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.

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.

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.

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.