Investigation of abdomen surface deformation due to life excitation: implications for implant selection and orientation in laparoscopic ventral hernia repair

Self-organising maps in the analysis of strains of human abdominal wall to identify areas of similar mechanical behaviour

The study refers to the application of a type of artificial neural network called the Self-Organising Map (SOM) for the identification of areas of the human abdominal wall that behave in a similar mechanical way. The research is based on data acquired during in vivo tests using the digital image correlation technique (DIC). The mechanical behaviour of the human abdominal wall is analysed during changing intra-abdominal pressure. SOM allow to study simultaneously three variables in four time/load steps. The variables refer to the principal strains and their directions. SOM classifies all the abdominal surface data points into clusters that behave similarly in accordance with the 12 variables. The analysis of the clusters provides a better insight into abdominal wall deformation and its evolution under pressure than when observing a single mechanical variable. The presented results may provide a better understanding of the mechanics of the living human abdominal wall. It might be particularly useful when selecting proper implants as well as for the design of surgical meshes for the treatment of abdominal hernias, which would be mechanically compatible with identified regions of the human anterior abdominal wall, and possibly open the way for patient-specific solutions.

Soft tissue material properties based on human abdominal in vivo macro-indenter measurements

Simulations of human-technology interaction in the context of product development require comprehensive knowledge of biomechanical in vivo behavior. To obtain this knowledge for the abdomen, we measured the continuous mechanical responses of the abdominal soft tissue of ten healthy participants in different lying positions anteriorly, laterally, and posteriorly under local compression depths of up to 30 mm. An experimental setup consisting of a mechatronic indenter with hemispherical tip and two time-of-flight (ToF) sensors for optical 3D displacement measurement of the surface was developed for this purpose. To account for the impact of muscle tone, experiments were conducted with both controlled activation and relaxation of the trunk muscles. Surface electromyography (sEMG) was used to monitor muscle activation levels. The obtained data sets comprise the continuous force-displacement data of six abdominal measurement regions, each synchronized with the local surface displacements resulting from the macro-indentation, and the bipolar sEMG signals at three key trunk muscles. We used inverse finite element analysis (FEA), to derive sets of nonlinear material parameters that numerically approximate the experimentally determined soft tissue behaviors. The physiological standard values obtained for all participants after data processing served as reference data. The mean stiffness of the abdomen was significantly different when the trunk muscles were activated or relaxed. No significant differences were found between the anterior-lateral measurement regions, with exception of those centered on the linea alba and centered on the muscle belly of the rectus abdominis below the intertubercular plane. The shapes and areas of deformation of the skin depended on the region and muscle activity. Using the hyperelastic Ogden model, we identified unique material parameter sets for all regions. Our findings confirmed that, in addition to the indenter force-displacement data, knowledge about tissue deformation is necessary to reliably determine unique material parameter sets using inverse FEA. The presented results can be used for finite element (FE) models of the abdomen, for example, in the context of orthopedic or biomedical product developments.

Spider-Silk-like Fiber Mat-Covered Polypropylene Warp-Knitted Hernia Mesh for Inhibition of Fibrosis under Dynamic Environment

Hernia surgery is a widely performed procedure, and the use of a polypropylene mesh is considered the standard approach. However, the mesh often leads to complications, including the development of scar tissue that wraps around the mesh and causes it to shrink. Consequently, there is a need to investigate the relationship between the mesh and scar formation as well as to develop a hernia mesh that can prevent fibrosis. In this study, three different commercial polypropylene hernia meshes were examined to explore the connection between the fabric structure and mechanical properties. In vitro dynamic culture was used to investigate the mechanism by which the mechanical properties of the mesh in a dynamic environment affect cell differentiation. Additionally, electrospinning was employed to create polycaprolactone spider-silk-like fiber mats to achieve mechanical energy dissipation in dynamic conditions. These fiber mats were then combined with the preferred hernia mesh. The results demonstrated that the composite mesh could reduce the activation of fibroblast mechanical signaling pathways and inhibit its differentiation into myofibroblasts in dynamic environments.

Development and Implantation of 3D Anatomically Tailored Polypropylene Mesh for Laparoscopic Inguinal Hernia Repair Designed on the Basis of CT Images (the ILAM Study)

OBJECTIVE

The aim of the ILAM (Individualized Laparoscopic Anatomical Mesh) study was to create and implant a fully individualized mesh based on CT scans, taking into account the published body of knowledge about the material and mechanical behavior of the implant for laparoscopic inguinal hernia repair.

SUMMARY BACKGROUND DATA

The team creating and conducting this study consisted of surgeons and engineers. A specific project was made and divided into 4 phases.

METHODS

The process of development and implantation was divided into 4 milestones: CT scans and modeling based on predefined subgroups, mesh manufacture, certification and clinical evaluation.

RESULTS

The result of the study was the first individually designed hernia mesh to have been implanted in a human subject. After 12 months of follow-up, no recurrences or other complications were reported.

CONCLUSIONS

The new mesh provides a better anatomic fit to the patients' inguinal region geometry. Mechanical stability is ensured by the multiple contact points between the implant and the tissues, which generate friction forces. Together with the possibility of shape design (proper overlap), the authors believe that there is no need for mesh fixation. If so, the use of such design meshes can change the guidelines in laparoendoscopic hernia repair in the future.

Cobweb-Inspired Micro/Nanostructured Scaffolds for Soft Tissue Regeneration with Inhibition Effect of Fibrosis under Dynamic Environment

In soft tissue repair, fibrosis can lead to repair failure and long-term chronic pain in patients. Excessive mechanical stimulation of fibroblasts is one of the causes of fibrosis during abdominal wall regeneration. Inspired by the cobweb, a polycaprolactone beaded fiber is prepared by electrospinning. The cobweb-inspired structure attenuates the mechanical stimulation of cells under a dynamic environment. Nano-protrusions are introduced into the scaffold for further inhibition of fibrosis by self-induced crystallization. A machine is built for in vitro dynamic culture and rat abdominal subcutaneous embedding experiments are performed to verify the inhibiting effect of fibrosis in a dynamic environment in vivo. Results show that the expression of integrin β1 and α-smooth muscle actin is inhibited by the cobweb-inspired structure under dynamic culture. The results of hematoxylin and eosin and Masson's trichrome indicate that the cobweb-inspired structure has a good inhibitory effect on fibrosis in a dynamic environment in vivo. In general, the cobweb-inspired scaffold with nano-protrusions has a good ability to inhibit fibrosis under both static and dynamic environments. It is believed that the scaffold has promising applications in the field of inhibiting fibrosis caused by mechanical stimulation.

Full-field in vivo experimental study of the strains of a breathing human abdominal wall with intra-abdominal pressure variation

The presented study aims to assess the mechanical behaviour of the anterior abdominal wall based on an in vivo experiment on humans. Full-field measurement of abdominal wall displacement during changes of intra-abdominal pressure is performed using a digital image correlation (DIC) system. Continuous measurement in time enables the observation of changes in the strain field during breathing. The understanding of the mechanical behaviour of a living human abdominal wall is important for the proper design of surgical meshes used for ventral hernia repair, which was also a motivation for the research presented below. The research refers to the strain field of a loaded abdominal wall and presents the evolution of principal strains and their directions in the case of 12 subjects, 8 male and 4 female. Peritoneal dialysis procedure allows for the measurement of intra-abdominal pressure after fluid introduction. High variability among patients is observed, also in terms of principal strain direction. Subjects exhibit intra-abdominal pressure of values from 11 to 21 cmH2O. However, the strain values are not strongly correlated with the pressure value, indicating variability of material properties.

A soft, bioinspired artificial lymphatic system for interactive ascites transfer

Low-flow removal of refractory ascites is critical to treating cirrhosis and digestive system tumor, and thus, commercial ascites pump emerged lately. The rigid structure of clinically available pumps rises complication rate and lack of flow rate monitoring hinders early warning of abnormalities. Herein, a soft artificial system was proposed inspired by lymph for interactive ascites transfer with great biocompatibility. The implantable system is composed of pump cavity, valves and tubes, which are soft and flexible made by silica gel. Therefore, the system possesses similar modulus to tissues and can naturally fit surrounding tissues. The cavity with magnetic tablet embedded is driven by extracorporeal magnetic field. Subsequently, the system can drain ascites with a top speed of 23 mL min-1, much higher than that of natural lymphatic system and state-of-art devices. Moreover, integrated flexible sensors enable wireless, real-time flow rate monitoring, serving as proof of treatment adjustment, detection and locating of malfunction at early stage. The liver function of experimental objects was improved, and no severe complications occurred for 4 weeks, which proved its safety and benefit to treatment. This artificial lymphatic system can serve as a bridge to recovery and pave the way for further clinical research.

Is mesh fixation necessary in laparoendoscopic techniques for M3 inguinal defects? An experimental study

BACKGROUND

Although international guidelines recommend not fixing the mesh in almost all cases of laparoendoscopic repairs, in case of large direct hernias (M3) mesh fixation is recommended to reduce recurrence risk. Despite lack of high-quality evidence, the recommendation was upgraded to strong by expert panel. The authors conducted a research experiment to verify the hypothesis that it is possible to preserve the mesh in the operating field in large direct hernias (M3) without the need to use fixing materials.

METHOD

The authors conducted an experiment with scientists from Universities of Technology in a model that reflects the conditions in the groin area. By simulating conditions of the highest possible intra-abdominal pressure, they examined the mesh behavior within the groin and its ability to dislocate under the forces generated by this pressure. The experiment involved six spatial implants and one flat macroporous mesh.

RESULTS

Heavyweight spatial meshes and lightweight spatial-individualized meshes showed no tendency to dislocate or move directly to the orifice, which was considered a rapid hernia recurrence. Lightweight meshes, both spatial and flat, underwent significant migration and shifting toward the hernial orifices.

CONCLUSION

Based on the results, we believe that mesh fixation is not the only alternative to preventing recurrence in complex defects. Similar effects can be achieved using a larger, more rigid, and anatomically fitted implant. The type of implant (rather than its fixation) seems to be a key factor from the point of view of mechanics and biophysics. Clinical trials confirming the results in vivo will allow to supplement or amend the guidelines for the treatment of large inguinal hernias.

Post-partum abdominal wall insufficiency syndrome (PPAWIS): lessons learned from a single surgeon's experience based on 200 cases

Background

Post-partum abdominal wall insufficiency (PPAWI) with rectus diastasis is present in over 30% of women after pregnancy. Little is known about how PPAWI affects the social, sexual life and self-esteem of patients. This study was designed to evaluate the safety of onlay mesh combined with abdominoplasty and its impact on the well-being of the patients.

Method

Two hundred patients with PPAWI underwent surgery with onlay mesh and abdominoplasty. The safety of the procedure was assessed by postoperative complications, time of hospitalization and time of drainage. Before the operation and 6 months later, a questionnaire asking about the patient’s sexual and social life and the presence of back pain was completed. The final cosmetic effect was assessed separately.

Results

The onlay procedure with abdominoplasty was found to be safe and fast. The mean operation time was 82 min, and the drainage time was 2.1 days. In this group < 2% postoperative complications were noted. There were no recurrences within the 6 month. Significant improvements in social and sexual life and the level of self-esteem were noted. Back pain was relieved or minimalized in all patients. The final cosmetic effect was insufficient for 2 patients (1%).

Conclusion

PPAWI can be treated safely with onlay mesh and abdominoplasty. The patients’ symptoms were strongly correlated with the morphological status of the front abdominal wall and improved after the procedure. Describing the psychological and social consequences of PPAWI should lead the surgical societies to propose a definition of a new disease called PPAWIS (post-partum abdominal wall insufficiency syndrome).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12893-022-01757-y.

Dynamic-MRI quantification of abdominal wall motion and deformation during breathing and muscular contraction

BACKGROUND AND OBJECTIVE

Biomechanical assessment of the abdominal wall represents a major prerequisite for a better understanding of physiological and pathological situations such as hernia, post-delivery recovery, muscle dystrophy or sarcopenia. Such an assessment is challenging and requires muscular deformations quantification which have been very scarcely reported in vivo. In the present study, we intended to characterize abdominal wall deformations in passive and active conditions using dynamic MRI combined to a semiautomatic segmentation procedure.

METHODS

Dynamic deformations resulting from three complementary exercises i.e. forced breathing, coughing and Valsalva maneuver were mapped in a transversal abdominal plane and so for twenty healthy volunteers. Real-time dynamic MRI series were acquired at a rate of 182 ms per image, then segmented semi-automatically to follow muscles deformation through each exercise. Circumferential and radial strains of each abdominal muscle were computed from the geometrical characteristics' quantification, namely the medial axis length and the thickness. Muscular radial displacement maps were computed using image registration.

RESULTS

Large variations in circumferential and radial strains were observed for the lateral muscles (LM) but remained low for the rectus abdominis muscles (RA). Contraction phases of each exercise led to LM muscle shortening down to -9.6 ± 5.9% during Valsalva maneuver with a 16.2 ± 9.6% thickness increase. Contraction also led to inward radial displacement of the LM up to 9.9 ± 4.1 mm during coughing. During maximal inhalation, a significant 10.0 ± 6.6% lengthening was quantified for LM while a significant thickness decrease was computed for the whole set of muscles (-14.7 ± 6.6% for LM and -7.3 ± 6.5% for RA). The largest displacement was observed for the medial part of RA (17.9 ± 8.0 mm) whereas the posterior part of LM underwent limited motion (2.8 ± 2.3 mm). Displacement rate and correlation between muscle thickness and medial axis length during each exercise provided insights regarding subject-specific muscle function.

CONCLUSIONS

Dynamic MRI is a promising tool for the assessment of the abdominal wall motion and deformations. The corresponding metrics which have been continuously recorded during the exercises provided global and regional quantitative information. These metrics offer perspectives for a genuine clinical evaluation tool dedicated to the assessment of abdominal muscles function in both healthy subjects and patients.

A novel in vivo approach to assess strains of the human abdominal wall under known intraabdominal pressure

The study concerns mechanical behaviour of a living human abdominal wall. A better mechanical understanding of a human abdominal wall and recognition of its material properties is required to find mechanically compatible surgical meshes to significantly improve the treatment of ventral hernias. A non-invasive methodology, based on in vivo optical measurements is proposed to determine strains of abdominal wall corresponding to a known intraabdominal pressure. The measurement is performed in the course of a standard procedure of peritoneal dialysis. A dedicated experimental stand is designed for the experiment. The photogrammetric technique is employed to recover the three-dimensional surface geometry of the anterior abdominal wall at the initial and terminal instants of the dialysis. This corresponds to two deformation states, before and after filling the abdominal cavity with dialysis fluid. The study provides information on strain fields of living human abdominal wall. The inquiry is aimed at principal strains and their directions, observed at the level from -10% to 17%. The intraabdominal pressure related to the amount of introduced dialysis fluid measured within the medical procedure covers the range 11-18.5 cmH₂O. The methodology leads to the deformation state of the abdominal wall according to the corresponding loading conditions. Therefore, the study is a step towards an identification of mechanical properties of living human abdominal wall.

In vivo performance of intraperitoneal onlay mesh after ventral hernia repair

BACKGROUND

Ventral hernia repair needs to be improved since recurrence, postoperative pain and other complications are still reported in many patients. The behavior of implants in vivo is not sufficiently understood to design a surgical mesh mechanically compatible with the human abdominal wall.

METHODS

This analysis was based on radiological pictures of patients who underwent laparoscopic ventral hernia repair. The pictures show the trunk of the patient at rest in a standing position and under side bending. The change in the distance between different tacks due to trunk movement was analyzed, which allowed us to determine the in vivo elongation of the mesh incorporated into the abdominal wall.

FINDINGS

The relative elongations of the surgical mesh varied from a few percent to greater than 100% in two cases. The median of the median relative elongations obtained for all patients is 9.5%, and the median of the maximum relative elongations for all patients is 32.6%. The maximum elongation occurs between tacks that are next to each other. Trunk movement causes implant deformation, and this study provides quantitative information regarding changes in the distance between fasteners.

INTERPRETATION

The physiological movement of the human abdomen must be regarded as a very important factor in mesh deformation and should be considered in surgical practice to reduce the hernia recurrence rate and postoperative pain.

Age-related changes in mechanical properties of human abdominal fascia

The purpose of this study is to assess and model age-related changes in the mechanical properties of human fascia. The samples were divided into three age groups: group A-up to 60 years (mean age 52.5 ± 6 years), group B-61-80 years (mean age 70.4 ± 5.2 years), and group C-81-90 years (mean age 83.2 ± 2 years). A uniaxial tensile test was applied to fascia specimens cut perpendicular and parallel to fibers. The secant modulus at 5% strain, the maximum stress, and the stretch at maximum stress were calculated from the stress-stretch ratio curves. The results indicated an increase in the secant modulus with the increased age. The trend is clearer in the longitudinal direction. Considering the strain energy function which accounts the isotropic and non-isotropic response of the fascia where isotropic and anisotropic parts are split, we evaluated which material model is the most suitable to present isotropic mechanical behavior of the tissue. The experimental stress-stretch ratio curves were approximated using Mooney-Rivlin, Yeoh, and neo-Hookean strain energy functions and a good match between theoretical and experimental results was obtained. On the basis of objective function values and normalized mean square root error, we recommend using the Yeoh model to describe the isotropic mechanical behavior of human abdominal fascia. Graphical abstract .

3D surface imaging of abdominal wall muscular contraction

BACKGROUND AND OBJECTIVE

The biomechanical analysis of the abdominal wall should take into account muscle activation and related phenomena, such as intra-abdominal pressure variation and abdomen surface deformation. The geometry of abdominal surface and its deformation during contraction have not been extensively characterized, while represent a key issue to be investigated.

METHODS

In this work, the antero-lateral abdominal wall surface of ten healthy volunteers in supine position is acquired via laser scanning in relaxed conditions and during abdominal muscles contraction, repeating each acquisition six times. The average relaxed and contracted abdominal surfaces are compared for each subject and displacements measured.

RESULTS

Muscular activation induces raising in the region adjacent to linea alba along the posterior-anterior direction and a simultaneous lowering along lateral-medial direction of the abdominal wall sides. Displacements reach a maximum value of 12.5 mm for the involved subjects. The coefficient of variation associated to the abdomen surface measurements in the same configuration (relaxed or contracted) is below 0.75%. Non-parametric Mann-Whitney U test highlights that the differences between relaxed and contracted abdominal wall surfaces are significant (p < 0.01).

CONCLUSIONS

Laser scanning is an accurate and reliable method to evaluate surface changes on the abdominal wall during muscular contraction. The results of this experimental activity can be useful to validate numerical models aimed at describing abdominal wall biomechanics.

Synthetic surgical meshes used in abdominal wall surgery: Part II-Biomechanical aspects

This work reports the second part of a review on synthetic surgical meshes used for abdominal hernia repair. While material and structural characteristics, together with mesh-tissue interaction, were considered in a previous article (Part I), biomechanical behavior is described here in more detail. The role of the prosthesis is to strengthen the impaired abdominal wall, mimicking autologous tissue without reducing its compliance. Consequently, mesh mechanical properties play a crucial role in a successful surgical repair. The main available techniques for mechanical testing, such as uniaxial and biaxial tensile testing, ball burst, suture retention strength, and tear resistance testing, are described in depth. Among these methods, the biaxial tensile test is the one that can more faithfully reproduce the physiological loading condition. An outline of the most significant results documented in the literature is reported, showing the variety of data on mesh mechanical properties. Synthetic surgical meshes generally follow a non-linear stress-strain behavior, with mechanical characteristics dependant on test direction due to mesh anisotropy. Ex-vivo tests revealed an increased stiffness in mesh explants due to the gradual ingrowth of the host tissue after implant. In general, the absence of standardization in test methods and terminology makes it difficult to compare results from different studies. Numerical models of the abdominal wall interacting with surgical meshes were also discussed representing a potential tool for the selection of suitable prostheses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 892-903, 2017.

Comparison of two different concepts of mesh and fixation technique in laparoscopic ventral hernia repair: a randomized controlled trial

BACKGROUND

Patients' need to improve outcomes and to reduce the number of complications triggers the development of new materials and surgery concepts. Currently, there are many implants and fixation systems dedicated for intraperitoneal onlay mesh procedure. The aim of this study was to compare two different mesh/fixation system concepts (PH: Physiomesh/Securestrap and VS: Ventralight ST/SorbaFix) for laparoscopic ventral hernia repair with respect to pain.

METHODS

A single-center, prospective, randomized study was designed to include 50 patients per group with a planned interim analysis for safety after 25 patients. The endpoints were pain occurrences and intensity, which was measured with the visual analogue scale 7 days, 30 days, 3 months and 6 months after surgery. The safety parameters included the number of recurrences and postoperative complications.

RESULTS

During the interim analysis, the study was stopped due to safety reasons. We observed five (20 %) recurrences in the PH group in first 6 months and none in the VS group. We observed a significantly higher pain rate in the PH group after 3 months (p < 0.0001) and no difference after 7 days (p = 0. 7019). The pain intensity decreased significantly over time (p < 0.0001) and was significantly higher in the PH group (p < 0.0001).

CONCLUSIONS

Although this clinical trial was terminated prior to the preplanned recruitment goal, the obtained results from the enrolled patients indicate that the PH system associated with significantly greater hernia recurrences and postoperative pain compared with the VS system. This confirms the superiority of the elastic mesh concept, which may be a safer and more efficacious option for laparoscopic ventral hernia repairs.

Titanium versus absorbable tacks comparative study (TACS): a multicenter, non-inferiority prospective evaluation during laparoscopic repair of ventral and incisional hernia: study protocol for randomized controlled trial

BACKGROUND

Laparoscopic repair of ventral and incisional hernias has gained popularity since many studies have reported encouraging results in terms of outcomee and recurrence. Choice of mesh and fixation methods are considered crucial issues in preventing recurrences and complications. Lightweight meshes are considered the first choice due to their biomechanical properties and the ability to integrate into the abdominal wall. Titanium helicoidal tacks still represent the "gold standard" for mesh fixation, even if they have been suggested to be involved in the genesis of post-operative pain and complications. Recently, absorbable tacks have been introduced, under the hypothesis that there will be no need to maintain a permanent fixation device after mesh integration. Nevertheless, there is no evidence that absorbable tacks may guarantee the same results as titanium tacks in terms of strength of fixation and recurrence rates. The primary end point of the present trial is to test the hypothesis that absorbable tacks are non-inferior to titanium tacks in laparoscopic incisional and ventral hernia repair (LIVHR) by lightweight polypropylene mesh, in terms of recurrence rates at 3-year follow-up. Surgical complications, post-operative stay, comfort and pain are secondary end points to be assessed.

METHODS/DESIGN

Two hundred and twenty patients with ventral hernia will be randomized into 2 groups: Group A (110) patients will be submitted to LIVHR by lightweight polypropylene mesh fixed by titanium tacks; Group B (110) patients will be submitted to LIVHR by lightweight polypropylene mesh fixed by absorbable tacks.

DISCUSSION

A few retrospective studies have reported similar results when comparing absorbable versus non-absorbable tacks in terms of intraoperative and early post-operative outcomes. These studies have the pitfalls to be retrospective evaluation of small series of patients, and the reported results still need to be validated by larger series and prospective studies. The aim of the present trial is to investigate and test the non-inferiority of absorbable versus non-absorbable tacks in terms of hernia recurrence rates, in order to assess whether the use of absorbable tacks may achieve the same results as non-absorbable tacks in mid-term and long-term settings.

TRIAL REGISTRATION NUMBER

NCT02076984: 5 June 2014 (ClinicalTrials.gov).

Physical and mathematical modelling of implant-fascia system in order to improve laparoscopic repair of ventral hernia

BACKGROUND

This paper describes an investigation of biomechanical behaviour of hernia repair, which is focused on the selection of safe linking of certain type of implant with fascia in laparoscopic operation. The strength of various fixations of the implant to the fascia is analysed.

METHODS

The research is based on experimental observations of operated hernia model behaviour during a dynamic impulse load corresponding to post-operative cough. Fifty seven different types of models of implanted mesh are considered. Five types of implants and five types of connectors are used. Mechanical properties of the implants as well as limit tearing forces of joints are identified in uni-axial tensile tests. Mathematical model of implanted mesh based on finite element method is proposed. The identified mechanical properties of the materials are applied and the model is calibrated using quantities measured during experiments.

FINDINGS

The presented results point at trans-abdominal sutures and ProTacks (connectors) and at DynaMesh (implant) as the most reliable materials used in ventral hernia operation, in the tested materials group. Desired properties of implants seem to be: elastic properties similar to the properties of tissues and high local strength, as fixation have a local character. The proposed mathematical model can be applied to simulate real behaviour of an implant with appropriate accuracy and to estimate the number of tacks for the implantation of hernia meshes.

INTERPRETATION

The presented results may help in the deeper understanding of the fascia-mesh system behaviour, and thus may lead to improve the fixation methods.

Lightweight polypropylene mesh fixation in laparoscopic incisional hernia repair

INTRODUCTION

The choice of the mesh and fixation methods in laparoscopic incisional hernia repair is a crucial issue in preventing complications and recurrence. The authors report a series of 40 consecutive laparoscopic incisional hernia repairs, focusing on the use of lightweight polypropylene mesh and on the way of mesh fixation.

MATERIAL AND METHODS

Forty laparoscopic incisional hernia repairs performed consecutively in 38 patients (16 males, 22 females) were retrospectively evaluated. Patients were divided into two groups depending on tacks used: Titanium tacks vs absorbable tacks.

RESULTS

All patients received totally laparoscopic incisional hernia repair by the use of lightweight polypropylene mesh. No major post-operative complications were reported. Post-operative pain (evaluated by VNS) was higher in Group A (titanium tacks, p < 0.05). No differences in follow-up as well as in recurrence incidence (one case in both groups, <6 months time interval) were reported.

CONCLUSIONS

Securestrap™ absorbable tacks are safe and effective and easy to use and did not increase the risk of mesh dislocation compared with non-absorbable tacks. The specific design well fits the lightweight polypropylene mesh Physiomesh™. Further evaluations in larger randomized studies are needed to confirm these preliminary data.

Mechanical Response of the Herniated Human Abdomen to the Placement of Different Prostheses

This paper describes a method designed to model the repaired herniated human abdomen just after surgery and examine its static mechanical response to the maximum intra-abdominal pressure provoked by a physiological movement (standing cough). The model is based on the real geometry of the human abdomen bearing a large incisional hernia with several anatomical structures differentiated by MRI. To analyze the outcome of hernia repair, the surgical procedure was simulated by modeling a prosthesis placed over the hernia. Three surgical meshes with different mechanical properties were considered: an isotropic heavy-weight mesh (Surgipro®), a slightly anisotropic light-weight mesh (Optilene®), and a highly anisotropic medium-weight mesh (Infinit®). Our findings confirm that anisotropic implants need to be positioned such that the most compliant axis of the mesh coincides with the craneo-caudal direction of the body.

Impact of the defect size, the mesh overlap and the fixation depth on ventral hernia repairs: a combined experimental and numerical approach

BACKGROUND

Ventral hernia repairs (VHRs) still exhibit clinical complications in terms of recurrence, pain, and discomfort. Factors such as surgical technique or mesh features are thought to be highly influent. The aim was to evaluate the impact of the defect size, the mesh overlap and the fixation depth on VHR using both physical and numerical models.

METHODS

The physical model was developed to mimic a passive abdominal wall. Healthy, damaged, and repaired configurations were evaluated using a spherical plunger. The associated numerical (Finite Elements) model was first loaded by a plunger for validation. A parametric study was then conducted with the numerical model loaded by a uniform pressure. Two defect sizes (3.5 × 5 cm and 8.25 × 12 cm elliptic shape), two overlaps (2 and 5 cm), and two fixation depths (peritoneum or muscle) were investigated for both passive and active abdominal walls.

RESULTS

With the physical model, the repaired configuration was 22 % stiffer than the damaged configuration. The statistical analysis of the parametric study showed that the defect size was the most influential parameter regarding the stress in the mesh, the bulging and the pull-out force at the fixation points. The overlap was influential in terms of stress in the mesh. The fixation depth was not influential. These trends increased with the abdominal wall activity.

CONCLUSION

Increase of the defect size and decrease of the overlap affected significantly the VHR mechanical performances. Such numerical models could help to better understand the behavior of the repaired abdominal wall and finally to reduce the clinical complications.

Mechanical response of animal abdominal walls in vitro: evaluation of the influence of a hernia defect and a repair with a mesh implanted intraperitoneally

Better mechanical knowledge of the abdominal wall is requested to further develop and validate numerical models. The aim of this study was to characterize the passive behaviour of the abdominal wall under three configurations: intact, after creating a defect simulating an incisional hernia, and after a repair with a mesh implanted intraperitonally. For each configuration, controlled boundary conditions were applied (air pressure and then contact loading) to the abdominal wall. 3D local strain fields were determined by digital image correlation. Local strains measured on the internal and external surfaces of the intact abdominal wall showed different patterns. The air pressure and the force applied to the abdominal wall during contact loading were measured and used to determine stiffness. The presence of a defect resulted in a significant decrease of the global stiffness compared to the intact abdominal wall (about 25%). In addition, the presence of the mesh enabled to restore the stiffness to values that were not significantly different from those of the intact wall. These results suggest that intraperitoneal mesh seems to restore the global biomechanics of the abdomen.

Biomechanics of the front abdominal wall as a potential factor leading to recurrence with laparoscopic ventral hernia repair

BACKGROUND

Intraabdominal pressure often is blamed as the cause of mesh-fascia junction failure after laparoscopic ventral hernia repair. Stretching of the mesh during a cough or defecation may lead to recurrence. Little is known about the movements of mesh in the abdominal cavity after this operation. This study investigated the front abdominal wall to describe its elasticity in vivo and searched for elongations that possibly stretched an implanted mesh, thereby causing fixation failure and subsequent recurrence.

METHODS

To measure front abdominal wall elongations, a model of fascia movements was created. Eight healthy volunteers were measured during exercise to determine the extent of elongations in their front abdominal wall. Videos were analyzed in three positions to create a mathematical shell structure. A computerized model based on the net movement of nodes was calculated to determine the axes and values for maximum elongations.

RESULTS

The largest average elongations were measured for the upper midline (32.08%) and the transverse line in the low lateral area (34.06%). The maximum values for these lines were larger than 100% for the middle line (133.78%) and exceeded 50% for the entire middle line. The values for the horizontal lines did not reach 10% at any level. According to these data, areas of both high and low elasticity were defined.

CONCLUSIONS

The presented experiment adds new parameters to the understanding of in vivo mesh behavior. Elongation of the front abdominal wall may stretch implanted mesh and could be a cause of recurrence in cases of insufficient fixation.