- 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;
-
EMG
- 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 DS Bailie MD and AS Kelikian 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 innervation;
- 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 JTC Lau and TR Daniels, 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. PE Kaplan et al. JBJS-Am. Vol 63. 1981. p 96-99.
Magnetic resonance imaging and the evaluation of tarsal tunnel syndrome. C. Frey. Foot Ankle. Vol 14. 1993. p 159-164.
Tarsal tunnel syndrome secondary to neurilemoma of the medial plantar nerve. J. Menon et al. JBJS. Vol 62-A. 1980. p 301-303.
Tibial nerve branching in the tarsal tunnel. PE Havel et al. Foot Ankle Int. Vol 9. 1988 p 117-119.
Tarsal tunnel syndrome: Review of the lterature. WR Cimino. Foot Ankle. Vol 11. p 47-52.
Effects of tarsal tunnel release and stabilization procedures on tibial nerve tension in a surgically created pes planus foot.
JTC Lau and TR Daniels. Foot and Ankle Internation. Vol 19. No 11. Nov 1998. p 770.
Tarsal tunnel syndrome: diagnosis, surgical technique, and functional outcome. DS Bailie MD et al. Vol 19 No 2. Feb 1998. p 65.
The effects of foot position and load on tibial nerve tension. TR Daniels et al. Foot and Ankle. Vol 19. No 2. Feb 1998. p 73.
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
