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The
Posterior Tibial Nerve
Posterior Tibial Nerve
The recording electrode is routinely placed over the abductor hallucis
muscle, located one fingerbreadth behind and below the navicular bone.
You can also place it over the abductor digiti quinti muscle, the latter
placement being useful for comparing the medial and lateral plantar nerve
functions. Place the reference electrode over the base of either the great
or little toe.
Stimulate the nerve distally posterior to the medial malleolus at the
ankle. The proximal stimulation point is in the popliteal space, about
a fingerbreadth lateral to midline.
At times, surface stimulation of the nerve in the popliteal space may
be difficult, especially in obese patients. Often you can get a response
if the stimulus voltage and duration are raised to uncomfortable levels.
Often, too, this response has an initial positive deflection and its amplitude
drops by more than 2 mv. It should however remain within 4 mv of the distal
response. You may need to position the patient in several ways before a
response is obtained, often the best one being with the patient prone.
Posterior
Tibial Entrapment, Compression or Injury Sites
The posterior tibial nerve may be involved as part of a sciatic nerve
injury; at the popliteal fossa; in the tarsal tunnel following ankle injury;
and rarely at an anterior opening of the abductor hallucis muscle.
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