Penile Circular Fasciocutaneous Flaps for Complex Anterior Urethral Strictures K.J

18 Penile Circular Fasciocutaneous Flaps for Complex Anterior Urethral Strictures K.J. Carney, J.W. McAninch 18.1 Penile Fascial Anatomy – 146 18.2 Flap Anatomy – 148 18.3 Patient Selection – 148 18.4 Preoperative Preparation – 148 18.5 Patient Positioning – 148 18.6 Flap Harvest – 149 18.7 Stricture Exposure – 150 18.8 Anastomosis – 151 18.9 Postoperative Care – 152 References – 152 146 Chapter 18 · Penile Circular Fasciocutaneous Flaps for Complex Anterior Urethral Strictures Surgical reconstruction of complex anterior urethral stric- Buck’s fascia is a well-defined fascial layer that is close- tures, 2.5–6 cm long, frequently requires tissue-transfer ly adherent to the tunica albuginea. Despite this intimate techniques [1–8]. The most successful are full-thickness association, a definite plane of cleavage exists between the free grafts (genital skin, bladder mucosa, or buccal muco- two, permitting separation and mobilization. Buck’s fascia sa) or pedicle-based flaps that carry a skin island. Of acts as the supporting layer, providing the foundation the latter, the penile circular fasciocutaneous flap, first for the circular fasciocutaneous penile flap. Dorsally, the described by McAninch in 1993 [9], produces excel- deep dorsal vein, dorsal arteries, and dorsal nerves lie in a lent cosmetic and functional results [10]. It is ideal for groove just deep to the superficial lamina of Buck’s fascia. reconstruction of the distal (pendulous) urethra, where The circumflex vessels branch from the dorsal vasculature the decreased substance of the corpus spongiosum may and lie just deep to Buck’s fascia over the lateral aspect jeopardize graft viability. of the penile shaft. Ventrally and dorsally, Buck’s fascia A circumferential island of hairless distal foreskin (or separates into superficial and deep lamellae that diverge loose penile skin in the circumcised patient) is mobili- to surround the corpus spongiosum and neurovascular zed on its vascular pedicle. The flap reliably provides a structures in envelope fashion. Only the superficial lamel- skin island approximately 13–15 cm long. We have not la is elevated with the fasciocutaneous flap. encountered any cases in which the donor site could not The superficial dartos fascia is a thin, membranous be closed primarily, even in circumcised patients. layer of loose subdermal tissue devoid of fat, which lies immediately beneath the skin. It is of utmost importance to preserve this layer, which must be reflected with the 18.1 Penile Fascial Anatomy penile skin to preserve the delicate subdermal vascular plexus and prevent subsequent skin necrosis. For proper surgical development of fasciocutaneous peni- Deep to the dartos fascia and superficial to Buck’s le flaps, a thorough knowledge of penile anatomy and fascia lies the tunica dartos. This layer of areolar tissue the relationships of the penile fasciae is critical (see moves freely over Buck’s fascia, is devoid of fat, and is ⊡ Fig. 18.1). Anatomically, the corpora cavernosa and cor- continuous with the membranous layer (Scarpa’s fascia) of pus spongiosum are invested by both a deep fascial layer the anterior abdominal wall fascia, the dartos tunic of the (classically referred to as Buck’s fascia) and a superficial scrotum, and Colles’ fascia of the perineum. A rich supply layer of loose areolar tissue known as the dartos fascia. of superficial blood vessels, nerves, and lymphatics runs The term »fasciocutaneous flap« refers to the use of Buck’s within the tunica dartos fascia. This is best perceived as a fascia as the primary supporting fascia of the tunica conduit containing the vascular pedicle [11]. dartos vascular pedicle as it passes to the island of penile Quartey has described the microcirculation of the skin [9]. penile skin and its relevance to reconstructive surgery of the genital tract [5, 12]. Briefly, the arterial blood supply is derived from the superficial (superior) and deep (inferior) external pudendal arteries, which are medial branches arising from the femoral artery. These arteries descend Skin Island inferiorly and enter the base of the penis as the dorsolateral and ventrolateral axial penile arteries to form an arterial Tunica Dartos network within the tunica dartos fascia (⊡ Fig. 18.2). Bran- (flap pedicle) ches from the axial penile arteries then pass superficially Buck’s Fascia: Superficial to form the subdermal plexus, which nourishes the penile lamella Deep skin (⊡ Fig. 18.3). Along the penile shaft, the connections Deep lamella Dorsal between the subcutaneous and subdermal arterial plexuses Vein are so fine that the skin and dartos fascia can usually be Dorsal Artery dissected off the tunica dartos with little bleeding. Dorsal Nerve The venous drainage of the penile skin is highly vari- Exposed able. In general, venous blood from the penile skin drains Tunica Albuginea into a subdermal venous plexus that in turn empties into 18 several tributaries at the penile base (⊡ Fig. 18.4). The deep and superficial (subcutaneous) dorsal veins origi- Buck’s Fascia: nate from the retrobalanic venous plexus, which lies in a Deep lamella Superficial lamella hollow posterior to the glans penis and distal to the ter- mination of the corpora cavernosa (⊡ Fig. 18.5). Usually ⊡ Fig. 18.1. Anatomy of CFF. Buck’s fascia is the transporting fascia for no large connections exist between the subdermal venous the island pedicle. (From [19, p. 47]) plexus and the subcutaneous veins. 147 18 18.1 · Penile Fascial Anatomy Superficial external Superficial external pudendal vein pudendal artery Femoral artery, vein Deep external pudendal artery Saphenous vein Ventrolateral branch artery Dorsolateral branch artery ⊡ Fig. 18.2. Blood circulation of the penile skin. Axial Subdermal Dorsal Cutaneous Preputial vein Deep dorsal Superficial dorsal Perforating median vein branch penile arterial artery branch median vein artery plexus artery Preputial Retrobalanic artery venous plexus Fascia Fascia penis penis (Bucks (Bucks fascia) fascia) ⊡ Fig. 18.3. Axial penile arteries from the subdermal plexus to nourish ⊡ Fig. 18.4. The venous drainage of the penile skin: superficial dorsal the penile skin medium vein arising directly from the deep dorsal median vein External pudendal Venae Dorsolateral axial vein comitantes penile artery Femoral artery Femoral vein Long saphenous vein Ventrolateral axial penile artery Subdermal venous plexus Tributary vein Deep external ⊡ pudendal artery from subdermal Fig. 18.5. Superficial venous drai- plexus nage of the penis and penile skin 148 Chapter 18 · Penile Circular Fasciocutaneous Flaps for Complex Anterior Urethral Strictures 18.2 Flap Anatomy The mechanics of flap elevation and transfer entail getting the flap to the recipient site with its blood supply The following principles must be borne in mind: (a) intact. As noted above, the fascia is the flap and the skin morbidity and coverage of the donor site; (c) flap vascu- island is merely a passenger. This is an important concept larity; (c) physical characteristics of the flap; and (d) the because fascial flaps with skin islands can endure some mechanics of flap elevation and transfer to the recipient twisting without vascular compromise, allowing them site [11]. to be oriented in many different directions at the reci- For circular fasciocutaneous penile flaps, the donor pient site. site is the distal penile shaft (or foreskin in uncircumcised All the above criteria are met by the circular fascio- patients). In this location, the skin is highly elastic, richly cutaneous penile flap. It reliably provides adequate length vascularized, flexible, and devoid of hair. Nearly all pati- (usually 13–15 cm) of hairless genital skin that can be ents, including those circumcised, have adequate preputi- used throughout the entire anterior urethra. The abundant al redundancy to permit circumferential flap harvesting vascularity of the tunica dartos fascia allows the skin island up to 2.5 cm wide without compromising primary closure to be reliably tailored and oriented at the recipient site, or functional results. without compromising vascularity. The skin island can be Flap vascularity is random or axial: a random flap has used as a single unit for long complex strictures, or divided no identifiable vessel at its base, and its survival depends and applied in two separate areas for multiple strictures. on the dermal and intradermal plexuses and length-to- width ratio [13]; axial flaps have an identifiable vessel at their base and, therefore, a well-defined and reproducible 18.3 Patient Selection vascular territory (⊡ Fig. 18.6). Genital skin flaps are axial. The identifiable vessel (the axial penile artery) is located Successful outcome begins with appropriate patient selec- within the tunica dartos fascia, which acts as a conduit tion. Numerous factors must be considered: patient age, and contains the vascular pedicle. However, one should stricture location and length, degree of spongiofibrosis, not visualize the vascularity of genital fasciocutaneous prior urethroplasty, the presence of penile skin diseases flaps as a single axial vessel, but rather as a blood supply such as balanitis xerotica obliterans, presence or absence of based on an axial vessel that includes immediate, wide foreskin, and distribution of hair along the penile shaft. arborizations [14]. As the blood supply is located within the tunica dartos, this constitutes the flap and the over- lying skin is best referred to as a skin island. Secondary 18.4 Preoperative Preparation perforator vessels are present that supply flow to the skin island (⊡ Fig. 18.3). In summary, the circular fasciocuta- Stricture length and characteristics should be well deli- neous penile flap is an axial flap that carries a skin island, neated. In addition to preoperative retrograde urethro- not an island flap. graphy and voiding cystourethrography, we have found Desirable physical characteristics for genital flaps used preoperative sonourethrography to be useful for precise in anterior urethral reconstruction include thin, non- determination of stricture length and degree of spongio- hirsute tissue that is easily tailored, as redundancy can fibrosis [15]. lead to the formation of diverticula.

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