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Practical Urology: EssEntial PrinciPlEs and PracticE

the use of a vacuum-assisted closure (VAC)

surgical practice. The approach to surgical

device.VAC dressings use a sponge with vacuum

incision and closure of wound defects should

suction underneath an occlusive dressing to

be via application of the simplest techniques

remove exudates from the wound and into the

first termed “the reconstructive ladder”.

sponge. VAC dressings reduce edema and

Primary closure and healing by secondary

increase local perfusion as well as decrease bac-

intention are straightforward concepts and

terial load, facilitating earlier wound closure.11

this chapter focuses on the principles of tissue

transfer. Tissue transfer refers to the move-

Remodeling

ment of tissue for reconstruction, which in

the field of urology, chiefly refers to the use

Three to four weeks following the initial injury,

of grafts and

local flaps. Innovations and

improvements

in tissue transfer techniques,

collagen synthesis balances collagen destruc-

tissue handling, and tissue engineering have

tion resulting in a steady level of collagen within

expanded the repertoire of the genitourinary

the wound.14 This collagen equilibrium defines

reconstructive surgeon.

the start of the remodeling phase of wound

The use of tissue transfer for reconstruction

healing. Collagen makes up 25% of all proteins

requires detailed knowledge of the anatomy

throughout the body and more than 50% of the

of both the donor and the recipient sites as well

protein found in scar tissue. Type III collagen

as of the principles that will allow that tissue

predominates early in the remodeling phase

to survive once it is transferred. Earlier in

but as collagen matures, type III collagen is

the chapter, the two layers of the skin were

replaced by type I. The rate of collagen synthe-

described (Fig. 19.1). The two layers of the der-

sis increases rapidly and continues at an accel-

mis were described, a superficial layer, the

erated rate for 2–4 weeks. Although collagen

adventitial (or periadnexal) dermis, and a deep

content is maximal, the strength of the wound

layer, the reticular dermis. For genitourinary

can be further increased by polarization of the

reconstruction,

skin without adnexal struc-

collagen fibrils from the preliminary random

tures is often used; thus, the papillary dermis is

configuration. At 6 weeks after the initial injury,

synonymous with the adventitial dermis. Other

the wound has reached 80–90% of its eventual

tissues commonly utilized for genitourinary

strength. At this point, the activity of the matrix

reconstruction

include bladder and buccal

metalloproteinases (e.g.,

collagenase)

is bal-

mucosa. The bladder epithelium is the superfi-

anced by the inhibition of tissue inhibitor met-

cial layer of the bladder (Fig. 19.2). The deep

alloproteinases

(TIMPs)

in

normal

wound

layer of the bladder, the lamina propria, is com-

healing. The number of capillaries and fibro-

posed of superficial and deep layers. The oral

blasts is decreased thereby

reducing the red

mucosa (buccal mucosa) is the superficial layer

color of the wound.16

of much of the oral cavity, which also has a

Surgical incisions achieve moderate strength

deeper layer termed the lamina propria, again

by 3 weeks postoperatively. To increase the

with superficial and deep layers (Fig. 19.3).18

strength of these wounds, sutures should be

placed in high collagen-containing structures

(e.g., dermis, muscular fascia, Scarpa’s

fascia,

Tissue Characteristics

etc.). Suture for abdominal fascia should be able

to hold tension for 6 weeks to gain 50% of its

Inherent in the use of tissue is a firm under-

eventual strength. The choice of suture is deter-

standing of tissue characteristics. These include

mined by the strength of the layer and the time

extensibility, tissue tension, and the viscoelastic

needed for suture strength to be replaced by

properties. Extensibility is the property of the

wound strength.16

tissue that allows it to be stretched. This is dif-

ferent from compliance, which is the ability of

Principles of Plastic Surgery

tissue to be stretched without increasing tissue

tension. As mentioned earlier, tissue is mostly a

collagen-rich elastin matrix “floating in”

The principles of plastic surgery, and thereby

mucosal polysaccharide. Extensibility is related

wound closure,

have obvious relevance to

to the distance that the collagen fibers can be