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Tarsal Tunnel Syndrome

- Tarsal Tunnel Syndrome:
- compression syndrome of the tibial nerve in the tarsal tunnel;
- tarsal tunnel is formed by the flexor retinaculum behind and distal to the medial malleolus;
- inciting causes:
- lipoma, ganglia, or neoplasms within the tarsal tunnel;
- an accessory flexor digitorum longus muscle is a common cause;
- exostosis within the tarsal tunnel;
- hindfoot valgus deformity will potentiate the deformity;
- in the study by Daniels et al 1998, tibial nerve tension was increased by erversion and dorsiflexion of the foot;
- diff dx:
- stress fractures (identified on 45 deg medial oblique view)
- inflammatory arthritides (RA or Reiter's Syndrome)
- plantar fasciitis
- herniated disk
- peripheral neuropathy
- disc herniation;
- clinical findings:
- patients may note pain when the ankle is placed in extremes of dorsiflexion (from nerve tension);
- patients note pain, paresthesias, foot numbness, and in somes cases atropy of foot intrinsics;
- pain will radiate along the plantar side of the foot, sometimes up into the calf;
- positive Tinel sign behind medial malleolus;
- manual compression for 30 sec. may reproduce symptoms;
- consider performing 2 point discrimination test both on medial and lateral sides of the foot (and opposite foot);
- if the 2 point discrimination is increased on one side of the foot, it may indicate which branch of the plantar nerve is compressed;
- in most cases, symptoms will be improved w/ rest;
- can be useful when the operator has experience w/ this condition;
- prolonged distal motor latency;
- terminal latencies of the ADQ (lateral plantar nerve) more than 7.0 msec are abnormal;
- terminal latencies of abductor hallucis (which is innervated by the medial plantar nerve) more than 6.2 msec is abnormal;
- fibrillations in the abductor hallucis;
- in the series by Bailie DS and Kelikian AS (1998), 81% of patients had abnormal EMG studies;
- MRI: may be used to identify ganglia or extrinsic masses and the specific site of compression;
- operative decompression:
- is considered for patients w/ space occupying lesions (there are numerous case reports of neurolemoma involving tibial nerve within  tarsal tunnel);
- concerns have been raised about tarsal tunnel decompressions, noting that the decompression would not alter stretch forces on the nerve (rather this
would have to be managed by stabilization of the foot  in a corrected position;
- the nerve is decompressed from the posterior tibial nerve from its flexor retinaculum to a point past the bifurcation;
- if an anomalous muscle if found with in the tunnel and is thought to be the cause of nerve compression then the muscle should be resected;
- cautions: nerve decompression of the tarsal tunnel may not produce the favorable long term results seen in other nerve decrompression procedures

- Distal Tibial Tarsal Tunnel Syndrome:
- a cause of heel pain arising from compression of the distal branches of the posterior tibial nerve by the deep fascia along the medial border
of the abductor hallucis;
- this can be exacerbated by by hyperpronation, thickening of the plantar fascia, thickening of the deep fascia of the abductor hallucis;
- first branch lateral plantar nerve:
- this nerve supplies the abductor digiti quinti (and possibly it innervates the quatratus plantae and FDB) as well as deep sensory
- nerve runs deep to the deep fascia of the abductor hallucis and then runs laterally and transversely superficial to the quadratus (and
deep to the FHB) on its way to innervate the abductor digiti quinti;
- nerve may be compressed by the superior-deep edge of abductor hallucis fascia & most medial edge of the plantar fascia, and in
addition the nerve may be compressed by medial edge of quadratus;
- the nerve is best exposed by superior retraction of the abductor hallucis, or in some cases, the abductor must be mobilized or
divided inorder to adequately expose (and decompress) the nerve;
- entrapment of the first branch occurs as the nerve changes from vertical to a horizontal direction around the medial plantar aspect
of the heel;
- the calcaneal heel spur lies just plantar to the course of the nerve and may be contributing to nerve compression or irritation;
- pts w/ flat feet are thought to be at risk for this compression;
- the nerve is decompressed by elevating the abductor hallucis and then releasing the deep fascia beneath the abductor and the
contiguous medial plantar fascia;
- medial calcaneal nerve:
- nerve branches that innervate the plantar medial aspect of the heel pass medial (superficial) to the abductor hallucis muscle and are
usually not involved with the entrapment of the first banch;
- some have theorized that a valgus hindfoot predisposes joggers to compression of this nerve branch;
- terminal latencies of abductor hallucis (which is innervated by the medial plantar nerve) more than 6.2 msec is abnormal

- Complications:
- iatrogenic nerve compression:
- as noted by Lau JTC and Daniels TR, a tarsal tunnel release w/ a concomitant pes planus may have the effect of increasing posterior
tibial nerve tension, which may explain the high rate of poor surgical results;
- in the same study, distraction calcaneo-cuboid arthrodesis reduced nerve tension

Treatment of chronic heel pain by surgical release of the first branch of the lateral plantar nerve.

Clinical Results after Tarsal Tunnel Decompression.

Tarsal tunnel syndrome: an electrodiagnostic and surgical correlation.

Magnetic resonance imaging and the evaluation of tarsal tunnel syndrome.

Tarsal tunnel syndrome secondary to neurilemoma of the medial plantar nerve.

Tibial nerve branching in the tarsal tunnel.

Tarsal tunnel syndrome: review of the literature.

Effects of tarsal tunnel release and stabilization procedures on tibial nerve tension in a surgically created pes planus foot.

Tarsal tunnel syndrome: diagnosis, surgical technique, and functional outcome.

The effects of foot position and load on tibial nerve tension.

Outcome of surgical treatment of tarsal tunnel syndrome.

An outcomes analysis of surgical treatment of tarsal tunnel syndrome.

Biomechanical evaluation of two clinical tests for plantar heel pain: the dorsiflexion-eversion test for tarsal tunnel syndrome and the windlass test for plantar fasciitis.

Prognostic ability of Tinel sign in determining outcome for decompression surgery in diabetic and nondiabetic neuropathy.