Anatomic considerations

Vascular supply

Skin vascularization may be direct or indirect. Direct vessels travel along nerve fibers, between muscles and along fascial planes to enter the skin. Indirect vessels arise from named vessels as perforators of the fascia from the underlying muscle. Free flaps, which require microsurgical anastomoses, depend on the direct vascular supply. Peninsular flaps (e.g. advancement flaps) may have a well-defined blood supply or depend upon intrafascial and suprafascial blood flow through the preserved skin bridge. Island flaps (e.g. gracilis flap) require a well-defined vascular pedicle to support the indirect blood supply to the overlying skin. Certain muscles used for flaps have a single dominant vascular pedicle (e.g. epigastric vessels for the rectus abdominis) or one dominant vascular pedicle with several minor ones (e.g. the medial femoral circumflex or femoral artery for the gracilis muscle) (Figures 1 and 2). It may not therefore be possible to identify a distinct blood supply for the gracilis flap. Some surgeons recommend confirming perfusion prior to completion of this flap. Pedicled flaps are also characterized by the ability to convert a nonterminal artery (e.g. the inferior epigastric artery) into a terminal artery. This is due to the blood flow reversal possible in the venae comitantes. The pudendal thigh flap, a peninsular flap, derives its blood supply mostly from the posterior labial vessels and the anastomotic channels involving the medial femoral circumflex and the

Pyramidalis Muscle

Figure 1

Sources of possible vascular pedicles

1 Pyramidalis muscle

2 Intercostal nerve

3 Internal mammary artery

4 Superior epigastric artery

5 Internal oblique muscle

6 Posterior rectus sheath

7 External oblique muscle

8 Arcuate line

9 Inferior epigastric artery

10 Femoral artery obturator arteries. The bulbocavernosus flap is supplied by the external pudendal arteries. Knowledge of the vascular anatomy will allow better planning of the available territories for covering defects.

Nerve supply

No major nerve should be encountered during these reconstructive procedures. Although the gracilis muscle is innervated by a branch of the obturator nerve, it is usually not identified as a distinct structure. As with all surgical procedures, some loss of sensation will be encountered in the operative field. Because

Rectus Abdominis Free Flap

Figure 2

Possible elliptical skin islands reconstructive surgery involves the retention of a large skin island after it is severed from its nerve supply (e.g. the rectus flap), the patient may be more aware of this deficiency than after nonreconstructive surgery. The orientation of the pudendal thigh flap may allow retention of some sensation.

Muscles involved

The rectus abdominis muscle inserts in the pubic tubercle and arises from the sixth, seventh and eighth ribs. It plays a role in protecting the abdominal contents, breathing and defecating, and stabilizes the pelvis during walking. The gracilis muscle arises from the pubic tubercle and inserts onto the medial tibia pes anserinus. It helps to stabilize the knee and laterally rotates the thigh. The bulbocavernosus muscle runs along the underside of the labia minora from the clitoris posteriorly. Loss of these muscles is usually compensated for by the remaining muscles in their functional group so that no significant motor defect remains.

Bony landmarks

A useful landmark in gynecologic reconstructive surgery involves the identification of the gracilis flap. A line drawn from the pubic symphysis to the medial epicondyle should approximate the anterior border of the gracilis muscle.

0 0

Post a comment