Use of oxidized cellulose for corporal body grafting and suture-less correction of severe penile chordee: an experimental study in rabbits

Authors


Ahmed El-Assmy, Urology and Nephrology Centre, Mansoura, Egypt.
e-mail: a_assmy@yahoo.com

Abstract

OBJECTIVE

To evaluate the efficacy of oxidized cellulose, SurgicelTM (Johnson & Johnson Medical, New Brunswick, NJ, USA) for patching defects in the tunica albuginea in a rabbit model, with a future application to correct chordee.

MATERIALS AND METHODS

The study comprised nine New Zealand white male rabbits; a rectangular 15 × 5-mm defect was created in the ventral tunica albuginea that was covered by Surgicel. The skin was closed with no catheters left in situ after the procedure. The rabbits were killed in groups of three at 2, 6 and 12 weeks after surgery. The evaluation included cavernosography and histopathological examination of sections of the penis stained with haematoxylin and eosin, and Masson’s trichrome.

RESULTS

No deaths were caused by the procedure, and none of the rabbits developed bleeding or haematoma after surgery. Cavernosography at 2 weeks showed contrast medium leaking from the site of the Surgicel, but at 6 and 12 weeks all rabbits had a straight erection with patent corpora and no evidence of narrowing or venous leak. Histopathological evaluation revealed evidence of the remnants of Surgicel surrounded by acute inflammatory cell infiltrate with early neovascularization at 2 weeks. At 6 and 12 weeks, there was complete normal regeneration of the tunica albuginea with no foreign-body reaction.

CONCLUSIONS

In this pilot study, Surgicel had a clear haemostatic effect when covering a defect in the tunica albuginea. Moreover, normal tunica albuginea regenerated by 6 weeks and was maintained at 12 weeks. These results suggest that Surgicel might be considered a safe and effective grafting material for tunica albuginea substitution, including the surgical management of penile chordee.

Abbreviations
SIS

small intestinal submucosa

PG

prostaglandin

H&E

haematoxylin and eosin

INTRODUCTION

Correcting severe penile chordee, secondary to disproportion between the ventral and dorsal surfaces of the corporeal bodies, is a challenging task for the hypospadiologist. Numerous procedures have been described; one approach was to lengthen the shorter ventral surface of the corporeal bodies with various natural or synthetic materials. Recently, biodegradable grafts such as porcine small intestinal submucosa (SIS) and tunica acellular matrix materials have been investigated in corporal body grafting for surgically managing chordee and Peyronie’s disease [1–6]. These materials have the advantages of being biodegradable, with faster surgery and the elimination of donor site morbidity. However, the functional outcome was dismal in some experimental and clinical studies [4,5]. In some of these reports, severe haematoma after surgery was a common cause of failure [4], and there was fibrosis and graft contracture with the use of four-layer SIS for tunical replacement [6].

Various topical haemostatics and sealants have been developed, including oxidized regenerated cellulose, e.g. SurgicelTM (Johnson & Johnson Medical, New Brunswick, NJ, USA) and GelfoamTM (Pharmacia & Upjohn, USA), gelatine matrix haemostatic sealant (FloSealTM, Baxter Healthcare, Deerfield, IL, USA) and fibrin glues such as TisseelTM (Baxter) and CrosssealTM (Omrix Pharmaceuticals, NY, USA). Recently fibrin glue has been used for the suture-less correction of penile chordee [7]. However, commercial fibrin sealant, like any other blood product, has a theoretical risk of viral transmission (e.g. hepatitis and HIV).

Surgicel is oxidized regenerated cellulose and is used as an adjunct in surgical procedures to assist in the control of capillary, venous and small arterial haemorrhage. Surgicel has been widely and effectively used as a haemostatic agent in different surgical fields, including urological surgery [8–10].

As the ideal material with which to close defects in the tunica albuginea has not been described, this study was undertaken to evaluate the feasibility of the use of commercially available Surgicel for covering corporal body defects for future application in the surgical management of severe chordee. In the present study the histological changes and the radiological findings at the site of Surgicel were investigated.

MATERIALS AND METHODS

The local ethics committee for animal experimentation reviewed and approved the study protocol. Nine New Zealand white male rabbits (3.5–4 kg) were used; all rabbits were vaccinated against the common infectious diseases and a veterinarian verified the health status of each. The rabbits were fasted the night before surgery. Pre-medication anaesthetics included ketamine hydrochloride (20 mg/kg i.m.) and atropine (0.2 mg/kg s.c.). Anaesthesia was induced using a mixture of ketamine hydrochloride (30 mg/kg i.m.), midazolam (0.2 mg/kg i.m.) and xylazine (3 mg/kg i.m.).

The penis was released by dividing the perineal skin web between the ventral aspect of the penis and the anus. The preputial glands were dissected off the midline to expose the corpus spongiosum. Buck’s fascia was incised at the junction between the corpus spongiosum and corpus cavernosum on each side. The urethra was carefully dissected and mobilized off the tunica albuginea. A defect of 15 × 5 mm was created in the ventral surface of the tunica albuginea. The defect in the corpora was covered with Surgicel and no sutures were used. The skin was closed using continuous 5/0 chromic catgut suture, and an antibiotic ointment was applied to the suture line. No dressing or catheter was left in place after surgery.

After surgery, the rabbits received a normal diet and were maintained in normal cages, with daily inspection for surgical complications. Analgesics (ketoprofen 3 mg/kg i.m.) and oral broad-spectrum antibiotic (enrofloxacin 5–10 mg/kg) were administered for 3 days after surgery. Three rabbits per group were then killed at 2, 6 and 12 weeks after surgery.

At the scheduled sampling time, the rabbits were sedated using a mixture of ketamine hydrochloride (25 mg/kg i.m.), xylazine (5 mg/kg i.m.) and atropine (0.2 mg/kg s.c.). Prostaglandin E1 (PGE1, 5 µg) was then injected into the corpus cavernosum, and cavernosography with a contrast medium was carried out. The rabbits were then killed and the whole penis excised and fixed in 10% buffered formalin for 48 h, followed by embedding in paraffin wax. Sequential sections were obtained from the penis at the Surgicel site and stained with haematoxylin and eosin (H&E), and Masson’s trichrome; one pathologist examined all slides under light microscopy.

RESULTS

There were no deaths related to the procedure; the mean (sd) operative duration was 27 (2.9) min. All rabbits voided spontaneously after surgery. Gross examination at autopsy showed no evidence of infection or haematoma at the site of Surgicel.

Of the three rabbits killed at 2 weeks, cavernosography showed contrast medium leaking from the site of the Surgicel (Fig. 1A). At 6 and 12 weeks, the remaining six rabbits developed a straight and rigid erection after intracavernosal injection of PGE1; the findings on cavernosography supported those after PGE1; all rabbits had patency in both corpora cavernosa, with no evidence of cavernosal blockage or leakage of contrast medium. There was minor venous outflow in the penis, not originating from the Surgicel site, in all animals (Fig. 1B).

Figure 1.

Contrast-enhanced cavernosography: A, at 2 weeks, showing contrast medium leaking from the site of Surgicel. B, at 6 weeks, showing a straight penis with no corporal narrowing or contrast medium leaking from the Surgicel site. There is minor venous outflow in the penis not originating from the Surgicel site.

Microscopic examination at 2 weeks showed remnants of the Surgicel layer surrounded by acute inflammatory cell infiltrate with early neovascularization and fibroblast migration (Fig. 2). By 6 and 12 weeks there was no evidence of the Surgicel and it was completely replaced by well-collagenized tissue similar to that of normal tunica albuginea, with no surrounding inflammatory reaction. (Fig. 3).

Figure 2.

A section in the penis at 2 weeks stained with H&E. A, low-power view showing remnants of Surgicel between the urethra and corpora (reduced from × 20). B, High-power view showing evident acute inflammatory cell infiltrate with early neovascularization and fibroblast migration surrounding the Surgicel remnants (arrow; reduced from × 100).

Figure 3.

A section in the penis at 6 weeks stained with H&E. A, low-power view showing normal new tunica albuginea between the urethra and cavernosal tissue (reduced from × 20); B, high-power view at 6 weeks, showing complete replacement of the Surgicel by well-collagenized tissue similar to that of normal tunica albuginea (reduced from × 100).

DISCUSSION

A major obstacle to corporal body grafting has been the inability to develop an optimal biomaterial that will act as a suitable scaffold for the natural process of regeneration, with no fibrosis or foreign-body reaction and at the same time preventing infection and haematoma formation. Synthetic biodegradable materials such as SIS and acellular matrix were developed in the hope that these grafts would allow the host tissue adequate time for regeneration, but would dissolve before the onset of severe foreign-body reaction. These materials have been used experimentally and clinically for corporal body grafting, and have shown promising results in some studies [2,3]. However, graft shrinkage [6] and haematoma after surgery [4] still limit their potential clinical use.

Various topical haemostatics and sealants have been developed. Surgicel is a d-glucuronic and d-glucose polymer used as a haemostatic agent to control surgical haemorrhage. It is also used in intra-abdominal interventions to reduce the surgical adherence of the serosal surfaces [11].

The mechanism of action whereby Surgicel accelerates clotting is not completely understood, but it appears to be a physical effect rather than any alteration of the normal physiological clotting mechanism. After Surgicel has been saturated with blood, it swells into a brownish or black gelatinous mass that aids in the formation of a clot, thereby serving as a haemostatic adjunct in the control of local haemorrhage. The haemostatic effect of Surgicel is greater when it is applied dry; therefore, it should not be moistened with water or saline. In addition to its local haemostatic properties, Surgicel is bactericidal in vitro against a wide range of Gram-positive and Gram-negative organisms, including antibiotic-resistant micro-organisms [12].

Although the manufacturer recommends its removal after use, it is generally left on the wound because of its high level of reabsorption, because it is susceptible to breakdown by endocytosis and enzymatic hydrolysis by macrophages. When used properly in minimal amounts, Surgicel is absorbed from the sites of implantation within 1–2 weeks with practically no tissue reaction [13]. Thus it has the distinct advantages of allowing normal wound healing with no significant tissue fibrosis.

Considering the previously mentioned effects, we used Surgicel to patch created tunical defects in the ventral surface of corpora cavernosa. We selected the ventral surface of the penis and dissected the urethra from the tunica albuginea to mimic the clinical scenario during the correction of chordee.

The application of Surgicel to the corporal bodies initiated an inflammatory reaction, with fibroblast migration and subsequent collagen deposition at the site of Surgicel. At 6 and 12 weeks there was no evidence of the Surgicel, and there was complete normal regeneration of the tunica albuginea. The absorption of Surgicel depends upon several factors, including the amount used, degree of saturation with blood, and the tissue bed. Recently some cases of foreign-body reactions to Surgicel were described, some of which were wrongly diagnosed as tumour [14–16], abscess [17] or xanthogranulomatous pyelonephritis [18]. In the present study there was complete absorption with no foreign-body reaction or fibrosis because we used Surgicel in minimal amounts (single layer), and any excess was excised before closure. Also, the use of an unfolded Surgicel might result in rapid cellular migration into the Surgicel, satisfactory remodelling with minimal fibrosis, and a better functional outcome.

Cavernosography at 6 and 12 weeks showed no leakage of contrast medium from the Surgicel site; this indicates that the reconstructed tunica over the Surgicel is functionally similar to the normal tunica. The follow-up of 12 weeks is relatively long, because collagen deposition and linkage average 40% at 3 weeks. Afterwards, there is a constant process of collagen breakdown and new collagen formation [19].

The manufacturer recommends removing the Surgicel after haemostasis because of the risk of migration from the site of application into foramina of bone or spinal cord, that might lead to paralysis [20]; Surgicel, by swelling, might exert pressure, resulting in paralysis and/or nerve damage. These risks are of no concern in the present procedure because the Surgicel is applied topically to the corpora cavernosa, with no risk of migration or compression into nearby nerves.

To the best of our knowledge, this is the first report of using Surgicel for tunical replacement; the study showed that Surgicel as a graft for covering defects in the tunica albuginea has several advantages: It is readily available and has effective haemostasis; it is nearly fully absorbed in 2 weeks with no fibrosis or foreign-body reaction; in addition being a plant-based product, it eliminates the possibility of animal or human-borne contaminants; and it has bactericidal activity against several organisms. Furthermore, it is easy to use, with no need for suturing (it wraps like no other haemostat and does not stick or fall apart), and the absence of sutures is ideal for better healing and less fibrosis. Finally, it induces a controlled increase in the number of endogenous collagen fibres. Thus, Surgicel might be considered a valid substance for corporal body grafting in the surgical management of severe chordee.

In conclusion, in this pilot study, Surgicel grafts for patching tunica albuginea defects provided satisfactory clinical and pathological results. The ease of surgical handling and placement, coupled with no adverse reactions, make this material an anatomical and functional tunical substitute for the surgical treatment of chordee. However, further well controlled studies are required before its clinical application in humans.

CONFLICT OF INTEREST

None declared. Source of funding: Urology and Nephrology Center, Mansoura University, Mansoura, Egypt.

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