Tremor Estimation and Removal in Robot-Assisted Surgery Using Improved Enhanced Band-Limited Multiple Fourier Linear Combiner

BACKGROUND

During a robot-assisted minimally invasive surgery, hand tremors in a surgeon's manipulation of the master manipulator can cause vibrations of the slave surgical instruments.

METHODS

This letter addresses this problem by proposing an improved Enhanced Band-Limited Multiple Linear Fourier Combiner (E-BMFLC) algorithm for filtering the physiological tremor signals of a surgeon's hand. The proposed method uses the amplitude of the input signal to adapt the learning rate and a dense division of the combiner bands for the higher amplitude bands of the tremor signals.

RESULTS

By using the proposed improved E-BMFLC algorithm, the compensation accuracy can be improved by 4.5%-8.9%, as well as a spatial position error of less than 1 mm.

CONCLUSION

The results show that among all filtering methods, the improved E-BMFLC filtering method has the highest number of successful experiments and the lowest experimental time.

Early introduction of simulation in the medical curriculum: the MedInTo perspective

Despite the increasing body of evidence supporting the use of simulation in medicine, a question remains: when should we introduce it into the medical school's curriculum? We present the experience and future perspectives of the MD program in Medicine and Surgery of University of Turin-MedInTo. Since its launch, MedInTo has been dedicated to integrating innovative teaching approaches at the early stages into the medical curriculum. Herewith, we describe a case-based approach for our activities, which includes the utilization of simulation for emergency medical care training for students and the integration of virtual and augmented reality technology. Dedicated surgical training activities using virtual-augmented reality and life-like simulator for students are also described.

Patient-specific computational simulations of wound healing following midline laparotomy closure

In the current study, we developed a new computational methodology to simulate wound healing in soft tissues. We assumed that the injured tissue recovers partially its mechanical strength and stiffness by gradually increasing the volume fraction of collagen fibers. Following the principles of the constrained mixture theory, we assumed that new collagen fibers are deposited at homeostatic tension while the already existing tissue undergoes a permanent deformation due to the effects of remodeling. The model was implemented in the finite-element software Abaqus® through a VUMAT subroutine and applied to a complex and realistic case: simulating wound healing following midline laparotomy closure. The incidence of incisional hernia is still quite significant clinically, and our goal was to investigate different conditions hampering the success of these procedures. We simulated wound healing over periods of 6 months on a patient-specific geometry. One of the outcomes of the finite-element simulations was the width of the wound tissue, which was found to be clinically correlated with the development of incisional hernia after midline laparotomy closure. We studied the impact of different suturing modalities and the effects of situations inducing increased intra-abdominal pressure or its intermittent variations such as coughing. Eventually, the results showed that the main risks of developing an incisional hernia mostly depend on the elastic strains reached in the wound tissue after degradation of the suturing wires. Despite the need for clinical validation, these results are promising for establishing a digital twin of wound healing in midline laparotomy incision.

In vivo bioprinting: Broadening the therapeutic horizon for tissue injuries

Tissue injury is a collective term for various disorders associated with organs and tissues induced by extrinsic or intrinsic factors, which significantly concerns human health. In vivo bioprinting, an emerging tissue engineering approach, allows for the direct deposition of bioink into the defect sites inside the patient's body, effectively addressing the challenges associated with the fabrication and implantation of irregularly shaped scaffolds and enabling the rapid on-site management of tissue injuries. This strategy complements operative therapy as well as pharmacotherapy, and broadens the therapeutic horizon for tissue injuries. The implementation of in vivo bioprinting requires targeted investigations in printing modalities, bioinks, and devices to accommodate the unique intracorporal microenvironment, as well as effective integrations with intraoperative procedures to facilitate its clinical application. In this review, we summarize the developments of in vivo bioprinting from three perspectives: modalities and bioinks, devices, and clinical integrations, and further discuss the current challenges and potential improvements in the future.

Close orthopedic surgery skin incision with combination of barbed sutures and running subcuticular suturing technique for less dermal tension concentration: a finite element analysis

BACKGROUND

Mechanical forces have an important role in the initiation and progression of orthopedic surgical incisions complications. To avoid incision complications with the reduction of dermal tension, surgeons may choose a buried continuous suture technique other than the traditional interrupted vertical mattress suture. Absorbable barbed sutures are widely used in orthopedics due to their convenience and reducing wound tension. The aim of this research is to compare and explain the advantages of running subcuticular suturing technique with absorbable barbed sutures for orthopedic surgical incisions closure.

METHODS

Finite element models of layered skin and two different suture techniques, running subcuticular suture and intradermal buried vertical mattress suture, ware constructed. The mechanical property difference between standard sutures and barbed sutures was modelled using different contact friction coefficient. Pulling the skin wound was simulated, and the sutures' pressure on the skin tissue was determined.

RESULTS

Compared with traditional smooth sutures, the barbed sutures effectively increased the contact force for subepidermal layers, which led the less force variation between different layers. The results also suggested that subcuticular suture caused less stress concentration compared with intradermal buried vertical mattress suture.

CONCLUSIONS

In conclusion, our study indicated that running subcuticular suturing technique with absorbable barbed sutures for orthopedic surgical incisions closure results in more uniform stress distribution in the dermis. We recommend this combination as the preferred method of skin closure in orthopedic surgery unless contraindicated.

Engineering and polymeric composition of drug-eluting suture: A review

Sutures are the most popular surgical implants in the global surgical equipment market. They are used for holding tissues together to achieve wound closure. However, controlling the body's immune response to these "foreign bodies" at site of infection is challenging. Natural polymers such as collagen, silk, nylon, and cotton, and synthetic polymers such as polycaprolactone, poly(lactic-co-glycolic acid), poly(p-dioxanone) and so forth, contribute the robust foundation for the engineering of drug-eluting sutures. The incorporation of active pharmaceutical ingredients (APIs) with polymeric composition of suture materials is an efficient way to reduce inflammatory reaction in the wound site as well as to control bacterial growth, while allowing wound healing. The incorporation of polymeric composition in surgical sutures has been found to add high flexibility as well as excellent physical and mechanical properties. Fabrication processes and polymer materials allow control over drug-eluting profiles to effectively address wound healing requirements. This review outlines and discusses (a) polymer materials and APIs used in suture applications, including absorbable and nonabsorbable sutures; (b) suture structures, such as monofilament, multifilament, barded and smart sutures; and (c) the existing manufacturing techniques for drug-eluting suture production, including electrospinning, melt-extrusion and coating.

Anticipating local flaps closed-form solution on 3D face models using finite element method

A realistic three-dimensional (3D) computational model of skin flap closures using Asian-like head templates from two different genders, male and female, has been developed. The current study aimed to understand the biomechanics of the local flap designs along with the effect of wound closures on the respective genders. Two Asian head templates from opposite genders were obtained to use as base models. A third-order Yeoh hyperelastic model was adapted to characterize as skin material properties. A single layer composed of combined epidermis and dermis was considered, and the models were thickened according to respective anatomical positions. Each model gender was excised with a fixed defect size which was consequently covered by three different local flap designs, namely advancement, rotation, and rhomboid flaps. Post-operative simulation presented various scenarios of skin flap closures. Rotation and rhomboid flaps demonstrated maximal tension at the apex of the flap for both genders as well as advancement flap in the female face model. However, advancement flap closure in the male face model was presented otherwise. Yet, the deformation patterns and the peak tension of the discussed flaps were consistent with conventional local flap surgery. Moreover, male face models generated higher stresses compared to the female face models with a 70.34% mean difference. Overall, the skin flap operations were executed manually, and the designed surgery model met the objectives successfully while acknowledging the study limitations. NOVELTY FILE: 3D head templates were considered to address the gap as 3D face models were uncommonly employed in understanding the biomechanics of the local flaps realistically. Most of the existing studies focus on the 2D and 3D planar geometry in their models. As gender comparison has yet to be addressed, we intended to fill this gap by exploring the stress contours of the local flap designs in different genders. Create a 3D face model from two opposite genders which is capable of simulating closure of wounds using local flaps with a focus on advancement, rotation, and rhomboid flaps.

Structural mechanics modeling reveals stress-adaptive features of cutaneous scars

The scar is a predominant outcome of adult mammalian wound healing despite being associated with partial function loss. Here in this paper, we have described the structure of a full-thickness normal scar as a "di-fork" with dual biomechanical compartments using in vivo and ex vivo experiments. We used structural mechanics simulations to model the deformation fields computationally and stress distribution in the scar in response to external forces. Despite its loss of tissue components, we have found that the scar has stress-adaptive features that cushion the underlying tissues from external mechanical impacts. Thus, this new finding can motivate research to understand the biomechanical advantages of a scar in maintaining the primary function of the skin, i.e., mechanical barrier despite permanent loss of some tissues and specialized functions.

Mechanical Modeling of Healthy and Diseased Calcaneal Fat Pad Surrogates

The calcaneal fat pad is a major load bearing component of the human foot due to daily gait activities such as standing, walking, and running. Heel and arch pain pathologies such as plantar fasciitis, which over one third of the world population suffers from, is a consequent effect of calcaneal fat pad damage. Also, fat pad stiffening and ulceration has been observed due to diabetes mellitus. To date, the biomechanics of fat pad damage is poorly understood due to the unavailability of live human models (because of ethical and biosafety issues) or biofidelic surrogates for testing. This also precludes the study of the effectiveness of preventive custom orthotics for foot pain pathologies caused due to fat pad damage. The current work addresses this key gap in the literature with the development of novel biofidelic surrogates， which simulate the in vivo and in vitro compressive mechanical properties of a healthy calcaneal fat pad. Also, surrogates were developed to simulate the in vivo mechanical behavior of the fat pad due to plantar fasciitis and diabetes. A four-part elastomeric material system was used to fabricate the surrogates, and their mechanical properties were characterized using dynamic and cyclic load testing. Different strain (or displacement) rates were tested to understand surrogate behavior due to high impact loads. These surrogates can be integrated with a prosthetic foot model and mechanically tested to characterize the shock absorption in different simulated gait activities, and due to varying fat pad material property in foot pain pathologies (i.e., plantar fasciitis, diabetes, and injury). Additionally, such a foot surrogate model, fitted with a custom orthotic and footwear, can be used for the experimental testing of shock absorption characteristics of preventive orthoses.

Biomechanical Modeling of Wounded Skin

Skin injury is the most common type of injury, which manifests itself in the form of wounds and cuts. A minor wound repairs itself within a short span of time. However, deep wounds require adequate care and sometime clinical interventions such as surgical suturing for their timely closure and healing. In literature, mechanical properties of skin and other tissues are well known. However, the anisotropic behavior of wounded skin has not been studied yet, specifically with respect to localized overstraining and possibilities of rupture. In the current work, the biomechanics of common skin wound geometries were studied with a biofidelic skin phantom, using uniaxial mechanical testing and Digital Image Correlation (DIC). Global and local mechanical properties were investigated, and possibilities of rupture due to localized overstraining were studied across different wound geometries and locations. Based on the experiments, a finite element (FE) model was developed for a common elliptical skin wound geometry. The fidelity of this FE model was evaluated with simulation of uniaxial tension tests. The induced strain distributions and stress-stretch responses of the FE model correlated very well with the experiments (R2 > 0.95). This model would be useful for prediction of the mechanical response of common wound geometries, especially with respect to their chances of rupture due to localized overstraining. This knowledge would be indispensable for pre-surgical planning, and also in robotic surgeries, for selection of appropriate wound closure techniques, which do not overstrain the skin tissue or initiate tearing.

Novel insole design for diabetic foot ulcer management

Around the world, over 400 million people suffer from diabetes. In a chronic diabetic condition, the skin underneath the foot often becomes extremely soft and brittle, resulting in the development of foot ulcers. In literature, a plethora of footwear designs have been developed to reduce the induced stresses on a diabetic foot and to consequently prevent the incidences of foot ulcers. However, to date, no insole design exists which can handle post-ulcer diabetic foot conditions without hindering the mobility of the patients. In the current work, a novel custom insole design with arch support and ulcer isolations was tested for effective stress reduction in a diabetic foot with ulcers using finite element modeling. A full-scale model of the foot was developed with ulcers of different geometries and sizes at the heel and metatarsal regions of the foot. The stresses at the ulcer locations were quantified for standing and walking with and without the novel custom insole model. The effect of material properties of the insole on the ulcer stress reduction was quantified extensively. Also, the effectivity of a novel synthetic skin material as the insole material was tested for stress offloading at the ulcers and the rest of the foot. From the analyses, peak stress reductions were observed at the ulcers up to 91.5% due to the ulcer isolation in the novel custom insole design and the skin-like material. Specifically, the ulcer isolation feature in the insole was found to be approximately 25% more effective in peak stress reduction for commonly occurring ulcers with irregular geometry, over the tested regular circular ulcer geometry. Also, a threshold material stiffness was found for the custom insole, below which the peak stresses at the ulcers did not decrease any further. Based on this information, a working prototype of the custom insole was developed with custom ulcer isolations, which will be subjected to further testing. The results of this study would inform better custom insole designing and material selection for post-ulcer diabetic conditions, with effective stress reduction at the ulcers, and the possibilities of preventing further ulceration.

Biomechanical Modeling of Prosthetic Mesh and Human Tissue Surrogate Interaction

Surgical repair of hernia and prolapse with prosthetic meshes are well-known to cause pain, infection, hernia recurrence, and mesh contraction and failures. In literature, mesh failure mechanics have been studied with uniaxial, biaxial, and cyclic load testing of dry and wet meshes. Also, extensive experimental studies have been conducted on surrogates, such as non-human primates and rodents, to understand the effect of mesh stiffness, pore size, and knitting patterns on mesh biocompatibility. However, the mechanical properties of such animal tissue surrogates are widely different from human tissues. Therefore, to date, mechanics of the interaction between mesh and human tissues is poorly understood. This work addresses this gap in literature by experimentally and computationally modeling the biomechanical behavior of mesh, sutured to human tissue phantom under tension. A commercially available mesh (Prolene®) was sutured to vaginal tissue phantom material and tested at different uniaxial strains and strain rates. Global and local stresses at the tissue phantom, suture, and mesh were analyzed. The results of this study provide important insights into the mechanics of prosthetic mesh failure and will be indispensable for better mesh design in the future.

Human Skin-Like Composite Materials for Blast Induced Injury Mitigation

Armors and military grade personal protection equipment (PPE) materials to date are bulky and are not designed to effectively mitigate blast impacts. In the current work, a human skin-like castable simulant material was developed and its blast mitigation characteristics (in terms of induced stress reduction at the bone and muscles) were characterized in the presence of composite reinforcements. The reinforcement employed was Kevlar 129 (commonly used in advanced combat helmets), which was embedded within the novel skin simulant material as the matrix and used to cover a representative extremity based human skin, muscle and bone section finite element (FE) model. The composite variations tested were continuous and short-fiber types, lay-ups (0/0, 90/0, and 45/45 orientations) and different fiber volume fractions. From the analyses, the 0/0 continuous fiber lay-up with a fiber volume fraction close to 0.1 (or 10%) was found to reduce the blast-induced dynamic stresses at the bone and muscle sections by 78% and 70% respectively. These findings indicate that this novel skin simulant material with Kevlar 129 reinforcement, with further experimental testing, may present future opportunities in blast resistant armor padding designing.

Tissue Anisotropy Modeling Using Soft Composite Materials

Soft tissues in general exhibit anisotropic mechanical behavior, which varies in three dimensions based on the location of the tissue in the body. In the past, there have been few attempts to numerically model tissue anisotropy using composite-based formulations (involving fibers embedded within a matrix material). However, so far, tissue anisotropy has not been modeled experimentally. In the current work, novel elastomer-based soft composite materials were developed in the form of experimental test coupons, to model the macroscopic anisotropy in tissue mechanical properties. A soft elastomer matrix was fabricated, and fibers made of a stiffer elastomer material were embedded within the matrix material to generate the test coupons. The coupons were tested on a mechanical testing machine, and the resulting stress-versus-stretch responses were studied. The fiber volume fraction (FVF), fiber spacing, and orientations were varied to estimate the changes in the mechanical responses. The mechanical behavior of the soft composites was characterized using hyperelastic material models such as Mooney-Rivlin's, Humphrey's, and Veronda-Westmann's model and also compared with the anisotropic mechanical behavior of the human skin, pelvic tissues, and brain tissues. This work lays the foundation for the experimental modelling of tissue anisotropy, which combined with microscopic studies on tissues can lead to refinements in the simulation of localized fiber distribution and orientations, and enable the development of biofidelic anisotropic tissue phantom materials for various tissue engineering and testing applications.