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

BACKGROUND: Prosthetic mesh implants are widely used in hernia surgery. To show long-term mesh-related complications such as shrinkage or adhesions, a precise visualization of meshes and their vicinity in vivo is important. By supplementing mesh fibers with ferro particles, magnetic resonance imaging (MRI) can help to delineate the mesh itself. This study aimed to demonstrate and quantify time-dependent mesh shrinkage in vivo by MRI. METHODS: Polyvinylidenfluoride (PVDF) meshes with incorporated superparamagnetic iron oxides (SPIOs) were implanted as an abdominal wall replacement in 30 rats. On days 1, 7, 14, or 21, MRI was performed using a gradient echo sequence with repetition time (TR)/echo time (TE) of 50/4.6 and a flip angle of 20°. The length, width, and area of the device were measured on axial, coronal, and sagittal images, and geometric deformations were assessed by surgical explantation. RESULTS: In all cases, the meshes were visualized and their area estimated by measuring the length and width of the mesh. The MRI presented a mean area shrinkage in vivo of 13% on day 7, 23% on day 14, and 23% on day 21. Postmortem measurements differed statistically from MRI, with a mean area shrinkage of 23% on day 7, 28% on day 14, and 30% on day 21. Ex vivo measurements of shrinkage showed in vivo measurements to be overestimated approximately 8%. Delineation of the mesh helped to show folding or adhesions close to the intestine. CONCLUSION: Loading of surgical meshes with SPIOs allows their precise visualization during MRI and guarantees an accurate in vivo assessment of their shrinkage. The authors' observation clearly indicates that shrinkage in vivo is remarkably less than that shown by illustrated explantation measurements. The use of MRI with such meshes could be a reliable technique for checking on proper operation of implanted meshes and showing related complications, obviating the need for exploratory open surgical revision.

Intrathoracic versus cervical anastomosis after resection of esophageal cancer: a matched pair analysis of 72 patients in a single center study.

BACKGROUND: The aim of this study was to analyze the early postoperative outcome of esophageal cancer treated by subtotal esophageal resection, gastric interposition and either intrathoracic or cervical anastomosis in a single center study. METHODS: 72 patients who received either a cervical or intrathoracic anastomosis after esophageal resection for esophageal cancer were matched by age and tumor stage. Collected data from these patients were analyzed retrospectively regarding morbidity and mortality rates. RESULTS: Anastomotic leakage rate was significantly lower in the intrathoracic anastomosis group than in the cervical anastomosis group (4 of 36 patients (11%) vs. 11 of 36 patients (31%); p = 0.040). The hospital stay was significantly shorter in the intrathoracic anastomosis group compared to the cervical anastomosis group (14 (range 10-110) vs. 26 days (range 12 - 105); p = 0.012). Wound infection and temporary paresis of the recurrent laryngeal nerve occurred significantly more often in the cervical anastomosis group compared to the intrathoracic anastomosis group (28% vs. 0%; p = 0.002 and 11% vs. 0%; p = 0.046). The overall In-hospital mortality rate was 6% (4 of 72 patients) without any differences between the study groups. CONCLUSIONS: The present data support the assumption that the transthoracic approach with an intrathoracic anastomosis compared to a cervical esophagogastrostomy is the safer and more beneficial procedure in patients with carcinoma of the lower and middle third of the esophagus due to a significant reduction of anastomotic leakage, wound infection, paresis of the recurrent laryngeal nerve and shorter hospital stay.

Erythropoietin (EPO) influences colonic anastomotic healing in a rat model by modulating collagen metabolism.

INTRODUCTION: Anastomotic failure is one of the most frequent complications in abdominal surgery. During anastomotic healing. the strength of the intestinal tissue nearby is closely related to the accumulation of collagen in interlinked scar tissue. This in turn is influenced, among other things, by single groups of matrixmetalloproteinases, especially collagenases (MMP-1, -8, and -13) and gelatinases (MMP-2 and -9). EPO is known to induce the expression of tissue-inhibitor-of-matrixmetalloproteinases-1 (TIMP-1) and thereby to down-regulate MMPs. MATERIALS AND METHODS: We used a rat as an experimental model and applied a high dose of EPO (5U/g BW s.c.), one dose 24 h before operation (as pre-conditioning) and one dose directly after performing a colonic anastomosis. After 3 and after 5 d, respectively, immunohistochemical stainings for MMP-2, -8, and -9 as well as TIMP-1 were carried out and evaluated semiquantitatively for each layer of the colonic wall. Sirius-red staining and cross-polarization microscopy were evaluated and the collagen I/III ratio calculated. Anastomotic and colonic tissue distal to the anastomosis were used to determine collagen content. RESULTS: We found increased bursting pressure 5 d post-surgery after applying erythropoietin. It was thus shown that EPO influences collagen metabolism and changes the collagen I/III ratio in the colon distal to the anastomosis. The evaluation of immunohistochemistry did not show the expected ubiquitous up-regulation of TIMP-1 and down-regulation of MMPs. Nevertheless, correlations between TIMP-1, MMP-8, and collagen I/III ratio could only be established after the application of EPO. CONCLUSION: Contrary to our hypothesis, the picture of TIMP-1 and of the regulation of the MMPs after the application of EPO is not as clear as expected. EPO improves anastomotic bursting strength and the correlation of TIMP-1, MMP-8, and collagen type I/III ratio can only be seen after the application of EPO.

Adhesion formation of a polyvinylidenfluoride/polypropylene mesh for intra-abdominal placement in a rodent animal model.

BACKGROUND: Effective laparoscopic ventral herniorrhaphy mandates the use of an intraperitoneal mesh. Visceral adhesions and shrinkage of prosthetics may complicate repairs. The aim of this study was to compare adhesion formation, mesh shrinkage and tissue ingrowth after intra-abdominal placement of a novel two-component monofilament mesh structure made of polypropylene (PP) and polyvinylidenfluoride (PVDF) with current alternatives. MATERIALS AND METHODS: Forty Sprague-Dawley rats were used in this study. Mesh samples were fixed as intra-abdominal only mesh at the right lateral abdominal wall. The study groups were: PVDF+PP (polypropylene parietally and polyvinylidenfluoride viscerally), PP+Col (polypropylene with a collagenoxidized film), ePTFE (smooth surface viscerally and a textured surface parietally), and PP (a pure polypropylene mesh serving as control). The meshes were explanted after 30 days. Adhesions were scored as a percentage of explanted biomaterials' affected surface area; prosthetic shrinkage was calculated. Foreign-body reaction to mesh materials was measured by investigating the amount of inflammatory infiltrate and fibrotic tissue formation. RESULTS: In terms of adhesion score, the pure PP mesh showed the highest values followed by the ePTFE, PVDF+PP, and PP+Col meshes. Quantitative assessment of adhesion area revealed a significantly higher value of the pure PP mesh sample (62.0 +/- 22.1%) compared with the PP+Col (26.8 +/- 12.1%) and the PVDF+PP mesh (34.6 +/- 8.2%). Percentage of shrinkage showed a significantly higher value of the ePTFE mesh (52.4 +/- 13.9%) compared with all other mesh modifications (PP+Col 19.8 +/- 13.9%, PVDF+PP 19.9 +/- 7.0%, and PP 26.8 +/- 9.5%). Inflammatory infiltrate was significantly reduced in the PVDF+PP mesh group compared with all other mesh samples. CONCLUSION: The use of the novel two-component monofilament mesh structure made of polypropylene and polyvinylidenfluoride was found to be favorable regarding adhesion formation and mesh shrinkage compared to conventional mesh materials used for intra-abdominal placement.

Direct intra-abdominal pressure monitoring via piezoresistive pressure measurement: a technical note.

BACKGROUND: Piezoresistive pressure measurement technique (PRM) has previously been applied for direct IAP measurement in a porcine model using two different devices. Aim of this clinical study was to assess both devices regarding complications, reliability and agreement with IVP in patients undergoing elective abdominal surgery. METHODS: A prospective cohort study was performed in 20 patients randomly scheduled to receive PRM either by a Coach-probe or an Accurate(++)-probe (both MIPM, Mammendorf, Germany). Probes were placed on the greater omentum and passed through the abdominal wall paralleling routine drainages. PRM was compared with IVP measurement by t-testing and by calculating mean difference as well as limits of agreement (LA). RESULTS: There were no probe related complications. Due to technical limitations, data could be collected in 3/10 patients with Coach and in 7/10 patients with Accurate++. Analysis was carried out only for Accurate++. Mean values did not differ to mean IVP values. Mean difference to IVP was 0.1 +/- 2.8 mmHg (LA: -5.5 to 5.6 mmHg). CONCLUSION: Direct IAP measurement was clinically uneventful. Although results of Accurate++ were comparable to IVP, the device might be too fragile for IAP measurements in the clinical setting. Local ethical committee trial registration: EK2024.

Different tissue reaction of oesophagus and diaphragm after mesh hiatoplasty. Results of an animal study.

BACKGROUND: Laparoscopic mesh-reinforcement of the hiatal region in the treatment of gastroesophageal reflux disease (GERD) and paraesophageal hernia (PEH) reduces the risk of recurrence. However, there are still controversies about the technique of mesh placement, shape, structure and material. We therefore compared tissue integration and scar formation after implantation of two different polypropylene-meshes in a rabbit model. METHODS: A total of 20 female chinchilla rabbits were included in this study. Two different meshes (Polypropylene PP, Polyglecaprone 25 Composite PP-PG) were implanted on the abdominal diaphragm around the oesophagus. After 3 months the implanted meshes were excised en-bloc. Histological and morphological analyses were carried out accordingly proliferation rate, apoptosis and collagen type I/III ratio. RESULTS: Regarding proliferation rate of oesophagus PP (9.31 +/- 3.4%) and PP-PG (13.26 +/- 2.54%) differ in a significant (p = 0.0097) way. In the diaphragm we found a significant (p = 0.00066) difference between PP (9.43 +/- 1.45%) and PP-PG (18.73 +/- 5.92%) respectively. Comparing oesophagus and diaphragm we could prove a significant difference within PP-PG-group (p = 0.0195). Within PP-group the difference reached no statistical significance (p = 0.88). We found analogous results regarding apoptosis.Furthermore, there is a significant (p = 0.00013) difference of collagen type I/III ratio in PP-PG (12.28 +/- 0.8) compared to PP (8.44 +/- 1,63) in case of oesophageal tissue. Concerning diaphragm we found a significant difference (p = 0.000099) between PP-PG (8.85 +/- 0.81) and PP (6.32 +/- 1.07) as well. CONCLUSION: The histologic and morphologic characteristics after prosthetic enforcement of the hiatus in this animal model show a more distinct tissue integration using PP-PG compared to PP. Additionally, different wound healing and remodelling capability influence tissue integration of the mesh in diaphragm and oesophagus.

Clinical evaluation of an air-capsule technique for the direct measurement of intra-abdominal pressure after elective abdominal surgery.

BACKGROUND: The gold standard for assessment of intraabdominal pressure (IAP) is via intravesicular pressure measurement (IVP). This accepted technique has some inherent problems, e.g. indirectness. Aim of this clinical study was to assess direct IAP measurement using an air-capsule method (ACM) regarding complications risks and agreement with IVP in patients undergoing abdominal surgery. METHODS: A prospective cohort study was performed in 30 patients undergoing elective colonic, hepatic, pancreatic and esophageal resection. For ACM a Probe 3 (Spiegelberg, Germany) was placed on the greater omentum. It was passed through the abdominal wall paralleling routine drainages. To compare ACM with IVP t-testing was performed and mean difference as well as limits of agreement were calculated. RESULTS: ACM did not lead to complications particularly with regard to organ lesion or surgical site infection. Mean insertion time of ACM was 4.4 days (min-max: 1-5 days). 168 pairwise measurements were made. Mean ACM value was 7.9 +/- 2.7 mmHg while mean IVP was 8.4 +/- 3.0 mmHg (n.s). Mean difference was 0.4 mmHg +/- 2.2 mmHg. Limits of agreement were -4.1 mmHg to 5.1 mmHg. CONCLUSION: Using ACM, direct IAP measurement is feasible and uncomplicated. Associated with relatively low pressure ranges (<17 mmHg), results are comparable to bladder pressure measurement.

Reduction of peritoneal carcinomatosis by intraperitoneal administration of phospholipids in rats.

BACKGROUND: Intraperitoneal tumor cell attachment after resection of gastrointestinal cancer may lead to a developing of peritoneal carcinosis. Intraabdominal application of phospholipids shows a significant decrease of adhesion formation even in case of rising tumor cell concentration. METHODS: In experiment A 2*106 colonic tumor cells (DHD/K12/Trb) were injected intraperitonely in female BD-IX-rats. A total of 30 rats were divided into three groups with treatments of phospholipids at 6% or 9% and the control group. In experiment B a total of 100 rats were divided into ten groups with treatments of phospholipids at 9% and the control group. A rising concentration of tumor cells (10,000, 50,000, 100,000, 250,000 and 500,000) were injected intraperitonely in female BD-IX-rats of the different groups. After 30 days, the extent of peritoneal carcinosis was determined by measuring the tumor volume, the area of attachment and the Peritoneal Cancer Index (PCI). RESULTS: In experiment A, we found a significant reduction (control group: tumor volume: 12.0 +/- 4.9 ml; area of tumor adhesion: 2434.4 +/- 766 mm2; PCI 28.5 +/- 10.0) of peritoneal dissemination according to all evaluation methods after treatment with phospholipids 6% (tumor volume: 5.2 +/- 2.2 ml; area of tumor adhesion: 1106.8 +/- 689 mm2; PCI 19.0 +/- 5.0) and phospholipids 9% (tumor volume: 4.0 +/- 3.5 ml; area of tumor adhesion: 362.7 +/- 339 mm2; PCI 13.8 +/- 5.1). In experiment B we found a significant reduction of tumor volume in all different groups of rising tumor cell concentration compared to the control. As detected by the area of attachment we found a significant reduction in the subgroups 1*104, 25*104 and 50*104. The reduction in the other subgroups shows no significance. The PCI could be reduced significantly in all subgroups apart from 5*104. CONCLUSION: In this animal study intraperitoneal application of phospholipids resulted in reduction of the extent of peritoneal carcinomatosis after intraperitoneal administration of free tumor cells. This effect was exceptionally noticed when the amount of intraperitoneal tumor cells was limited. Consequently, intraperitoneal administration of phospholipids might be effective in reducing peritoneal carcinomatosis after surgery of gastrointestinal tumors in humans.

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

[This corrects the article DOI: 10.1371/journal.pone.0155717.].

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.

High structural stability of textile implants prevents pore collapse and preserves effective porosity at strain.

Reinforcement of tissues by use of textiles is encouraged by the reduced rate of recurrent tissue dehiscence but for the price of an inflammatory and fibrotic tissue reaction to the implant. The latter mainly is affected by the size of the pores, whereas only sufficiently large pores are effective in preventing a complete scar entrapment. Comparing two different sling implants (TVT and SIS), which are used for the treatment of urinary incontinence, we can demonstrate that the measurement of the effective porosity reveals considerable differences in the textile construction. Furthermore the changes of porosity after application of a tensile load can indicate a structural instability, favouring pore collapse at stress and questioning the use for purposes that are not "tension-free."

Utility of Magnetic Resonance Imaging to Monitor Surgical Meshes: Correlating Imaging and Clinical Outcome of Patients Undergoing Inguinal Hernia Repair.

OBJECTIVES: From a surgeon's point of view, meshes implanted for inguinal hernia repair should overlap the defect by 3 cm or more during implantation to avoid hernia recurrence secondary to mesh shrinkage. The use of magnetic resonance imaging (MRI)-visible meshes now offers the opportunity to noninvasively monitor whether a hernia is still covered sufficiently in the living patient. The purpose of this study was therefore to evaluate the efficacy of hernia repair after mesh implantation based on MRI findings (mesh coverage, visibility of hernia structures) and based on the patient's postoperative symptoms. MATERIALS AND METHODS: In this prospective study approved by the ethics committee, 13 MRI-visible meshes were implanted in 10 patients (3 bilaterally) for inguinal hernia repair between March 2012 and January 2013. Senior visceral surgeons (>7 years of experience) implanted the meshes via laparoscopic transabdominal preperitoneal procedure. Magnetic resonance imaging was performed within 1 week and at 3 months after surgery at a 1.5-T system. Mesh position, deformation, and coverage of the hernia were visually assessed in consensus and rated on a 4-point semiquantitative scoring system. Distances of hernia center point to the mesh borders (overlap) were measured. Mesh position and hernia coverage postoperatively and at 3 months after implantation were correlated with the respective patients' clinical symptoms. Statistical analysis was performed using the Wilcoxon signed rank test. RESULTS: Two of the 13 meshes presented with an atypical mesh configuration along the course of psoas muscle with a short medial overlap of less than 2 cm. Eleven of the 13 meshes exhibited a typical mesh configuration with lateral folding and initial overlap of more than 2 cm. Between baseline and 3 months' follow-up, average overlap decreased in the medial direction by -10% (3.75 cm vs 3.36 cm, P = 0.22), in the lateral direction by -20% (3.55 cm vs 2.82 cm, P = 0.01), in the superior direction by -2% (5.82 cm vs 5.72 cm, P = 0.55), and in the posterior direction by -19% (4.11 cm vs 3.34 cm, P = 0.01). Between baseline and 3 months' follow-up, mesh folding increased mildly in the medial direction, whereas no change was found in the other directions. Individual folds of the mesh were flexible over time, whereas the gross visual configuration and location of meshes did not change. Four of the 13 former hernia sites were mildly painful at follow-up, whereas 9 of the 13 were completely asymptomatic. No correlation between clinical symptoms and mesh position or hernia coverage was found. CONCLUSIONS: Our results suggest that the actual postoperative mesh position after release of laparoscopic pneumoperitoneum may deviate from its position during surgery. Gross mesh position and configuration differed between patients but did not change within a given patient over the observation period of 3 months after surgery. We did not find a correlation between clinical symptoms and mesh configuration or position. Shrinkage of meshes does occur, yet not as concentric process, but regionally variable, leading to a reduced hernia coverage of up to -20% in the lateral and posterior directions.

Phospholipids reduce gastric cancer cell adhesion to extracellular matrix in vitro.

BACKGROUND: Nidation of floating tumour cells initiates peritoneal carcinosis and limits prognosis of gastro-intestinal tumours. Adhesion of tumour cells to extracellular matrix components is a pivotal step in developing peritoneal dissemination of intraabdominal malignancies. Since phospholipids efficaciously prevented peritoneal adhesion formation in numerous animal studies we investigated their capacity to reduce adhesions of gastric cancer cells to extracellular matrix components (ECM). METHODS: Human gastric cancer cells (NUGC-4, Japanese Cancer Research Resources Bank, Tokyo, Japan) were used in this study. Microtiter plates were coated with collagen IV (coll), laminin (ln) and fibronectin (fn). Non-specific protein binding of the coated wells was blocked by adding 1% (w/v) BSA (4 degrees C, 12 h) and rinsing the wells with Hepes buffer. 50.000 tumour cells in 100 microl medium were seeded into each well. Beside the controls, phospholipids were added in concentrations of 0.05, 0.1, 0.5, 0.75 and 1.0/100 microl medium. After an incubation interval of 30 min, attached cells were fixed and stained with 0.1% (w/v) crystal violet. The dye was resuspended with 50 microl of 0.2% (v/v) Triton X-100 per well and colour yields were then measured by an ELISA reader at 590 nm. Optical density (OD) showed a linear relationship to the amount of cells and was corrected for dying of BSA/polystyrene without cells. RESULTS: The attachment of gastric cancer cells to collagen IV, laminin, and fibronectin could be significantly reduced up to 53% by phospholipid concentrations of 0.5 mg/100 microl and higher. CONCLUSION: These results, within the scope of additional experimental studies on mice and rats which showed a significant reduction of peritoneal carcinosis, demonstrated the capacity of phospholipids in controlling abdominal nidation of tumour cells to ECM components. Lipid emulsions may be a beneficial adjunct in surgery of gastrointestinal malignancies.

Elongation of textile pelvic floor implants under load is related to complete loss of effective porosity, thereby favoring incorporation in scar plates.

Use of textile structures for reinforcement of pelvic floor structures has to consider mechanical forces to the implant, which are quite different to the tension free conditions of the abdominal wall. Thus, biomechanical analysis of textile devices has to include the impact of strain on stretchability and effective porosity. Prolift(®) and Prolift + M(®), developed for tension free conditions, were tested by measuring stretchability and effective porosity applying mechanical strain. For comparison, we used Dynamesh-PR4(®), which was designed for pelvic floor repair to withstand mechanical strain. Prolift(®) at rest showed moderate porosity with little stretchability but complete loss of effective porosity at strain of 4.9 N/cm. Prolift + M(®) revealed an increased porosity at rest, but at strain showed high stretchability, with subsequent loss of effective porosity at strain of 2.5 N/cm. Dynamesh PR4(®) preserved its high porosity even under strain, but as consequence of limited stretchability. Though in tension free conditions Prolift(®) and Prolift + M(®) can be considered as large pore class I meshes, application of mechanical strain rapidly lead to collapse of pores. The loss of porosity at mechanical stress can be prevented by constructions with high structural stability. Assessment of porosity under strain was found helpful to define requirements for pelvic floor devices. Clinical studies have to prove whether devices with high porosity as well as high structural stability can improve the patients' outcome.

First in vivo visualization of MRI-visible IPOM in a rabbit model.

BACKGROUND: Application of a mesh in presence of pneumoperitoneum may cause deformation or wave formation when gas is released. Moreover, mesh shrinkage during subsequent wound healing cannot be detected in vivo without invasive diagnostics. Using MRI-visible polyvinylidene fluoride (PVDF) mesh, the extend of mesh deformation and shrinkage could be objectified by MRI for the first time. MATERIALS AND METHODS: Laparoscopic intraperitoneal onlay mesh (IPOM) implantation was performed in 10 female rabbits using ferro-oxide loaded PVDF meshes. MRI measurements were performed postoperatively at days 1 and 90. After three-dimensional reconstruction of all MRI images the total surface and the effective surface of the implanted mesh were explored and calculated computer-assisted. RESULTS: In all cases, the mesh could be identified in MRI. The subsequent three-dimensional reconstruction always allowed a calculation of the mesh area. In relation to the original size of the used textile implant, we found neither a significant reduction of the effective mesh surface after release of the pneumoperitoneum at day 1 after laparoscopic surgery nor a significant change of the total surface of this large pore mesh by the end of the observation period. CONCLUSIONS: In vivo investigation of mesh surface via MRI could exclude a significant initial reduction of the effective mesh surface after release of pneumoperitoneum, in this IPOM rabbit model. A further subsequent shrinkage of these large pore PVDF meshes could be excluded, as well. Imaging of MRI-visible IPOM mesh turned out to be a sufficient tool to objectify mesh configuration and position in vivo.

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.

Biomechanical analyses of prosthetic mesh repair in a hiatal hernia model.

Recurrence rate of hiatal hernia can be reduced with prosthetic mesh repair; however, type and shape of the mesh are still a matter of controversy. The purpose of this study was to investigate the biomechanical properties of four conventional meshes: pure polypropylene mesh (PP-P), polypropylene/poliglecaprone mesh (PP-U), polyvinylidenefluoride/polypropylene mesh (PVDF-I), and pure polyvinylidenefluoride mesh (PVDF-S). Meshes were tested either in warp direction (parallel to production direction) or perpendicular to the warp direction. A Zwick testing machine was used to measure elasticity and effective porosity of the textile probes. Stretching of the meshes in warp direction required forces that were up to 85-fold higher than the same elongation in perpendicular direction. Stretch stress led to loss of effective porosity in most meshes, except for PVDF-S. Biomechanical impact of the mesh was additionally evaluated in a hiatal hernia model. The different meshes were used either as rectangular patches or as circular meshes. Circular meshes led to a significant reinforcement of the hiatus, largely unaffected by the orientation of the warp fibers. In contrast, rectangular meshes provided a significant reinforcement only when warp fibers ran perpendicular to the crura. Anisotropic elasticity of prosthetic meshes should therefore be considered in hiatal closure with rectangular patches.

In vivo visualization of polymer-based mesh implants using conventional magnetic resonance imaging and positive-contrast susceptibility imaging.

PURPOSE: Polymer-based textile meshes for abdominal hernia treatment are invisible by conventional imaging methods, including magnetic resonance imaging (MRI). Integration of iron particles in the mesh base material allows MRI visualization of meshes. Positive-contrast susceptibility imaging (PCSI) was implemented to separate susceptibility-induced voids from proton-deficient voids. The purpose of this study was to compare PCSI with conventional gradient echo and turbo spin echo (TSE) sequences for the in vivo assessment of superparamagnetic iron oxide particle-loaded surgical meshes in an animal model. METHODS AND MATERIALS: Iron-loaded polymer meshes were implanted into the abdominal wall of 10 rabbits. At days 1, 30, and 90 after surgery, conventional gradient echo, TSE, and PCSI were performed at 1.5 T in the sagittal and axial planes. Images were scored by 2 radiologists with respect to mesh visibility, delineation of the surrounding tissue, differentiation from other structures, and overall diagnostic use, on a 4-point scale ranging from 1 (insufficient) to 4 (excellent). The results were compared using Wilcoxon signed-rank tests. The mesh shape, possible deformation or fracture, and possible mesh migration were evaluated on the different pulse sequences and compared with the results at surgery and autopsy. RESULTS: The iron-loaded meshes appeared as hypointense signal voids on gradient echo sequences, as a hyperintense line on PCSI, and as a very thin dark line on TSE images. In all animals, a precise depiction of the mesh location and its spatial configuration and integrity was possible by MRI and confirmed by surgical and autopsy results. In all 4 categories and at all 3 time points of imaging, image quality scores were significantly higher for gradient echo imaging (range, 3.60-3.80) compared with PCSI (range, 3.12-3.42) and TSE (range, 1.64-1.89). At day 90, the image quality ratings of gradient echo and PCSI were comparable. In 2 cases, the complete delineation of mesh borders was impossible because of signal voids of adjacent anatomical structures, whereas PCSI helped achieve this differentiation. CONCLUSION: In this rabbit model of iron-loaded implanted abdominal meshes, standard gradient echo imaging was best suitable to assess implant location, integrity, and configuration. In 2 of 10 animals, PCSI helped achieve a complete delineation of mesh borders.

First in-human magnetic resonance visualization of surgical mesh implants for inguinal hernia treatment.

OBJECTIVES: Until today, there have been no conventional imaging methods available to visualize surgical mesh implants and related complications. In a new approach, we incorporated iron particles into polymer-based implants and visualized them by magnetic resonance imaging (MRI).After clinical approval of such implants, the purposes of this study were to evaluate the MRI conspicuity of such iron-loaded mesh implants in patients treated for inguinal hernias and to assess the immediate postsurgical mesh configuration. MATERIALS AND METHODS: Approved by the ethics committee, in this prospective cohort study, 13 patients (3 patients with bilateral hernia treatment) were surgically treated for inguinal hernia receiving iron-loaded mesh implants between March and October 2012. The implants were applied via laparoscopic technique (transabdominal preperitoneal technique; n = 8, 3 patients with bilateral hernia treatment) or via open surgical procedure (Lichtenstein surgery; n = 5). Magnetic resonance imaging was performed 1 day after the surgery at a 1.5-T scanner (Achieva; Philips, Best, The Netherlands) with a 16-channel receiver coil using 3 different gradient echo sequences (first gradient echo sequence, second gradient echo sequence, and third gradient echo sequence [GRE1-3]) and 1 T2-weighted turbo spin-echo sequence (T2wTSE). Three radiologists independently evaluated mesh conspicuity and diagnostic value with respect to different structures using a semiquantitative scoring system (1, insufficient; 2, sufficient; 3, good; 4, optimal). Mesh deformation and coverage of the hernia were visually assessed and rated using a 5-point semiquantitative scoring system. Statistical analysis was performed using mixed models and linear contrast. RESULTS: All 16 implants were successfully visualized by MRI. On gradient echo sequences, the mesh is clearly delineated as a thick hypointense line. On T2wTSE, the mesh was depicted as a faint hypointense line, which was difficult to identify. The first gradient echo sequence was rated best for visual conspicuity (mean [SD], 3.8 [0.4]). T2-weighted turbo spin-echo sequence was preferred for evaluation of the surrounding anatomy (mean [SD], 3.7 [0.3]). For the combined assessment of both mesh and anatomy, GRE3 was rated best (mean [SD], 2.9 [0.7]). Local air slightly reduced mesh delineation (lowest mean [SD] rating, 2.9 [0.7] for GRE3). Overall, in both implantation techniques, the meshes exhibited mild to moderate deformations (mean [SD], 3.3 [0.4], 3.1 [0.3], and 2.8 [0.3] on average with open technique, 2.7 [0.3], 2.7 [0.2], and 2.3 [0.3] with laparoscopic technique). Coverage of the hernia was achieved in 15 of the 16 implants. CONCLUSIONS: Combining iron-loaded implants and MRI, we achieved mesh visualization for the first time in patients. For MRI protocol, we propose a combination of different gradient echo sequences and T2-weighted turbo spin-echo sequences: first gradient echo sequence for mesh configuration, T2wTSE for anatomy assessment, and GRE3 for evaluation of hernia coverage and mesh localization. Using our approach, MRI could become a noninvasive alternative to open surgical exploration if mesh-related complications were suspected.