Review Question - QID 3850

All of the above answers are potential sites of tibial nerve compression in the setting of tarsal tunnel syndrome EXCEPT the medial band of the plantar fascia, which is not a documented cause of tarsal tunnel syndrome.

Tarsal tunnel syndrome may result from either proximal compression of the tibial nerve or from distal compression of any of the terminal branches. As a result pain may be referred to any of the terminal branches distally within the foot or more proximally along the calf. Diagnosis is largely clinical but should be supplemented with MRI or ultrasound to rule out any compressive lesions. The dorsiflexion-eversion test is described, consisting of ankle dorsiflexion, heel eversion, and dorsiflexion of the toes, which should reproduce the characteristic foot pain and/or paresthesias. Electrodiagnostic studies are of questionable utility. Nonsurgical management should always be exhausted first, followed by complete neurolysis should this fail. The tibial nerve runs along the fascia of the tibialis posterior within the deep posterior compartment of the leg. Just proximal to the ankle, it gives off the medial calcaneal nerve, then dives deep to the flexor retinaculum of the tarsal tunnel, where it most often bifurcates into the medial and lateral plantar nerves. These in turn pass through two separate tunnels within and eventually deep to the abductor hallucis, involving both superficial and deep fascial layers.

Pomeroy et al. review the presentation and management of compressive neuropathies of the lower leg. The authors discuss sites of compression and possible etiologies of tarsal tunnel syndrome, most commonly be compression by space-occupying lesions within the tarsal tunnel proper. They conclude that accurate diagnosis of the cause and location of the compression as well as complete release of the tibial nerve and its branches are essential to surgical success. The authors caution however that surgery should only be pursued in select patients with concordant history and exam findings and only after having failed an appropriate course of nonoperative management.

Ahmad et al. performed a literature review highlighting the difficulties in diagnosis of tarsal tunnel syndrome. They note that clinical symptoms may be vague and misleading, and that electrodiagnostic studies are not very sensitive or specific. However prompt diagnosis is important, as early and complete surgical decompression provides the greatest chance of a successful outcome.

Illustrations:
Illustration A depicts the possible sites of compression of the tibial nerve and its branches.

Incorrect Answers:
Answers 1-4: These are all possible sites of tibial nerve entrapment in posterior tarsal tunnel syndrome.