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Let's talk about the foot and ankle entrapment

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neuropathies and specifically, let's focus

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on the anatomy of the nerves of the foot

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in the anterior extensor compartment.

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First, the most important is the deep peroneal

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nerve depicted as our yellow structure.

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It's located lateral to the anterior

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tibial artery or the dorsalis pedis pulse.

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About 1.3cm above the ankle,

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the nerve divides into two terminal

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branches, one lateral and one medial.

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The lateral one, as you'll see, will innervate

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the sinus tarsi in the lateral ankle.

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The medial one is the more important one and

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considered in anterior tarsal tunnel syndrome.

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The lateral one passes deep

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to the extensor retinaculum.

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There's the extensor.

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And also deep to the extensor digitorum brevis and

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extensor hallucis muscle.

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It provides motor innervation and divides

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into several thin dorsal branches, which

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are known as dorsal interosseous nerves.

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The lateral branch also provides

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sensory innervation to the ankle

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and, as stated, the sinus tarsi.

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Now, the medial branch, the more important of

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the two, as we said, travels with the dorsalis

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pedis and then as you get closer to the big toe,

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it starts to assume a more intertoe position

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between the web space of digit 1 and digit 2.

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It also courses in very close

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proximity to the extensor hallucis.

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And, in fact, it crosses over the

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extensor hallucis tendon, or, shall I

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say, the extensor hallucis tendon crosses

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over top of the nerve right there.

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And that's an important landmark.

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The deep peroneal nerve may become

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entrapped between the retinacula up higher,

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or it may become entrapped due to compression

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by osteophytes that project off the bone.

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And when it is entrapped, this is known

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as anterior tarsal tunnel syndrome.

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Now the reason that this is so important

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is because this produces burning between

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the base of the big toe and the second toe.

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And it's often misconstrued

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for disease coming from the lumbar spine,

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specifically the lower lumbar spine.

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And patients have had disc resections and spinal

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fusions when in fact what they really had was a

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peripheral neuropathy caused by entrapment of the

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deep peroneal nerve from either osteophytes or

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injuries or scars of the extensor retinaculum.

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This nerve may also become entrapped by

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tight fitting shoes, or tight fitting boots.

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I used to see it a lot in people that do a

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lot of sit ups, that put their, their feet

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on the edge of a bar to pull themselves up.

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And this constant compression of

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rubbing during the sit up activity may

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produce irritation of this structure.

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You can also see entrapment at this crossover

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point between the extensor digitorum brevis and

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extensor hallucis brevis and the nerve itself.

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Especially if there's an abnormality or an

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injury to this tendon with focal scarring.

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And sometimes you can even get a perineural

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fibrous reaction or a focal sort of pseudoneuroma

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forming around the deep peroneal nerve.

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So, the deep peroneal nerve,

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we'll show you on MRI.

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This is known as anterior tarsal tunnel syndrome.

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The most important aspect of it is the

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burning that occurs between the first and

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second toe, which may often be misconstrued

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as disease coming from the spine.

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Disease from the spine produces

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numbness, it may produce weakness,

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it may produce abnormal reflexes.

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Not so for anterior tarsal tunnel syndrome.

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It's simulator.