The Use of Free Grafts for Urethroplasty
D.E. Andrich, A.R. Mundy
21.1 Introduction – 176 21.2 Grafts Versus Flaps – 176 21.3 The Principles of Grafting – 176 21.4 Summary of Principles – 177
21.5 Urethroplasty Using Free Grafts – 177 21.6 Bulbar Urethroplasty – 177
21.7 Penile Urethroplasty – 177 21.8 Points of Technique – 178
References – 179
21.1
Introduction
Apart from isolated reports, substitution urethroplasty really began in the 1940s with Humby [1]. He used full- thickness skin grafts for urethral reconstruction, hypos- padias, and urethral strictures and also described the first recorded case of buccal mucosal graft urethroplasty. After him, sporadic cases were reported in the British, European, and American literature. By the mid-1960s grafts were in regular use for urethral reconstruction for both hypospa- dias and strictures. The foremost proponents were Devine and Horton from Norfolk, Virginia, USA [2]. They and others continued with graft repairs into the 1970s, but by then Yaxley [3] and others began developing flap repairs.
Most notable were Turner-Warwick [4] and Blandy [5] for the repair of urethral strictures in adults and Duckett [6]
for the repair of hypospadias in children.
The prevailing view seemed to be that a flap was more reliable because it carried its own blood supply, although this was never proved. Quartey [7] studied the vascu- lar basis of flap repair and through the 1980s and early 1990s flap repairs dominated genital reconstructive sur- gery until the Mainz group reintroduced buccal mucosal free grafts [8]. This led to a resurgence of interests in graft repairs – whatever the material used – so at the beginning of the 21st century, free grafts have regained their place in the reconstructive urologists armamentarium.
21.2
Grafts Versus Flaps
The flaps used in urethral reconstruction are random island flaps of penile or scrotal skin carried on a dartos pedicle – random, because there is no defined artery sup- plying them and so for the skin paddle to remain viable, an extensive dartos pedicle must be created. The disad- vantage with a flap repair is that it is time-consuming (and tedious) to harvest the flap and the dissection is extensive.
This produces scarring and loss of the normal contour of the penis when its dartos layer has been redeployed from part or all of its circumference.
Grafts are inherently less reliable – in theory – because they have to be revascularized. On the other hand, they are quick and relatively easier to harvest and deploy.
There are numerous short- and mid-term follow-up studies of both grafts and flaps, which essentially show about the same restricture rates [9]. In other words, there is no real difference between grafts and flaps in terms of their restricture rate and therefore unless there is a positi- ve indication or contraindication for one or the other, the simplicity and speed by which a graft can be harvested and deployed means that this is the procedure of choice as far as we are concerned.
Positive indications in favor of a flap rather than a graft include some instances of revision surgery; any
cause of local devascularization such as radiotherapy (or severe peripheral vascular disease); and local infection – all of which interfere with the ability of a graft to take.
21.3
The Principles of Grafting
Graft »take« occurs in two phases, each of which lasts about 2 days. The first phase is imbibition in which the graft is kept alive by absorbing nutrients from the plasma oozed from the surface of the graft bed. The second phase is inosculation in which the microvasculature of the graft bed links up with the microvasculature exposed on the under surface of the graft. Clearly the process leading to inosculation begins during the imbibition phase, but for the viability of the graft itself the two phases are distinct.
By the 5th day after grafting, the graft has either taken or has sloughed off. For the graft to take it must be kept in close contact with the recipient area (and not subject to either undue pressure or hematoma) and free of infection.
It is clearly an advantage if the graft has a dense plexus on its undersurface, and likewise the opposing surface of the recipient bed, to facilitate inosculation. It is an advan- tage if the graft is not too thick, as there is less bulk of tissue to be kept alive during the processes of imbibition and inosculation. For both these reasons, split-thickness grafts have an advantage over full-thickness grafts. A split-thickness graft is thin and depends for its take on the relatively dense intradermal plexus, which is exposed on its undersurface, whereas a full-thickness graft is sub- stantially thicker and has to be inosculated through the subdermal plexus, which is much sparser.
On the other hand, a split-thickness graft tends to contract because of the relative absence of dermal colla- gen. A full-thickness graft, on the other hand, does not contract because the presence of a normal amount of dermal collagen inhibits the contraction process. Thus, if a take can be assured a full-thickness graft is much better than a split-thickness graft because it does not contract and therefore retains its natural characteristics.
The exceptions to the rule that full-thickness grafts have a rather sparse subdermal plexus are genital skin and skin from above the jaw line, including buccal mucosa.
Not only do full-thickness grafts from these areas have a particularly dense subdermal plexus, but they are also thin when compared with skin from other sites. Skin from above the jaw line or from the genitalia therefore does well as a full-thickness skin graft. Few would sacrifice the skin of the face for urethral reconstruction but the skin from behind the ears (the post auricular Wolfe graft), buccal mucosa (applied as a full-thickness graft), and full-thick- ness grafts of penile and preputial skin are expendable within the limits of the amount usually required.
Grafts take best when they are applied as patches to place by the recipient graft bed. It is difficult to apply
21
a free graft as a tube because it is difficult to provide a supporting recipient bed equally all around the circumfe- rence of the tube and therefore ensure take (
⊡ Fig. 21.1).
Thus at 1–3 years of follow-up, the restricture rate of tube grafts is three times the restricture rate of patch grafts [10]. A complete circumferential reconstruction of the urethra is not commonly indicated except in the penile urethra, but when it is, it is therefore safer to apply the graft as a patch in the first instance and then to roll it into a tube as a second stage in order to achieve the lowest possible long-term restricture rate.
21.4
Summary of Principles
In short, there is no significant difference in terms of cure of the stricture between a graft repair and a flap repair but a graft repair is generally quicker and easier and so a graft is best unless there is a positive indication for a flap.
Full-thickness grafts contract less and retain their characteristics better than split-thickness grafts and so full-thickness grafts should be used whenever possible.
The best sources of material for a full-thickness graft are the postauricular skin, buccal mucosa, and penile and preputial skin.
Patch grafts do better than tube grafts and so when a circumferential reconstruction of the urethra is required, it is best to do it in two stages.
21.5
Urethroplasty Using Free Grafts
There is little or no place for substitution urethroplasty in the posterior urethra and this will not be discussed further.
21.6
Bulbar Urethroplasty
The vast majority of bulbar urethral strictures are fairly straightforward strictures in which a one-stage repair is possible. These were (and, by some surgeons, still are) commonly repaired with a preputial/penile skin flap.
These days, a graft of buccal mucosa or full-thickness penile shaft skin is more commonly used. Until recently, the bulbar stricture was opened on its ventral aspect and the graft (or flap) was sewn in ventrally to close the defect. Recently, Barbagli [11] has introduced the dorsal stricturotomy and patch as the dorsal siting of the graft provides better support, with a better vascular bed and better long-term stricture-free survival as a consequence.
A particular problem of a ventral patch was out-pouching of the patch because of lack of support. This in turn led to postmicturition dribbling, postcoital pooling of semen and a variety or irritative symptoms in addition. In this regard, a ventral buccal mucosal graft – being tougher than skin – gives better results than a ventral skin graft.
With a dorsally placed stricturotomy and patch, there is probably no difference between the two [12].
There are still a few occasions when a two-stage bulbar urethroplasty is indicated: with grossly infected strictures;
after excision of tumors; amyloid disease or vascular mal- formations of the urethra; or after excision of a Urolume stent, all of which will leave a defect that will need to be circumferentially reconstructed. Such reconstructions, as already argued, are best done in two stages. Here a graft can be placed between the two ends of healthy urethra with a scrotal funnel sutured to the margins of the graft and the proximal and distal urethrostomies. The graft is then rolled into a tube at a second stage.
21.7
Penile Urethroplasty
Simple strictures of the penile urethra are probably best treated by a one-stage flap procedure such as the Orandi flap [13].
Unfortunately, simple strictures of the penile urethra are not that common. Many are caused by either previous hypospadias repair or to lichen sclerosus (balanitis xerotica obliterans, BXO) which will usually require excision of the urethra [14]. In lichen sclerosus, this is almost always the case. In hypospadias retrieval surgery, it is less commonly necessary and indeed if the natural urethral plate is still present and can be preserved, then it should be preserved.
Lichen sclerosus is a disease of genital skin and there- fore repairs using genital skin almost always lead to restricturing. Nongenital skin is less affected and so, for example, a postauricular Wolfe graft is much less likely to lead to restricturing but still occurs in approximately 30%–40% of cases. Buccal mucosa rarely suffers lichen sclerosus and so a buccal mucosal free graft should pro-
⊡ Fig. 21.1. This illustrates the problems of providing vascular support for a tubular free graft. Dorsally and ventrally (hatched areas) are well supported but laterally on each side (X) support is poor
21 bably be used as the material of choice for the reconstruc- tion of the urethra after excision for this disease.
Reconstruction of a previously failed hypospadias repair is not subject to this proviso. The only requirement is for sufficient skin for the repairs. If this can be harves- ted locally, all is well and good, otherwise a postauricular Wolfe graft provides the best material.
21.8
Points of Technique
Quilt the graft in position. This ensures fixation; provides drainage holes for any hematoma or seroma; and guaran- tees take at the site of each quilting stitch (and therefore of the whole graft).
In staged reconstructions, quilt the graft directly on to the tunic albuginea in the mid-line and 0.5 cm or so on either side. More laterally on each side, incorporate some dartos with the quilting stitch (
⊡ Fig. 21.2). This will make the edges of the graft easier to mobilize at the second stage (
⊡ Fig. 21.3).
At the second stage, don’t over-mobilise the two edges of the graft. Aim to produce an oval urethra rather than a circular tube. This is less likely to interfere with the vascu- larity of the neourethral tube (
⊡ Fig. 21.4).
At the second stage, close the neourethral tube with stitches through the dermis rather than the epidermis to reduce the risk of fistulation (
⊡ Fig. 21.5).
⊡ Fig. 21.3. To show how incorporating the dartos on each lateral aspect facilitates mobilization of the graft at the second stage of a two-stage procedure
⊡ Fig. 21.4. To illustrate how closing the neourethra as an oval in the second stage of a two-stage procedure requires less mobilization and therefore less risk of ischemia
NOT
⊡ Fig. 21.5. To show how closing the dermal layer rather than the epidermal layer at the second stage of a two-stage procedure reduces the risks of postoperative fistulation
NOT
⊡ Fig. 21.2. To illustrate the incorporation of the dartos layer on the lateral aspects of the graft at the first stage of a two-stage procedure
Always overclose suture lines with a layer of dartos, particularly at the corona, which is the most vulnerable area.
If a hematoma develops in the wound after the second stage, drain it. Hematomas and seromas are a common cause of fistulation because of secondary infection.
References
1. Humby G (1999) A one-stage operation for hypospadias. Br J Surg 29:84–92
2. Devine CJ, Horton CE (1961) A one-stage hypospadias repair. J Urol 85:166–172
3. Yaxley RP (1968) Another one-stage hypospadias operation. Aust N Z J Surg 38:63–65
4. Turner-Warwick RT (1960) A technique of posterior urethroplasty.
J Urol 83:416–419
5. Blandy JP (1980) Urethral stricture. Postgrad Med J 56:383–418 6. Duckett JW Jr (1980) Transverse preputial island flap technique for
repair of severe hypospadias. Urol Clin North Am 7:423–431 7. Quartey JKM (1985) One-stage penile/preputial island flap ureth-
roplasty for urethral stricture. J Urol 134:474–487
8. Burger R, Muller SC, Hohenfellner R (1992) Buccal mucosal graft: a preliminary report. J Urol 147:662–664
9. Wessells H, McAninch JW (1998) Current controversies in ante- rior urethral stricture repair: free-graft versus pedicle skin-flap reconstruction. World J Urol 16:175–180
10. Greenwell TJ, Venn SN, Mundy AR (1998) Changing practice in anterior urethroplasty. BJU Int 83:631–635
11. Barbagli G, Selli C, di Cello V, Mottola A (1996) A one-stage dorsal free-graft urethroplasty for bulbar urethral strictures. B J Urol 78:929–932
12. Andrich DE, Mundy AR (2001) The Barbagli procedure gives the best results for patch urethroplasty of the bulbar urethra. BJU Int 88:385–389
13. Orandi A (1968) One-stage urethroplasty. B J Urol 40:77
14. Venn SN, Mundy AR (1998) Urethroplasty for balanitis xerotica obliterans. B J Urol 81:735–737
