In vivo MRI visualization of mesh shrinkage using surgical implants loaded with superparamagnetic iron oxides

X-Ray Visible Protein Scaffolds by Bulk Iodination

Protein-based biomaterial use is expanding within medicine, together with the demand to visualize their placement and behavior in vivo. However, current medical imaging techniques struggle to differentiate between protein-based implants and surrounding tissue. Here a fast, simple, and translational solution for tracking transplanted protein-based scaffolds is presented using X-ray CT-facilitating long-term, non-invasive, and high-resolution imaging. X-ray visible scaffolds are engineered by selectively iodinating tyrosine residues under mild conditions using readily available reagents. To illustrate translatability, a clinically approved hernia repair mesh (based on decellularized porcine dermis) is labeled, preserving morphological and mechanical properties. In a mouse model of mesh implantation, implants retain marked X-ray contrast up to 3 months, together with an unchanged degradation rate and inflammatory response. The technique's compatibility is demonstrated with a range of therapeutically relevant protein formats including bovine, porcine, and jellyfish collagen, as well as silk sutures, enabling a wide range of surgical and regenerative medicine uses. This solution tackles the challenge of visualizing implanted protein-based biomaterials, which conventional imaging methods fail to differentiate from endogenous tissue. This will address previously unanswered questions regarding the accuracy of implantation, degradation rate, migration, and structural integrity, thereby accelerating optimization and safe translation of therapeutic biomaterials.

Mesh shrinkage after transabdominal preperitoneal inguinal hernia repair

Synthetic mesh is now used for inguinal hernia repair in most cases. It is well known that the indwelling mesh contracts after placement in the body, regardless of the material. The aim of this study was to develop a method for indirect measurement of the mesh area postoperatively that allows for easy comparison with the condition of the mesh immediately after surgery. X-ray-impermeable tackers were used to fix the mesh, and changes of the indwelling mesh after surgery were measured indirectly using two mesh materials. This study involved 26 patients who underwent inguinal hernia repair with a polypropylene or polyester mesh (13 patients each). Polypropylene showed a stronger tendency to shrink, but there was no significant difference between the materials. For both materials, some patients showed relatively strong shrinkage and others showed relatively weak shrinkage. The group with the strong shrinkage had significantly higher body mass index. The results of the present study showed that mesh surly shrinked over time and there was no adverse effect of mesh shrinkage on the patients outcomes in this population. Mesh would shrink over time regardless of the sort of mesh but it did not affect the patients outcomes.

Analyzing material changes consistent with degradation of explanted polymeric hernia mesh related to clinical characteristics

BACKGROUND

Proposed mechanisms that potentially contribute to polypropylene mesh degradation after in vivo exposure include oxidizing species and mechanical strains induced by normal healing, tissue integration, muscle contraction, and the immediate and chronic inflammatory responses.

METHODS

This study explores these potential degradation mechanisms using 63 mesh implants retrieved from patients after a median implantation time of 24 months following hernia repair surgery (mesh explants) and analysis of multivariate associations between the material changes and clinical characteristics. Specifically, polypropylene mesh degradation was characterized in terms of material changes in surface oxidation, crystallinity and mechanical properties, and clinical characteristics included mesh placement location, medical history and mesh selection.

RESULTS

Compared to pristine control samples, subsets of mesh explants had evidence of surface oxidation, altered crystallinity, or changed mechanical properties. Using multivariate statistical approach to control for clinical characteristics, infection was a significant factor affecting changes in mesh stiffness and mesh class was a significant factor affecting polypropylene crystallinity changes.

CONCLUSIONS

Highly variable in vivo conditions expose mesh to mechanisms that alter clinical outcomes and potentially contribute to mesh degradation. These PP mesh explants after 0.5 to 13 years in vivo had measurable changes in surface chemistry, crystallinity and mechanical properties, with significant trends associated with factors of mesh placement, mesh class, and infection.

The Myopectineal Orifice: A Study of Thai Cadavers

Objective

This study aimed to determine the myopectineal orifice size measured in Thai human cadavers.

Materials and Methods

A total of 30 human cadavers, comprising 55 groins, were assessed. Myopectineal orifices (MPOs) were measured in two dimensions: height from the lower border of the conjoined tendon to the upper border of the pectineal ligament and width from the lateral border of pubic tubercle to the medial border of the iliopsoas muscle.

Results

The mean MPO size is 7.13 + 0.14 cm in width and 6.66 + 0.32 m in height. The mean width and height in male cadavers are 7.16 + 0.14 and 6.84 + 0.27 cm, respectively. The mean width and height in female cadavers are 7.09 + 0.12 and 6.45 + 0.24 cm, respectively. The mean MPO area is 37.26 ± 0.027 cm², compared with the area of mesh graft 10 cm × 15 cm, 150 cm². Although the shrinkage of cadaveric tissue and mesh size were adjusted, which were 39.56 ± 0.029 and 81 cm², respectively, they were found to be sufficient for the mean MPO area. It was found that the mesh size was sufficient for the mean MPO area.

Conclusion

A mesh size of 10 cm × 15 cm is found to be the appropriate size to cover the MPO among Thais.

Development of a risk score for choledocholithiasis in pediatric patients

PURPOSE

The prevalence of gallstones in children has increased over the last years. Choledocholithiasis (CD) is present in up to 30% of the cases. There is a scarcity of studies on the management of choledocholithiasis in children. The aim of this study was to develop a score that would allow predicting accurately the risk of CD in children with gallstones and reduce the number of non-therapeutic ERCP.

MATERIALS AND METHODS

We conducted a retrospective study in children with gallstones and suspected CD seen between January 2010 and December 2019. The main outcome was the presence of CD confirmed by at least one of the following diagnostic tests: magnetic resonance cholangiopancreatography (MRCP), endoscopic retrograde cholangiopancreatography (ERCP), and/or intraoperative cholangiography (IOC). We developed a risk score based on the presence or absence of the following risk factors: acute biliary pancreatitis, ascending cholangitis, elevated liver function tests (AST, ALT, total bilirubin [TB, ≥ 2 mg/dl], conjugated bilirubin, gamma-glutamyl transpeptidase, and alkaline phosphatase), CD on ultrasound (US; this was considered predictive but not confirmatory of CD), and dilation of the common bile duct (> 6 mm) by US. The score was divided into three different categories: low risk (no risk factors), intermediate risk (one risk factor present), high risk (≥ 2 risk factors present or ascending cholangitis). Given the main goal of reducing the number of diagnostic ERCPs, a very-high-risk subgroup (3 risk factors present or ascending cholangitis) was identified.

RESULTS

We reviewed 133 patients with gallstones and suspected CD. In 56 (42.1%) patients, the presence of CD was confirmed by one or more of the definitive diagnostic tests (MRCP, ERCP, and IOC). The following variables were found to be the strongest predictors of CD: ascending cholangitis, TB ≥ 2 mg/dl, common bile duct > 6 mm, and the presence of CD by US. The positive predictive value for CD was 7.5% in the low-risk group (OR 0.06, P = < 0.001); 22.9% in the intermediate-risk group (OR 0.31, P = 0.007); 77.6% in the high-risk group (OR 20.14, P = < 0.001); and 95.7% in very-high-risk subgroup (OR 49.18, P = < 0.001).

CONCLUSION

The risk score proposed in this study predicts accurately the presence of CD in children with gallstones. It can serve as a helpful tool to triage the need for costly and complex studies in the workup of CD, particularly in centers with limited resources. Finally, due to its high specificity and positive predictive value (PPV), the use of the very-high-risk criteria would allow for an important decrease in the number of non-therapeutic ERCP.

Long-term in vivo performances of polylactide/iron oxide nanoparticles core-shell fibrous nanocomposites as MRI-visible magneto-scaffolds

There is a growing interest in magnetic nanocomposites in biomaterials science. In particular, nanocomposites that combine poly(lactide) (PLA) nanofibers and superparamagnetic iron oxide nanoparticles (SPIONs), which can be obtained by either electrospinning of a SPION suspension in PLA or by precipitating SPIONs at the surface of PLA, are well documented in the literature. However, these two classical processes yield nanocomposites with altered materials properties, and their long-term in vivo fate and performances have in most cases only been evaluated over short periods of time. Recently, we reported a new strategy to prepare well-defined PLA@SPION nanofibers with a quasi-monolayer of SPIONs anchored at the surface of PLA electrospun fibers. Herein, we report on a 6-month in vivo rat implantation study with the aim of evaluating the long-term magnetic resonance imaging (MRI) properties of this new class of magnetic nanocomposites, as well as their tissue integration and degradation. Using clinically relevant T2-weighted MRI conditions, we show that the PLA@SPION nanocomposites are clearly visible up to 6 months. We also evaluate here by histological analyses the slow degradation of the PLA@SPIONs, as well as their biocompatibility. Overall, these results make these nanocomposites attractive for the development of magnetic biomaterials for biomedical applications.

Pore texture analysis in automated 3D breast ultrasound images for implanted lightweight hernia mesh identification: a preliminary study

Background

Precise visualization of meshes and their position would greatly aid in mesh shrinkage evaluation, hernia recurrence risk assessment, and the preoperative planning of salvage repair. Lightweight (LW) meshes are able to preserve abdominal wall compliance by generating less post-implantation fibrosis and rigidity. However, conventional 3D imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) cannot visualize the LW meshes. Patients sometimes have to undergo a second-look operation for visualizing the mesh implants. The goal of this work is to investigate the potential advantages of Automated 3D breast ultrasound (ABUS) pore texture analysis for implanted LW hernia mesh identification.

Methods

In vitro, the appearances of four different flat meshes in both ABUS and 2D hand-held ultrasound (HHUS) images were evaluated and compared. In vivo, pore texture patterns of 87 hernia regions were analyzed both in ABUS images and their corresponding HHUS images.

Results

In vitro studies, the imaging results of ABUS for implanted LW meshes are much more visualized and effective in comparison to HHUS. In vivo, the inter-class distance of 40 texture features was calculated. The texture features of 2D sectional plans (axial and sagittal plane) have no significant contribution to implanted LW mesh identification. Significant contribution was observed in coronal plane. However, since the mesh may have spatial variation such as shrinkage after implantation surgery, the inter-class distance of 3D coronal plane pore texture features are bigger than 2D coronal plane, so the contribution of 3D coronal plane pore texture features are more valuable than 2D coronal plane for implanted LW mesh identification. The use of 3D pore texture features significantly improved the robustness of the identification method in distinguishing between LW mesh and fascia.

Conclusions

An innovative new ABUS provides additional pore texture visualization, by separating the LW mesh from the fascia tissues. Therefore, ABUS has the potential to provides more accurate features to characterize pore texture patterns, and ultimately provide more accurate measures for implanted LW mesh identification.

Deformation of Transvaginal Mesh in Response to Multiaxial Loading

Synthetic mesh for pelvic organ prolapse (POP) repair is associated with high complication rates. While current devices incorporate large pores (>1 mm), recent studies have shown that uniaxial loading of mesh reduces pore size, raising the risk for complications. However, it is difficult to translate uniaxial results to transvaginal meshes, as in vivo loading is multidirectional. Thus, the aim of this study was to (1) experimentally characterize deformation of pore diameters in a transvaginal mesh in response to clinically relevant multidirectional loading and (2) develop a computational model to simulate mesh behavior in response to in vivo loading conditions. Tension (2.5 N) was applied to each of mesh arm to simulate surgical implantation. Two loading conditions were assessed where the angle of the applied tension was altered and image analysis was used to quantify changes in pore dimensions. A computational model was developed and used to simulate pore behavior in response to these same loading conditions and the results were compared to experimental findings. For both conditions, between 26.4% and 56.6% of all pores were found to have diameters <1 mm. Significant reductions in pore diameter were noted in the inferior arms and between the two superior arms. The computational model identified the same regions, though the model generally underestimated pore deformation. This study demonstrates that multiaxial loading applied clinically has the potential to locally reduce porosity in transvaginal mesh, increasing the risk for complications. Computational simulations show potential of predicting this behavior for more complex loading conditions.

Surgical and radiological behavior of MRI-depictable mesh implants after TAPP repair: the IRONMAN study

PURPOSE

Knowledge of postoperative behavior of mesh implants used for hernia repair is generally limited to cases of recurrence, local complications or return to the previous operative field in other pathological conditions. Previous studies with MRI-visible mesh implants in different parts of the abdominal wall have led to variable findings with regard to mesh properties and mostly described a reduction in size over time with subsequently limited mesh overlap over hernia defects which could contribute to recurrence. We aimed to evaluate implant properties in a mechanically stable anatomical region after TAPP repair of primary unilateral inguinal hernias in men with clinical and MRI examinations 4 weeks and 1 year after surgery.

METHODS

From 11/2015 to 01/2019, 23 men with primary, unilateral, inguinal hernias underwent TAPP repair with iron particle-loaded, MRI-visible mesh implants in a prospective cohort study. In 16 patients the operative outcome could be evaluated 4 weeks and 12 months after surgery by clinical examination and MRI evaluation with regard to postoperative course, possible adverse outcomes and radiological findings related to implant behavior-namely MRI-identifiability, mesh dislocation or reduction in surface area.

RESULTS

All included patients had an uneventful postoperative clinical course. MRI after 4 weeks revealed one postoperative seroma, which resolved spontaneously. No recurrence was detected. Mesh implants could be accurately delineated in DIXON-IN studies and showed neither clinically nor statistically significant changes in size or position.

CONCLUSION

4 weeks and 1 year after a standardized TAPP procedure the mesh implant used in this study showed no tendency towards dislocation or reduction in size in this anatomical position. Its MRI visibility allows accurate delineation during the postoperative course by experienced radiologists in appropriate MRI protocols. Larger patient series are desirable to further support these findings. Shrinkage of implants in the groin as a reason for early recurrence may be overestimated.

Ultrasound visualization of sacrocolpopexy polyvinylidene fluoride meshes containing paramagnetic Fe particles compared with polypropylene mesh

INTRODUCTION AND HYPOTHESIS

Paramagnetic Fe particles can be added during synthetic mesh production to allow visibility on magnetic resonance imaging. Our aim was to evaluate whether transperineal ultrasound (TPUS) allows visualization, measurement, and characterization of polyvinylidene fluoride (PVDF mesh) containing Fe particles compared with regular polypropylene (PP) meshes used for sacrocolpopexy.

METHODS

Women up to 1.5 years after laparoscopic sacrocolpopexy who were implanted with a PP or PVDF mesh underwent clinical examination and 2D, 3D, and 4D TPUS. Acquired volumes were analyzed offline for mesh position at rest and maximal Valsalva and for mesh dimensions and characteristics, with the operator blinded to group assignment. The two groups were compared.

RESULTS

There were 17 women in the PP and 25 in the PVDF mesh group, without differences in baseline demographics. None had significant prolapse, recurrence, symptoms, or complications. On TPUS, mesh was visible in all patients both caudally (perineal) and cranially but was more echogenic in the PVDF mesh group. Mesh length from distal to proximal that was visible on TPUS was longer for PVDF mesh, for both anterior and posterior vaginal arms (all P < 0.05), and for mesh above the vaginal apex (P = 0.002). The inferior aspects of the mesh showed areas of double mesh layers, suggesting folding in 80% of women in both groups, without symptoms.

CONCLUSIONS

PVDF mesh permits clearer visualization and is seen over a longer stretch on TPUS, with longer visible mesh arms. The latter can be due to differences in operative technique, presence of microparticles, implant textile structure, or patient characteristics.

International guidelines for groin hernia management

INTRODUCTION

Worldwide, more than 20 million patients undergo groin hernia repair annually. The many different approaches, treatment indications and a significant array of techniques for groin hernia repair warrant guidelines to standardize care, minimize complications, and improve results. The main goal of these guidelines is to improve patient outcomes, specifically to decrease recurrence rates and reduce chronic pain, the most frequent problems following groin hernia repair. They have been endorsed by all five continental hernia societies, the International Endo Hernia Society and the European Association for Endoscopic Surgery.

METHODS

An expert group of international surgeons (the HerniaSurge Group) and one anesthesiologist pain expert was formed. The group consisted of members from all continents with specific experience in hernia-related research. Care was taken to include surgeons who perform different types of repair and had preferably performed research on groin hernia surgery. During the Group's first meeting, evidence-based medicine (EBM) training occurred and 166 key questions (KQ) were formulated. EBM rules were followed in complete literature searches (including a complete search by The Dutch Cochrane database) to January 1, 2015 and to July 1, 2015 for level 1 publications. The articles were scored by teams of two or three according to Oxford, SIGN and Grade methodologies. During five 2-day meetings, results were discussed with the working group members leading to 136 statements and 88 recommendations. Recommendations were graded as "strong" (recommendations) or "weak" (suggestions) and by consensus in some cases upgraded. In the Results and summary section below, the term "should" refers to a recommendation. The AGREE II instrument was used to validate the guidelines. An external review was performed by three international experts. They recommended the guidelines with high scores. The risk factors for inguinal hernia (IH) include: family history, previous contra-lateral hernia, male gender, age, abnormal collagen metabolism, prostatectomy, and low body mass index. Peri-operative risk factors for recurrence include poor surgical techniques, low surgical volumes, surgical inexperience and local anesthesia. These should be considered when treating IH patients. IH diagnosis can be confirmed by physical examination alone in the vast majority of patients with appropriate signs and symptoms. Rarely, ultrasound is necessary. Less commonly still, a dynamic MRI or CT scan or herniography may be needed. The EHS classification system is suggested to stratify IH patients for tailored treatment, research and audit. Symptomatic groin hernias should be treated surgically. Asymptomatic or minimally symptomatic male IH patients may be managed with "watchful waiting" since their risk of hernia-related emergencies is low. The majority of these individuals will eventually require surgery; therefore, surgical risks and the watchful waiting strategy should be discussed with patients. Surgical treatment should be tailored to the surgeon's expertise, patient- and hernia-related characteristics and local/national resources. Furthermore, patient health-related, life style and social factors should all influence the shared decision-making process leading up to hernia management. Mesh repair is recommended as first choice, either by an open procedure or a laparo-endoscopic repair technique. One standard repair technique for all groin hernias does not exist. It is recommended that surgeons/surgical services provide both anterior and posterior approach options. Lichtenstein and laparo-endoscopic repair are best evaluated. Many other techniques need further evaluation. Provided that resources and expertise are available, laparo-endoscopic techniques have faster recovery times, lower chronic pain risk and are cost effective. There is discussion concerning laparo-endoscopic management of potential bilateral hernias (occult hernia issue). After patient consent, during TAPP, the contra-lateral side should be inspected. This is not suggested during unilateral TEP repair. After appropriate discussions with patients concerning results tissue repair (first choice is the Shouldice technique) can be offered. Day surgery is recommended for the majority of groin hernia repair provided aftercare is organized. Surgeons should be aware of the intrinsic characteristics of the meshes they use. Use of so-called low-weight mesh may have slight short-term benefits like reduced postoperative pain and shorter convalescence, but are not associated with better longer-term outcomes like recurrence and chronic pain. Mesh selection on weight alone is not recommended. The incidence of erosion seems higher with plug versus flat mesh. It is suggested not to use plug repair techniques. The use of other implants to replace the standard flat mesh in the Lichtenstein technique is currently not recommended. In almost all cases, mesh fixation in TEP is unnecessary. In both TEP and TAPP it is recommended to fix mesh in M3 hernias (large medial) to reduce recurrence risk. Antibiotic prophylaxis in average-risk patients in low-risk environments is not recommended in open surgery. In laparo-endoscopic repair it is never recommended. Local anesthesia in open repair has many advantages, and its use is recommended provided the surgeon is experienced in this technique. General anesthesia is suggested over regional in patients aged 65 and older as it might be associated with fewer complications like myocardial infarction, pneumonia and thromboembolism. Perioperative field blocks and/or subfascial/subcutaneous infiltrations are recommended in all cases of open repair. Patients are recommended to resume normal activities without restrictions as soon as they feel comfortable. Provided expertise is available, it is suggested that women with groin hernias undergo laparo-endoscopic repair in order to decrease the risk of chronic pain and avoid missing a femoral hernia. Watchful waiting is suggested in pregnant women as groin swelling most often consists of self-limited round ligament varicosities. Timely mesh repair by a laparo-endoscopic approach is suggested for femoral hernias provided expertise is available. All complications of groin hernia management are discussed in an extensive chapter on the topic. Overall, the incidence of clinically significant chronic pain is in the 10-12% range, decreasing over time. Debilitating chronic pain affecting normal daily activities or work ranges from 0.5 to 6%. Chronic postoperative inguinal pain (CPIP) is defined as bothersome moderate pain impacting daily activities lasting at least 3 months postoperatively and decreasing over time. CPIP risk factors include: young age, female gender, high preoperative pain, early high postoperative pain, recurrent hernia and open repair. For CPIP the focus should be on nerve recognition in open surgery and, in selected cases, prophylactic pragmatic nerve resection (planned resection is not suggested). It is suggested that CPIP management be performed by multi-disciplinary teams. It is also suggested that CPIP be managed by a combination of pharmacological and interventional measures and, if this is unsuccessful, followed by, in selected cases (triple) neurectomy and (in selected cases) mesh removal. For recurrent hernia after anterior repair, posterior repair is recommended. If recurrence occurs after a posterior repair, an anterior repair is recommended. After a failed anterior and posterior approach, management by a specialist hernia surgeon is recommended. Risk factors for hernia incarceration/strangulation include: female gender, femoral hernia and a history of hospitalization related to groin hernia. It is suggested that treatment of emergencies be tailored according to patient- and hernia-related factors, local expertise and resources. Learning curves vary between different techniques. Probably about 100 supervised laparo-endoscopic repairs are needed to achieve the same results as open mesh surgery like Lichtenstein. It is suggested that case load per surgeon is more important than center volume. It is recommended that minimum requirements be developed to certify individuals as expert hernia surgeon. The same is true for the designation "Hernia Center". From a cost-effectiveness perspective, day-case laparoscopic IH repair with minimal use of disposables is recommended. The development and implementation of national groin hernia registries in every country (or region, in the case of small country populations) is suggested. They should include patient follow-up data and account for local healthcare structures. A dissemination and implementation plan of the guidelines will be developed by global (HerniaSurge), regional (international societies) and local (national chapters) initiatives through internet websites, social media and smartphone apps. An overarching plan to improve access to safe IH surgery in low-resource settings (LRSs) is needed. It is suggested that this plan contains simple guidelines and a sustainability strategy, independent of international aid. It is suggested that in LRSs the focus be on performing high-volume Lichtenstein repair under local anesthesia using low-cost mesh. Three chapters discuss future research, guidelines for general practitioners and guidelines for patients.

CONCLUSIONS

The HerniaSurge Group has developed these extensive and inclusive guidelines for the management of adult groin hernia patients. It is hoped that they will lead to better outcomes for groin hernia patients wherever they live. More knowledge, better training, national audit and specialization in groin hernia management will standardize care for these patients, lead to more effective and efficient healthcare and provide direction for future research.

Prospective cohort study on mesh shrinkage measured with MRI after laparoscopic ventral hernia repair with an intraperitoneal iron oxide-loaded PVDF mesh

BACKGROUND

Current data on shrinkage of intraperitoneal meshes come mainly from animal studies. High-quality human data in prospective studies are scarce.

METHODS

We used the ability to visualize intraperitoneal PVDF meshes enhanced with iron particles (DynaMesh IPOM visible) with magnetic resonance imaging (MRI) to determine the amount of shrinkage between 1 and 13 months postoperatively. All measurements of the width, length, and surface area of the mesh were performed with a standardized methodology independently by four radiologists blinded for the timing of the MRI.

RESULTS

Of the 15 patients undergoing laparoscopic ventral hernia repair, 13 patients received an MRI both at 1 and at 13 months. Evaluation of inter-rater reliability between the radiologists showed intra-class correlations of 0.95 (95% CI 0.92-0.98) for the width, 0.96 (95% CI 0.93-0.98) for the length, and 0.99 (90% CI 0.99-1.00) for the surface area of the mesh. The change between measurement at implantation and 1-month MRI was - 0.7 cm (P = 0.023; - 3.6%) for the width and - 1.9 cm (P = 0.001; - 7.2%) for the length. The change between 1 and 13 months was - 0.06 cm (P = 0.74; shrinkage = 0.3%) for the width, - 0.12 cm (P = 0.56; shrinkage = 0.5%) for the length, and - 4.0 cm² (P = 0.20; shrinkage = 1.0%) for the surface area of the mesh.

CONCLUSION

There is excellent inter-rater reliability between radiologists when measuring width, length, and surface area of visible intraperitoneal PVDF mesh with MRI. There is no significant shrinkage between 1 and 13 months of intraperitoneal PVDF mesh after laparoscopic ventral hernia repair.

MRI Evaluation of an Elastic TPU Mesh under Pneumoperitoneum in IPOM Position in a Porcine Model

BACKGROUND

The frequency of laparoscopic approaches increased in hernia surgery over the past years. After mesh placement in IPOM position, the real extent of the meshes configurational changes after termination of pneumoperitoneum is still largely unknown. To prevent a later mesh folding it might be useful to place the mesh while it is kept under tension. Conventionally used meshes may lose their Effective Porosity under these conditions due to poor elastic properties. The aim of this study was to evaluate a newly developed elastic thermoplastic polyurethane (TPU) containing mesh that retains its Effective Porosity under mechanical strain in IPOM position in a porcine model. It was visualized under pneumoperitoneum using MRI in comparison to polyvinylidenefluoride (PVDF) meshes with similar structure.

METHODS

In each of ten minipigs, a mesh (TPU containing or native PVDF, 10 × 20 cm) was randomly placed in IPOM position at the center of the abdominal wall. After 8 weeks, six pigs underwent MRI evaluation with and without pneumoperitoneum to assess the visibility and elasticity of the mesh. Finally, pigs were euthanized and abdominal walls were explanted for histological and immunohistochemical assessment. The degree of adhesion formation was documented.

RESULTS

Laparoscopic implantation of elastic TPU meshes in IPOM position was feasible and safe in a minipig model. Mesh position could be precisely visualized and assessed with and without pneumoperitoneum using MRI after 8 weeks. Elastic TPU meshes showed a significantly higher surface increase under pneumoperitoneum in comparison to PVDF. Immunohistochemically, the amount of CD45-positive cells was significantly lower and the Collagen I/III ratio was significantly higher in TPU meshes after 8 weeks. There were no differences regarding adhesion formation between study groups.

CONCLUSIONS

The TPU mesh preserves its elastic properties in IPOM position in a porcine model after 8 weeks. Immunohistochemistry indicates superior biocompatibility regarding CD45-positive cells and Collagen I/III ratio in comparison to PVDF meshes with a similar structure.

MRI visible Fe3O4 polypropylene mesh: 3D reconstruction of spatial relation to bony pelvis and neurovascular structures

INTRODUCTION AND HYPOTHESIS

To demonstrate mesh magnetic resonance imaging (MRI) visibility in living women, the feasibility of reconstructing the full mesh course in 3D, and to document its spatial relationship to pelvic anatomical structures.

METHODS

This is a proof of concept study of three patients from a prospective multi-center trial evaluating women with anterior vaginal mesh repair using a MRI-visible Fe₃O₄ polypropylene implant for pelvic floor reconstruction. High-resolution sagittal T2-weighted (T2w) sequences, transverse T1-weighted (T1w) FLASH 2D, and transverse T1w FLASH 3D sequences were performed to evaluate Fe₃O₄ polypropylene mesh MRI visibility and overall post-surgical pelvic anatomy 3 months after reconstructive surgery. Full mesh course in addition to important pelvic structures were reconstructed using the 3D Slicer® software program based on T1w and T2w MRI.

RESULTS

Three women with POP-Q grade III cystoceles were successfully treated with a partially absorbable MRI-visible anterior vaginal mesh with six fixation arms and showed no recurrent cystocele at the 3-month follow-up examination. The course of mesh in the pelvis was visible on MRI in all three women. The mesh body and arms could be reconstructed allowing visualization of the full course of the mesh in relationship to important pelvic structures such as the obturator or pudendal vessel nerve bundles in 3D.

CONCLUSIONS

The use of MRI-visible Fe₃O₄ polypropylene meshes in combination with post-surgical 3D reconstruction of the mesh and adjacent structures is feasible suggesting that it might be a useful tool for evaluating mesh complications more precisely and a valuable interactive feedback tool for surgeons and mesh design engineers.

Evidence-Based Hernia Treatment in Adults

BACKGROUND

Inguinal hernia repair is the most common general surgical procedure in industrialized countries, with a frequency of about 200 operations per 100 000 persons per year. Suture- and mesh-based techniques can be used, and the procedure can be either open or minimally invasive.

METHODS

This review is based on a selective search of the literature, with interpretation of the published findings according to the principles of evidence-based medicine.

RESULTS

Inguinal hernia is diagnosed by physical examination. Surgery is not necessarily indicated for a primary, asymptomatic inguinal hernia in a male patient, but all inguinal hernias in women should be operated on. For hernias in women, and for all bilateral hernias, a laparoscopic or endoscopic procedure is preferable to an open procedure. Primary unilateral hernias in men can be treated either by open surgery or by laparoscopy/endoscopy. Patients treated by laparoscopy/endoscopy develop chronic pain less often than those treated by open surgery. A mesh-based repair is generally recommended; this seems reasonable in view of the pathogenesis of the condition, which involves an abnormality of the extracellular matrix.

CONCLUSION

The choice of procedure has been addressed by international guidelines based on high-level evidence. Surgeons should deviate from their recommendations only in exceptional cases and for special reasons. Guideline conformity implies that hernia surgeons must master both open and endoscopic/laparoscopic techniques.

Positive Contrast MRI Techniques for Visualization of Iron-Loaded Hernia Mesh Implants in Patients

Object

In MRI, implants and devices can be delineated via susceptibility artefacts. To discriminate susceptibility voids from proton-free structures, different positive contrast techniques were implemented. The purpose of this study was to evaluate a pulse sequence-based positive contrast technique (PCSI) and a post-processing susceptibility gradient mapping algorithm (SGM) for visualization of iron loaded mesh implants in patients.

Material and Methods

Five patients with iron-loaded MR-visible inguinal hernia mesh implants were examined at 1.5 Tesla. A gradient echo sequence (GRE; parameters: TR: 8.3ms; TE: 4.3ms; NSA:2; FA:20°; FOV:350mm²) and a PCSI sequence (parameters: TR: 25ms; TE: 4.6ms; NSA:4; FA:20°; FOV:350mm²) with on-resonant proton suppression were performed. SGM maps were calculated using two algorithms. Image quality and mesh delineation were independently evaluated by three radiologists.

Results

On GRE, the iron-loaded meshes generated distinct susceptibility-induced signal voids. PCSI exhibited susceptibility differences including the meshes as hyperintense signals. SGM exhibited susceptibility differences with positive contrast. Visually, the different algorithms presented no significant differences. Overall, the diagnostic value was rated best in GRE whereas PCSI and SGM were barely “sufficient”.

Conclusion

Both “positive contrast” techniques depicted implanted meshes with hyperintense signal. SGM comes without additional acquisition time and can therefore be utilized in every patient.

Magnetic resonance-visible meshes for laparoscopic ventral hernia repair

Background and Objectives:

We aimed to evaluate the first human use of magnetic resonance–visible implants for intraperitoneal onlay repair of incisional hernias regarding magnetic resonance presentability.

Methods:

Ten patients were surgically treated with intraperitoneally positioned superparamagnetic flat meshes. A magnetic resonance investigation with a qualified protocol was performed on postoperative day 1 and at 3 months postoperatively to assess mesh appearance and demarcation. The total magnetic resonance–visible mesh surface area of each implant was calculated and compared with the original physical mesh size to evaluate potential reduction of the functional mesh surfaces.

Results:

We were able to show a precise mesh demarcation, as well as accurate assessment of the surrounding tissue, in all 10 cases. We documented a significant decrease in the magnetic resonance–visualized total mesh surface area after release of the pneumoperitoneum compared with the original mesh size (mean, 190 cm² vs 225 cm²; mean reduction of mesh area, 35 cm²; P < .001). At 3 months postoperatively, a further reduction of the surface area due to significant mesh shrinkage could be observed (mean, 182 cm² vs 190 cm²; mean reduction of mesh area, 8 cm²; P < .001).

Conclusion:

The new method of combining magnetic resonance imaging and meshes that provide enhanced signal capacity through direct integration of iron particles into the polyvinylidene fluoride base material allows for detailed mesh depiction and quantification of structural changes. In addition to a significant early postoperative decrease in effective mesh surface area, a further considerable reduction in size occurred within 3 months after implantation.

MRI-visible polymer based on poly(methyl methacrylate) for imaging applications

Macromolecular contrast agents are very attractive to afford efficient magnetic resonance imaging (MRI) visualization of implantable medical devices.

Emerging Trends in Abdominal Wall Reinforcement: Bringing Bio-Functionality to Meshes

Abdominal wall hernia is a recurrent issue world-wide and requires the implantation of over 1 million meshes per year. Because permanent meshes such as polypropylene and polyester are not free of complications after implantation, many mesh modifications and new functionalities have been investigated over the last decade. Indeed, mesh optimization is the focus of intense development and the biomaterials utilized are now envisioned as being bioactive substrates that trigger various physiological processes in order to prevent complications and to promote tissue integration. In this context, it is of paramount interest to review the most relevant bio-functionalities being brought to new meshes and to open new avenues for the innovative development of the next generation of meshes with enhanced properties for functional abdominal wall hernia repair.

First human magnetic resonance visualisation of prosthetics for laparoscopic large hiatal hernia repair

PURPOSE

Mesh repair of large hiatal hernias has increasingly gained popularity to reduce recurrence rates. Integration of iron particles into the polyvinylidene fluoride mesh-based material allows for magnetic resonance visualisation (MR).

METHODS

In a pilot prospective case series eight patients underwent surgical repair of hiatal hernias repair with pre-shaped meshes, which were fixated with fibrin glue. An MR investigation with a qualified protocol was performed on postoperative day four and 3 months postoperatively to evaluate the correct position of the mesh by assessing mesh appearance and demarcation. The total MR-visible mesh surface area of each implant was calculated and compared with the original physical mesh size to evaluate potential reduction of the functional mesh surfaces.

RESULTS

We documented no mesh migrations or dislocations but we found a significant decrease of MR-visualised total mesh surface area after release of the pneumoperitoneum compared to the original mesh size (mean 78.9 vs 84 cm(2); mean reduction of mesh area = 5.1 cm(2), p < 0.001). At 3 months postoperatively, a further reduction of the mesh surface area could be observed (mean 78.5 vs 78.9 cm(2); mean reduction of mesh area = 0.4 cm(2), p < 0.037).

CONCLUSION

Detailed mesh depiction and accurate assessment of the surrounding anatomy could be successfully achieved in all cases. Fibrin glue seems to provide effective mesh fixation. In addition to a significant early postoperative decrease in effective mesh surface area a further reduction in size occurred within 3 months after implantation.

Three-dimensional analysis of implanted magnetic-resonance-visible meshes

OBJECTIVE

Our primary objective was to develop relevant algorithms for quantification of mesh position and 3D shape in magnetic resonance (MR) images.

METHODS

In this proof-of-principle study, one patient with severe anterior vaginal wall prolapse was implanted with an MR-visible mesh. High-resolution MR images of the pelvis were acquired 6 weeks and 8 months postsurgery. 3D models were created using semiautomatic segmentation techniques. Conformational changes were recorded quantitatively using part-comparison analysis. An ellipticity measure is proposed to record longitudinal conformational changes in the mesh arms. The surface that is the effective reinforcement provided by the mesh is calculated using a novel methodology. The area of this surface is the effective support area (ESA).

RESULTS

MR-visible mesh was clearly outlined in the images, which allowed us to longitudinally quantify mesh configuration between 6 weeks and 8 months after implantation. No significant changes were found in mesh position, effective support area, conformation of the mesh's main body, and arm length during the period of observation. Ellipticity profiles show longitudinal conformational changes in posterior arms.

CONCLUSIONS

This paper proposes novel methodologies for a systematic 3D assessment of the position and morphology of MR-visible meshes. A novel semiautomatic tool was developed to calculate the effective area of support provided by the mesh, a potentially clinically important parameter.

Time-dependent changes of magnetic resonance imaging-visible mesh implants in patients

OBJECTIVES

Shrinkage and deformation of mesh implants used for hernia treatment can be the cause of long-term complications. The purpose of this study was to quantify noninvasively time-dependent mesh shrinkage, migration, and configuration changes in patients who were surgically treated for inguinal hernia using magnetic resonance imaging (MRI)-visible mesh implants.

MATERIALS AND METHODS

In an agarose phantom, meshes in different shrinkage and folding conditions were used to validate the quantification process. Seven patients who were surgically (3 bilaterally) treated for inguinal hernia using iron-loaded mesh implants were prospectively examined using MRI. Gradient echo sequences in sagittal and transverse orientations were performed on day 1 after surgery and at day 90. The mesh-induced signal voids were semiautomatically segmented and a polygonal surface model was generated. A comparison of area and centroid position was performed between the 2 calculated surfaces (day 1 vs day 90).

RESULTS

The phantom study revealed a maximum deviation of 3.6% between the MRI-based quantification and the actual mesh size. All 10 implants were successfully reconstructed. The mean (SD) observed mesh shrinkage 90 days after surgery was 20.9% (7.1%). The mean (SD) centroid movement was 1.17 (0.47) cm. Topographic analysis revealed mean (SD) local configuration changes of 0.23 (0.03) cm.

CONCLUSIONS

In this study, significant mesh shrinkage (20.9%) but marginal changes in local mesh configuration occurred within 90 days after mesh implantation. Centroid shift of the mesh implant can be traced back to different patient positioning and abdominal distension. The developed algorithm facilitates noninvasive assessment of key figures regarding MRI-visible meshes. Consequently, it might help to improve mesh technology as well as surgical skills.

Nanoparticles for imaging: top or flop?

Nanoparticles are frequently suggested as diagnostic agents. However, except for iron oxide nanoparticles, diagnostic nanoparticles have been barely incorporated into clinical use so far. This is predominantly due to difficulties in achieving acceptable pharmacokinetic properties and reproducible particle uniformity as well as to concerns about toxicity, biodegradation, and elimination. Reasonable indications for the clinical utilization of nanoparticles should consider their biologic behavior. For example, many nanoparticles are taken up by macrophages and accumulate in macrophage-rich tissues. Thus, they can be used to provide contrast in liver, spleen, lymph nodes, and inflammatory lesions (eg, atherosclerotic plaques). Furthermore, cells can be efficiently labeled with nanoparticles, enabling the localization of implanted (stem) cells and tissue-engineered grafts as well as in vivo migration studies of cells. The potential of using nanoparticles for molecular imaging is compromised because their pharmacokinetic properties are difficult to control. Ideal targets for nanoparticles are localized on the endothelial luminal surface, whereas targeted nanoparticle delivery to extravascular structures is often limited and difficult to separate from an underlying enhanced permeability and retention (EPR) effect. The majority of clinically used nanoparticle-based drug delivery systems are based on the EPR effect, and, for their more personalized use, imaging markers can be incorporated to monitor biodistribution, target site accumulation, drug release, and treatment efficacy. In conclusion, although nanoparticles are not always the right choice for molecular imaging (because smaller or larger molecules might provide more specific information), there are other diagnostic and theranostic applications for which nanoparticles hold substantial clinical potential.

Imaging visceral adhesion to polymeric mesh using pneumoperitoneal-MRI in an experimental rat model

BACKGROUND

Intraperitoneal mesh implantation is often associated with formation of adhesion to the mesh. This experimental study examines the potential of minimally invasive pneumoperitoneal-MRI to assess these adhesions in a preclinical context.

METHODS

Uncoated polyethylene terephthalate meshes were placed intraperitoneally in rats, in regard to the caecum previously scraped to promote petechial bleeding and subsequent adhesions. Examinations were performed 2-weeks post mesh implantation using a rodent dedicated high field MRI. Respiratory-triggered T2-weighted images were acquired prior to and after intraperitoneal injection of ~8-10 mL gas to induce a mechanical stress on the abdominal wall.

RESULTS

Adhesions are occasionally seen in sham-operated rats as opposed to rats receiving polyethylene terephthalate meshes. On high-resolution images, meshes can be detected due to their characteristic net shape. However, evidence of adherence is only found if intraperitoneal gas injection is performed, when a ~1-cm elevation of the abdominal wall is observed. When adherence occurs between the mesh and the caecum, the latter remains in contact with the wall. Looser adherences between visceral tissue and meshes are also observed.

CONCLUSIONS

T2-weighted pneumoperitoneal-MRI is a powerful tool for assessing adherence after intraperitoneal mesh implantation. According to the mini-invasive procedure adopted here, this approach may allow a temporal follow-up of adherence fate.

Mesh contraction: in vivo documentation of changes in apparent surface area utilizing meshes visible on magnetic resonance imaging in the rabbit abdominal wall model

INTRODUCTION AND HYPOTHESIS

Our aim was to analyze the apparent contraction of meshes in vivo after abdominal wall reconstruction and evaluate histological and biomechanical properties after explantation.

METHODS

Nine New Zealand female rabbits underwent repair of two full-thickness 25 × 30-mm midline defects in the upper and lower parts of the abdomen. These were primarily overlaid by 35 × 40-mm implants of a polyvinylidene fluoride (PVDF) DynaMesh (n = 6) or polypropylene meshes Ultrapro (n = 6) and Marlex (n = 6). Edges of the meshes were secured with iron(II,III) oxide (Fe(3)O(4))-loaded PVDF sutures. Magnetic resonance images (MRIs) were taken at days 2, 30 and 90 after implantation. The perimeter of the mesh was traced using a 3D spline curve. The apparent surface area or the area within the PVDF sutures was compared with the initial size using the one-sample t test. A two-way repeat analysis of variance (ANOVA) was used to compare the apparent surface area over time and between groups.

RESULTS

PVDF meshes and sutures with Fe(3)O(4) could be well visualized on MRI. DynaMesh and Marlex each had a 17 % decrease in apparent surface area by day 2 (p < 0.001 and p = 0.001), respectively, which persisted after day 90. Whereas there was a decrease in apparent surface area in Ultrapro, it did not reach significance until day 90 (p = 0.01). Overall, the apparent surface area decreased 21 % in all meshes by day 90. No differences in histological or biomechanical properties were observed at day 90.

CONCLUSIONS

There was a reduction in the apparent surface area between implantation and day 2, indicating that most mesh deformation occurs prior to tissue in-growth.

Translabial ultrasonography for evaluation of synthetic mesh in the vagina

OBJECTIVE

To compare the clinical and surgical findings using translabial ultrasonography (US) in the evaluation of symptoms after transvaginal synthetic mesh placement.

METHODS

From 2009 through 2010, a retrospective observational study was conducted to evaluate patients presenting with complaints after transvaginal mesh implantation for the treatment of stress urinary incontinence or pelvic organ prolapse repair. The clinical and translabial US findings were compared with the intraoperative findings, with a focus on mesh location, erosion, and extrusion.

RESULTS

A total of 51 consecutive patients (mean age 59 years) were evaluated by history and physical examination, translabial US, and intraoperative findings. Using intraoperative findings as the reference standard, translabial US was able to predict the location of the sling in relationship to the urethra (6 distal, 25 mid-urethral, and 20 at the bladder neck), to differentiate between transobturator (n = 21) and retropubic (n = 30) slings, and to detect all anterior (n = 21) and posterior (n = 15) placed mesh. Translabial US was superior to physical examination in identifying mesh erosion into the periurethral fascia or sphincteric unit. US was inferior to physical examination in diagnosing vaginal extrusion but was superior for locating the mesh.

CONCLUSION

Translabial US can identify the mesh material used to treat stress urinary incontinence and pelvic organ prolapse. It provides additional information on sling type, mesh location, and morphology compared with the clinical findings and could help in surgical planning and counseling. Prospective clinical studies evaluating the reliability of this technique in larger patient populations are warranted.

'The ideal mesh?'

Currently, more than 200 different textile constructions, so-called 'meshes', are available for use world-wide in the more than 20 million operations performed annually for the reinforcement of tissues. As any reintervention at the mesh-tissue compound is a surgical challenge, sometimes resulting in almost untreatable defects, huge efforts are being made to improve the biological and functional performance of the meshes. Based on numerous experimental and clinical studies in the past 20 years, our understanding of them has improved markedly. This includes the biomechanical aspects and the histopathological evaluation of the recipient tissue. Sufficiently large pores as well as structural stability in case of mechanical strain have been identified to be crucial to reduce excessive inflammation and fibrosis. Furthermore, large pores prevent bridging of the foreign body reaction through the pore and thereby help to reduce clinical adverse events as erosion, shrinkage or pain. However, with regard to the many different indications for meshes, there will never be one single ideal mesh for all purposes. To achieve an optimal performance, every construction should be designed according to the specific functional requirements, charging the surgeon to identify the best mesh for his purpose.

Surface modification of iron oxide nanoparticles by biocompatible polymers for tissue imaging and targeting

Superparamagnetic iron oxide nanoparticles (SPIONs) are excellent MR contrast agents when coated with biocompatible polymers such as hydrophilic synthetic polymers, proteins, polysaccharides, and lipids, which improve their stability and biocompatibility and reduce their aggregation. Various biocompatible materials, coated or conjugated with targeting moieties such as galactose, mannose, folic acid, antibodies and RGD, have been applied to SPION surfaces to provide tissue specificity to hepatocytes, macrophages, and tumor regions in order to reduce non-specific uptake and improve biocompatibility. This review discusses the recent progress in the development of biocompatible and hydrophilic polymers for improving stability of SPIONs and describes the carbohydrates based biocompatible materials that are providing SPIONs with cell/tissue specificity as ligands.