Simple in Theory, Complex in Execution

         

 

 

**Before reading further, please visit the “Before & After- Reconstructive” gallery located elsewhere on this website.

 

The entity we will be discussing here is called a Radial Forearm Flap so let me start with some important definitions. The word “flap”, as it is used in medicine, has the same meaning as in ordinary English conversation. It is a thin piece of something usually attached at one end. e.g. the flaps on an airplane wing.  In plastic surgery, it is a piece of tissue that has been partially detached from its original location and moved some distance to fill a surgical defect. There is also an entity known as a “free flap” which I will describe shortly but this is something of a misnomer.

The specific procedure utilized here involved harvesting forearm tissue in the form of an “island flap” (see below) to fill the defect in the face created when the burned skin was excised. It is a fairly common operation for a surgeon who does facial reconstruction often. I have used it 4 or 5 times in my career. 

 

It’s too bad surgeons can’t just cut the piece they need from the forearm and sew it in to the face. It would die and rot away if we did that. We must provide the tissue with a blood supply. The blood carries cells containing hemoglobin and it is this hemoglobin that carries the oxygen necessary for the graft to survive.  

The blood supply can be preserved from the donor location in the forearm in which case it is called an “island flap” or the vessels can be cut loose and anastamosed or attached to vessels in the recipient area. The latter is the so-called “free flap” I referred to above. It requires a microscope because the vessels are very small. It’s equivalent to sewing two pieces of hollow spaghetti together end to end without any leaking and without impinging on the lumen and therefore constricting the blood flow. Constricting the blood flow leads to all sorts of problems, chief of which is flap necrosis.  I won’t talk about free flaps any more here because I don’t have a microscope.

So I must keep the forearm blood supply attached. Of course this requires that I sew the patient’s arm to her face. This is painful for the doctor and torture for the patient. If you don’t believe me, tape your right forearm to your left cheek for 24 hours. If it comes loose or even stretches a little, you’ve just jerked the artery and vein loose from your forearm, blood is going everywhere and all is lost. Now you have a rotten graft on your face which will need to be removed and discarded and that ugly split thickness skin graft on your forearm and that burning sensation in your thigh are all for naught, let alone that huge hole in your face that will still need covering. NOW, imagine keeping your forearm in that position for 3 – 4 weeks, knowing that any movement during that time means “the end”.

The  Septocutaneous Radial Forearm Flap

The Chinese came up with this flap in 1978. The blood supply I have been referring to above is via the septocutaneous perforating branches of the radial artery, hence the name.  The radial artery is the artery that is used to take someone’s pulse as it crosses the wrist bones in the anterior forearm. The skin flap is designed on the inside (we say anterior) forearm (see the image below) and can extend from the wrist crease to the elbow. This is quite convenient. It means that we can fill virtually any defect of the face.

It’s not simply a matter of raising the flap and its artery though. First you have to confirm that the artery on the other side of the wrist, the ulnar artery, will be able to supply the hand after you tie off the radial. The arteries ordinarily anastamose or meet at the superficial palmar arch which supplies the fingers and if it is the radial, not the ulnar, that is supplying the lion’s share of the blood, you can’t cut it or the hand will get necrotic. What a disaster! Always make sure the ulnar is patent and can supply the palmar arch on its own.

What about venous drainage and what about sensation to the skin of the flap? For venous drainage, bring the cephalic vein along with the flap. If it fails, you can use medical leeches to suck the blood through the skin. Yes, leeches: it sounds like a gross science fiction movie but it’s a last resort that works. As far as sensation goes, the flap can be harvested with the superficial radial nerve or the medial or lateral antebrachial cutaneous nerves.

Here’s a photo I lifted from the internet showing the flap. (Sorry, I don’t have the pre-op design photo of our patient. I’ll get a post-op photo of her forearm the next time she comes in ). UA stands for ulnar artery and RA stands for radial artery. It looks like they’re preparing to use it retrograde. We used it antegrade but that’s not important here. The principles are the same. The defect created by the removal of tissue is easily covered by a split thickness skin graft taken from the thigh. One pearl of wisdom: when grafting onto tendon, make sure you leave some paratenon or the graft won’t take; same with periosteum if you’re down to bone.

 

I want the proximal end of the flap to go to the mouth in our patient- otherwise it won’t fit- so the part shown near her wrist will be next to her ear after it is flipped around. What happens to arteries and more-so veins when they are twisted 180 degrees? They kink! That constricts blood flow and threatens the viability of the flap.  So here’s another pearl: Dissect the radial artery all the way back to its source at the brachial so the affect of twisting is dissipated over a greater length. Someday, I will put on my M.I.T. physics cap and write an equation that describes this effect quantitatively but for now let’s forge ahead.

 

Where is Leonardo Da Vinci When You Need Him?

You don't have to make the flap a rectangle as in the picture but do make it slightly greater in all dimensions than the defect. You DON’T want to sew it in too tightly, to stretch it in any way, because this will compromise the already-tenuous blood supply, especially distally. On the other hand, you don’t want to make the flap too large or it won’t look good. It’ll be too bulky. Here is where you have to summon all of your artistic ability tempered by a healthy dose of conservatism.

Sew it in with the knowledge that you can trim it later if need be.

 

All Dressed Up and Nowhere to Go

Patent vessels beget success. What good is a pretty insert that dies? By the way, which forearm are you going to use to fill a left face defect? Would using the left forearm injure her left shoulder joint over the course of four weeks? Would using her right arm block her mouth so she wouldn't be able to eat solid food?

 

The End Game

 

When will the flap be nourished adequately by nascent vessels (so you can cut the arm loose) and how will you know it is viable? I recommend clamping the artery at three weeks and looking at the flap. If it turns gray or bluish, unclamp it immediately and wait another week. Clamping is good because it stresses the flap in the same way that “delay” improves the viability of all flaps, but exercise caution. Don’t leave it clamped too long and whatever you do, don’t cut the artery until the flap demonstrates that it can survive on its own.

YOU HAVE ONLY ONE CHANCE TO CUT THE ARTERIAL SUPPLY AND YOU CAN’T BE WRONG.

3 Responses so far.

  1. casey says:

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    tnx for info!!