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Starting off with our first set of cases.

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So we have a CTA runoff and its

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variants. Now, typically, we've seen

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that the common iliac artery, it bifurcates into the external and the

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internal iliac artery, and then really it's the external iliac artery

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that then continues as the common femoral and superficial artery that

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provides all of the blood flow to the lower extremity.

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There are branching variations of pelvic inflow

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vessels, an aberrant embryologic regression that occasionally results

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in variant anatomy in the thigh and runoff, and one of the more common

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ones is persistent sciatic artery, which is a rarely encountered

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variant in the thigh, and it occurs as a continuation of the

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internal iliac artery down via the greater

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sciatic foramen, often has a tortuous course deep to the gluteus

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muscles, and then along the adductor magnus, all along the

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thigh and then into the popliteal fossa.

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It's a rare anomaly wherein there's persistence of this axial limb artery,

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and it serves as the dominant supply, especially

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when the ipsilateral superficial femoral artery may be

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correspondingly small. So while rare,

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sometimes it might be the dominant supply of that artery.

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There are very many types, which is easily searchable, and you don't

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necessarily need to know all of them.

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But just know that there are types, and we'll go over in our case what this

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would look like.

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The second variant that we're going to be discussing is popliteal

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artery branching patterns. This is important because one of the

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common indications for a lower extremity angiogram runoff

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is to assess for fibular free flap.

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Mandibular reconstructions is often performed by these free flaps and

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provides the benefit of bone and soft tissue from a single donor site, and

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having a pre-operative CT is helpful in assessing the anatomic

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variant branching patterns and is of interest to surgeons.

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The most common branching pattern of the popliteal artery is when the popliteal

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artery divides and gives off the anterior tibial artery, continues

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as the tibial peroneal trunk, and then divides into the

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peroneal artery and then the posterior tibial artery.

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In general, for the fibular free flaps,

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the CT is helpful when there's anatomic variation, such as a

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congenitally hypoplastic or absent anterior or posterior

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tibial arteries, which can occur in up to 3% of the population.

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And then the predominant plantar supply would come in those settings

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from just the peroneal artery. And that becomes a problem

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because it would preclude harvesting of the peroneal artery in conjunction with the

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fibula.

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There are many different types of branching pattern.

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These are imaging depicting type one through type four.

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We've gone over how type Ia is really the most common branching

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pattern.

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Type III is which is clinically significant.

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So in IIIa and IIIb,

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you respectively have hypoplasia of either the posterior tibial

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artery, in which case the dominant supply, if

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one did do a fibular free flap to the arteries, would

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just be the anterior tibial artery, as opposed to in IIIb, where

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the anterior tibial artery is hypoplastic.

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So if you did do a free flap using the peroneal artery here,

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the only dominant supply remaining to the foot would be the posterior tibial

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artery. Type IIIC is the one which would be a

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contraindication for using a fibular free flap because here, both the

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anterior and the posterior tibial arteries are hypoplastic, and

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so the peroneal artery becomes the dominant supply to the

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distal limb, and obviously that would not be ideal.