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

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.

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.

Essential anatomical landmarks in placement of an adequate size mesh for a successful ventral hernia repair

Safe and effective hernia repair requires a surgeon to have the appropriate knowledge necessary to learn details of the surgical technique. Long-term results of treatment, even with the use of synthetic implants, have shown that recurrences were still a significant clinical problem concerning up to every fourth patient. Therefore, it was pointed out that the mere presence of synthetic material is not a solitary circumstance sufficient for a successful repair. A key finding in recurrence prevention has been to focus surgeons&apos; attention on the relationship between the size of the hernia orifice and the mesh surface. An optimal ratio of these values has not been established yet, however, it is considered that the mesh surface area should be at least sixteen times larger than the area of the abdominal wall defect. In cases of medium and large hernias, in order to place an extensive mesh sheet in the appropriate anatomical space of the abdominal wall, an extensive dissection needs to be performed, including several different compartments. Therefore, a surgeon undertaking a hernia repair needs to know perfectly the anatomy and function of all the myofascial structures involved. Performing an incorrect dissection of a mistaken structure may lead to catastrophic abdominal deformities. Depriving the patient of the natural support of the abdominal wall provided by the muscles may lead to total or partial destabilization of the trunk and lead to disability. In this paper a detailed description of anatomical structures and its practical use has been presented.

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.

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

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.

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.

Kinematical analysis of the trunk, upper limbs and fingers during minimal access surgery when using an armrest

This study investigated whether using an armrest could reduce the movements of the trunk, upper limb and hand of surgeons during simulated minimal access surgery. Sixteen surgeons carried out two trials of simulated laparoscopic surgery, one using an armrest and the other without. Reflective markers were attached on the trunk, upper limbs, fingers, minimal access camera (MAC) and scissors, allowing a motion capture system to record the movements. The error ratios during operation, subjective opinions and operative durations were collected. The results showed that total displacements at the trunk and shoulders were reduced by at least 25% when using an armrest compared with not using one; error ratios were reduced by 7%; velocity and acceleration in the trunk, shoulder and MAC were reduced. After simulated operations, 78% of the participants preferred using the armrest. The study indicates that an armrest could improve surgical outcomes by reducing trunk movements.

PRACTITIONER SUMMARY

An armrest may help surgeons to reduce unnecessary movements during operations. The error ratios were reduced by 7% when using an armrest compared with no armrest. Displacements at the trunk and shoulders were reduced by 25% when using an armrest. Seventy-eight per cent of participants preferred to use an armrest after the experiment.

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.