Pretest

I. Core Knowledge^1,2

1. Etiology^1,2-compression of the posterior tibial nerve beneath the retinacular tissues that comprise the tarsal tunnel
1. Posterior tibial nerve and tendons of the long toe flexors [flexor hallucis longus (FHL) and flexor digitorum longus (FDL)] and posterior tibialis
2. Anatomy
1. Superficial-flexor retinaculum covers the tarsal tunnel
2. Deep-medial surface of talus, sustentaculum tali, medial calcaneal wall
3. Superior-deep fascia of the leg
4. Inferior-abductor hallucis muscle
2. Causes^1,2-entities that might occupy the space where the nerve is and compress it
1. Tendon sheath or subtalar ganglia
2. Inflammatory synovitis
3. Engorged veins
4. Schwannomas
5. Lipomas
6. Perineural fibrosis secondary to trauma
7. Accessory muscles
8. Fixed hindfoot valgus
3. Presentation²
1. Burning sensation of the plantar aspect of the foot
2. Sharp pain or paresthesias on the plantar aspect of the foot
3. Prolonged walking or standing can accentuate the symptoms
4. Night pain
4. Physical examination
1. Compression of the tarsal tunnel reproduces the pain
2. Tinel's sign may be present
3. May have pain on palpation-proximal and distal to the tarsal tunnel
5. Electromyogram (EMG) studies-very controversial, there may or may not be abnormal findings in 10% to 50%
1. Standard motor nerve latencies
1. Medial plantar nerve-3.8 seconds
2. Lateral plantar nerve-3.9 seconds
2. Changes greater than 2 standard deviations are considered pathologic
3. Standard sensory latencies
1. Medial plantar nerve-6.4 ms, abnormal 6.8 ms
6. Magnetic Resonance Imaging (MRI)-MRI is useful for detecting space-occupying lesions
7. Conservative management
1. Physical Therapy
2. Steroid Injections
3. Orthotics
8. Surgical management
1. Release of the posterior tibial nerve and all sites of potential compression
2. Release of
1. Deep fascia proximal to the tarsal tunnel
2. Flexor retinaculum
3. Fascia over the abductor muscle
3. Removal of any compressing structures
9. Results-45% to 80% of patients get good to excellent results; patients with space-occupying lesions tend to have the best results.

References

1. Richardson E. Disorders of the foot and ankle. In: Miller E, ed. Review of Orthopaedics. 4th ed. Philadelphia, Pa: Saunders; 2004:323-325.
2. Haddad S. Compressive neuropathies of the foot and ankle. In: Myerson M, ed. Foot and Ankle Disorders. Philadelphia, Pa: Saunders; 2000:825-830.