Tensile strength and host response towards silk and type i polypropylene implants used for augmentation of fascial repair in a rat model

OBJECTIVE: We compared host response, architectural integration and tensile strength of two different macroporous silk constructs to a polypropylene type I implant in a rat model for augmentation of primary fascial defect repair. MATERIALS AND METHODS: Animals were sacrificed on days 7, 14, 30 and 90 after implantation. The explants were evaluated macroscopically for infections, herniations and adhesions, mechanically for tensile strength, and histopathologically, to evaluate collagen deposition and inflammatory response. RESULTS: The tensile strength of the explants showed a gradual increase for all materials. All implants uniformly shrank around one fifth by 90 days. In the silk implants, the inflammatory reaction showed a remarkable higher number of foreign body giant cells that characteristically spread from the periphery into implants. Collagen deposition was comparable for all the materials. In Silk a higher grade of neovascularisation was observed. CONCLUSION: Silk explants expressed high tensiometric strength, which was associated with a marked fibrotic process. The silk implants induced a strong foreign body reaction accompanied by microscopic signs of architectural degradation at 90 days. Polypropylene explants showed a more moderate foreign body reaction without architectural disturbance.     

Host response after reconstruction of abdominal wall defects with porcine dermal collagen in a rat model

OBJECTIVE: The purpose of this study was to compare the inflammatory response after implantation of Pelvicol with Prolene in a rat model. STUDY DESIGN: Full-thickness abdominal wall defects were created in 64 Wistar rats, and reconstructed with either Pelvicol or Prolene. Animals were sacrificed on days 7, 14, 30, and 90 to evaluate the presence of herniation, infection, adhesions, and changes in thickness and tensile strength of the implants. Histopathology and immunohistochemistry were performed to evaluate the collagen deposition and the inflammatory response. Statistics were done with unpaired t test and Mann-Whitney rank test. RESULTS: Pelvicol implantation induced infiltration of granulocytes, macrophages, and NK cells, which showed up-regulated expression of surface activation markers ICAM-1 and CD11b. This inflammatory response was significantly milder, and declined faster than in Prolene-implanted rats, and was also associated with fewer adhesions. Moreover, Pelvicol induced a slower, but more orderly collagen deposition, paralleling the surface of the implant. Pelvicol implants showed a slower increase in thickness and tensile strength early on, but this difference disappeared by day 90. CONCLUSION: Pelvicol induces a milder inflammatory response, less adhesion formation, more orderly collagen deposition than Prolene, and reaches a comparable tensile strength only after 90 days.     

猪小肠黏膜下层补片植入兔膀胱阴道间隙的转归研究

目的观察猪小肠黏膜下层(SIS)补片植入兔膀胱阴道间隙的转归,探讨SIS补片在妇科盆底手术中的应用价值。方法以家兔作为动物模型,16只雌性家兔随机(抽签法)分为4组,即7 d组、30 d组、90 d组和180 d组,每组4只家兔。4组家兔均通过手术方式于膀胱阴道间隙内植入SIS补片,分别于术后7、30、90、180 d处死各组家兔,并同时整块取出补片及其周围的膀胱阴道组织。标本均制成蜡块后切片,采用HE染色观察补片内部及周围组织产生的形态学变化,采用Masson染色观察补片组织内胶原形态和数量的变化。结果(1)HE染色后光镜下观察,7 d组SIS补片周围可见大量以嗜酸性粒细胞和淋巴细胞为主的炎性细胞浸润,并可见新生血管形成;30 d组炎性细胞浸润区域进一步增大;90 d组炎性细胞浸润区域明显缩小;180天组炎性反应基本消退。(2)Masson染色后光镜下观察,7 d组4只家兔SIS补片胶原结构清晰,保留完整;30 d组4只家兔SIS补片已有部分降解,但仍可见SIS胶原结构;90 d组有2只家兔尚可见少量残留SIS碎片结构,另2只家兔的SIS补片已被完全降解;180 d组4只家兔的SIS补片均被完全降解,其中1只家兔似可见部分有排序的胶原结构。结论SIS补片植入兔膀胱阴道间隙后可导致一过性的非感染性炎症反应,植入180 d后可被完全降解并有少量新生胶原结构产生。SIS补片用于盆底重建手术需谨慎。     

丝蛋白涂层轻质聚丙烯网片对兔腹壁疝模型组织学反应的影响

目的:探讨宿主对有丝蛋白涂层和无丝蛋白涂层的2种不同轻质聚丙烯网片组织学反应的差别。方法:2种聚丙烯网片(Gynemesh网片和法国G819P网片)的有丝蛋白涂层和无丝蛋白涂层网片各6片,共计24片,裁剪为30 mm×30 mm大小。6只新西兰大白兔,每只均制作6个腹壁缺损,并分别植入有丝蛋白和无丝蛋白涂层Gy-nemesh誖网片和有丝蛋白和无丝蛋白涂层G819P网片各1片,另2个腹壁缺损作为空白对照。植入后30,60和90 d时各处死2只动物,取出包括网片在内的腹壁全层,做大体观察、组织学观察以及免疫组化研究,包括炎症、纤维化反应、网片周围血管化反应以及胶原形成等。结果:所有网片均未发生侵蚀。有丝蛋白涂层网片组炎症反应和纤维化反应较轻,网片与组织融合良好。无涂层组可见少量的凋亡和坏死。结论:有丝蛋白涂层聚丙烯网片引起实验动物的组织学反应较轻,可以降低早期炎症反应和纤维化程度,减少组织粘连,降低网片相关并发症的产生。     

Absorbable versus permanent mesh in abdominal operations

Because previous studies evaluating prosthetic mesh have yielded conflicting results, we compared two permanent (polypropylene and polytetrafluoroethylene) and two absorbable (polyglactin and polyglycolic acid) meshes with respect to histologic appearance, development of adhesions, tensile strength and occurrence of hernias in rabbits in which defects of the abdominal wall measuring 2 by 3 centimeters were repaired with one of the meshes. Twenty experiments were performed with each material, and observations were made at two, five, seven and ten weeks. The inflammatory response was minimal with all products. Adhesions were more marked with polypropylene (Marlex) than with polytetrafluoroethylene (Gore-tex); there was no difference between the absorbable meshes. In vitro tensile strength measurements at ten weeks indicated that Marlex was superior to the other materials, and between the absorbable products, polyglactin (Vicryl) was superior to polyglycolic acid (Dexon). No hernias were observed with the nonabsorbable meshes, but all of the rabbits repaired with absorbable meshes had ventral hernias by the tenth week. Thus, absorbable meshes are not indicated when prolonged tensile strength is required, but they may be useful for other purposes, including the temporary repair of fascial defects, since evisceration was not observed.     

Augmenting myometrial healing after cesarean delivery: use of an adjuvant biologic graft placement in an ovine model

We sought to reduce long-term complications after cesarean delivery by improving myometrial healing. Eight sheep (three with twins) underwent cesarean delivery. Hysterotomy sites were repaired in equal parts by suture alone or suture with a juxtaposed graft (Cook Medical, Bloomington, IN). At 90 days postsurgery, scar characteristics and tensile strength testing were assessed. The mean hysterotomy closure time was on average 1 minute, 14 seconds longer for those undergoing graft placement ( P=0.36). The mean scar thickness was 3.0?±?0.4 mm for controls versus 3.8?±?1.2 mm for the intervention group ( P=0.047). Tensile strength testing did not demonstrate a significant difference between groups. Histological examination of the myometrial scar showed no significant differences in inflammatory reaction or endometrial inclusions; however, neoangiogenesis was significantly enhanced. Myometrial repair incorporating a graft increased scar thickness and neoangiogenesis. This methodology did not incite adenomyosis or enhance inflammation within the scar.     

A comparative study of suture materials: chromic gut and chromic gut treated with glycerin

Histologic and mechanical properties of chromic gut and glycerin-treated chromic gut were evaluated. Zero gauges of both materials were implanted for 7 days to evaluate inflammatory response. No difference was found in the degree of inflammatory response. Scanning electron micrographs showed a more uniform surface for the glycerin-treated chromic gut. Regular chromic material was stronger in unknotted tensile strength and fracture load for all gauges. The 1-0 gauge glycerin-treated chromic gut stabilized with the knot configuration of 1 = 1 = 1 = 1; and the 1,2-0, and 3-0 gauges reached knot security at 1 = 1 = 1. The in vivo studies showed marked difference in the tensile strength of stable knots between the two materials. Only with five throws (1 = 1 = 1 = 1 = 1) did the strength of glycerin-treated chromic gut overlap that of regular chromic gut.     

Poly(L-lactide/glycolide) suture: the effect of acute radiation

The physical properties of Poly(L-lactide/glycolide) indicate that the suture retains approximately 80% of its original strength at 3 months and 60% of its original strength at 6 months. This new long-term synthetic absorbable suture offers postoperative fascial strength for an extended period when compared to other available absorbables. Importantly, many women with gynecologic cancer will undergo radiation therapy during this interval. This report is intended to evaluate the effects of ionizing radiation on this suture. METHODS: One lot (op strands) of size 1 PLG suture was used. Ten (10) strands were used for baseline study of out of package tensile strength. Eighty (80) strands were placed in a buffer solution (pH approximately 9.0) and incubated in an in vitro water bath approximately 48 h at 55 degrees C to simulate 4 weeks in vitro residence time. Following this in vitro hydrolysis 20 strands were tested. Sixty strands were placed beneath a piece of fresh full thickness porcine skin and subcutaneous tissue and exposed to 3, 30, and 70 Gy. All samples were evaluated for breaking strength and elongation-at-break using an Instron tensiometer. RESULTS: Analysis of variance performed at the different exposure level revealed no significant effect on tensile properties (p>0.1). CONCLUSION: The tensile properties of PLG suture are not adversely affected by ionizing radiation. This long-term absorbable suture is an alternative for fascial closure when extended periods of support are necessary in patients destined to receive therapeutic ionizing radiation.     

Histologic reaction to a new microsurgical suture in rabbit reproductive tissue

A newly introduced coated polyglactin suture was compared with a polyglycolic acid suture following microsurgical repair of standard rabbit uterine incisions. The degree of inflammatory response and tissue fibrosis for each suture was scored, and the results were compared. At 30 days, an inflammatory response was noted in both groups, with a greater response noted in the polyglycolic acid group. At 90 days, the inflammatory response and tissue fibrosis at the site of repair was evident in both groups, with no significant difference between the groups. The previously reported difference between these two absorbable suture materials in their earlier formulations could not be demonstrated in rabbit reproductive tissue. If an absorbable suture is used for tubal surgery, the choice can be made on considerations other than tissue reactivity.     

Lightweight meshes: evaluation of mesh tissue integration and host tissue response

Introduction

Differences in mesh composition may affect outcomes such as erosion, tissue integration and inflammation. The majority of commercially available meshes are type 1, manufactured from monofilament polypropylene with differing pore sizes and mechanical properties.

Objective

To assess the local tolerance of four commercially available meshes in terms of mesh integration and host tissue response.

Method

Using an animal model, mesh was implanted onto the abdominal sheath. Animals were sacrificed at 7, 30 and 90 days and data collected.

Results

Strength of mesh-skin integration increased in all groups across the three time points. Polyform displayed highest strength of separation overall. VM PFR and Iprolite reached their maximum integration earliest. In regard to mesh abdominal wall integration Polyform had the greatest strength of separation, with Ultrapro displaying some weakening of integration at 30 and 90 days. Host tissue response was similar in all groups at each time point.

Conclusion

Polyform and VM PFR have enhanced tissue integration when compared to Ultrapro. This decreased integration in Ultrapro may lead to increased mesh failure. The composition of mesh affects its integration and potentially its failure rate but not host tissue response. These observations in mesh characteristics may benefit the design of next generation meshes with a view to reducing failure rates and erosion.     

Clinical and histological safety assessment of rectocele repair using collagen mesh

AIM: To clinically and histologically evaluate inflammatory response following rectocele repair using porcine collagen mesh. METHODS: Seventeen patients underwent rectocele repair using porcine collagen mesh. Inflammatory response was assessed by clinical and histological inflammatory grading pre- and postoperatively. Postoperative body temperature, complications and hospital stay was compared with 15 patients undergoing posterior colporraphy. RESULTS: Postoperative clinical examination did not demonstrate any inflammatory reaction. There were no significant changes in fibroblast count (P = 0.43), connective tissue density grading (P = 0.54), macrophage count (P = 0.20), inflammatory cell count (P = 0.48), total cell count (P = 0.51), or inflammatory grading (P = 0.87) postoperatively compared with preoperative values. Body temperature was significantly elevated for both the study and control group, although higher for the study group, postoperatively day 1 (P < 0.001). There were no significant differences in hospital stay and postoperative complications. CONCLUSION: Porcine collagen mesh was not associated with an adverse inflammatory response at clinical or histological evaluation and appears to be a safe material when used for rectocele repair.     

Studies on the healing of anastomoses of small and large intestines.

It is well known that large intestine anastomoses tend to leak much more frequently than do small intestine anastomoses. These studies were undertaken to elucidate the pathophysioplogic basis of this phenomenom. Single layer interrupted silk suture anastomoses were performed in both the distal part of the ileum and the distal part of the colon in 29 dogs. The anastomoses were resected at one through eight days and 19 to 31 days after operations. Collagen response, vascular response and bursting strength at the site of anastomoses were investigated. The results demonstrated a statistically significant decrease in the collagen and vascular response of the large versus the small intestine. This differential response may play a role in the mechanism of the relatively high incidence of suture line separations observed after colonic anastomoses.     

Persistence of polypropylene mesh anisotropy after implantation: an experimental study

OBJECTIVE: To determine whether anisotropy persisted after incorporation into the host, using a standardised rabbit model for abdominal wall reconstruction. DESIGN: Investigator-initiated prospective-controlled experimental study. SETTING: Centre for Surgical Technologies, Medical Faculty KU-Leuven. SAMPLE: Fifteen New Zealand White rabbits. METHODS: In each rabbit, four full thickness primarily repaired abdominal wall defects were covered by a 4 × 5-cm Prolift+M implant (Johnson & Johnson, Norderstedt, Germany), either with the stiffest (n = 6 rabbits) or most elastic (n = 6) direction parallel to the body axis. Prolift+M contains 32 g/m2 polypropylene, reinforced with polyglecaprone fibres. Harvesting was performed after 30, 60 and 120 days (n = 2 each time-point). The abdominal wall of three unoperated rabbits was used as negative control. MAIN OUTCOME MEASURES: Contraction, compliance and maximal strain and stress determined by uniaxial tensiometry. Results: Anisotropy properties persist at lower, more physiological displacements, but not at higher displacements. The stiffness of a mesh-augmented repair in the lower strain range remains above that of native tissue. Eventual mesh contraction was limited to 4.3%. Conclusions: Anisotropic properties of Prolift+M persist in vivo and shrinkage is minimal. Compliance of mesh-augmented repair remains less than that of native tissue. The functional consequences of this remain to be studied.     

The prognostic virtue of inflammatory markers during late-onset sepsis in preterm infants

AIM: Late-onset sepsis (occurring after the first three days of life) is a serious complication in preterm infants. In order to assess the possible prognostic virtues of the acute phase inflammatory response in the disease, we compared the inflammatory response of preterm infants who died within 72 hours (h) (fulminant sepsis) to infants who recovered from the disease (non-fulminant sepsis). METHODS: Of 42 preterm infants that were evaluated: 10 had fulminant sepsis and 32 non-fulminant sepsis. Acute phase inflammatory response markers-C-reactive protein (CRP), serum amyloid A (SAA), interleukin (IL)-6 levels and white blood cell (WBC) counts were measured at the first suspicion of LOS and after 8, 24 and 48 h. RESULTS: Small for gestational age (SGA) infants who were treated with fewer days of antibiotics characterized the fulminant sepsis group. The initial high levels of inflammatory markers were similar in both groups, but as early as 8 h after onset significantly lower levels of SAA, CRP and WBC counts were documented in the fulminant sepsis group. The inflammatory response remained low at 24 and 48 h in the fulminant sepsis group, while in the survivors, significantly increased inflammatory markers were measured. Decreases in the levels of the inflammatory markers preceded episodes of metabolic acidosis and arterial hypotension that were more common in the fulminant sepsis group. Infant mortality correlated inversely with SAA levels at 8 h and with CRP and WBC counts at 24 h after onset. CONCLUSION: SAA, CRP and WBC counts can be used as prognostic markers in LOS in preterm infants, with SAA being the earliest prognostic marker.     

Tissue reaction to polypropylene mono-or multi-filament tapes used in surgical techniques of stress urinary incontinence treatment

OBJECTIVES: The "gold standard" in surgical treatment of stress urinary incontinence (SUI) is sling operation with polypropylene tape appliance under the mid urethra. There are two types of polypropylene tape which are the most popular nowadays. These two tapes are differently knitted so they have different biomechanical features. The TVT tape is monofilament, rarely knitted and highly elastic but the IVS mesh is multifilament, densly knitted and has only little possibility to stretch. The aim of our study was to assess the tissue reaction to the mono-(TVT) and multifilament (IVS) tapes. MATERIAL AND METHODS: The 10 mm x 10 mm pieces of TVT and IVS tapes were implanted inlay the fascia of musculus abdominis rectus of 14 rat females (2 groups of 7 animals). The tapes with the margin of surrounding fascia were taken off after 6 weeks of healing. All samples were fixed in 10% Formaldehyde in phosphate buffered saline and embedded in paraffin. Four micron tissue sections were stained with hematoxylin and eosin, the reticulin silver impregnation stain according to Gomori (for collagen type III) and periodic acid Schiff and alcian blue (for proteoglycan). RESULTS: In all sections filaments visible as elipsoids were surrounded by resorptive granulation with large multinucleated giant cells like around "foreign body". The diameter of monofilaments was about 150 microns. The connective tissue in the vicinity of mesh was rich of inflammatory cells like histiocytes, lymphocytes, a few polymorphonuclear leucocytes as well as adipocytes and fibroblasts. The large multinucleated giant cells adjacent to monofilaments were relatively bigger than these cells around multifilaments. Moreover, this granulation tissue has a lot of new blood vessels and collagenous fibrous tissue. The multifilaments were about 40 microns in diameter. The inflammatory granulation infiltrated aggregates of multifilaments. This tissue had only few inflammatory cells in comparison to tissue around monofilaments. The large multinucleated giant cells apposed to the mesh were small and collagen created thicker, more compacted bundles. CONCLUSION: The multifilament polypropylene tape induces weaker inflammatory tissue reaction than monofilament mesh. The thicker and more compacted collagen bundles are created around multifilaments so the natural tensile strength of the surrounding tissue is probably higher.     

Experimental splenic regeneration

The results of studies which indicate that splenic resection of residual parenchyma is able to regenerate are based primarily upon the weight increase of the splenic remnant at specified times after partial resection. This study was done to determine the histologic characteristics of the residual splenic tissue at 30 and 90 days after partial splenectomy in rats. The average increase in weight of the splenic polar residual after subtotal resection was 43 per cent at 30 days and 44 per cent at 90 days, and 10 per cent at 30 days and 30 per cent at 90 days for residual half spleen after hemisplenectomy. Histologic alterations, mainly present in the parenchyma near the section surface at 30 days were clearly inflammatory secondary to surgical trauma. There was no regenerative significance. At 90 days, the results of histologic study demonstrate a readjustment of the vascular net and the lymphoid tissue of the white pulp. The result is new structures which reproduces the follicular morphologic characteristics. This process requires 90 days to predominate over inflammatory postsurgical changes. Only during this phase may it have an important role in determining the increase of the residual weight. Further research into the functional capacity of the newly formed structures is necessary to confirm that the histologic modifications observed are comparable to true regeneration.     

The time at which infected postoperative wounds demonstrate increased strength.

It was again shown in this study that laparotomy wounds purposely infected with a known inoculum of live gram-negative bacteria exhibited greater tensile strength than did those in the normal control group. The organisms used were Escherichia coli and Pseudomonas aeruginosa. The phenomenon was not present during the first ten days after wounding but was quite evident in wounds tested at 14 and 21 days. By histologic examination, there was evidence of much more new collagen in the wounds that exhibited increased strength.     

Comparison of wound strength in normal, radiated and infected tissues closed with polyglycolic and chromic catgut sutures

Wound strength in the rectus muscle of rabbits is greater at any measured time interval when sutured with polyglycolic acid than when sutured with chromic catgut. This is true for both irradiated and nonirradiated tissues. No significant advantage is seen for either suture in nonirradiated bladder, although the trend favors polyglycolic acid. In irradiated bladders, a significant advantage is seen for polyglycolic acid at 15 days. In measuring repaired ureteral orifice size, only chronic catgut suture in nonirradiated rabbits caused marked edema and unreteral obstruction. Postoperative ureteral dilation with both materials resolved over a 90 day period. In the irradiated ureter, however, resolution of this obstruction appears to occur earlier and more dependably when polyglycolic acid suture has been used. Polyglycolic acid showed a trend for superior strength in urothelial wounds tested. The healing of bladder epithelium is usually completed in ten to 14 days. The entire bladder wound gains strength rapidly until day 21 and gains little strength thereafter. A suture material that does not increase the inflammatory response but lasts long enough for complete bladder healing is advisable. Using the criterion of wound breaking strength in our experimental work, polyglycolic acid was shown to be superior to chromic catgut suture material.     

Sonohysterography versus transvaginal sonography for screening of patients with abnormal uterine bleeding.

OBJECTIVES: To compare the accuracy of saline infusion sonohysterography (SIS) with transvaginal sonography (TVS) for the screening of causes of abnormal uterine bleeding (AUB) in out-patients. METHODS: 81 patients with AUB were studied. All cases who were examined with TVS, were further investigated with SIS using saline as contrast medium, finally hysteroscopy was used as the gold standard. RESULTS: TVS had sensitivity of 72%, specificity of 92%, positive predictive value of 94% and negative predictive value of 65%, while SIS had sensitivity of 94.1%, specificity of 95%, positive predictive value of 96% and negative predictive value of 90%. TVS had kappa measure of agreement of 0.60 while 0.86 was reported for SIS. CONCLUSIONS: In this study SIS was more sensitive and specific in diagnosing polyp, myoma and adenomyosis with high positive and negative predictive value. Furthermore, results obtained by SIS demonstrate more agreement with that obtained by hysteroscopy than TVS.     

A new synthetic monofilament absorbable suture made from polytrimethylene carbonate

The physical and biologic characteristics of a new synthetic absorbable monofilament suture, glycolide trimethylene carbonate (GTMC) are presented. The suture was formulated to combine predictable in vivo performance of synthetic absorbable sutures with the handling characteristics of a monofilament suture. Three in vivo studies were described: strength, gross and microscopic absorption and reaction, and radiolabelled decay. The studies carried out in rats showed cumulative strength retention of sizes 0, 00, 4-0 and 5-0 of 81 per cent at 14 days, 59 per cent at 28 days and 30 per cent at 42 days. Strength retention was consistent throughout the size spectrum. Absorption of sizes 00 and 4-0 were studied in subcutaneous implantations in rabbits. Histologic assessment of absorption obtained from serial sections at intervals of three to nine months showed that, in both sizes, complete absorption occurred between six and seven months. At six months, 83 per cent of size 00 was absorbed and size 4-0 was 93 per cent absorbed. At seven months, no implanted material was discernible histologically. Untoward tissue reactions, such as acute inflammatory cells, abscesses or tissue necrosis, were not observed. There were no signs of cellular mobilization of any kind observed remote from the implant. Absorption of GTMC sutures was achieved through the action of mononuclear and multinuclear macrophages which were confined to the implant and sequestered by a fibrous connective tissue capsule. When implant absorption was complete, resorbtion of the macrophage component was observed which was replaced by a narrow cord of fibrous tissue and collagen. The results of studies of radiolabelled sutures carried out in the subcutaneous tissues of rats revealed urine and expired CO2 to be the major excretary routes of the metabolites. By 22 to 24 weeks, 0.1 to 0.7 per cent of the total implanted radioactivity remained at the suture sites. Tissue deposition and excretion of radioactivity suggests similar metabolism of the sutures in both species. We conclude that GTMC sutures maintain good strength with little or no absorption during the critical wound healing period, absorbs completely from tissues in six to seven months with minimal tissue reaction and, therefore, provides an absorbable, flexible, monofilament material with extended support that is strong and effective.