Biomechanical Modeling of Prosthetic Mesh and Human Tissue Surrogate Interaction

In vivo comparison of mesh fixation solutions in open and laparoscopic procedures for inguinal hernia repair: A meta-analysis

Background

Abdominal hernia repair surgeries involve the fixation of a surgical mesh to the abdominal wall with different means such as suture, tacks, and glues. Currently, the most effective mesh fixation system is still debated. This review compares outcomes of mesh fixation in different surgical procedures, aiding surgeons in identifying the optimal technique.

Methods

A meta-analysis was conducted according to PRISMA guidelines. Articles published between January 2003 and January 2023 were searched in electronic databases. Randomized controlled trials (RCTs) comparing mesh fixation with cyanoacrylate-based or fibrin glues with classical fixation techniques (sutures, tacks) in open and laparoscopic procedures were included.

Results

17 RCTs were identified; the cumulative study population included 3919 patients and a total of 3976 inguinal hernias. Cyanoacrylate-based and fibrin glues were used in 1639 different defects, suture and tacks in 1912 defects, self-gripping mesh in 404 cases, and no mesh fixation in 21 defects. Glue fixation resulted in lower early postoperative pain, and chronic pain occurred less frequently. The incidence of hematoma was lower with glue fixation than with mechanical fixation. Recurrence rate, seroma formation, operative and hospitalization time showed no significant differences; but significantly, a higher number of people in the glue group returned to work by 15- and 30-days after surgery when compared to the tacker and suture groups in the same time frame.

Conclusion

Cyanoacrylate and fibrin glue may be effective in reducing early and chronic pain and hematoma incidence without increasing the recurrence rate, the seroma formation, or the operative and hospitalization time.

Mechanical properties of whole-body soft human tissues: a review

The mechanical properties of soft tissues play a key role in studying human injuries and their mitigation strategies. While such properties are indispensable for computational modelling of biological systems, they serve as important references in loading and failure experiments, and also for the development of tissue simulants. To date, experimental studies have measured the mechanical properties of peripheral tissues (e.g. skin)in-vivoand limited internal tissuesex-vivoin cadavers (e.g. brain and the heart). The lack of knowledge on a majority of human tissues inhibit their study for applications ranging from surgical planning, ballistic testing, implantable medical device development, and the assessment of traumatic injuries. The purpose of this work is to overcome such challenges through an extensive review of the literature reporting the mechanical properties of whole-body soft tissues from head to toe. Specifically, the available linear mechanical properties of all human tissues were compiled. Non-linear biomechanical models were also introduced, and the soft human tissues characterized using such models were summarized. The literature gaps identified from this work will help future biomechanical studies on soft human tissue characterization and the development of accurate medical models for the study and mitigation of injuries.

The Grip Concept of Incisional Hernia Repair-Dynamic Bench Test, CT Abdomen With Valsalva and 1-Year Clinical Results

Incisional hernia is a frequent consequence of major surgery. Most repairs augment the abdominal wall with artificial meshes fixed to the tissues with sutures, tacks, or glue. Pain and recurrences plague at least 10-20% of the patients after repair of the abdominal defect. How should a repair of incisional hernias be constructed to achieve durability? Incisional hernia repair can be regarded as a compound technique. The biomechanical properties of a compound made of tissue, textile, and linking materials vary to a large extent. Tissues differ in age, exercise levels, and comorbidities. Textiles are currently optimized for tensile strength, but frequently fail to provide tackiness, dynamic stiction, and strain resistance to pulse impacts. Linking strength with and without fixation devices depends on the retention forces between surfaces to sustain stiction under dynamic load. Impacts such a coughing or sharp bending can easily overburden clinically applied composite structures and can lead to a breakdown of incisional hernia repair. Our group developed a bench test with tissues, fixation, and textiles using dynamic intermittent strain (DIS), which resembles coughing. Tissue elasticity, the size of the hernia under pressure, and the area of instability of the abdominal wall of the individual patient was assessed with low-dose computed tomography of the abdomen preoperatively. A surgical concept was developed based on biomechanical considerations. Observations in a clinical registry based on consecutive patients from four hospitals demonstrate low failure rates and low pain levels after 1 year. Here, results from the bench test, the application of CT abdomen with Valsalva's maneuver, considerations of the surgical concept, and the clinical application of our approach are outlined.

Biomechanics applied to incisional hernia repair - Considering the critical and the gained resistance towards impacts related to pressure

BACKGROUND

Incisional hernia repair is burdened with recurrence, pain and disability. The repair is usually carried out with a textile mesh fixed between the layers of the abdominal wall.

METHODS

We developed a bench test with low cyclic loading. The test uses dynamic intermittent strain resembling coughs. We applied preoperative computed tomography of the abdomen at rest and during Valsalva's maneuver to the individual patient to analyze tissue elasticity.

FINDINGS

The mesh, its placements and overlap, the type and distribution of fixation elements, the elasticity of the tissue of the individual and the closure of the abdominal defect-all aspects influence the reconstruction necessary. Each influence can be attributed to a relative numerical quantity which can be summed up into a characterizing value. The elasticity of the tissues within the abdominal wall of the individual patient can be assessed with low-dose computed tomography of the abdomen with Valsalva's maneuver. We established a procedure to integrate the results into a surgical concept. We demonstrate potential computer algorithms using non-rigid b-spline registration and artificial intelligence to further improve the evaluation process.

INTERPRETATION

The bench test yields relative values for the characterization of hernia, mesh and fixation. It can be applied to patient care using established procedures. The clinical application in the first ninety-six patients shows no recurrences and reduced pain levels after one year. The concept has been spread to other surgical groups with the same results in another fifty patients. Future efforts will make the abdominal wall reconstruction more predictable.

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.