Fascial incisions heal faster than skin: a new model of abdominal wall repair

[Physical Strain after Abdominal Surgery - Results of a Patient Survey]

INTRODUCTION

Incision hernias are common complications after abdominal surgery and affect the recommendations on postoperative physical strain, as it is thought that excessively early strain causes incisional hernias. However, there is no evidence to justify this. This study evaluates the effect of postoperative strain on the risk of incisional hernia.

MATERIALS AND METHODS

Patients with a laparoscopy (LS) or laparotomy (LT) were asked to complete a questionnaire on postoperative strain, complaints and quality of life. Patients with hernia surgery, or open abdomen therapy for complicated courses (Clavien-Dindo > III) were excluded.

RESULTS

393 patients completed the questionnaire (43.6%). 274 were LS and 128 LT. The incidence of incisional hernias was 5.2% (LS) and 18.0% (LT, p = 0.001). Incisional hernia patients were younger and more commonly males. 30.5% of incisional hernia patients did not return to normal physical strain postoperatively. Abdominal binders did not affect the hernia rate. The incisional hernia patients showed decreased quality of life scores in both mental and physical domains.

CONCLUSION

Early postoperative physical strain was not a risk factor for incisional hernia development in this study. However, prospective studies are needed to create necessary evidence to recommend earlier postoperative return to normal physical strain.

Recommendations on postoperative strain and physical labor after abdominal and hernia surgery: an expert survey of attendants of the 41st EHS Annual International Congress of the European Hernia Society

BACKGROUND

There are no valid recommendations or reliable guidelines available to guide patients how long they should refrain from lifting weights or returning to heavy physical labor after abdominal or hernia surgery. Recent studies found that surgeons' recommendations not to be evidence-based and might be too restrictive considering data on fascial healing and incisional hernia development. It is likely that this impairs the patient's quality of life and leads to remarkable socio-economic costs. Hence, we conducted this survey to gather international expert's opinions on this topic.

MATERIALS AND METHODS

At the 41st Annual International Congress of the EHS, attending international experts were asked to complete a questionnaire concerning recommendations on given proposals for postoperative refrain from heavy work or lifting after abdominal surgery and also after hernia repairs.

RESULTS

In total, 127 experts took part in the survey. 83.9% were consultants with a mean experience since specialization of more than 11 years. Two weeks of no heavy physical strain after laparoscopic surgery were considered sufficient by more than 50% of the participants. For laparotomy, more than 50% rated 4 weeks appropriate. For mesh-augmented sublay and IPOM repair of ventral or incisional hernias, more than 50% rated 4 weeks of rest appropriate. For complex hernia repair, 37% rated 4 weeks reasonable. Two weeks after, groin hernia surgery was considered sufficient by more than 50% of the participants.

CONCLUSION

Following groin hernia repair (Lichtenstein/endoscopic technique) and laparoscopic operation, the majority agreed on the proposal of 2 weeks refraining from physical strain. Four weeks of no physical strain were considered appropriate by a majority after laparotomy and open incisional hernia repair. However, the results showed substantial variation in the ratings, which indicates uncertainty even in this selected cohort of hernia surgery experts and emphasizes the need for further scientific evaluation. This is particularly remarkable, because a lack of evidence that early postoperative strain leads to higher incisional hernia rates.

TRIAL REGISTRATION

Number DRKS00023887.

Wound healing in weaning, adult, and old rats with provoked incisional hernias. A comparative study

BACKGROUND

Incisional hernias are more frequent in adults than in children. It is hypothesized that a more efficient healing process in pediatric patients could explain this difference in incidence. Certain elements of healing such as neovascularization, degree of inflammation, percentage of mature and immature collagen, the proliferation of fibroblasts, and expression of certain genes could explain why healing in children is more efficient when compared to the adult and elderly populations.

MATERIALS AND METHODS

Seventy-one rats of 3 different age groups (weaning, adult, and old) underwent surgery with 3 different incisions (vertical, oblique, and horizontal). During the procedure, the skin and abdominal wall of the animal were sectioned and only the skin was sutured to mimic incisional hernia in the animals. Four weeks after surgery, the rats were euthanized, their skin was removed, and the extent of scar tissue formed in the muscle opening was measured. In addition, samples of the scar tissue were collected for histological, immunohistochemical, and molecular analyzes. Nine rats served as controls.

RESULTS

Shorter-length hernias were formed in weaning rats when compared to old ones when the surgical incision was horizontal (p = 0.03). There was a greater proliferation of fibroblasts in rats in the younger age groups, regardless of the type of incision. The Lox gene was more expressed in weaning rats with vertical and oblique incisions.

CONCLUSIONS

These differences could explain the better healing and lower incidence of hernias in the pediatric population, although this aspect requires further studies.

Examination of lipid profiles in abdominal fascial healing using MALDI-TOF to identify potential therapeutic targets

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Lipids change overtime in normal fascial healing in the early post-surgery period.

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Specific lipid species are correlated with the changes of inflammation cells and fibroblasts.

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Lipid species in the present study are considered as predictive markers for the formation of incisional hernia.

Background

Failure of fascial healing in the abdominal wall can result in incisional hernia, which is one of the most common complications after laparotomy. Understanding the molecular healing process of abdominal fascia may provide lipid markers of incisional hernia or therapeutic targets that allow prevention or treatment of incisional hernias.

Purpose

This study aims to investigate temporal and in situ changes of lipids during the normal healing process of abdominal fascia in the first postoperative week.

Methods

Open hemicolectomy was performed in a total of 35 Wistar rats. The midline fascia was closed identically for all rats using a single continuous suturing technique. These animals were sacrificed with equal numbers (n = 5) at each of 7-time points (6, 12, 24, 48, 72, 120, and 168 h. The local and temporal changes of lipids were examined with mass spectrometry imaging and correlated to histologically scored changes during healing using hematoxylin and eosin staining.

Results

Two phosphatidylcholine lipid species (PC O-38:5 and PC 38:4) and one phosphatidylethanolamine lipid (PE O-16:1_20:4) were found to significantly correlate with temporal changes of inflammation. A phosphatidylcholine (PC 32:0) and a monosialodihexosylganglioside (GM3 34:1;2) were found to correlate with fibroblast cell growth.

Conclusion

Glycerophospholipids and gangliosides are strongly involved in the normal healing process of abdominal fascia and their locally fluctuating concentrations are considered as potential lipid markers and therapeutic targets of fascial healing.

A joint analysis using exome and transcriptome data identifiescandidate polymorphisms and genes involved with umbilical hernia in pigs

BACKGROUND

Umbilical Hernia (UH) is characterized by the passage of part of the intestine through the umbilical canal forming the herniary sac. There are several potential causes that can lead to the umbilical hernia such as bacterial infections, management conditions and genetic factors. Since the genetic components involved with UH are poorly understood, this study aimed to identify polymorphisms and genes associated with the manifestation of umbilical hernia in pigs using exome and transcriptome sequencing in a case and control design.

RESULTS

In the exome sequencing, 119 variants located in 58 genes were identified differing between normal and UH-affected pigs, and in the umbilical ring transcriptome, 46 variants were identified, located in 27 genes. Comparing the two methodologies, we obtained 34 concordant variants between the exome and transcriptome analyses, which were located in 17 genes, distributed in 64 biological processes (BP). Among the BP involved with UH it is possible to highlight cell adhesion, cell junction regulation, embryonic morphogenesis, ion transport, muscle contraction, within others.

CONCLUSIONS

We have generated the first exome sequencing related to normal and umbilical hernia-affected pigs, which allowed us to identify several variants possibly involved with this disorder. Many of those variants present in the DNA were confirmed with the RNA-Seq results. The combination of both exome and transcriptome sequencing approaches allowed us to better understand the complex molecular mechanisms underlying UH in pigs and possibly in other mammals, including humans. Some variants found in genes and other regulatory regions are highlighted as strong candidates to the development of UH in pigs and should be further investigated.

Postoperative Work and Activity Restrictions After Abdominal Surgery: A Systematic Review

OBJECTIVE

This systematic review aims to assess what is known about convalescence following abdominal surgery. Through a review of the basic science and clinical literature, we explored the effect of physical activity on the healing fascia and the optimal timing for postoperative activity.

BACKGROUND

Abdominal surgery confers a 30% risk of incisional hernia development. To mitigate this, surgeons often impose postoperative activity restrictions. However, it is unclear whether this is effective or potentially harmful in preventing hernias.

METHODS

We conducted 2 separate systematic reviews using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The first assessed available basic science literature on fascial healing. The second assessed available clinical literature on activity after abdominal surgery.

RESULTS

Seven articles met inclusion criteria for the basic science review and 22 for the clinical studies review. The basic science data demonstrated variability in maximal tensile strength and time for fascial healing, in part due to differences in layer of abdominal wall measured. Some animal studies indicated a positive effect of physical activity on the healing wound. Most clinical studies were qualitative, with only 3 randomized controlled trials on this topic. Variability was reported on clinician recommendations, time to return to activity, and factors that influence return to activity. Interventions designed to shorten convalescence demonstrated improvements only in patient-reported symptoms. None reported an association between activity and complications, such as incisional hernia.

CONCLUSIONS

This systematic review identified gaps in our understanding of what is best for patients recovering from abdominal surgery. Randomized controlled trials are crucial in safely optimizing the recovery period.

Lack of Standardized Advice on Physical Strain Following Abdominal Surgery

BACKGROUND

In Germany as elsewhere, standardized recommendations are lacking on the avoidance of physical exertion to protect the abdom - inal wall in patients who have recently undergone abdominal surgery. It is unclear how much stress the abdominal wall can withstand and how long the patient should be exempted from work. The goal of this review is to determine whether there are any standardized, evidence-based recommendations for postoperative care from which valid recommendations for Germany can be derived.

METHODS

We systematically searched the literature for evidence-based recommendations on exertion avoidance after abdominal surgery, as well as for information on the extent to which postoperative abdominal wall stress contributes to incisional hernia formation. We then created a questionnaire on recommendation practices and sent it to all of the chiefs of general and visceral surgery services that were listed in the German hospital registry (1078 chiefs of service as of June 2016).

RESULTS

All 16 of the included studies on postoperative exertion avoidance contained low-level evidence that could only be used to formulate weak recommendations ("can," rather than "should" or "must"). Some 50 000 incisional hernia repair procedures are performed in Germany each year, with a reported incidence of 12.8% in the first two years after surgery. The scientifically documented risk factors for incisional herniation are related to techniques of wound closure, the suture materials used, wound infections, and the patient risk profile. From the biological point of view, the abdominal wall regains full, normal resistance to exertional stress 30 days after a laparotomy with uncomplicated healing. Most incisional hernias (>50%) arise 18 months or more after surgery; they are more common in patients who have avoided exertion for longer periods of time (more than 8 weeks). Our questionnaire was returned by 386 surgical clinics. The responses showed that 78% of recommendations were based on personal experience only. The recommendations varied widely; exertion avoidance was recommended for as long as 6 months.

CONCLUSION

The dilemma of a deficient evidence base for postoperative exertion avoidance to protect the abdominal wall should be resolved with the much higher-quality evidence available from hernia research, which concerns the patient population with the biologically least favorable starting conditions. Based on our analysis of the available literature in light of the biomechanical principles of abdominal wall healing, we propose a new set of recommendations on postoperative exertion avoidance after abdominal surgery, with the goal of eliminating excessively protracted exertion avoidance and enabling a timely return to work.

The effect of different suturing materials for abdominal fascia wound closure on the collagen I/III expression ratio in rats

Background

Incisional hernia is a frequent complication of abdominal wall incision and has a high rate of recurrence. Most of the studies stated that non-absorbable sutures decreased incisional hernia incidences, but some stated otherwise. We aimed to compare the collagen type I/III ratio between monofilament non-absorbable sutures and multifilament absorbable sutures for abdominal fascia closure in Wistar albino rats.

Methods

Forty rats were divided into four groups. Groups 1 and 3 were sutured with monofilament non-absorbable (polyvinylidene fluoride). Groups 2 and 4 were sutured with multifilament absorbable (polyglycolide). Then, groups 1 and 2 were euthanized on day 4 (POD 4), while groups 3 and 4 were euthanized on day 7 (POD 7). Samples of fascia (1 × 0.5 cm) were taken for analysis. Collagen I/III ratios were measured using immunohistochemistry staining methods.

Results

While the expression of collagen I was not significantly different between monofilament non-absorbable and multifilament absorbable at POD 4 and 7 (p = 0.45 and 0.81, respectively), the expression of collagen III reached a significant level with p-values of 0.0003 and 0.0004 for POD 4 and 7, respectively. Moreover, the collagen I/III ratio was also significantly different between the two groups either at POD 4 (0.88 ± 0.23 vs. 0.53 ± 0.08; p = 0.0003) and 7 (1.77 ± 0.65 vs. 1.03 ± 0.28; p = 0.004).

Conclusions

Monofilament non-absorbable sutures show a significantly higher collagen I/III ratio than multifilament absorbable sutures for abdominal fascia closure in rats. Our findings imply that the usage of monofilament non-absorbable sutures might have a beneficial effect on decreasing the incisional hernia occurrence.

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One of the most important factors that influences the occurrence of incisional hernia is suturing material.

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Collagen is a major component of the extracellular matrix and plays an important role in maintaining tissue elasticity and tensility.

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The usage of monofilament non-absorbable sutures might have a beneficial effect on decreasing the incisional hernia occurrence.

The impact of different suturing techniques for abdominal fascia closure on the Interleukin-6 expressions in Rattus norvegicus

OBJECTIVE

Incisional hernia is a frequent complication of midline laparotomy. The suturing technique is an important determinant of the risk of developing an incisional hernia. Moreover, IL-6 has crucial roles in the wound-healing process. We aimed to compare the large stitch vs. small stitch technique for abdominal fascial closure on IL-6 expressions in rats.

RESULTS

Twenty rats were used. The small stitch group received small tissue bites of 5 mm and the large stitch group received large bites of 10 mm. The incisions of fascia were closed by running sutures. Animals were euthanized on days 4 and 7. Histological sections of the tissue-embedded sutures were analyzed for IL-6 expressions. Two-way ANOVA showed that rats in the small stitch group had similar IL-6 expressions on days 4 and 7 to those in the large stitch group (p = 0.36). In conclusion, the IL-6 expressions are similar between the small and the large stitch groups, implying that different suturing techniques might not have an impact on the incisional hernia occurrence.

Comparison of ıncisional hernia models ın rats: an experimental study

PURPOSE

Incisional hernia repair is a frequently performed operation worldwide. In this experimental study, our aim is to present the incisional hernia model after creating midline laparotomy and several type of defects on abdominal wall of the rats. Thereby, the method determined here may be used in future experimental incisional hernia repair studies.

METHODS

After approval, 32 male rats were randomly seperated into 4 groups of 8 animals each, and were operated to form an incisional hernia; Sham group, 5 cm incision group, 5 cm incision plus capitonnage group, and 5 cm incision plus 2 × 4 cm muscle excision group, respectively. On the 28th postoperative day after killing, the abdominal anterior wall of rats were removed for histopathological and biomechanic examination.

RESULTS

The incisional hernia size was found to be statistically different in at least one group (p = 0.001). The incisional hernia size in Group 4 was found to be significantly higher than Group 2 (p = 0.001). When the tension and elongation values were examined, there was a difference in at least one group (p < 0.001 and p = 0.029, respectively). Histopathological examination shows that the degree of inflammation and fibrosis varies significantly (p = 0.001 and p = 0.002, respectively).

CONCLUSION

This study has lead us to believe that the rat model created by applying muscle excision from the midline of the abdomen is the ideal incisional hernia model that can be used in future experimental incisional hernia studies.

Miniaturized Sensors Registering the Long-Term Course of Suture Tension In Vivo under Varying Intra-Abdominal Pressure

BACKGROUND

Failure of laparotomy closure develops after up to 20% of abdominal operations. Suture tension has an influence on the quality of tissue regeneration. No sensors are available to register suture tension dynamics in vivo.

METHODS

In a series of animal experiments, the effect of suture tension on the ultrastructure of the healing incision was examined. Surgeons' ability to suture with target tension was tested. An implantable sensor and data logger were developed and tested experimentally in sutures closing midline laparotomies in pigs both under normal and elevated intra-abdominal pressure.

RESULTS

High suture tension has a negative influence on the regeneration of laparotomy incisions. Running sutures for laparotomy closure lose 45% of their initial tension over periods of 23 h. Intermittent elevation of intra-abdominal pressure to 30 mm Hg leads to a near total loss of suture tension after 23 h.

CONCLUSION

Surgeons are not able to control and reproduce suture tension. Suture tension dynamics can be measured in vivo by the sensor developed. Further research is needed to define a tissue-specific suture tension optimum to reduce the incidence of complications after laparotomy. Techniques for laparotomy closure need to be modified.

Prosthetics and Techniques in Repair of Animal's Abdominal Wall

The management of abdominal wall repair continues to present a challenging problem, especially in the repair of major defects. Many abdominal wall defects can be repaired by primary closure; however, if the defect is large and there is a tension on the closure of the wound, the use of prosthetic materials becomes indispensable. Many studies have been performed with various materials and implant techniques, without the comparison of their degrees of success, based on sound meta-analysis and/or inclusive epidemiologic studies. This review covered the effectiveness of recent advances in prosthetic materials and implant procedures used in repair of abdominal wall, based on biomechanical properties and economic aspects of reconstructed large abdominal wall defects and hernias in animals. The presented results in this review helped to reach treatment algorithms that could maximize outcomes and minimize morbidity.

Surgical mesh for ventral incisional hernia repairs: Understanding mesh design

Surgical mesh has become an indispensable tool in hernia repair to improve outcomes and reduce costs; however, efforts are constantly being undertaken in mesh development to overcome postoperative complications. Common complications include infection, pain, adhesions, mesh extrusion and hernia recurrence. Reducing the complications of mesh implantation is of utmost importance given that hernias occur in hundreds of thousands of patients per year in the United States. In the present review, the authors present the different types of hernia meshes, discuss the key properties of mesh design, and demonstrate how each design element affects performance and complications. The present article will provide a basis for surgeons to understand which mesh to choose for patient care and why, and will explain the important technological aspects that will continue to evolve over the ensuing years.

Surgical mesh for ventral incisional hernia repairs: Understanding mesh design

Surgical mesh has become an indispensable tool in hernia repair to improve outcomes and reduce costs; however, efforts are constantly being undertaken in mesh development to overcome postoperative complications. Common complications include infection, pain, adhesions, mesh extrusion and hernia recurrence. Reducing the complications of mesh implantation is of utmost importance given that hernias occur in hundreds of thousands of patients per year in the United States. In the present review, the authors present the different types of hernia meshes, discuss the key properties of mesh design, and demonstrate how each design element affects performance and complications. The present article will provide a basis for surgeons to understand which mesh to choose for patient care and why, and will explain the important technological aspects that will continue to evolve over the ensuing years.

Wound healing in acutely injured fascia

Fascial healing following acute injury, such as that occurring during surgical procedures, is defined functionally. For example, failure of fascial healing following celiotomy is only identified when incisional hernias are diagnosed. Such hernias incur billions of dollars per year in medical costs. Despite the importance of fascial healing, there is a paucity of data regarding the quality such healing. In clinical settings, the quantification of fascial wound healing is limited to a binary state: either there is no clinically apparent functional deficit and full fascia healing is assumed, or an incisional hernia or other functional failure is visible and the fascia did not heal. There are no clinical methods to isolate and functionally test fascia in patients. Recent studies have revealed unexpected findings regarding the recovery of tensile strength, specific surgical methods that optimize fascial healing, and the potential impact of biological pharmaceuticals in eliminating fascial healing failure. However, much remains unknown about the biology of fascial healing.

Early laparotomy wound failure as the mechanism for incisional hernia formation

BACKGROUND

Incisional hernia is the most common complication of abdominal surgery leading to reoperation. In the United States, 200,000 incisional hernia repairs are performed annually, often with significant morbidity. Obesity is increasing the risk of laparotomy wound failure.

METHODS

We used a validated animal model of incisional hernia formation. We intentionally induced laparotomy wound failure in otherwise normal adult, male Sprague-Dawley rats. Radio-opaque, metal surgical clips served as markers for the use of x-ray images to follow the progress of laparotomy wound failure. We confirmed radiographic findings of the time course for mechanical laparotomy wound failure by necropsy.

RESULTS

Noninvasive radiographic imaging predicts early laparotomy wound failure and incisional hernia formation. We confirmed both transverse and craniocaudad migration of radio-opaque markers at necropsy after 28 d that was uniformly associated with the clinical development of incisional hernias.

CONCLUSIONS

Early laparotomy wound failure is a primary mechanism for incisional hernia formation. A noninvasive radiographic method for studying laparotomy wound healing may help design clinical trials to prevent and treat this common general surgical complication.

Impaired laparotomy wound healing in obese rats

BACKGROUND

Obesity increases the risk of laparotomy dehiscence and incisional hernia. The aim of this study was to measure the biological effect of obesity on laparotomy wound healing and the formation of incisional hernias.

METHODS

Normal-weight Sprague-Dawley (SD) and obese Zucker rats were used in an established laparotomy wound healing and incisional ventral hernia model. Mechanical testing was performed on abdominal wall strips collected from laparotomy wounds. Hernia size was measured by digital imaging. Picrosirius staining for collagen isoforms was observed with polarized microscopy. Abdominal wall fibroblasts were cultured to measure collagen matrix remodeling and proliferation.

RESULTS

Laparotomy wound healing was significantly impaired in obese rats. Mechanical strength was lower than in normal-weight rats. Yield load was reduced in the obese group at all time points. Picrosirius red staining showed increased immature type III collagen content and disorganized type I collagen fibers within laparotomy wounds of obese rats. Wound size was significantly larger in the obese group. Collagen matrix remodeling was impaired with fibroblasts from obese rats, but there was no difference in fibroblast proliferation between the obese and normal-weight groups.

CONCLUSIONS

We observed for the first time that laparotomy wound healing is impaired in obese rats. The recovery of laparotomy wound strength is delayed due to abnormal collagen maturation and remodeling, possibly due to a defect in fibroblast function. Strategies to improve outcomes for laparotomy wound healing in obese patients should include correcting the wound healing defect, possibly with growth factor or cell therapy.

Tensile properties of the murine ventral vertical midline incision

Background

In clinical surgery, the vertical midline abdominal incision is popular but associated with healing failures. A murine model of the ventral vertical midline incision was developed in order to study the healing of this incision type.

Methodology/Principal Findings

The strength of the wild type murine ventral abdominal wall in the midline was contained within the dermis; the linea alba made a negligible contribution. Unwounded abdominal wall had a downward trend (nonsignificant) in maximal tension between 12 and 29 weeks of age. The incision attained 50% of its final strength by postoperative day 40. The maximal tension of the ventral vertical midline incision was nearly that of unwounded abdominal wall by postwounding day 60; there was no difference in unwounded vs. wounded maximal tension at postwounding day 120.

Conclusions/Significance

After 120 days of healing, the ventral vertical midline incision in the wild type mouse was not significantly different from age-matched nonwounded controls. About half of the final incisional strength was attained after 6 weeks of healing. The significance of this work was to establish the kinetics of wild type incisional healing in a model for which numerous genotypes and genetic tools would be available for subsequent study.

Connective tissue alteration in abdominal wall hernia

BACKGROUND

The aetiology and pathogenesis of abdominal wall hernia formation is complex. Optimal treatment of hernias depends on a full understanding of the pathophysiological mechanisms involved in their formation. The aim of this study was to review the literature on specific collagen alterations in abdominal wall hernia formation.

METHODS

A computer-assisted search of the medical databases PubMed and Embase was performed, together with a cross-reference search of eligible papers.

RESULTS

Fifty-two papers were included. Collagen alteration depended on the type of hernia; there were more pronounced changes in patients with a direct inguinal hernia than in those with an indirect inguinal hernia, recurrent inguinal hernia or incisional hernia. A consistent finding was a significant increase in immature type III collagen relative to the stronger type I collagen in patients with a hernia. This resulted in thinner collagen fibres with a correspondingly diminished biomechanical strength. It has been suggested that these alterations are due to variation in the synthesis, maturation or degradation of collagen by matrix metalloproteinases, in combination or alone.

CONCLUSION

Hernia formation and recurrence is associated with altered collagen metabolism manifested by a decreased type I:III collagen ratio.

Comparative healing of rat fascia following incision with three surgical instruments

BACKGROUND

Incisional hernia and fascial dehiscence are associated with significant postoperative morbidity. Electrosurgical devices using pulsed radiofrequency energy and a novel electrode design markedly reduce thermal injury during cutting and coagulation while maintaining equal surgical performance. In this study, we examine fascial healing dynamics in a rat model following incision with a pulsed radiofrequency energy device (PRE), a conventional electrosurgical device, and a standard "cold" scalpel. We hypothesize that incisions made with the pulsed radiofrequency energy device will result in a superior fascial healing profile compared with conventional electrosurgery.

MATERIALS AND METHODS

Full thickness surgical incisions were created in rat fascia using a commercially available PRE device, conventional electrosurgery, and a scalpel. Harvested fascial specimens were analyzed for burst strength testing and healing-associated histologic characteristics at d 7, 14, 21, and 42.

RESULTS

PRE incisions were fully healed by 6 wk with normal tissue architecture. By all measures, wounds created by the PRE device were comparable to those made with the standard scalpel. Compared with PRE, conventional electrosurgery incisions exhibited a larger zone of tissue injury (68% greater in Coag mode, P < 0.0001; 46% greater in Cut mode, P < 0.001), an increased inflammatory response and a less favorable wound architecture. In the immediate postoperative period (1 wk), burst strength testing demonstrated that PRE fascial wounds were significantly stronger than those made by electrosurgery in Coag mode (318%, P = 0.001).

CONCLUSIONS

The favorable fascial healing profile of the PRE device suggests that it is a promising new surgical technology. The early improved strength of wounds made with this device is of particular interest, as wound dehiscence is of greatest concern early in the healing process.

Effect of cytokine growth factors on the prevention of acute wound failure

Cytokine growth factor treatment of chronic wounds has met with mixed results. The chronic wound presents a hostile environment to peptides such as growth factors. Cytokine growth factors have not been studied extensively in acute wounds. However, incisional hernias are a major example of acute wound failure that has not been solved by various mechanical approaches. A biological approach to acute wound failure by use of cytokine growth factors may offer a new strategy. A rodent incisional hernia model was used. Seventy-six rats underwent 3-cm midline celiotomies and were closed with fine, fast-absorbing sutures to induce intentional acute wound failure. Group 1 received no other treatment. The midline fascia in Groups 2-10 was infiltrated with 100 microl of vehicle alone or vehicle containing various test cytokine growth factors. Necropsy was performed on postoperative day 28 and the wounds were examined for herniation. Incisional hernias developed in 83 percent (13/16) of untreated incisional and 88 percent (7/8) and 83 percent (5/6) of the two vehicle-treated incisions (PBS and carboxymethylcellulose). Hernia incidences were decreased by priming of the fascial incision with transforming growth factor-beta(2) (12%, 1/8), basic fibroblast growth factor (25%, 2/8) and interleukin-1 beta (50%, 3/6) (p < 0.05). Aqueous platelet-derived growth factor, becaplermin, insulin-like growth factor, and granulocyte macrophage-colony stimulating factor did not significantly decrease the incidence of acute wound failure (p > 0.05). A biological approach to acute wound failure as measured by incisional hernia formation can be useful in reducing the incidence of this complication. Transforming growth factor-beta(2), basic fibroblast growth factor, and interleukin 1 beta all eliminated or significantly reduced the development of incisional hernias in the rat model.

The biology of hernia formation

Abdominal wall hernias occur when tissue structure and function are lost at the load-bearing muscle, tendon, and fascial layer. The fundamental biologic mechanisms are primary fascial pathology or surgical wound failure. In both cases, cellular and extracellular molecular matrix defects occur. Primary abdominal wall hernias have been associated with extracellular matrix diseases. Incisional hernias and recurrent inguinal hernias more often involve a combination of technical and biologic limitations. Defects in wound healing and extracellular matrix synthesis contribute to the high incidence of incisional hernia formation following laparotomy.

Re-laparotomy after cesarean section

OBJECTIVE

To assess the rate, indications, and outcome of re-laparotomy after cesarean section in the early postoperative period.

DESIGN

A retrospective observational study during a 121-month period.

SETTING

A tertiary care university center.

POPULATION

A cohort of 3380 women who underwent cesarean section out of 18,609 parturients.

MAIN OUTCOME MEASURES

Incidence of re-laparotomy after cesarean section in the early postoperative period.

RESULTS

The incidence of re-laparotomy after cesarean section was 0.53% (18/3380). Of these 18 women, 12 (66%) were operated for hemorrhage, 3 (17%) for eventration, and 3 (17%) for formation of intra-abdominal abscess. Hysterectomy was required in one case (5.5%). We had no maternal mortalities.

CONCLUSION

Although the incidence of re-laparotomy after cesarean in the early postoperative period is low and the outcome is favorable, several measures must be undertaken to reduce the need for re-laparotomy.

The effect of different temporary abdominal closure techniques on fascial wound healing and postoperative adhesions in experimental secondary peritonitis

BACKGROUND

Secondary peritonitis causes considerable mortality and morbidity. New strategies have been introduced like relaparotomy and temporary abdominal closure in the management of such persistent intra-abdominal infections.

MATERIALS AND METHODS

Rats were divided into five groups each having ten animals. After induction of peritonitis, relaparotomies were done, and the abdomen was closed by different temporary abdominal closure techniques. After performing two relaparotomies during a 48-h period, all fascias closed primarily and incisional tensile strengths, hydroxyproline contents, and adhesions were measured on the following seventh day.

RESULTS

The median values of tensile strength and hydroxyproline concentrations were lowest in skin-only closure rats. Intraperitoneal adhesion scores were highest in Bogota bag closure group.

CONCLUSION

Primary, Bogota bag, and polyprolene mesh closures seem to be safe in terms of early fascial wound healing. Although it is easy to perform, skin-only closure technique has deleterious effects on fascial wound healing probably due to fascial retraction. Interestingly, Bogota bag has caused increased intraperitoneal adhesion formation.

Incisional herniation induces decreased abdominal wall compliance via oblique muscle atrophy and fibrosis

OBJECTIVE

The purpose of this study is to measure abdominal wall myopathic histologic and mechanical changes during incisional herniation and its effect on incisional hernia repairs.

SUMMARY BACKGROUND DATA

Unloaded skeletal muscles undergo characteristic atrophic changes, including change in fiber type composition, decreased cross-sectional area, and pathologic fibrosis. We hypothesize that these atrophic changes decrease muscle elastic properties and may contribute to the high laparotomy wound failure rate observed following incisional hernia repair.

METHODS

A rat model of chronic incisional hernia formation was used. Failing midline laparotomy incisions developed into incisional hernias. Controls were uninjured and sham laparotomy (healed) groups. Internal oblique muscles were harvested for fiber typing, measurement of cross-sectional area, collagen deposition, and mechanical analysis. Mesh hernia repairs were performed on a second group of rats with chronic incisional hernias or acute anterior abdominal wall myofascial defects.

RESULTS

The hernia group developed lateral abdominal wall shortening and oblique muscle atrophy. This was associated with a change in the distribution of oblique muscle fiber types, decreased cross-sectional area, and pathologic fibrosis consistent with myopathic disuse atrophy. These muscles exhibited significant decreased extensibility and increased stiffness. The healed (sham) laparotomy group expressed an intermediate phenotype between the uninjured and hernia groups. Recurrent hernia formation was most frequent in the chronic hernia model, and hernia repairs mechanically disrupted at a lower force compared with nonherniated abdominal walls.

CONCLUSIONS

The internal oblique muscles of the abdominal wall express a pattern of changes consistent with those seen in chronically unloaded skeletal muscles. The internal oblique muscles become fibrotic during herniation, reducing abdominal wall compliance and increasing the transfer of load forces to the midline wound at the time of hernia repair.

Changes in Abdominal Wounds Following Treatment With Sirolimus and Steroids in a Rat Model

Wound healing complications have been observed in patients receiving sirolimus (SLR). This study examined the degree and duration of delayed healing in various protocols using SLR. Sprague-Dawley rats underwent a standard midline abdominal incision and wound closure. Groups of 6 rats each were randomized to receive different doses of SLR (2 and 5 mg/kg) with or without loading dose (10 mg/kg x3 days), and with or without steroids (20 mg/kg x3 days followed by 5 mg/kg for 2 weeks). Rats were humanely killed on postoperative days 5, 10, or 15. Wound breaking force was measured using the EHMI BIAX-II instrument and tensile strength was calculated. Wounds in control animals had gradual increase in tensile strength during the 15-day observation. In contrast, high and loading doses of SLR caused reduction in wound strength until day 10, but the wounds' tensile strength became equivalent to control by day 15. The addition of steroids prolonged wound recovery with low doses of SLR until day 15 and had very profound effects on healing in high-dose SLR-treated animals (>50% reduction) that continued beyond the 2 weeks of observation. Low doses of SLR in non-steroid-treated animals had a short-term (5-day) impact on wound healing; high dose and loading doses delayed healing for 10 to 15 days. The addition of steroids had a synergistic effect on delayed wound healing, particularly in animals receiving high-dose SLR, which demonstrated prolonged wound weakness. These results may provide practical guidelines for postoperative introduction of SLR in the context of various clinical protocols.

Effect of plasma fibronectin on the incisional wound healing in rats

BACKGROUND

Abdominal wall repair after celiotomy is important because insufficient incisional wound strength results in wound failures such as fascial dehiscence and herniation. Plasma fibronectin (pFn) has been shown to play an important role in wound healing. The purpose of this study was to investigate whether pFn improves incisional wound healing in a rat skin incision and celiotomy model.

METHODS

Rats underwent a linear skin incision in the dorsal plane or a full-thickness incisional wound (celiotomy) in the abdominal wall. The same operative procedures were performed on rats whose pFn levels were reduced by antirat pFn serum. The wounds were sutured, and purified human pFn or albumin was given intravenously.

RESULTS

After the celiotomy, pFn levels decreased immediately and reached a minimum at 3 h after incision. A single injection of pFn (10 mg/kg) significantly increased the breaking strength of the skin and the bursting pressure of the abdominal wall. The amount of hydroxyproline in the skin incisional wound with pFn was significantly greater than with an injection of albumin as control. In rats with pFn levels decreased by antirat pFn serum, a single administration of pFn significantly increased the breaking strength of the skin and the bursting pressure of the abdominal wall compared to a control injection of albumin.

CONCLUSIONS

It is important for wound healing to maintain sufficiently high levels of pFn. A single intravenous injection of pFn after celiotomy may be useful in the prevention of fascial dehiscence and herniation.

Mesh incisional herniorrhaphy increases abdominal wall elastic properties: a mechanism for decreased hernia recurrences in comparison with suture repair

BACKGROUND

An improved understanding of load-bearing soft tissue repair suggests that the mechanism for the improved outcomes after alloplastic incisional herniorrhaphy involves more than simple tissue replacement or material strength. We test the hypothesis that postrepair abdominal wall elastic properties are most predictive of successful abdominal wall reconstruction.

METHODS

A rodent model of chronic incisional hernia formation was used. Midline incisional hernias were repaired primarily with suture (n = 24) or polypropylene mesh (n = 24). Rodents were sacrificed at serial postoperative time points over 60 days. Intact abdominal wall strips were cut perpendicular to the wound for tensiometric analysis. Biopsies of wound provisional matrix were obtained for biochemical analysis.

RESULTS

Recurrent incisional hernia formation was significantly decreased in the mesh-repair group, compared with the suture-repair group (5/24 vs 14/24, P = .02). Mesh-repaired abdominal walls demonstrated significantly more elongation (P < .01) and less stiffness (P < .01). Toughness was equal between wounds, although the suture-repaired wounds had increased recovery of tensile strength (P < .01). There were no significant differences in collagen deposition after postoperative day 7.

CONCLUSIONS

Mesh incisional herniorrhaphy increases abdominal wall elastic properties as measured by increased elongation and reduced stiffness. Increased abdominal wall elasticity after incisional hernia repair in turn results in lower recurrence rates.

Progressive fascial wound failure impairs subsequent abdominal wall repairs: a new animal model of incisional hernia formation

BACKGROUND

Fascial wound failure alters the phenotype of the abdominal wall. This study introduces a novel animal model of progressive failure of the ventral abdominal wall fascia, which generates large incisional hernias.

MATERIAL AND METHODS

A mechanistic model of incisional hernia was compared with a model of acute myofascial defect hernia repair. Using biological tissue repair markers, tensiometric measurements and recurrent hernia rate, we measured the mechanism by which incisional hernias regenerate abdominal wall structure and function after mesh and suture herniorrhaphy.

RESULTS

Recurrent incisional hernia formation was significantly increased after repairs of the hernia model, compared with the myofascial defect model (6/16 vs 0/16, P < .05). In the hernia model, there were significant decreases in the recovery of wound strength, energy, and extensibility before mechanical disruption, compared with the myofascial defect model. Unexpectedly, excision of fascial hernia wound edges did not significantly improve tissue repair outcomes in the hernia model group.

CONCLUSIONS

Clinically accurate animal modeling can recreate the wound pathology expressed in mature incisional hernias. Progressive fascial wound failure decreases the fidelity of subsequent incisional hernia repair, compared with identically sized acute abdominal wall defect repairs. The mechanism appears to include decreased fascial wound strength and decreased tissue compliance after herniorrhaphy.

Rat models of skin wound healing: a review

Rats have been widely used in the study of skin wound healing and the efficacy of different treatment modalities. This particular animal species is often selected for its availability, low cost, and small size. To define the current use of rat skin wound healing models, this manuscript provides a review of articles published between 2000 and 2003 that chose rats as their research animals. Of the 55 articles reviewed, it was found that 38.2% of the studies used incisional models and 38.2% used excisional models, with some studies using combinations. The majority of the studies (78.2%) used the rat's dorsum as the wound location. Male Sprague Dawley in the 250-300 gram weight range were the most preferred rats. Sodium pentobarbital/pentobarbitone was the most commonly used anesthetic choice. Similarities and differences in the selected experimental conditions are noted and questions are raised with regard to comparability between studies and the ability to transfer the data from the animal model to the human clinical situation. Attempts to compare studies for the advancement of wound healing knowledge are being hampered by the differences found between the studies. Standardization in reporting could facilitate comparisons and may instigate additional research that favors the inevitable comparisons between the studies. Thus, universal reporting requirements need to be developed for animal wound healing studies.

Fascial fibroblast kinetic activity is increased during abdominal wall repair compared to dermal fibroblasts

Abdominal wall fascial wound healing failure is a common clinical problem for general surgeons, manifesting in early postoperative fascial dehiscence as well as delayed development of incisional hernias. We previously reported that abdominal wall fascial incisions normally recover breaking strength faster than simultaneous dermal incisions in a rodent model. The accelerated fascial repair was associated with greater fibroblast cellularity within fascial wounds and increased wound collagen deposition. The current study was designed to determine whether accelerated fascial healing is the result of increased fascial fibroblast kinetic activity as measured by a more efficient fibroblast phenotype for binding to and remodeling a collagen matrix. Using a new model of abdominal wall repair, fibroblast cell cultures were developed from uninjured and wounded fascia and compared to dermal fibroblasts in order to define the fibroproliferative kinetic properties of abdominal wall fibroblasts. Fascial wound fibroblasts produced a more efficient and greater overall collagen lattice compaction compared to dermal fibroblasts. Acute fascial wound fibroblasts also showed enhanced cell proliferation compared to dermal fibroblasts but no significant differences in collagen production when normalized to cell number. These results suggest that fascial fibroblasts express distinct acute repair phenotypes and therefore a specific mechanism for fascial repair following injury.

The prevention of incisional hernia formation using a delayed-release polymer of basic fibroblast growth factor

OBJECTIVE

We sought to reduce the high incidence of abdominal wall incisional hernias using sustained release growth factor therapy.

SUMMARY BACKGROUND DATA

Incisional hernias complicate 11% of abdominal wall closures, resulting in 200,000 incisional hernia repairs in the United States each year. Mechanical improvements alone in mesh, suture material, and surgical technique have failed to reduce the high rate of fascial wound failure.

METHODS

Sprague-Dawley rats underwent midline celiotomies that were closed with fast-absorbing suture to induce early biomechanical wound failure and incisional hernia formation. In primary wounds, fascial incisions were closed adjacent to a continuous release polygalactone polymer rod containing basic fibroblast growth factor (bFGF), no growth factor (control-rod), or without rods. In a second group, incisional hernias were repaired with either bFGF or control-rod therapy. Breaking strength was measured on postoperative day (POD) 7, and the incidence of incisional hernia formation was determined on POD 28.

RESULTS

Treatment with bFGF rods significantly increased fascial wound breaking strength. In the "hernia-prevention" experiments, incisional hernias developed in 90% of untreated incisions, 60% of control-rod incisions, and only 30% of bFGF-rod incisions (P < 0.05). In the "hernia-treatment" experiments, recurrent incisional hernias developed in 86% of control-rod incisions compared with only 23% of bFGF-rod treated incisions (P < 0.05). Immunohistochemistry demonstrated increased angiogenesis and collagen protein production in bFGF treated incisions.

CONCLUSION

The treatment of abdominal fascial incisions with a sustained-release bFGF polymer significantly lowered the incidence of incisional hernias and the recurrence rate after repair.

Transforming growth factor beta(2) lowers the incidence of incisional hernias

BACKGROUND

Approximately 200,000 incisional hernias are repaired annually in the United States. The high incidence (11-20%) and recurrence rate (24-54%) for incisional hernias have not changed appreciably in 75 years. Mechanical advances in suture material, incision orientation, and closure technique have failed to eliminate this common surgical complication. A biological approach to acute wound failure may offer a new strategy.

METHODS

A rodent incisional hernia model was used. Seventy rats underwent 5-cm midline celiotomies and were closed with fine, fast-absorbing sutures to induce intentional acute wound failure. Group 1 received no other treatment. The midline fascia in groups 2 and 3 was injected immediately prior to incision with 100 microl of vehicle alone or vehicle containing 1 microg of transforming growth factor beta(2) (TGF-beta(2)). Necropsy was performed on Postoperative Day 28 and the wounds were examined for herniation.

RESULTS

Incisional hernias developed in 88% (35/40) and 79% (11/14) of untreated incisions and those treated with vehicle alone. No hernias formed in the TGF-beta(2)-treated incisions (0/16, P < 0.05). Standard histology and immunohistochemistry demonstrated enhanced macrophage, lymphocyte, and fibroblast chemotaxis and increased collagen I and III production in TGF-beta(2) treated incisions.

CONCLUSIONS

Treatment of abdominal wall fascial incisions with TGF-beta(2) prevented the development of incisional hernias in this rat model. TGF-beta(2) stimulated fascial macrophage and fibroblast chemotaxis as well as acute wound collagen production. A biological approach such as this may reduce the incidence of incisional hernia formation in humans.