Soft tissue covers in hypospadias surgery: Is tunica vaginalis better than dartos flap?

AIM: To compare tunica vaginalis with dartos flap as soft tissue cover in primary hypospadias repair.
MATERIALS AND METHODS: 25 cases (age range: 12-132 months; all fresh cases) of primary hypospadias were prospectively repaired by tubularized incised plate (TIP)/TIP + graft urethroplasty using tunica vaginalis flap (TVF) as soft tissue cover to urethroplasty (group A). Their results were compared with another set (group B) of age- and anatomy-matched controls (25 patients operated during the previous 3 years) who had undergone TIP repair using dartos flap as soft tissue cover. Statistical analysis of results was done with Fischer's exact test. GROUP A: No fistula, skin necrosis, meatal stenosis, urethral stricture. One case had partial wound dehiscence that resolved on conservative treatment with no sequelae. One case required catheter removal on 3(rd) day because of severe bladder spasm. There was no testicular atrophy/ascent. Group B: 3 fistulae - all required surgery. There were three cases of superficial skin necrosis that healed spontaneously without sequel. There was no meatal stenosis/urethral stricture. The difference in fistula rate between both the groups, however, was not statistically significant (P = 0.4).
CONCLUSION: TVF may have an edge over dartos fascia for soft tissue coverage of the neourethra.

INTRODUCTION

The commonest complication of hypospadias surgery is fistula formation which usually requires re-operation. Several techniques of providing vascularized soft tissue cover to the neourethra have been described. They include de-epithelialized skin,[12] corpus spongiosum,[3] dartos fascia,[4] and tunica vaginalis.[5-7] Both dartos fascia and tunica vaginalis provide robust cover to the urethra and act as a barrier between the suture lines. Dartos fascia, harvested from the dorsal penile skin, is more frequently used. Harvesting dartos fascia may be difficult for beginners as it requires precise and skilful dissection to raise the dartos flap without damaging the intrinsic blood supply to the outer skin. This outer skin when transposed ventrally to provide skin cover may consequently devitalize leading to skin necrosis. The tunica vaginalis flap (TVF) has sound vascularity, as it has a separate blood supply and does not depend on the vascularity of penile skin, unlike the dartos fascia. The choice between the two depends more on surgeon's choice and experience rather than scientific evidence.

This study aims to compare the results of these two common soft tissue covers, i.e. dartos and tunica vaginalis, for hypospadias repair.

MATERIALS AND METHODS

Over a period of 1 year, 25 patients (group A), who were suitable for a primary single-stage urethroplasty, were prospectively selected for repair using TVF for soft tissue cover. An equal number of patients, comparable in age and type of hypospadias, who underwent hypospadias repair by the same senior author in the preceding 3 years, but using dartos as soft tissue cover, were selected to serve as controls (group B).

All the patients in groups A and B were similar in their demography. The type of hypospadias varied from coronal, mid-penile, and proximal hypospadias in similar distribution in both the groups. Twenty patients in group A and 19 patients in group B had chordee on examination. Detailed distribution is shown in Table 1.

Table 1

Observations and results

In both the groups, only those patients were selected where a tubularized incised plate (TIP) repair (with or without graft in the dorsal raw area caused by the incision in the urethral plate) was possible. Cases with onlay flap repair, redo cases and previous inguino-scrotal surgery, i.e. hernia or hydrocele repair or orchidopexy, were excluded.

Operative technique

In both the groups, the general technique was the same. Magnification (2.5× Loupes), fine instruments and bipolar electrocautery were used. The urethral plate was tubularized over an appropriate sized catheter using 6-0 polyglactin suture. The epithelium was not included in the bites, thus ensuring inversion of all epithelium toward the lumen of the urethra. The technique of putting a soft tissue cover over this neourethra differed among the groups. In group A, TVF was harvested by bringing the testis with its tunics and cord into the operative field. Tunica vaginalis was incised near the lower pole of the testis and a flap was raised off the testis and the cord structures, taking care not to damage the vas and vessels. Sufficient length of the flap was ensured by careful dissection even up to the external ring. The testis was put back in the scrotum after achieving hemostasis. The TVF was brought over the urethral tube to provide a cover along the entire length [Figures 1 and 2]. For the portion meant to go underneath the glans, the TVF was trimmed to prevent tight glans closure. A few tacking 6-0 polyglactin sutures were placed to secure the flap in position. Glansplasty was done with polydioxanone sutures. The coronal collar of skin was also reconstructed in continuity with the glansplasty.

Figure 1

Prepucial graft harvested for raw area over dorsal incised urethral plate. Also shown is the completed glansplasty over Tunica vaginalis flap

Figure 2

Tunica vaginalis flap covering the urethroplasty

In group B, the dartos was used to cover the ventral suture line. It was harvested from the dorsal prepuce and the penile skin with meticulous dissection between the dartos and the skin. The dartos fascia was then swung ventrally over the neourethra and tacked with 6-0 polyglactin sutures. The distal part was thinned to cover the glanular portion of the neourethra. If there had been torsion of the phallus preoperatively, the dartos flap was swung ventrally in the opposite direction of the torsion. In such cases, the dissection of the flap was left short so as to correct the torsion by pull of the dartos flap. Excess skin was excised and the dorsal skin was transposed ventrally from both sides to provide a neat circumcised look. Light compression dressing antibiotic impregnated gauge was done. Intravenous antibiotics were given for 3 days, followed by oral antibiotics. Dressing and the catheter were removed on the 7th day.Later the children were followed periodically

Statistical analysis

Descriptive statistics were employed to characterize the data. Fisher's exact test was used for categorical data. A P value of <0.05 was considered statistically significant. The analysis was carried out using the Statistical Package for the Social Sciences (SPSS 12.0 version; SPSS, Inc., Chicago, IL, USA).

RESULTS

The results are summarized in Table 1. Group A consisted of 25 patients with a mean age of 37 months (range: 12–132 months). The type of hypospadias was anterior in 15, mid-penile in 6, and posterior in 4. Three had circumcision done elsewhere prior to being referred to us for hypospadias repair. Nine cases required TIP + graft procedure, while the rest 16 were managed by TIP procedure. All had successful repair. One patient had severe bladder spasms, requiring catheter removal on the 3rd post-op day. He remained well with no complication. One patient developed superficial wound dehiscence, which was managed conservatively. No patient in the group had fistula or meatal stenosis.

The mean age in group B was 40 months (range: 14–144 months). Seventeen patients had anterior penile hypospadias, while 7 had mid-penile and only 1 had posterior penile hypospadias. TIP was done in 18 patients and the rest 7 cases required TIP + graft procedure. Three patients developed fistula at corona, requiring a delayed closure. Three patients developed localized superficial necrosis of the ventral penile skin, which healed without sequel.

Follow-up was from 1 to 12 months in group A. There was no incidence of fistula, meatal stenosis or testicular ascent in this period. The three patients in group B, who had fistula, were repaired by reoperation and have been doing well since then.

Harvesting the TVF was easy. The ventral penile incision was continued posteriorly along the midline raphe which gave good access to the testis. Although this endeavor took some extra time, this gradually decreased as we climbed the learning curve. The mean duration of operation was 87 min (range: 75–115 min). The trend showing decrease in the operating time as the study progressed. Pleasing cosmetic outcome with a vertically oriented slit like meatus at the tip of glans was obtained in all the cases.

DISCUSSION

Surgery for hypospadias is continuously evolving, implying that no single technique is considered perfect.[18-10] The use of interposition flaps is well documented in the literature. Those harvested from the prepuce are the triangular soft tissue flaps[11] and Belman flaps.[2] Penile skin based flap is Smith D flap,[1] whereas Buck's fascial flap is harvested from penile shaft. Corpus spongiosum either from the normal native urethra as a turnover perimeatal flap or from the diverging spongiosa[3] has also been used. Either a scrotal dartos flap from the scrotum[45] or a TVF[6] from the testis can also be used.

Snodgrass[12] described additional coverage of neourethra by vascularized subcutaneous tissue dissected from dorsal prepucial and shaft skin. This dissection requires skill and there are chances that vascularity of the skin cover may get compromised resulting in subsequent dermal necrosis. Duckett[13] has ascribed it to hypovascularity of the overlying skin when dartos is separated from skin. Although there are various options for soft tissue coverage, the ideal one is still not found. Dartos based flaps have the advantage that they are available locally and do not require another incision or extension of the incision.

Snow et al.,[14] in 1995, were the first to report the use of tunica vaginalis as interposition graft. The fistula rate reported was 9%. Similar results have also been reported by Shankar et al.[15] and Handoo.[16] It is a dependable soft tissue cover for redo cases and posterior hypospadias surgery.[17] In his recent experience, Snodgrass could reduce the fistula rate to 0% with the use of TVF.[18]

In our study, four cases in group A had posterior hypospadias. They had long suture line from a long urethroplasty. Despite this, no leak or fistula occurred due to the robust tissue cover provided by the TVF. Harvesting TVF was easy in these cases as the ventral incision on the penis as such extended very close to the scrotum. Our series shows that TVF may be of particular benefit in circumcised cases. Using dartos in such cases may result in shortage of skin or skin necrosis from damage to the intrinsic blood supply to the outer skin. Since TVF does not depend on the skin, the ventral skin cover is never compromised.

In group A, there was no fistula during follow-up. Three fistulas occurred in group B; all three of them required reoperations for closure. In two of them, it was possibly related to relatively poor anatomy of glans and urethral plate, which resulted in a relatively tight closure of the glans over the dartos flap. In the third, no reason could be assigned. The difference in the fistula rates in the two groups is not statistically significant (P = 0.4 by Fischer's exact test), possibly because of the small sample size.

We could find only one article comparing these two methods of soft tissue cover. Chatterjee et al.[19] have prospectively compared the two techniques of neourethral coverage after a TIP procedure. They have concluded that TIP with TVF could be an alternative to other techniques in a primary case of hypospadias. However, it was a multi-institutional study inviting surgeon variations. In their study, the fistula rate for cases with TVF and dartos flap were 0% and 15–20%, respectively. Our fistula rate for dartos flap is 12% which is in tune with other reported series. More importantly, we have seen three cases of superficial skin necrosis following dartos flap. Although it was inconsequential in the long run, it did cause anxiety and distress to the families and invited more hospital visits. Hence, we consider that dartos flap had significant morbidity because of this inconsequential complication. Total breakdown of repair is also known after this operation. Chatterjee's study has used only TIP repair in all the cases. We selected cases on the basis of glans anatomy and urethral plate quality and projection on the glans. In some cases, poor projection of the urethral plate on the glans has required additional grafting and meatoplasty to achieve good meatus without compromising on the glansplasty. We feel that every case of hypospadias has an imprint of the meatus and the ventral glansplasty. We have to design our operation based on this imprint. In such difficult cases, the TVF serves a good purpose by providing a thin but nicely vascularized tissue underneath the glans. This prevents tight glans closure, achieves good cosmesis and prevents fistula formation.

CONCLUSION

Our study has shown that TVF may have an edge over dartos fascia for soft tissue coverage of the neourethra. It can be used in primary cases as well. It is of particular benefit in difficult cases.