Histologic analysis of acellular dermal matrix in the treatment of anal fistula in an animal model

Preclinical testing of a new radiofrequency ablation device in a porcine perianal fistula model

PURPOSE

Anorectal fistulas present a treatment challenge, with conventional surgical methods potentially resulting in complications such as fecal incontinence. To improve patient outcomes, more effective and minimally invasive therapies are critically needed. In this study, an optimal porcine model for the creation of anorectal fistulas was developed and used to evaluate the efficacy of radiofrequency ablation (RFA) therapy.

METHODS

Two distinct but related experiments were conducted. In the first experiment, a reliable and standardized porcine anorectal fistula model was developed. In the second, the healing process was assessed, and outcomes were compared between the RFA-treated group and the control group using the established porcine model.

RESULTS

The results indicated that a 3.5-cm fistula tract length and a 14-day evaluation period following seton removal are optimal for the porcine anorectal fistula model. In the second experiment, the RFA group tended to exhibit better outcomes regarding fistula closure, although the differences were not statistically significant. Histopathologically, no significant difference in inflammation grade was observed between groups; however, scar tissue was more predominant in the RFA group.

CONCLUSIONS

The findings suggest that RFA therapy may offer potential benefits in the treatment of anorectal fistulas, as demonstrated using a porcine model. To validate these results and explore the mechanisms of action underlying RFA therapy for anorectal fistulas, further research involving larger sample sizes and a more robust study design is required.

Fascia Lata Biological Plug: A Novel Technique for Treating Anal Fistulae

BACKGROUND

An anal fistula is a prevalent condition characterised by an abnormal connection between the epithelialised surface of the anal canal and the skin. Surgeons are continually developing new techniques to effectively treat anal fistulae while preserving the patient's continence. This study aims to evaluate the outcomes and complications associated with the management of high perianal fistulae using the fascia lata biological plug (FBP) technique.

METHODS

This prospective cohort study included all adult patients who presented to the Kasr Al-Ainy Outpatient Surgery Clinic, Cairo, Egypt, between March 2020 and December 2021, with a single-tract high perianal fistula.

RESULTS

A total of 46 eligible patients were included in the study. The insertion of the FBP was associated with complete healing without recurrence in 37 patients (80.4%) at six months post-surgery. Among the 46 patients, only nine (19.6%) experienced fistula recurrence. The recurrence rate increased to 30.4% at 18 months post-surgery, resulting in an overall success rate of 69.6%. Complete continence was maintained in all patients. At 18 months, extra-sphincteric (14.3% vs 0.0%) and supra-sphincteric (21.4% vs 0.0%) types exhibited significantly higher recurrence rates (p=0.006). Anterior fistulae also demonstrated a significantly higher recurrence rate compared to posterior fistulae (64.3% vs 25.0%, p=0.011).

CONCLUSIONS

The use of a FBP for the treatment of single-tract high perianal fistulae yields promising results without compromising patients' continence. It is essential to consider the type and nature of the anal fistula when selecting the most appropriate procedure for effective treatment.

A Novel Patient-like Swine Model of Perianal Crohn's Disease

BACKGROUND

Perianal Crohn's disease is associated with poor outcomes and high medical costs. It is notoriously difficult to treat despite therapeutic advancements for luminal disease. A large animal model that mimics human perianal disease is needed to test innovative therapies.

OBJECTIVE

This study aimed to create a swine model that replicates the inflammatory component and therapeutic challenges found in patients with perianal Crohn's disease.

DESIGN

This was an animal preclinical study.

SETTINGS

The experiments were performed at the animal laboratory at the Johns Hopkins University.

PATIENTS

Four sus scrufus female pigs were included in the study.

INTERVENTIONS

Four female pigs underwent creation of 3 surgical perianal fistulas each, 1 rectovaginal and 2 perianal. Size 24 French setons were placed to maintain patency of the fistula tracts for 4 weeks. After removal of the setons, trinitrobenzene sulfonic acid was administered into the fistula tract to create and maintain local inflammation mimicking perianal Crohn's disease.

MAIN OUTCOMES MEASURES

An MRI was obtained to assess the fistulas and the pigs were euthanized to review histopathology.

RESULTS

Three inflammatory chronic fistula tracts were successfully created in each pig as confirmed by MRI and examination under anesthesia. This is the first report of maintaining patent fistulas in swine 2 weeks after removal of setons. For the first time, we reported that 2 pigs developed branching fistulas and small abscesses reminiscent of human perianal Crohn's disease. The corresponding histopathologic examination found significant chronic active inflammation on standard hematoxylin and eosin staining.

LIMITATIONS

The fistulas were surgically induced and did not occur naturally.

CONCLUSIONS

A chronic perianal fistula model in pigs that strongly resembles human perianal Crohn's disease was successfully created. This model can be used to test novel therapeutics and techniques to pave the path for human trials. See Video Abstract at http://links.lww.com/DCR/B969 .

UN NUEVO MODELO PORCINO SIMILAR A UN PACIENTE DE LA ENFERMEDAD DE CROHN PERIANAL ANTECEDENTES

La enfermedad de Crohn perianal se asocia con malos resultados y altos costos médicos. Es notoriamente difícil de tratar a pesar de los avances terapéuticos para la enfermedad luminal. Se precisa de un modelo animal grande que imite la enfermedad perianal humana para probar terapias innovadoras.OBJETIVO:Nuestro objetivo de este estudio fue crear un modelo porcino que replique el componente inflamatorio y los desafíos terapéuticos que se encuentran en los pacientes con enfermedad de Crohn perianal.DISEÑO:Este fue un estudio preclínico en animales.AJUSTES:Los experimentos se realizaron en el laboratorio de animales de la Universidad Johns Hopkins.PACIENTES:Se incluyeron en el estudio cuatro cerdas sus scrofa.INTERVENCIONES:Cuatro cerdas fueron sometidas a la creación de 3 fístulas perianales quirúrgicas cada una: 1 recto vaginal y 2 perianales. Se colocaron sedales de 24 French para mantener la permeabilidad de los trayectos fistulosos durante 4 semanas. Tras el retiro de los sedales, se administró ácido trinitrobenceno sulfónico en el trayecto de la fístula para crear y mantener la inflamación local simulando la enfermedad de Crohn perianal.PRINCIPALES MEDIDAS DE RESULTADOS:Se obtuvo una resonancia magnética para evaluar las fístulas y los cerdos fueron sacrificados para revisar la histopatología.RESULTADOS:Se crearon de manera exitosa tres trayectos fistulosos inflamatorios crónicos en cada cerdo, confirmados por imágenes de resonancia magnética y examen bajo anestesia. Este es el primer informe de preservación de fístulas permeables en cerdos 2 semanas tras el retiro de los setones. Por primera vez, informamos que dos cerdos desarrollaron fístulas ramificadas y pequeños abscesos que recuerdan a la enfermedad de Crohn perianal humana. El examen histopatológico correspondiente encontró una significativa inflamación crónica activa en la tinción estándar de hematoxilina y eosina.LIMITACIONES:Las fístulas se indujeron quirúrgicamente y no se produjeron de forma natural.CONCLUSIONES:Se logro recrear con éxito un modelo de fístula perianal crónica en cerdos que se asemeja mucho a la enfermedad de Crohn perianal humana. Este modelo se puede utilizar para probar nuevas terapias y técnicas para allanar el camino para los ensayos en humanos. Consulte Video Resumen en http://links.lww.com/DCR/B969 . (Traducción-Dr Osvaldo Gauto).

From waste to wealth: Repurposing slaughterhouse waste for xenotransplantation

Slaughterhouses produce large quantities of biological waste, and most of these materials are underutilized. In many published reports, the possibility of repurposing this form of waste to create biomaterials, fertilizers, biogas, and feeds has been discussed. However, the employment of particular offal wastes in xenotransplantation has yet to be extensively uncovered. Overall, viable transplantable tissues and organs are scarce, and developing bioartificial components using such discarded materials may help increase their supply. This perspective manuscript explores the viability and sustainability of readily available and easily sourced slaughterhouse waste, such as blood vessels, eyes, kidneys, and tracheas, as starting materials in xenotransplantation derived from decellularization technologies. The manuscript also examines the innovative use of animal stem cells derived from the excreta to create a bioartificial tissue/organ platform that can be translated to humans. Institutional and governmental regulatory approaches will also be outlined to support this endeavor.

Multifunctional all-in-one adhesive hydrogel for the treatment of perianal infectious wounds

Postoperative wound of perianal infectious disease represents a common but unique refractory wound in clinical practice. The reasons that hinder the wound healing process include not only the severe bacterial infection of the wound itself and the narrow and deep shape of the wound, but also its frequent bacterial contact. Therefore, the development of biofunctional dressings to aid in therapy is essential. In this study, we synthesized a new type of dressing comprising a hydrogel host based on the Schiff base principle and catechol groups between polydopamine, oxidized dextran, and quaternized chitosan, and then loaded it with traditional Chinese medicine molecules. These formed an integrated hydrogel for accelerated wound repair in a perianal infection model. The prepared hydrogels exhibited excellent wet tissue adhesion, antifouling, morphological variability, suitable swelling properties, and complete degradability, as well as remarkable contact antibacterial ability and the ability to rapidly scavenge free radicals. Hemostatic experiments showed excellent hemostatic properties, as the integrated hydrogel could instantly gel to seal the hemorrhage. Hemocompatibility and in vitro cell experiments showed that the integrated hydrogel had good biosafety and significantly promoted cell proliferation, which in turn accelerated the repair of infected whole cortexes in rats. A histomorphological evaluation showed that the integrated hydrogel promoted the recovery of normal anatomical tissue in rats by promoting the formation of collagen fibers and inhibiting inflammation. The results showed that this multifunctional integrated hydrogel has great potential for the treatment of continuously infected skin regeneration, providing a promising therapeutic strategy for postoperative wound healing in perianal infectious diseases.

Acellular dermal matrix decorated with collagen-affinity peptide accelerate diabetic wound healing through sustained releasing Histatin-1 mediated promotion of angiogenesis

Treating diabetic ulcers is a major challenge in clinical practice, persecuting millions of patients with diabetes and increasing the medical burden. Recombinant growth factor application can accelerate diabetic wound healing via angiogenesis. The local administration of recombinant growth factors has no robust clinical efficiency because of the degradation of append short duration of the molecules in the hostile inflammatoryenvironment.The present study focused on the pathophysiology of impaired neovascularization and growth factor short duration in the diabetic wound. We prepared a collagen-binding domain (CBD)-fused recombinant peptide (C-Histatin-1) that had both pro-angiogenesis capacity and collagen-affinity properties. Next, we created a biocompatible acellular dermal matrix (ADM) as a drug delivery carrier that featured collagen-richness, high porosity, and non-cytotoxicity. C-Histatin-1 was then tethered on ADM to obtain a sustained-release effect. Finally, a functional scaffold (C-Hst1/ADM) was developed. C-Hst1/ADM can sustain-release Histatin-1 to promote the adhesion, migration, and angiogenesisof vascular endothelial cells in vitro. Using a diabetic wound model, we showed that C-Hst1/ADM could significantly promote angiogenesis, reduce scar widths, and improve extracellular collagen accumulation. Therefore, the results of this study provide a foundation for the clinical application of C-Hst1/ADM covering scaffold in the treatment of diabetic wounds.

Comparison of perineal morbidity between biologic mesh reconstruction and primary closure following extralevator abdominoperineal excision: a systematic review and meta-analysis

AIM

Extralevator abdominoperineal excision (ELAPE) for rectal cancer leaves a greater perineal defect which might result in significant perineal morbidity, and how to effectively close perineal defects remains a challenge for surgeons. This study aimed to comparatively evaluate the perineal-related complications of biologic mesh reconstruction and primary closure following ELAPE.

METHOD

The electronic databases PubMed, EMBASE, Cochrane Library, and Web of Science were searched to screen out all eligible studies, which compared biologic mesh reconstruction with primary closure for perineal-related complications following ELAPE. Pooled data of perineal-related complications including overall wound complications, hernia, infection, dehiscence, chronic sinus, and chronic pain (12 months after surgery) were analyzed.

RESULTS

A total of four studies (one randomized controlled trial and three cohort studies) involving 544 patients (346 biologic mesh vs 198 primary closure) were included. With a median follow-up of 18.5 months (range, 2-71.5 months). Analysis of the pooled data indicated that the perineal hernia rate was significantly lower in biologic mesh reconstruction as compared to primary closure (OR, 0.38; 95% CI, 0.22-0.69; P = 0.001). There were no statistically significant differences between the two groups in terms of total perineal wound complications rate (P = 0.70), as well as rates of perineal wound infection (P = 0.97), wound dehiscence (P = 0.43), chronic sinus (P = 0.28), and chronic pain (12 months after surgery; P = 0.75).

CONCLUSION

Biologic mesh reconstruction after extralevator abdominoperineal excision appears to have a lower hernia rate, with no differences in perineal wound complications.

The application possibility of acellular dermal matrix decorated with nano-silver in the reconstruction of contaminated abdominal wall

Acellular dermal matrix (ADM) is a biomaterial, which commonly used for repair of tissue defects; however, infection is the main factor underlying the failure of treatments involving ADM. To enhance the anti-infection ability of ADM, we constructed a new form of ADM that was decorated with nano-silver ('NS-ADM'). The introduction of nano-silver did not destroy the decellularized structure of ADM, and no significant difference was detected with regards to the maximum tensile force when compared between NS-ADM and ADM (P = 0.351). NS-ADM was not cytotoxic to cell growth when the concentration of nano-silver solution ≤ 25 ppm and exhibited strong antibacterial activity in vitro. Besides, when rats were inoculated with 104 CFU/mL, there were significantly lower bacterial counts in the NS-ADM group than in the ADM group when assessed seven days after surgery (P = 0.047); no significant differences were detected on days 14 and 28. Although there were no significant differences in bacterial counts on days 7, 14, or 21 between the two groups (rats were inoculated with 106 CFU/mL), the number of rats showing reduced bacterial counts or clearing was higher in the NS-ADM group than in the ADM group. Rats that were inoculated with 108 CFU/mL showed repair failure. Overall, NS-ADM is a promising antibacterial biomaterial for repairing contaminated soft-tissue defects, in which antibacterial properties are superior to ADM. The antibacterial activity of NS-ADM was limited for severe infections, and further in vivo studies are needed to evaluate its efficacy and biosafety.

Addition of platelet-rich plasma supports immune modulation and improved mechanical integrity in Alloderm mesh for ventral hernia repair in a rat model

The recurrence of ventral hernias continues to be a problem faced by surgeons, in spite of efforts toward implementing novel repair techniques and utilizing different materials to promote healing. Cadaveric acellular dermal matrices (Alloderm) have shown some promise in numerous surgical subspecialties, but these meshes still suffer from subsequent failure and necessitation of re-intervention. Here, it is demonstrated that the addition of platelet rich plasma to Alloderm meshes temporally modulates both the innate and cytotoxic inflammatory responses to the implanted material. This results in decreased inflammatory cytokine production at early time points, decreased matrix metalloproteinase expression, and decreased CD8+ T cell infiltration. Collectively, these immune effects result in a healing phenotype that is free from mesh thinning and characterized by increased material stiffness.

Long-Term Clinical Results of Use of an Anal Fistula Plug for Treatment of Low Trans-Sphincteric Anal Fistulas

BACKGROUND An anal fistula plug is a sphincter-sparing procedure that uses biological substances to close an anorectal fistula. This study aimed to evaluate the long-term therapeutic effect of an anal fistula plug procedure in patients with trans-sphincteric fistula-in-ano and to determine the risk factors affecting fistula healing. MATERIAL AND METHODS A single-center retrospective study was performed assessing long-term treatment outcomes of patients with low trans-sphincteric anal fistulas who initially underwent anal fistula plug procedures between August 2008 and September 2012. Risk factors affecting fistula healing were identified using univariate and multivariate analyses. RESULTS A total of 135 patients who had low trans-sphincteric anal fistulas and underwent anal fistula plug procedures were analysed. The overall healing rate was 56% (75/135) with a median follow-up time of 8 years (range, 72-121 months). The primary reasons for treatment failure were plug extrusion (n=12, 20%) and surgical site infection (n=9, 15%), occurring within 30 days after surgery. Multiple logistic regression analysis showed that the duration of anal fistula ≥6 months was significantly associated with treatment failure using an anal fistula plug (OR=3.187, 95% CI: 1.361-7.466, P=0.008). Of the patients who failed initial treatment with an anal fistula plug, 6 (9%) had anal fistulas that healed spontaneously after 2-3 years without additional treatment. CONCLUSIONS As a sphincter-preserving procedure, the anal fistula plug can effectively promote healing of low trans-sphincteric anal fistulas. The long-term efficacy is good and the procedure warrants wider use in clinical practice.

Long-Term Outcomes of Ligation of the Inter-Sphincteric Fistula Tract Plus Bioprosthetic Anal Fistula Plug (LIFT-Plug) in the Treatment of Trans-Sphincteric Perianal Fistula

BACKGROUND The ligation of the inter-sphincteric fistula tract plus bioprosthetic anal fistula plug (LIFT-plug) is a new procedure in the treatment of trans-sphincteric perianal fistulas. The aim of this study was to evaluate its long-term outcomes. MATERIAL AND METHODS Clinical data of 78 patients with trans-sphincteric perianal fistula who were managed by the LIFT-plug technique between March 2014 to October 2016 were analyzed retrospectively. The operation time, healing rate, postoperative complications, recurrences, and length of stay were reviewed. RESULTS No serious complications occurred during the operation in all patients. The median follow-up was 30 months (16 to 47 months), clinical healing of the anal fistula occurred in 75 patients (96.2%). The median operative time was 25 minutes (18 to 45 minutes). The mean complete healing time was 16 days (9 to 46 days). The median healing time for the external anal fistula opening was 2 weeks (range, 2 to 3 weeks), and the inter-sphincteric groove incision healing time was 4 weeks (range, 3 to 7 weeks). The median hospital stay after operation was 5 days. Fistula recurred in 2 patients because of spontaneous expulsion of the plug at 7 days post-surgery; perianal abscess occurred in 1 patient. The anal function was evaluated in 70 patients of the 78 patients. Perfect control of continence was recorded for 97.1% of the patients (68 out of 70 patients). Two patients were identified to a rare complication of gas incontinence (Wexner score 1). CONCLUSIONS LIFT-plug procedure for the treatment of trans-sphincteric fistulas is a simple procedure with a high healing rate, minimal invasiveness, quick healing, and without disturbance to anal function. LIFT-plug is an ideal procedure for trans-sphincteric fistula.

Extracellular Matrix Bioscaffolds for Building Gastrointestinal Tissue

Regenerative medicine is a rapidly advancing field that uses principles of tissue engineering, developmental biology, stem cell biology, immunology, and bioengineering to reconstruct diseased or damaged tissues. Biologic scaffolds composed of extracellular matrix have shown great promise as an inductive substrate to facilitate the constructive remodeling of gastrointestinal (GI) tissue damaged by neoplasia, inflammatory bowel disease, and congenital or acquired defects. The present review summarizes the preparation and use of extracellular matrix scaffolds for bioengineering of the GI tract, identifies significant advances made in regenerative medicine for the reconstruction of functional GI tissue, and describes an emerging therapeutic approach.

Experimental porcine model of complex fistula-in-ano

AIM

To establish and evaluate an experimental porcine model of fistula-in-ano.

METHODS

Twelve healthy pigs were randomly divided into two groups. Under general anesthesia, the experimental group underwent rubber band ligation surgery, and the control group underwent an artificial damage technique. Clinical magnetic resonance imaging (MRI) and histopathological evaluation were performed on the 38^th d and 48^th d after surgery in both groups, respectively.

RESULTS

There were no significant differences between the experimental group and the control group in general characteristics such as body weight, gender, and the number of fistula (P > 0.05). In the experimental group, 15 fistulas were confirmed clinically, 13 complex fistulas were confirmed by MRI, and 11 complex fistulas were confirmed by histopathology. The success rate in the porcine complex fistula model establishment was 83.33%. Among the 18 fistulas in the control group, 5 fistulas were confirmed clinically, 4 complex fistulas were confirmed by MRI, and 3 fistulas were confirmed by histopathology. The success rate in the porcine fistula model establishment was 27.78%. Thus, the success rate of the rubber band ligation group was significantly higher than the control group (P < 0.05).

CONCLUSION

Rubber band ligation is a stable and reliable method to establish complex fistula-in-ano models. Large animal models of complex anal fistulas can be used for the diagnosis and treatment of anal fistulas.

Fistula tract curettage and the use of biological dermal plugs improve high transsphincteric fistula healing in an animal model

PURPOSE

The treatment of high transsphincteric fistula is a complex procedure, which may be associated with the risk of recurrence and fecal incontinence. In this study, we used an animal model to compare different types of sphincter-preserving treatments for transsphincteric fistula.

METHODS

Sixteen female New Zealand rabbits, weighing 2.8-4.8 kg underwent a surgical creation of high transsphincteric fistula. After 6 weeks, magnetic resonance imaging (MRI) was performed in order to confirm fistula formation and measure the fistula diameter. The rabbits were divided into three groups. Group 1 received no plug treatment (control). Autologous dermal graft and acellular dermal matrix were used as a plug in groups 2 and 3, respectively. Five weeks after treatment, fistula tract healing was determined by measuring the largest fistula diameter with MRI. All rabbits were euthanized and the anorectum excised en bloc for histopathological examination.

RESULTS

According to the MRI findings, all groups showed significant healing after the treatment (p < 0.05). The healing rate of fistula diameters after treatment was 40, 66, and 29% in the control, dermal graft, and acellular dermal matrix groups, respectively. In terms of negative healing parameters such as neutrophil, eosinophil, lymphocyte, and plasmocyte accumulation, dermal graft and acellular dermal matrix groups showed significantly lower results than those in the control group (p < 0.05).

CONCLUSION

According to MRI and histopathological results, fistula tract curettage and fistula orifice closure improved transsphincteric anal fistula healing. Additionally, in this study, plug treatment favoring autologous dermal graft resulted in better healing.

Tissue-Engineered External Anal Sphincter Using Autologous Myogenic Satellite Cells and Extracellular Matrix: Functional and Histological Studies

The aim of the present study was to demonstrate the regaining histological characteristics of bioengineered external anal sphincters (EAS) in rabbit fecal incontinence model. The EAS of 16 rabbits were resected and decellularized. The decellularized scaffolds were transplanted to the terminal rectum following a period of 6 months of fecal incontinency (5 days after sterilization). The rabbits were divided into two groups: in group 1 (n = 8), myogenic satellite cells were injected into the transplanted sphincters. In group 2 (n = 8), the transplanted scaffolds remained in situ without cellular injection. The histological evaluation was performed with desmin, myosin, smooth muscle actin, CD31, and CD34 at 3-month intervals. The rabbits were followed for 2 years. Electromyography (EMG) with needle and electrical stimulation, pudendal and muscle electrical stimulation were also performed after 2 years of transplantation. At the time of biopsy, no evidence of inflammation or rejection was observed and the transplanted EAS appeared histologically and anatomically normal. The immunohistochemistry staining validated that the histological features of EAS was more satisfactory in group 1 in short-term follow-up. However, no statistically significant difference was detected between two groups in long-term follow-ups (p value > 0.05). In both groups, grafted EAS contracted in response to electrical signals delivered to the muscle and the pudendal nerve. However, more signals were detected in group 1 in EMG evaluation. In conclusion, bioengineered EAS with myogenic satellite cells can gain more satisfactory histological outcomes in short-term follow-ups with better muscle electrical stimulation outcomes.

A newly designed anal fistula plug: clinicopathological study in an experimental iatrogenic fistula model

We report on a clinicopathologic study in an animal model of treatment with a new bioabsorbable polymer plug (BAPP). Over a 2-week period, 6 porcine models, which each had 4 anal fistulae, were created using Blake drains. The pigs were divided into 2 groups: the BAPP-treatment group (n = 12 fistulae) and the control group (n = 12 fistulae). Two weeks later, the pigs were humanely killed, and the perianal sites were excised and examined with gross and pathologic studies. Each fistula in the BAPP group was completely cured. In the pathologic study, the treatment sites had little disarray, few defects in the muscular layer, and small numbers of inflammatory cells. The control group had a significantly greater number of inflammatory cells and microabscesses than the BAPP group. The newly developed BAPP reduced the infection and induced good healing in anal fistulae. The BAPP may be a useful new device for the clinical treatment of anal fistulae.

Ligation of the intersphincteric fistula tract plus a bioprosthetic anal fistula plug (LIFT-Plug): a new technique for fistula-in-ano

AIM

Ligation of the intersphincteric fistula tract and reinforcement with a bioprosthetic graft are two recently reported procedures that have shown promise in the treatment of anal fistula. This study was undertaken to validate combining ligation of the intersphincteric fistula tract plus bioprosthetic anal fistula plug and report our preliminary results and experience.

METHOD

Twenty-one patients with transsphincteric anal fistula were treated with ligation of the intersphincteric fistula tract plus concurrent bioprosthetic plug of the anal fistula. We evaluated healing time, fistula closure rate and postoperative anal function according to the Wexner continence score.

RESULTS

No mortality or major complications were observed. Median operative time was 20 (range 15-40) min. After a median follow-up of 14 (range 12-15) months, the overall success rate was 95% (20/21), with a median healing time of 2 (range 2-3) weeks for external anal fistula opening and 4 (range 3-7) weeks for intersphincteric groove incision. Only 1 (5%) patient reported rare incontinence for gas postoperatively (Wexner score 1).

CONCLUSIONS

Ligation of the intersphincteric fistula tract plus a bioprosthetic anal fistula plug is an easy, safe, effective and useful alternative in the management of anal fistula. Further randomized controlled studies are necessary to better evaluate long-term results.

Novel biological strategies in the management of anal fistula

BACKGROUND

The mostly widely studied biomaterials for the sphincter sparing treatment of anal fistulas are fibrin glue and the anal fistula plug (AFP). However their overall mean clinical success is only 50-60%. As the understanding of the pathology of anal fistula, wound healing and the host response to materials has improved, so new biological sphincter-sparing strategies have been developed. The aim of this review is to assess the safety and efficacy of these novel techniques.

METHOD

PubMed, the Cochrane database and EMBASE were independently searched. All studies that investigated the potential of a biomaterial (defined as any synthetic or biologically derived substance in contact with host tissue) to augment the healing of anal fistula without sphincter division were included. Studies solely describing the role of fibrin glue or an AFP were excluded. Data extraction included type of material, fistula aetiology, treatment of the primary tract, fistula healing, incontinence, duration of follow-up and any specific complications. Systematic quality assessment of the included articles was performed.

RESULTS

Twenty-three articles were finally selected for review. These included a variety of biological and synthetic systems that were employed to deliver selected components of the extracellular matrix, growth factors, cytokines, stem cells or drugs to the fistula tract.

CONCLUSION

To date no study matches fistulotomy with regard to long-term fistula eradication rate. This is probably due to implant extrusion, inadequate track preparation or an unsuitable material. Future techniques need to address all these issues to ensure success. Success should be validated by MRI or long-term follow-up.

Corneal reinforcement using an acellular dermal matrix for an analysis of biocompatibility, mechanical properties, and transparency

The aim of this study was to analyze the viability of using an acellular dermal matrix (ADM) as a reinforcement material for peripheral corneal thinning disease. The complete removal of cell components was confirmed by hematoxylin and eosin (H&E) and 4',6-diamidino-2-phenylindole (DAPI) staining. Transmission electron microscopy determined that the stromal structure was well preserved. Uniaxial tests revealed that the ADM had strong mechanical properties. After being implanted into rabbit cornea the ADM showed no sign of rejection and even achieved good transparency 24weeks post-surgery. H&E staining demonstrated that keratocytes grew in the ADM and the ADM-cornea interface became blurry. Picrosirius red staining revealed great changes of collagen in the ADM. Uniaxial testing of the reinforced cornea showed better mechanical strength than the normal rabbit cornea, but this did not exhibit statistical significance. These results suggest that ADM is a worthy candidate for future exploration as a reinforcement material for peripheral corneal thinning problems.

The anal fistula claw: the OTSC clip for anal fistula closure

AIM

Surgical closure of high or complex anal fistulae is often a difficult challenge. A special Nitinol clip, the OTSC clip (Ovesco AG), was evaluated for fistula closure in a porcine model.

METHOD

A total of 20 fistulae were created in 10 animals by seton insertion. Four weeks after fistula induction the setons were removed: one internal fistula opening per animal was left untreated as control whereas the other opening was closed by the OTSC clip using a specially developed transanal clip applicator. The safety and technical feasibility of the clip application were tested. Another 4 weeks later, fistulae were macroscopically assessed for closure. For histological examination, the anorectum including the fistula tract was excised en bloc.

RESULTS

Four weeks after clip placement, all external and internal fistula openings were macroscopically closed. The clip application site presented with an increased scarring. Microscopically, 40% of residual tracts and a more intense chronic inflammation were seen in the untreated control fistulae. After clip placement, 10% of the fistulae persisted associated with a higher density of collagen fibres indicating a better fistula scarring and healing. No unexpected side-effects or complications caused by the clip were observed.

CONCLUSION

Fistula closure using the OTSC clip represents a promising sphincter-preserving minimally invasive procedure. This study demonstrated the safety and feasibility of the 'anal fistula claw' for fistula closure. In spite of limitations of the porcine model the results justify clinical applications and further investigations.

Long-term outcomes of human acellular dermal matrix plug in closure of complex anal fistulas with a single tract

BACKGROUND

Bioprosthetic plugs represent a promising technique for the treatment of anal fistula simple because they allow simple and repeatable application, preservation of sphincter integrity, minimal patient discomfort, and subsequent surgical options if needed. However, success rates vary widely.

OBJECTIVE

The aim of this study was to assess long-term outcome in patients treated with an acellular dermal matrix plug for closure of complex single-tract anal fistulas.

DESIGN

This was a retrospective analysis of a prospective database.

SETTING

The study was conducted at a university hospital in Beijing, People's Republic of China.

PATIENTS

The study population comprised 114 patients treated between January 2007 and May 2010 for complex high transsphincteric anal fistula with a single tract.

INTERVENTION

Fistulas were treated with an acellular dermal matrix plug derived from donated human skin.

MAIN OUTCOME MEASURES

The main outcome measures were fistula closure rate and postoperative incontinence (Wexner scores).

RESULTS

No mortality or major complications were observed. The overall success rate was 54.4% (62/114), with a median follow-up of 19.5 (range, 11-46) months. Of the 52 patients with plug failure, 11 (21%) had plug extrusion and 9 (17%) had sepsis. Most plug failures occurred within 30 days, with only 1 plug failure occurring 6 months after surgery. On multiple logistic regression analysis, smoking (P < .001), long distance between external opening (P < .001), and performance of the operation by a nonexpert surgeon (P = .018) were significantly associated with plug failure. Of 40 patients who underwent cutting seton placement after plug failure, 33 (82.5%) reported a successful outcome. However, the rate of incontinence 6 months after seton placement was 75% (30/40), whereas the rate in the overall study population 6 months after insertion of the ADM plug was 1.75% (2/114; P < .001).

LIMITATIONS

This study was limited by its retrospective nature.

CONCLUSIONS

Given the low morbidity and relative simplicity of the procedure, we suggest that an acellular dermal matrix plug is a reasonable option for closure of complex anal fistulas with a single tract.

Application of acellular dermal matrix for intestinal elongation in animal models

AIM

To investigate the efficacy of acellular dermal matrix (ADM) for intestinal elongation in animal models.

METHODS

Japanese white big-ear rabbits (n = 9) and Wuzhishan miniature pigs (n = 5) were used in the study. Home-made and commercial ADM materials were used as grafts, respectively. A 3-cm long graft was interposed in continuity with the small bowel and a side-to-side anastomosis, distal to the graft about 3-4 cm, was performed. The animals were sacrificed at 2 wk, 4 wk, 8 wk and 3 mo after surgery and the histological changes were evaluated under light microscope and electron microscope.

RESULTS

The animals survived after the operation with no evidence of peritonitis and sepsis. Severe adhesions were found between the graft and surrounding intestine. The grafts were completely absorbed within postoperative two or three months except one. Histological observation showed inflammation in the grafts with fibrinoid necroses, infiltration of a large amount of neutrophils and leukomonocytes, and the degree varied in different stages. The neointestine with well-formed structures was not observed in the study.

CONCLUSION

It is not suitable to use acellular dermal matrix alone as a scaffold for the intestinal elongation in animal models.