First In-Human Magnetic Resonance Visualization of Surgical Mesh Implants for Inguinal Hernia Treatment:

Tissue engineered drug delivery vehicles: Methods to monitor and regulate the release behavior

Tissue engineering is a rapidly evolving, multidisciplinary field that aims at generating or regenerating 3D functional tissues for in vitro disease modeling and drug screening applications or for in vivo therapies. A variety of advanced biological and engineering methods are increasingly being used to further enhance and customize the functionality of tissue engineered scaffolds. To this end, tunable drug delivery and release mechanisms are incorporated into tissue engineering modalities to promote different therapeutic processes, thus, addressing challenges faced in the clinical applications. In this review, we elaborate the mechanisms and recent developments in different drug delivery vehicles, including the quantum dots, nano/micro particles, and molecular agents. Different loading strategies to incorporate the therapeutic reagents into the scaffolding structures are explored. Further, we discuss the main mechanisms to tune and monitor/quantify the release kinetics of embedded drugs from engineered scaffolds. We also survey the current trend of drug delivery using stimuli driven biopolymer scaffolds to enable precise spatiotemporal control of the release behavior. Recent advancements, challenges facing current scaffold-based drug delivery approaches, and areas of future research are discussed.

Magnetic resonance visualization of iron-loaded meshes in patients with pain after inguinal hernia repair

PURPOSE

Chronic post-operative inguinal pain (CPIP) is defined as pain lasting more than 3 months and the incidence is less than 4% after laparoscopic hernia repair. CPIP can have several causes. In this study, we aimed to show that 3D-iron loaded mesh preparations are useful in radiological evaluation of post-operative complications, especially patients with chronic pain and the mesh status of operated inguinal hernia cases.

METHODS

A total of 450 cases who had been operated for inguinal hernia with 3D-iron loaded mesh and who had ongoing pain at the post-operative period were included in this study. MRI (Magnetic Resonance Imaging) was performed at the post-operative 90th day of the seven symptomatic (groin pain, limitation of movement) cases which were operated using a 3D-iron loaded mesh, 10 × 15 cm in size, (DynaMeshEndolap visible with 25% MRI-visible filaments, FEG TextiltechnikmbH, Aachen, Germany) for inguinal hernia repair to evaluate mesh status, localization, and local complications. Gradient echo sequences in the sagittal, axial, and coronal sections on MRI were discussed by two radiologists. Mesh localizations, their relationship with surrounding structures and their complications related with mesh were evaluated by two radiologists (D.Y, D.E.T.Ş).

RESULTS

No significant radiological findings related to defined anatomical structures were found in the MRI images of the study group. The dimensions measured on the sagittal, axial and coronal images were correlated with original mesh sizes and no significant shrinkage was detected.

CONCLUSION

Mesh position and deformation as shrinkage can be the mesh-related cause of pain. The incidence of CPIP in our patients is less than 2%. 3D-iron loaded meshes were monitored with MRI in CPIP patients and there was no mesh-related changes found in our study. The use of MRI-visible meshes will most likely help us to monitor mesh preparations and show potential time-dependent changes in mesh characteristics and consequent complications. In case of doubtful clinical postoperative hernia recurrence or chronic groin pain, mesh position can be identified by MRI and unnecessary surgical intervention can be avoided.

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.

Labeling of Collagen Type I Templates with a Naturally Derived Contrast Agent for Noninvasive MR Imaging in Soft Tissue Engineering

In vivo monitoring of tissue-engineered constructs is important to assess their integrity, remodeling, and degradation. However, this is challenging when the contrast with neighboring tissues is low, necessitating labeling with contrast agents (CAs), but current CAs have limitations (i.e., toxicity, negative contrast, label instability, and/or inappropriate size). Therefore, a naturally derived hemin-L-lysine (HL) complex is used as a potential CA to label collagen-based templates for magnetic resonance imaging (MRI). Labeling does not change the basic characteristics of the collagen templates. When hybrid templates composed of collagen type I reinforced with degradable polymers are subcutaneously implanted in mice, longitudinal visualization by MRI is possible with good contrast and in correlation with template remodeling. In contrast, unlabeled collagen templates are hardly detectable and the fate of these templates cannot be monitored by MRI. Interestingly, tissue remodeling and vascularization are enhanced within HL-labeled templates. Thus, HL labeling is presented as a promising universal imaging marker to label tissue-engineered implants for MRI, which additionally seems to accelerate tissue regeneration.

Surgical treatment of vaginal vault prolapse using different prosthetic mesh implants: a finite element analysis

Particularly multiparous elderly women may suffer from vaginal vault prolapse after hysterectomy due to weak support from lax apical ligaments. A decreased amount of estrogen and progesterone in older age is assumed to remodel the collagen thereby reducing tissue stiffness. Sacrocolpopexy is either performed as open or laparoscopic surgery using prosthetic mesh implants to substitute lax ligaments. Y-shaped mesh models (DynaMesh, Gynemesh, and Ultrapro) are implanted in a 3D female pelvic floor finite element model in the extraperitoneal space from the vaginal cuff to the first sacral (S1) bone below promontory. Numerical simulations are conducted during Valsalva maneuver with weakened tissues modeled by reduced tissue stiffness. Tissues are modeled as incompressible, isotropic hyperelastic materials whereas the meshes are modeled either as orthotropic linear elastic or as isotropic hyperlastic materials. The positions of the vaginal cuff and the bladder base are calculated from the pubococcygeal line for female pelvic floor at rest, for prolapse and after repair using the three meshes. Due to mesh mechanics and mesh pore deformation along the loaded direction, the DynaMesh with regular rectangular mesh pores is found to provide better mechanical support to the organs than the Gynemesh and the Ultrapro with irregular hexagonal mesh pores.

Validation of Single C-Arm Fluoroscopic Technique for Measuring In Vivo Abdominal Wall Deformation

Hernia meshes significantly reduce the recurrence rates in hernia repair. It is known that they affect the abdominal wall postimplantation, yet the understanding of in vivo mechanics in the mesh placement area is lacking. We established a single C-arm biplane fluoroscopic system to study strains at the interface between the mesh and repaired abdominal tissues. We aimed to validate this system for future porcine hernia repair studies. Custom matlab programs were written to correct for pincushion distortion, and direct linear transformation (DLT) reconstructed objects in 3D. Using a custom biplane-trough setup, image sets were acquired throughout the calibrated volume to evaluate a radio-opaque test piece with known distances between adjacent beads. Distances were measured postprocessing and compared to known measurements. Repeatability testing was conducted by taking image sets of the test piece in a fixed location to determine system movement. The error in areal stretch tracking was evaluated by imaging a square plate with fixed radio-opaque beads and using matlab programs to compare the measured areal stretch to known bead positions. Minor differences between measured and known distances in the test piece were not statistically different, and the system yielded a 0.01 mm bias in the XY plane and a precision of 0.61 mm. The measured areal stretch was 0.996, which was not significantly different than the expected value of 1. In addition, preliminary stretch data for a hernia mesh in a porcine model demonstrated technique feasibility to measure in vivo porcine abdominal mechanics.

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.

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.

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.

A Novel Operative Procedure for Pelvic Organ Prolapse Utilizing a MRI-Visible Mesh Implant: Safety and Outcome of Modified Laparoscopic Bilateral Sacropexy

Introduction. Sacropexy is a generally applied treatment of prolapse, yet there are known possible complications of it. An essential need exists for better alloplastic materials. Methods. Between April 2013 and June 2014, we performed a modified laparoscopic bilateral sacropexy (MLBS) in 10 patients using a MRI-visible PVDF mesh implant. Selected patients had prolapse POP-Q stages II-III and concomitant OAB. We studied surgery-related morbidity, anatomical and functional outcome, and mesh-visibility in MRI. Mean follow-up was 7.4 months. Results. Concomitant colporrhaphy was conducted in 1/10 patients. Anatomical success was defined as POP-Q stage 0-I. Apical success rate was 100% and remained stable. A recurrent cystocele was seen in 1/10 patients during follow-up without need for intervention. Out of 6 (6/10) patients with preoperative SUI, 5/6 were healed and 1/6 persisted. De-novo SUI was seen in 1/10 patients. Complications requiring a relaparoscopy were seen in 2/10 patients. 8/10 patients with OAB were relieved postoperatively. The first in-human magnetic resonance visualization of a prolapse mesh implant was performed and showed good quality of visualization. Conclusion. MLBS is a feasible and safe procedure with favorable anatomical and functional outcome and good concomitant healing rates of SUI and OAB. Prospective data and larger samples are required.

Magnetic resonance imaging has no role in diagnosing the origin of pain in patients with overwhelmingly painful inguinal hernia

PURPOSE

Clinical tools for predicting postoperative pain should be developed to provide better care for patients. The aims of this study were to evaluate preoperative magnetic resonance imaging (MRI) findings to reveal reasons for overwhelming pain in patients with inguinal hernia and to detect changes in quality-of-life (QoL) and pain scores preoperatively and following laparoscopic totally extraperitoneal (TEP) repair of inguinal hernia.

METHODS

Twenty-two patients aged 18-50 years presenting with extremely painful inguinal hernias (highest pain scores >50, scale 0-100) were examined with MRI prior to operative treatment with TEP repair. Postoperative follow-up lasted 6 months and consisted of questionnaires regarding functional status, pain, QoL and possible complications. Postoperative MRI scans were performed only in cases of preoperative findings on the MRI or prolonged inguinal pain persisting over 6 months.

RESULTS

Prolonged postoperative pain could not be predicted from preoperative MRI scans, because no signs of the pain's origin such as pubic periostal irritation, bone marrow edema, pelvic bone or hip joint abnormalities, or lower abdominal muscle hemorrhage were detected in MRI. TEP repair of inguinal hernia significantly improved the patients' quality of life and relieved pain symptoms. High preoperative pain scores were major predictors of prolonged postoperative pain.

CONCLUSIONS

Carefully evaluated preoperative pelvic MRI was usually normal in patients with high pain scores prior to operation. Preoperative pain scores may serve as indicators of development of prolonged inguinal pain.

Tolerance and long-term MRI imaging of gadolinium-modified meshes used in soft organ repair

Background

Synthetic meshes are frequently used to reinforce soft tissues. The aim of this translational study is to evaluate tolerance and long-term MRI visibility of two recently developed Gadolinium-modified meshes in a rat animal model.

Materials and Methods

Gadolinium-poly-ε-caprolactone (Gd-PCL) and Gadolinium-polymethylacrylate (Gd-PMA) modified meshes were implanted in Wistar rats and their tolerance was assessed daily. Inflammation and biocompatibility of the implants were assessed by histology and immunohistochemistry after 30 days post implantation. Implants were visualised by 7T and 3T MRI at day 30 and at day 90. Diffusion of Gadolinium in the tissues of the implanted animals was assessed by Inductively Coupled Plasma Mass Spectrometry.

Results

Overall Gd-PMA coated implants were better tolerated as compared to those coated with Gd-PCL. In fact, Gd-PMA implants were characterised by a high ratio collagen I/III and good vascularisation of the integration tissues. High resolution images of the coated mesh were obtained in vivo with experimental 7T as well as 3T clinical MRI. Mass spectrometry analyses showed that levels of Gadolinium in animals implanted with coated mesh were similar to those of the control group.

Conclusions

Meshes coated with Gd-PMA are better tolerated as compared to those coated with Gd-PCL as no signs of erosion or significant inflammation were detected at 30 days post implantation. Also, Gd-PMA coated meshes were clearly visualised with both 7T and 3T MRI devices. This new technique of mesh optimisation may represent a valuable tool in soft tissue repair and management.