One such improvement is the implementation and amalgamation of haptic feedback technology into RS which will permit the operating surgeon on the console to receive haptic information on the type of tissue being operated on. The main advantage of using this is to allow the operating surgeon to feel and control the amount of force applied to different tissues during surgery thus minimising the risk of tissue damage due to both the direct and indirect effects of excessive tissue force or tension being applied during RS. We performed a two-rater systematic review to identify the latest developments and potential avenues of improving technology in the application and implementation of haptic feedback technology to the operating surgeon on the console during RS. This review provides a summary of technological enhancements in RS, considering different stages of work, from proof of concept to cadaver tissue testing, surgery in animals, and finally real implementation in surgical practice. We identify that at the time of this review, while there is a unanimous agreement regarding need for haptic and tactile feedback, there are no solutions or products available that address this need. There is a scope and need for new developments in haptic augmentation for robot-mediated surgery with the aim of improving patient care and robotic surgical technology further.

Micro/nano-particle decorated metal wire for cutting soft matter

To cut soft materials such as biological tissues with minimal damage and reduced positional error is highly desired in medical surgery and biomechanics. After years of natural selection and evolution, mosquitoes have acquired the ability to insert their proboscises into human skin with astonishingly tiny forces. This can be associated with the unique structure of their proboscises, with micro/nano sawteeth, and the distinctive insertion manner: high frequency reciprocating saw cutting. Inspired by these, this communication describes the successful implantation of metal oxide particles onto molybdenum wire surfaces through a sol-calcination process, to form a biomimetic sawblade with a high density of micro/nano saw teeth, where the acidification is essential in terms of generating active anchoring sites on the wire. When used as a sawblade in conjunction with reciprocating action to cut the viscoelastic gel, both the cut-in force and cut-in displacement could be decreased substantially. The cutting speed and frequency of reciprocating action are important operating parameters influencing cut-in force.

Optimal needle design for minimal insertion force and bevel length

This research presents a methodology for optimal design of the needle geometry to minimize the insertion force and bevel length based on mathematical models of cutting edge inclination and rake angles and the insertion force. In brachytherapy, the needle with lower insertion force typically is easier for guidance and has less deflection. In this study, the needle with lancet point (denoted as lancet needle) is applied to demonstrate the model-based optimization for needle design. Mathematical models to calculate the bevel length and inclination and rake angles for lancet needle are presented. A needle insertion force model is developed to predict the insertion force for lancet needle. The genetic algorithm is utilized to optimize the needle geometry for two cases. One is to minimize the needle insertion force. Using the geometry of a commercial lancet needle as the baseline, the optimized needle has 11% lower insertion force with the same bevel length. The other case is to minimize the bevel length under the same needle insertion force. The optimized design can reduce the bevel length by 46%. Both optimized needle designs were validated experimentally in ex vivo porcine liver needle insertion tests and demonstrated the methodology of the model-based optimal needle design.