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.

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.

Biomechanical causes for failure of the Physiomesh/Securestrap system.

This study investigates the mechanical behavior of the Physiomesh/Securestrap system, a hernia repair system used for IPOM procedures associated with high failure rates. The study involved conducting mechanical experiments and numerical simulations to investigate the mechanical behavior of the Physiomesh/Securestrap system under pressure load. Uniaxial tension tests were conducted to determine the elasticity modulus of the Physiomesh in various directions and the strength of the mesh-tissue-staple junction. Ex-vivo experiments on porcine abdominal wall models were performed to observe the system's behavior under simulated intra-abdominal pressure load. Numerical simulations using finite element analysis were employed to support the experimental findings. The results reveal nonlinearity, anisotropy, and non-homogeneity in the mechanical properties of the Physiomesh, with stress concentration observed in the polydioxanone (PDO) stripe. The mesh-tissue junction exhibited inadequate fixation strength, leading to staple pull-out or breakage. The ex-vivo models demonstrated failure under higher pressure loads. Numerical simulations supported these findings, revealing the reaction forces exceeding the experimentally determined strength of the mesh-tissue-staple junction. The implications of this study extend beyond the specific case of the Physiomesh/Securestrap system, providing insights into the mechanics of implant-tissue systems. By considering biomechanical factors, researchers and clinicians can make informed decisions to develop improved implants that mimic the mechanics of a healthy abdominal wall. This knowledge can contribute to better surgical outcomes and reduce complications in abdominal hernia repair and to avoid similar failures in future.

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.

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.

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.

Mechanics of mesh implanted into abdominal wall under repetitive load. Experimental and numerical study.

There are a number of papers discussing medical and mechanical aspects of ventral hernia management. Despite intensive work on the problem understanding, recurrences of the sickness still happen too often. For that reason, new aspects of the problem must be considered. In this article, a change in the abdominal implant's stiffness is discussed, which is caused by cyclic loading. Such loading influence abdominal implant, for example, while patient is coughing or exercising. For the first time, this stiffness change is quantitatively described for a selected knitted mesh. The influence of mesh stiffness changes on repaired hernia persistence is studied. Then, ex vivo experiments on a repaired hernia model under cyclic pressure loading are performed. Finally, numerical simulations of the experiments are made in which stresses and forces in the system are calculated. The two following cases are considered. In the first case, the mesh has its baseline stiffness, and in the second case, the mesh is preconditioned by former loading; thus, it is stiffened. Reaction forces at the mesh fixation points appear to be approximately twofold higher in the second case than in the first case. That may be a reason for a fixation damage in operated hernia system. The results presented shed new light on the necessary strength of mesh fixation in the abdominal wall. They enlarge the state of the art on laparoscopic hernia management with the use of a synthetic implant. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1400-1409, 2019.

Two-criteria optimisation problem for ventral hernia repair.

Two-criteria optimisation problem related to laparoscopic ventral hernia repair is formulated in this paper. An optimal implant from a given set and its orientation is sought. The implant is subjected to kinematic extortions due to a patient's body movement and intra-abdominal pressure. The first criterion of the optimisation problem deals with the reaction force in the implant fastener, while the deflection of the implant constitutes the second criterion. A two-stage optimization procedure is proposed and the optimal solution is determined with the aid of minimization of an additional objective function. Numerical examples for typical locations of hernia are provided.

Mechanical properties of mosquito nets in the context of hernia repair.

The paper deals with issue of applying mosquito nets as implants in hernia repair, which have already been used in resource-poor developing countries. Uniaxial tensile tests have been conducted on polyester mosquito meshes in two orthogonal directions. Non-linear elastic constitutive laws parameters have been identified to be applied in dense net material models. Mechanical performance of tested mosquito nets has been compared with properties of commercial implants used in treatment of hernia and with properties of human tissue. This study contributes to mechanical knowledge of hernia repair issue by investigation of cheaper alternative to commercial implants.

Safety and efficacy of a Ventralight ST echo ps implant for a laparoscopic ventral hernia repair - a prospective cohort study with a one-year follow-up.

UNLABELLED: Laparoscopic ventral hernia repair has become popular technique. Every year, companies are introducing new products Thus, every mesh prior to introduction in clinical settings should be tested with a dedicated tacker to discover the proper fixation algorithm. The aim of the study was to assess the safety and efficacy of the Ventralight ST implant with an ECHO positioning system and a dedicated fixation device, the SorbaFix stapler, in a prospective cohort of patients. MATERIAL AND METHODS: The study was a prospective single centre cohort study with a one-year followup period. Fifty-two patients received operations for a ventral hernia using a laparoscopic IPOM mesh - Ventralight ST ECHO PS. The size of the mesh and the fixation method were based on mathematical considerations. A recurrence of the hernia and pain after 1, 2 and 12 months were assessed as the primary endpoints. RESULTS: Two recurrences were noted, one in parastomal and one in a large incisional hernia. Pain was observed in 22 patients (41%) and mostly disappeared after 3 months (7%). The intensity of pain was low (VAS <2). However, 2 patients still experienced severe pain (VAS>6) until the end of the study. CONCLUSION: The Ventralight ST Echo PS implant fixed with a Sorbafix stapler is a valuable and safe option for a laparoscopic ventral hernia repair. In our opinion, the implant could be used in all patients due to the hernia ring diameter. According to the mathematical models and clinical practice, we do not recommend this implant in orifices with a width larger than 10 cm.

Behaviour of orthotropic surgical implant in hernia repair due to the material orientation and abdomen surface deformation.

Surgical implants used in hernia repair reveal isotropic as well as orthotropic properties. In particular, its orthotropy, in relation to the different range of typical deformations observed in different directions and zones of abdomen surface due to the patients' life activities, has a significant influence on the extreme junction forces in the mesh-tissue connections and hence the repair persistence. The finite element model of the orthotropic implant was developed, and the junction forces in the connections of tissue and mesh were studied. The kinematical extortions representing the abdomen surface deformations identified in specific zones of hernia placement were applied to the model. The sensitive analysis was applied to specify the influence of the orthotropy (implant orientation) direction to the repair persistence. Due to the anisotropy of the human abdomen and also the different range of deformations observed in different areas of abdomen surface, the behaviour of the implant differs significantly depending on the hernia placement and the implant orientation. Especially, it is observed in the values of the implant-tissue junction forces which determinate considerably the repair persistence. The provided results and conclusions may be useful in some clinical recommendations for implantation of orthotropic surgical mesh specifying the hernia placement as well as the orthotropic implant orientation. This can also be considered in the design of new synthetic implants with more physiologic tissue-like properties also taking into account the human abdomen anisotropy.

Mathematical modelling of implant in an operated hernia for estimation of the repair persistence.

This paper presents mathematical modelling of an implanted surgical mesh used in the repair process of the abdominal hernia. The synthetic implant is simulated by a membrane structure. The author provides a material modelling of the implant based on the dense net model appropriate for technical fabrics. The accuracy of the proposed solution is evaluated by comparing the simulations of the dynamic behaviour of the system with the experiments carried out on physical models of implanted mesh. The model can be used to estimate the repair persistence for different mesh materials, fixing systems and different numbers of tacks to be provided during the surgery in order to resist the cough pressure and required action to avoid hernia recurrence. The persistence of the repaired hernia is assessed on the basis of the values of the forces in the tissue-implant joints because the usual form of the repair failure is due to as the joint disconnection or tissue failure.

Mechanical behaviour of the implant used in human hernia repair under physiological loads.

In laparoscopic operations of abdominal hernias some recurrences still take place, even when applying a surgical mesh. This is usually caused by a failure of the connection between the tissue and the implant. The study deals with the influence of an implant's orientation on forces in joints, which connect the mesh to human tissues. In the paper, the implant is modelled as a membrane structure within framework of the Finite Element Method. Two models are analysed: in the first one interaction between the mesh and a fascia is taken into account, in the second this interaction is not considered. Computations are conducted for two different material types of the implants: one with isotropic properties and second one with orthotropic properties. The models are validated by comparing dynamic numerical analysis with experimental outcomes, where load was simulating intraabdominal pressure during postoperative cough. Due to displacements of joints during activities like bending sideways or torsion of an abdomen, influence of kinematic extortions on forces in the joints is analysed. The outcome shows that position of the orthotropic implants is crucial and may strongly change the level of forces in the joints.

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

BACKGROUND: Ventral hernia is a common medical problem. Statistically there are around 10% recurrences of the sickness. The authors' former investigation proved edges of the hernia orifice displacements to be one of the factors causing recurrence. Thus, experimental investigation of the abdomen surface deformation due to some normal activities of people is studied. METHODS: Eight slim, healthy people were asked to extremely stretch their abdomens. Bending, stretching and expiration were considered. The deformations registration was made by two cameras located in front of the patient on both sides. Special calculation procedure was used in order to transform characteristic point displacements to strains of abdomen in different directions. FINDINGS: The extreme strains, their localization and directions are identified. The study proves that the highest strains, bigger than 25% on average, appear in the upper part of the central vertical line of the abdomen and in lower sides in semi-vertical direction. The lowest strains, smaller than 7%, occur in a horizontal line situated low in the abdomen. For each patient similar zones of smaller or bigger strains are identified, however a wide discrepancy of the strain values obtained for different patients is stated. For example the strains in lower part in semi-vertical direction for one patient equals 9% and for another 134%! INTERPRETATION: The acquired conclusions may be useful for surgeons in finding practical solutions to dilemmas concerning the choice of an implant (elastic or stiff) for a specific ventral hernia, its proper connection with fascia and orientation in the abdomen.