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.     

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.     

Relationship Between Tissue Ingrowth and Mesh Contraction

Contraction is a well-documented phenomenon occurring within two months of mesh implantation. Its etiology is unknown, but it is suggested to occur as a result of inadequate tissue ingrowth into the mesh and has been associated with hernia recurrence. In continuation of our previous studies, we compared tissue ingrowth characteristics of large patches of polyester (PE) and heavyweight polypropylene (PP) and their effect on mesh contraction. The materials used were eight PE and eight PP meshes measuring 10 × 10 cm². After random assignment to the implantation sites, the meshes were fixed to the abdominal wall fascia of swine using interrupted polypropylene sutures. A necropsy was performed three months after surgery for evaluation of mesh contraction/shrinkage. Using a tensiometer, tissue ingrowth was assessed by measuring the force necessary to detach the mesh from the fascia. Histologic analysis included inflammatory and fibroblastic reactions, scored on a 0–4 point scale. One swine developed a severe wound infection that involved two PP meshes and was therefore excluded from the study. The mean area covered by the PE meshes (87 ± 7 cm²) was significantly larger than the area covered by the PP meshes (67 ± 14 cm²) (p = 0.006). Tissue ingrowth force of the PE meshes (194 ± 37 N) had a trend toward being higher than that of the PP meshes (159 ± 43 N), although it did not reach statistical significance. There was no difference in histologic inflammatory and fibroblastic reactions between mesh types. There was a significant correlation between tissue ingrowth force and mesh size (p = 0.03, 95% CI: 0.05–0.84). Our results confirm those from previous studies in that mesh materials undergo significant contraction after suture fixation to the fascia. PE resulted in less contraction than polypropylene. A strong integration of the mesh into the tissue helps prevent this phenomenon, which is evidenced by a significant correlation between tissue ingrowth force and mesh size. Presented at the Southeastern Surgical Congress 2004 Meeting, Atlanta, GA, January 31–February 3, 2004 This study was sponsored by Promethian Surgical Devices, Boston, MA, USA.     

Assessment of microcirculatory influence on cellular morphology in human burn wound healing using reflectance-mode-confocal microscopy

Previous studies have assessed the effects of changes in microcirculation on wound healing; however, the influence of microcirculation on tissue histomorphology remains widely unknown. Reflectance‐mode‐confocal microscopy (RMCM) enables in vivo tissue observation on a cellular level. We present RMCM data evaluating the local microcirculation and assess the influence on histomorphology during burn healing. RMCM was performed in 12 patients (aged; 36.2±14.2 years, maximum‐burn‐extent: 4% total body surface area) at times 12, 36, and 72 hours after a superficial burn. The following parameters were assessed: quantitative blood‐cell‐flow (cbf), epidermal thickness (Emin), basal‐layer thickness (tbl), and granular cell‐size (Agran). Cbf was found to be 54±3.6 cells/minutes (control), increased to 91±3.6 cells/minutes (p<0.05) 12 hours postburn; decreased to 71±6.1 cells/minutes (p<0.05) (36 hours), and to 63±2.3 cells/minutes (p>0.05) 72 hours postburn. Emin was 43.74±3.87 μm (control), increased to 51.67±4.04 μm (p<0.05) 12 hours, decreased to 48.67±3.51 μm (p<0.05) 36 hours, and to 45.33±3.21 μm (p>0.05) at 72 hours postburn. Tbl was 14.17±0.6 μm (control), increased to 16.93±1.15 μm (p<0.05) 12 hours, decreased to 15.93±1.20 μm (p<0.05) 32 hours, and to 15.00±0.85 μm (p>0.05) 72 hours postburn. Agran was 718±56.20 μm² (control), increased to 901±66.02 μm² (p<0.05) 12 hours, decreased to 826±56.86 μm² 36 hours, and 766±65.06 μm² at 72 hours postburn. RMCM enables in vivo observation of wound microcirculation and allows direct assessment of vascular effects on cutaneous histomorphology during the healing course of superficial burns.     

Myofibroblasts and colonic anastomosis healing in Wistar rats

Background

Mesh repair of incisional hernia is superior to the conventional technique. From all available materials for open surgery polypropylene (PP) is the most widely used. Development resulted in meshes with larger pore size, decreased mesh surface and lower weight. The aim of this retrospective non randomized study was to compare the quality of life in the long term follow up (> 72 month) after incisional hernia repair with "light weight"(LW) and "heavy weight"(HW) PP meshes.

Methods

12 patients who underwent midline open incisional hernia repair with a HW-PP mesh (Prolene^® 109 g/m² pore size 1.6 mm) between January 1996 and December 1997 were compared with 12 consecutive patients who underwent the same procedure with a LW-PP mesh (Vypro^® 54 g/m², pore size 4-5 mm) from January 1998. The standard technique was the sublay mesh-plasty with the retromuscular positioning of the mesh. The two groups were equal in BMI, age, gender and hernia size. Patients were routinely seen back in the clinic.

Results

In the long term run (mean follow up 112 ± 22 months) patients of the HW mesh group revealed no significant difference in the SF-36 Health Survey domains compared to the LW group (mean follow up 75 ± 16 months).

Conclusions

In this study the health related quality of life based on the SF 36 survey after open incisional hernia repair with light or heavy weight meshes is not related to the mesh type in the long term follow up.     

Improved ventilation-perfusion matching with increasing abdominal pressure during CO(2) -pneumoperitoneum in pigs

Background: CO₂‐pneumoperitoneum (PP) is performed at varying abdominal pressures. We studied in an animal preparation the effect of increasing abdominal pressures on gas exchange during PP. Methods: Eighteen anaesthetized pigs were studied. Three abdominal pressures (8, 12 and 16 mmHg) were randomly selected in each animal. In six pigs, single‐photon emission computed tomography (SPECT) was used for the analysis of V/Q distributions; in another six pigs, multiple inert gas elimination technique (MIGET) was used for assessing V/Q matching. In further six pigs, computed tomography (CT) was performed for the analysis of regional aeration. MIGET, CT and central haemodynamics and pulmonary gas exchange were recorded during anaesthesia and after 60 min on each of the three abdominal pressures. SPECT was performed three times, corresponding to each PP level. Results: Atelectasis, as assessed by CT, increased during PP and in proportion to abdominal pressure [from 9 ± 2% (mean ± standard deviation) at 8 mmHg to 15 ± 2% at 16 mmHg, P<0.05]. SPECT during increasing abdominal CO₂ pressures showed a shift of blood flow towards better ventilated areas. V/Q analysis by MIGET showed no change in shunt during 8 mmHg PP (9 ± 1.9% compared with baseline 9 ± 1.2%) but a decrease during 12 mmHg PP (7 ± 0.9%, P<0.05) and 16 mmHg PP (5 ± 1%, P<0.01). PaO₂ increased from 39 ± 10 to 52 ± 9 kPa (baseline to 16 mmHg PP, P<0.01). Arterial carbon dioxide (PCO₂) increased during PP and increased further with increasing abdominal pressures. Conclusion: With increasing abdominal pressure during PP perfusion was redistributed more than ventilation away from dorsal, collapsed lung regions. This resulted in a better V/Q match. A possible mechanism is enhanced hypoxic pulmonary vasoconstriction mediated by increasing PCO₂.     

Characterization of innate and adaptive immune cells involved in the foreign body reaction to polypropylene meshes in the human abdomen

Background

Polypropylene (PP) mesh is widely used to reinforce tissues. The foreign body reaction (FBR) to the implant is dominated by innate immune cells, especially macrophages. However, considerable numbers of adaptive immune cells, namely T cells, have also been regularly observed, which appear to play a crucial role in the long-term host response.

Methods

This study investigated the FBR to seven human PP meshes, which were removed from the abdomen for recurrence after a median of one year. Using immunofluorescence microscopy, the FBR was examined for various innate (CD11b⁺ myeloid, CD68⁺ macrophages, CD56⁺ NK) and adaptive immune cells (CD3⁺ T, CD4⁺ T-helper, CD8⁺ cytotoxic, FoxP3⁺ T-regulatory, CD20⁺ B) as well as “conventional” immune cells (defined as cells expressing their specific immune cell marker without co-expressing CD68).

Results

T-helper cells (19%) and regulatory T-cells (25%) were present at comparable rates to macrophages, and clustered significantly toward the mesh fibers. For all cell types the lowest proportions of “conventional” cells (<?60%) were observed at the mesh–tissue interface, but increased considerably at about 50–100 µm, indicating reduced stimulation with rising distance to the mesh fibers.

Conclusion

Both innate and adaptive immune cells participate in the chronic FBR to PP meshes with T cells and macrophages being the predominant cell types, respectively. In concordance with the previous data, many cells presented a “hybrid” pattern near the mesh fibers. The complexity of the immune reaction seen within the foreign body granuloma may explain why approaches focusing on specific cell types have not been very successful in reducing the chronic FBR.

     

Polypropylene meshes coated with a polysaccharide based bioadhesive for intra-abdominal mesh fixation in a rabbit model

Background

In this study, we evaluate a new bioadhesive for intra-abdominal onlay mesh fixation of a polypropylene–polyvinylchloride graft.

Methods

Three pieces of a commercially available polypropylene/polyvinylfluoride mesh, each 3 × 3 cm in size, and three pieces of the same mesh coated with a polysaccharide bioadhesive were fixated to the surface of the anterior abdominal wall of 30 New Zealand white rabbits. The fixation was performed either by using four transabdominal Prolene^® 4/0 sutures, four spiral tacks (Protack 5 mm Tyco), or cyanoacrylate glue (Glubran^® GEM, Viareggio, Italy). Each mesh position and the according kind of fixation were randomized before implantation. The animals were sacrificed 12 weeks postoperatively. After determining the extent of intra-abdominal adhesions, the meshes were excised en bloc with the anterior abdominal wall for tensile strength measurements and histological analysis.

Results

All meshes coated with the bioadhesive adhered to the intact peritoneum without extra fixation. Irrespective of the fixation technique coated meshes led to more and stronger adhesions. Mesh shrinkage by scarring was increased in coated meshes fixed with glue and low in uncoated meshes fixed with tacks. Testing the tensile strength, coated meshes fixed with transfascial sutures achieved the best results (16.14 ± 6.1 N), whereas coated meshes fixed with glue showed the lowest strength (10.39 ± 4.81 N). The foreign body reaction was considerably more distinctive using coated mesh. The mesh ingrowth was not influenced by this reaction.

Conclusions

All meshes coated with the new bioadhesive were self-adhesive in that way; they stayed in position when attached to the peritoneum. Although this may facilitate intra-operative mesh fixation, the bioadhesive displayed several disadvantages, such as stronger adhesions and an increased shrinkage of the implant. The tensile strength was not influenced by the use of the bioadhesive. At present, we see no major advantage for polysaccharide bioadhesive applied in this study.     

Polylactide (LTS) causes less inflammation response than polydioxanone (PDS): a meniscus repair model in sheep

Background Incidence of meniscus injury has increased in today’s active society. Arthroscopical refixation yields better results than partial meniscectomy. The best healing rates are achieved by sutures. As non-degradable sutures are permanent foreign bodies, slow absorbable materials are needed. A slow degradable suture with high concentration of polylactide acid, the so-called “long-term suture” (LTS, Panacryl), has been suggested to produce a higher inflammatory response than conventional polymer sutures [Vicryl, Dexon or polydioxanone (PDS)]. The aim of the study was to assess LTS for meniscus repair after a traumatic lesion and to evaluate immunological response, biodegradation and healing.Methods In 24 randomised sheep, a radial tear of the medial meniscus was sutured by either PDS or LTS. Twelve sham-operated animals served as control. Half of the sheep were killed after 6 months, the other half after 12 months. The medial and lateral meniscus, synovial membrane, articular cartilage and ascendant lymph nodes up to the kidney were examined. Joint effusion was evaluated by MRI.Results The synovial membrane was significantly thinner in the LTS group (6 months 85 ± 10 μm, 1 year 100 ± 28 μm) than in the PDS group (6 months 165 ± 10 μm, 1 year 175 ± 23 μm, P < 0.001) and the controls (6 months 150 ± 17 μm, 12 months 192 ± 21 μm, P < 0.001). The joint effusion was higher in the PDS than in the LTS group after 6 months, and tended to be higher in controls. In controls, effusion tended to be higher than in the LTS group. In all medial departments, osteoarthritis evolved much more intensely than in the lateral knee departments (P < 0.01). Bilateral lymph nodes from the groin up to the kidneys were larger (crosscut area) after 6 months in the controls (2.28 ± 0.7 mm2) and PDS treated animals (2.3 ± 0.7 mm2) than in the LTS group (1.3 ± 0.3 mm2, P < 0.001). After 1 year, node size differed significantly between controls and animals from the LTS group (1.98 ± 0.4 mm2 vs. 1.5 ± 0.2 mm2, P < 0.05), and between animals from the PDS and the LTS group (2.5 ± 0.1 mm2 vs. 1.5 ± 0.2 mm2, P < 0.001).Conclusion The polylactide thread LTS causes less immunological reaction and synovitis than a polydioxanone suture (PDS). Clinical relevance: LTS may serve as an alternative to PDS for repair of slow healing structures such as tendons and menisci.Christof Burger and Koroush Kabir have contributed equally to this paper.     

Immunohistochemical analysis of host reaction to heavyweight-, reduced-weight-, and expanded polytetrafluoroethylene (ePTFE)-based meshes after short- and long-term intraabdominal implantations

Background Prosthetic meshes induce a variety of inflammatory changes in the host, which may lead to excessive scarring with detrimental clinical consequences, especially in the long term. This study aimed to characterize the degree of short- and long-term inflammatory changes induced by common prosthetic meshes. Methods Twenty 4 × 4-cm samples each of expanded polytetrafluoroethylene (ePTFE), heavyweight polypropylene (hPP), ePTFE/heavyweight polypropylene (ePTFE/hPP), and reduced-weight polypropylene/regenerated cellulose (rPP) were implanted intraperitoneally in 40 rabbits for 4 or 12 months. After explantation, samples of mesh/tissue complex were analyzed for the degrees of cellular apoptosis (enzyme-linked immunoassay [ELISA]) and cellular turnover (mouse monoclonal antibody). Results In the short term, the degree of apoptosis in the hPP mesh was significantly higher than in the ePTFE and rPP groups. Similarly, it was higher in the ePTFE/hPP group than in either the ePTFE or the rPP group. The amount of Ki-67-positive cells was significantly higher in the hPP group than in the ePTFE or rPP group. The cell turnover in the ePTFE/hPP group was similar to that in the hPP group, but significantly higher than in either the ePTFE or the rPP group. The rPP group, in turn, had a higher Ki-67 score than the ePTFE group. In the long term, both the degree of apoptosis and Ki-67 positivity were significantly lower in the rPP and ePTFE groups than in either the ePTFE/hPP or the hPP group. A significant decrease in Ki-67 scores between the short and long-term groups was found only in the rPP group. Conclusion In the short term, heavyweight polypropylene-based meshes were associated with significantly higher cell proliferation and death. A significantly higher degree of apoptosis and cell turnover were associated with heavyweight polypropylene-based meshes even 1 year after implantation, indicating ongoing inflammation and scar remodeling. On the other hand, ePTFE and reduced-weight polypropylene meshes were associated with nearly physiologic levels of inflammatory markers. Overall, an exaggerated and persistent host foreign body response to heavyweight polypropylene-based meshes indicates poor biocompatibility, with potential detrimental clinical sequela.     

Mesh migration into the esophageal wall after mesh hiatoplasty: comparison of two alloplastic materials

Background

Hiatal mesh implantation in the operative treatment of gastroesophageal reflux disease has become an increasing therapy option. Besides clinical results little is known about histological changes in the esophageal wall.

Methods

Two different meshes [polypropylene (PP), Prolene^®; polypropylene–polyglecaprone 25 composite (PP–PG), Ultrapro^®] were placed on the diaphragm circular the esophagus of 20 female rabbits. After three months a swallow with iodine water-soluble contrast medium for functional analysis was performed. After the animals were sacrificed, histopathological evaluation of the foreign-body reaction, the localization of the mesh relating to the esophageal wall was analyzed.

Results

Sixteen rabbits survived the complete observation period of three months. After three months distinctive mesh shrinkage was observed in all animals and meshes had lost up to 50% of their original size before implantation. We found a delayed passage of the fluid into the stomach in all operated animals. There was a significant increased diameter of the outer ring of granulomas in the PP group (76.5 ± 8.0) compared to the PP–PG group (64 ± 8.5; p = 0.002). However, we found a mesh migration into the esophageal wall in six out of seven animals (PP) and five out of nine animals (PP-PG), respectively.

Conclusion

Experimental data suggest that more knowledge is necessary to assess the optimal size, structure, and position of prosthetic materials for mesh hiatoplasty. The indication for mesh implantation in the hiatal region should be carried out very carefully.

     

Comparison of etoricoxib vs. ketorolac in postoperative pain relief

Background: COX‐2 inhibitors have been claimed to have equal analgesic efficacy as non‐selective nonsteroidal anti‐inflammatory drugs, but this has been disputed in animal experiments. Methods: One hundred thirty‐three women scheduled for ambulatory, laparoscopic gynaecological surgery were included in this randomised, double‐blind study. Group E received 120 mg etoricoxib orally as premedication. Group K received 30 mg ketorolac i.v. after induction of anaesthesia. General anaesthesia was induced and maintained with propofol and remifentanil. Fentanyl 0.5 μg/kg i.v. and local wound anaesthesia was administered at the end of surgery. Postoperatively, the patients received fentanyl 0.5 μg/kg i.v. if visual analogue scale (VAS) ≥30 mm. Before discharge, Group K received 30 mg ketorolac i.v. Twenty‐four hours postoperatively, Group E received 120 mg etoricoxib. Results: The first 4 h postoperatively, Group K required 83±65 μg and Group E required 123±91 μg fentanyl [mean (SD), P=0.004]. After 30 min VAS in Group K was 31.3±19.7 mm and 43.8±16.9 mm in Group E [mean (SD), P<0.001]. Discharge readiness was significantly shorter in Group K (222±40 min) compared with Group E (244±47 min) [mean (SD), P=0.004]. There were no differences in pain scores or rescue pain medication at 24 or 48 h postoperatively. Less nausea was observed in the 4–24‐h period in Group E. Conclusions: Thirty milligram ketorolac i.v. after induction of anaesthesia resulted in significantly less immediate pain and opioid consumption during the first 4 h postoperatively compared with 120 mg etoricoxib preoperatively.     

Composite prostheses for the repair of abdominal wall defects: effect of the structure of the adhesion barrier component

The component of a composite prosthesis, which makes contact with the visceral peritoneum, can be reabsorbable or non-reabsorbable, and laminar or reticular. This study was designed to determine whether the composition of this second, barrier component could improve its behavior at this interface. Abdominal wall defects in rabbits were repaired using a polypropylene prosthesis (PP), or the composites Sepramesh (PP+h) or Vicryl (PP+v). Fourteen days after surgery, the implants were evaluated by light and scanning electron microscopy, and immunohistochemistry. Prosthetic areas occupied by adhesions (PP: 71.08±5.09, PP+h: 18.55±4.96, P+v: 69.69±16.81%), neoperitoneal thickness (PP: 256.17±21.68, PP+h: 83.11±19.63, PP+v:213.72±35.90 μm) and macrophage counts (PP: 8.73±1.16, PP+h: 27.33±4.13, PP+v: 31.24±3.08%) showed significant differences (P<0.05). The tested biomaterials induced an optimal recipient tissue infiltration. Least adhesion formation was observed on the PP+h implants. This suggests that the second component, although reabsorbable, should be smooth in structure.     

Cardiac Pacing Following Surgery for Acquired Heart Disease

Abstract Background: This study is comprised of 3493 consecutive patients who underwent open heart surgery at our institution. Data on all patients were collected prospectively. Methods: In 45 patients (Group P) (1.3%), a permanent pacemaker (PP) was inserted postoperatively. For the purpose of the study, these patients were compared to 3448 patients (Group NP) who did not require insertion of a PP after surgery. Mean follow-up was 33 months (range 1.5 to 66). Results: We found Group P patients were older (64.8 ± 11.0 vs 61.0 ± 11.0 years, p < 0.05), had a higher proportion of elderly (> 70 years) (36% vs 19%, p = 0.01), and of female patients (48.8% vs 22.7%, p < 0.001) compared to Group NP. Group P also had a higher incidence of preoperative rhythm abnormalities (26.6% vs 5.7%, p < 0.0001), redo surgery (13.3% vs 4.6%, p = 0.02), aortic valve surgery (48.8% vs 10.8%, p < 0.001), and tricuspid valve surgery (repair 3, replacement 1) (8.8% vs 0.5%, p < 0.001), in addition to a higher proportion of patients in whom cold (vs warm) blood cardioplegia was used (68.8% vs 52.3%, p = 0.03). Indication for postoperative PP was sick sinus syndrome (SSS) in nine patients; atrial fibrillation in eight patients; atrioventricular block (AVB) in 27 patients; and combined AVB/SSS in 1 patient. There were no operative deaths in Group P. Necessity for PP after heart surgery had a significant impact on resource utilization resulting in prolonged ventilation (3.1 ± 7.5 vs 1.4 ± 3.3 days, p < 0.01), intensive care unit (5.1 ± 10.2 vs 2.5 ± 4.0 days, p < 0.01), and postoperative hospital stay (18.0 ± 13.4 vs 8.1 ± 9.4 days, p < 0.01). Conclusions: By multivariate logistic regression (odds ratio and p value in parentheses), aortic valve surgery (8.23, p = 0.001), the absence of preoperative sinus rhythm (5.60, p = 0.001), postoperative myocardial infarction (3.46, p = 0.024), and female gender (2.52, p = 0.003), were found to be independent predictors for PP requirement post surgery.     

Effects of reactive oxygen species on the physical properties of polypropylene surgical mesh at various concentrations: a model for inflammatory reaction as a cause for mesh embrittlement and failure

Background

Oxidative degradation by reactive oxygen species (ROS) from inflammation initiates cross-linking, depolymerization, and formation of a quasi-crystalline quality in polypropylene (PP) meshes that cause embrittlement (J Urol 188:1052, 2012). Embrittlement leads to change in tensile strength and is associated with post-operative complications that include pain, adhesion, dislodgment, and fragmentation.

Methods

A laboratory environment was constructed to study the relationship between concentration of ROS and change in tensile strength. Samples of Ethicon Ultrapro© PP mesh were exposed to 1 mM, 0.1 M, or 1 M hydrogen peroxide solutions for 6 months and were subjected to load displacement tensile testing (LDTT) and compared to unexposed (0 M) meshes of the same brand.

Results

Load at failure and elongation to failure after LDTT were determined with 95 % confidence interval. For unexposed (0 M) samples, tensile strength was 28.0 ± 2.4 lbf and elongation to failure was 2.0 ± 0.3 in. For samples exposed to 1 mM, tensile strength was 19.2 ± 1.1 lbf and the elongation to failure was 2.0 ± 0.1 in. For samples exposed to 0.1 M, tensile strength was 19.3 ± 1.6 lbf and elongation to failure was 1.9 ± 0.1 in. For samples exposed to 1 M, tensile strength was 20.7 ± 1.2 lbf and elongation to failure was 0.47 ± 0.02 in.

Conclusion

The results demonstrated that a 6-month exposure to a physiologic range of ROS (1 mM) decreased tensile strength of PP mesh by 31 %. 1 mM and 0.1 M samples behaved similarly demonstrating properties of a quasi-crystalline nature. 1 M samples displayed qualities of extreme embrittlement. Scanning electron microscopy (SEM) observed fiber changes. 1 M meshes had features of brittle materials. Knowledge of changes in physical properties of PP meshes is useful for considerations for the development of a more biocompatible surgical mesh.

     

Mesh repair for postoperative wound dehiscence in the presence of infection: is absorbable mesh safer than non-absorbable mesh?

Objective In patients with postoperative wound dehiscence in the presence of infection, extensive visceral oedema often necessitates mechanical containment of bowel. Prosthetic mesh is often used for this purpose. The aim of the present study was to assess the safety of the use of non-absorbable and absorbable meshes for this purpose. Method All patients that had undergone mesh repair of abdominal wound dehiscence between January 1988 and January 1998 in the presence of intra-abdominal infection were included in a retrospective cohort study. All surviving patients had physical follow-up in February 2001. Result Eighteen patients were included in the study. Meshes consisted of polyglactin (n = 6), polypropylene (n = 8), polyester (n = 1), or a combination of a polypropylene mesh with a polyglactin mesh on the visceral side (n = 3). All patients developed complications, consisting mainly of mesh infection (77%), intra-abdominal abscess (17%), enterocutaneous fistula (17%), or mesh migration through the bowel (11%). Mesh removal was necessary in eight patients (44%). Within four months postoperatively, six patients (33%) had died because of progressive abdominal sepsis. The incidence of progressive abdominal sepsis was significantly higher in the group with absorbable polyglactin mesh than in the group with nonabsorbable mesh (67 vs. 11%, p = 0.02) After a mean follow-up of 49 months, 63% of the surviving patients had developed incisional hernia. Absorbable meshes did not yield better outcomes than nonabsorbable meshes in terms of complications and mortality rate. Conclusion Synthetic graft placement in the presence of intra-abdominal infection has a high risk of complications, regardless of whether absorbable (polyglactin) or non-absorbable mesh material (polypropylene or polyester) is used, and should be avoided if possible.     

Sleeve Gastrectomy and Gastric Banding: Effects on Plasma Ghrelin Levels

Background: Different changes of plasma ghrelin levels have been reported following gastric banding, Roux-en-Y gastric bypass, and biliopancreatic diversion. Methods: This prospective study compares plasma ghrelin levels and weight loss following laparoscopic sleeve gastrectomy (LSG) and laparoscopic adjustable gastric banding (LAGB) in 20 patients. Results: Patients who underwent LSG (n=10) showed a significant decrease of plasma ghrelin at day 1 compared to preoperative values (35.8 ± 12.3 fmol/ml vs 109.6 ± 32.6 fmol/ml, P=0.005). Plasma ghrelin remained low and stable at 1 and 6 months postoperatively. In contrast, no change of plasma ghrelin at day 1 (71.8 ± 35.3 fmol/ml vs 73.7 ± 24.8 fmol/ml, P=0.441) was found in patients after LAGB (n=10). Increased plasma ghrelin levels compared with the preoperative levels at 1 (101.9 ± 30.3 fmol/ml vs 73.7 ± 24.8 fmol/ml, P=0.028) and 6 months (104.9 ± 51.1 fmol/ml vs 73.7 ± 24.8 fmol/ml, P=0.012) after surgery were observed. Mean excess weight loss was higher in the LSG group at 1 (30 ± 13% vs 17 ± 7%, P=0.005) and 6 months (61 ± 16% vs 29 ± 11%, P=0.001) compared with the LAGB group. Conclusions: As a consequence of resection of the gastric fundus, the predominant area of human ghrelin production, ghrelin is significantly reduced after LSG but not after LAGB. This reduction remains stable at follow-up 6 months postoperatively, which may contribute to the superior weight loss when compared with LAGB.     

A comparison of Progrip® and Adhesix® self-adhering hernia meshes in an onlay model in the rat

Background

Atraumatic fixation is a key element of modern hernia repair. Two different concepts of self-adhering meshes were directly compared in this study. Adhesix^® (AH) is coated with polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP), whereas Parietene Progrip^® (PP) relies on the mechanical principle of micro grips made of polylactic acid (PLA). These meshes are the main competitors in the field.

Methods

AH and PP were tested in Sprague–Dawley rats at 14 and 90 days. Four groups were operated (n = 8 animals per group). Two meshes were implanted per animal in an operation model of onlay hernia repair. Dislocation, tissue integration and foreign-body reaction were evaluated.

Results

AH dislocated significantly more frequently (every second mesh) at both time points of observation than PP. Tissue integration was good with PP and could not be reliably assessed in AH due to frequent dislocation. Histologic examination revealed only a mild foreign body reaction in all groups.

Conclusions

In our hands, PP (mechanical grip fixation) was superior to hydrogel fixation with PEG and PVP in AH in an onlay model. The reason for dislocation of AH requires further clarification as well as the impact of long-term degradation of the PLA grips.     

Anterior thoracolumbar column reconstruction with the vertebral body stent—safety and efficacy

Purpose

The aim of this study was to assess safety and efficacy of vertebral body stenting (VBS) by analyzing (1) radiographic outcome, (2) clinical outcome, and (3) perioperative complications in patients with vertebral compression fractures treated with VBS at minimum 6-month follow-up.

Methods

In this retrospective cohort study, 78 patients (61 ± 14 [21–90] years; 67% female) who have received a vertebral body stent due to a traumatic, osteoporotic or metastatic thoracolumbar compression fracture at our hospital between 2012 and 2020 were included. Median follow-up was 0.9 years with a minimum follow-up of 6 months. Radiographic and clinical outcome was analyzed directly, 6 weeks, 12 weeks, 6 months postoperatively, and at last follow-up.

Results

Anterior vertebral body height of all patients improved significantly by mean 6.2 ± 4.8 mm directly postoperatively (p < 0.0001) and remained at 4.3 ± 5.1 mm at last follow-up compared to preoperatively (p < 0.0001). The fracture kyphosis angle of all patients improved significantly by mean 5.8 ± 6.9 degrees directly postoperatively (p < 0.0001) and remained at mean 4.9 ± 6.9 degrees at last follow-up compared to preoperatively (p < 0.0001). The segmental kyphosis angle of all patients improved significantly by mean 7.1 ± 7.6 degrees directly postoperatively (p < 0.0001) and remained at mean 2.8 ± 7.8 degrees at last follow-up compared to preoperatively (p = 0.03). Back pain was ameliorated from a preoperative median Numeric Rating Scale value of 6.5 to 3.0 directly postoperatively and further bettered to 1.0 six months postoperatively (p = 0.0001). Revision surgery was required in one patient after 0.4 years.

Conclusion

Vertebral body stenting is a safe and effective treatment option for osteoporotic, traumatic and metastatic compression fractures.

     

Comparative evaluation of adhesion formation, strength of ingrowth, and textile properties of prosthetic meshes after long-term intra-abdominal implantation in a rabbit

BACKGROUND: Effective laparoscopic ventral herniorrhaphy usually mandates the use of an intraperitoneal prosthetic. Visceral adhesions and changes in textile characteristics of prosthetics may complicate repairs, especially long-term. The aim of this study was to compare the adhesion formation, tissue ingrowth, and textile characteristics one year after intra-abdominal placement of the commonly used prosthetic meshes. MATERIALS AND METHODS: Forty (4 x 4 cm) meshes were sutured using absorbable suture to an intact peritoneum in 20 New Zealand white rabbits. The study groups included: polypropylene (PP) [Marlex; C.R. Bard Inc, Cranston, NJ], expanded polytetrafluoroethylene (ePTFE) [DualMesh; WL Gore, Flagstaff, AZ], ePTFE and PP (ePTFE/PP) [Composix, C.R. Bard Inc], reduced weight PP and oxidized regenerated cellulose (rPP/C) [Proceed; Ethicon, Inc, Somerville, NJ]. The meshes were explanted after one year. Adhesions were scored as a percentage of explanted biomaterials' affected surface area. Prosthetic shrinkage was calculated. The strength of incorporation and mesh compliance were evaluated using differential variable reluctance transducers. Mesh ingrowth was measured as the load necessary to distract the mesh/tissue complex. Mesh compliance was calculated as the change in linear displacement of the sensors due to applied load. The groups were compared using Student's t-test and Fisher's exact test. RESULTS: ePTFE had significantly less adhesions (0%) than both ePTFE/PP (40%) and PP (80%) groups (P < 0.001). The mean area of adhesions for the rPP/C (10%) and the ePTFE/PP (14%) groups was less than that for the PP group (40%) (P = 0.02). Prosthetic shrinkage was greatest in the ePTFE (32%) group than in any other group (P = 0.001). There were no differences in mesh incorporation between the groups. At explantation, mesh compliance in the ePTFE group was superior to other meshes (P < 0.0001). The rPP/C mesh induced the smallest change in the compliance of the tissue adjacent to the mesh (P = 0.0001). CONCLUSIONS: Prosthetic materials demonstrate a wide variety of characteristics. Although exposed PP formed the most adhesions, up to 40% of the other PP-based meshes formed adhesions despite protective barriers. The ePTFE mesh did not induce adhesions and was the most compliant, however, this prosthetic's contraction was greatest. Reduced weight polypropylene (rPP/C) mesh induced the smallest change in the adjacent tissue pliability/compliance. Understanding of the long-term effects of various prosthetic materials is important to ensure an adequate hernia repair while minimizing postoperative morbidity and patient discomfort.