Abstract
Posterior tarsal tunnel syndrome is caused by compression of the posterior tibial nerve as it passes through the posterior tarsal tunnel. The posterior tarsal tunnel is made up of the flexor retinaculum, the bones of the ankle, and the laciniate ligament. In addition to the posterior tibial nerve, the tunnel contains the posterior tibial artery and certain flexor tendons that are subject to tenosynovitis. The most common cause of compression of the posterior tibial nerve at this location is trauma to the ankle, including fracture, dislocation, and crush injury. Thrombophlebitis involving the posterior tibial artery has also been implicated in the development of posterior tarsal tunnel syndrome as has the wearing of tight high-heeled shoes with straps. Tumors of the posterior tibial nerve can also cause symptoms in the distribution of the posterior tibial nerve. Patients with rheumatoid arthritis have a higher incidence of posterior tarsal tunnel syndrome than does the general population. Posterior tarsal tunnel syndrome is much more common than anterior tarsal tunnel syndrome.
Keywords
anterior tarsal tunnel, posterior tarsal tunnel, entrapment neuropathy, electormyography, nerve conduction testing, sports injury, thrombophlebitis, Tinel sign, ultrasound guided injection, diagnostic sonography
ICD-10 CODE G57.50
The Clinical Syndrome
Posterior tarsal tunnel syndrome is caused by compression of the posterior tibial nerve as it passes through the posterior tarsal tunnel. The posterior tarsal tunnel is made up of the flexor retinaculum, the bones of the ankle, and the lacunate ligament. In addition to the posterior tibial nerve, the tunnel contains the posterior tibial artery and certain flexor tendons that are subject to tenosynovitis. The most common cause of compression of the posterior tibial nerve at this location is trauma to the ankle, including fracture, dislocation, and crush injury. Thrombophlebitis involving the posterior tibial artery has also been implicated in the development of posterior tarsal tunnel syndrome as has the wearing of tight high-heeled shoes with straps. Tumors of the posterior tibial nerve can also cause symptoms in the distribution of the posterior tibial nerve ( Fig. 125.1 ). Patients with rheumatoid arthritis have a higher incidence of posterior tarsal tunnel syndrome than does the general population. Posterior tarsal tunnel syndrome is much more common than anterior tarsal tunnel syndrome.
Signs and Symptoms
Posterior tarsal tunnel syndrome manifests in a manner analogous to carpal tunnel syndrome. Patients complain of pain, numbness, and paresthesias in the sole of the foot; these symptoms may also radiate proximal to the entrapment, into the medial ankle ( Fig. 125.2 ). Patients may note weakness of the toe flexors and instability of the foot resulting from weakness of the lumbrical muscles. Nighttime foot pain analogous to that of carpal tunnel syndrome is often present.
Physical findings include tenderness over the posterior tibial nerve at the medial malleolus. A positive Tinel sign just below and behind the medial malleolus over the posterior tibial nerve is usually present ( Fig. 125.3 ). Active inversion of the ankle often reproduces the symptoms of posterior tarsal tunnel syndromes. Medial and lateral plantar divisions of the posterior tibial nerve provide motor innervation to the intrinsic muscles of the foot; thus, weakness of the flexor digitorum brevis and the lumbrical muscles may be present if these branches of the nerve are affected.
Testing
Electromyography (EMG) can distinguish lumbar radiculopathy and diabetic polyneuropathy from posterior tarsal tunnel syndrome. Plain radiographs, magnetic resonance imaging (MRI), and ultrasound imaging are indicated for all patients who present with posterior tarsal tunnel syndrome, to rule out occult bony disease ( Fig. 125.4 ). MRI and ultrasound imaging of the ankle and foot are also indicated if joint instability or a space-occupying lesion is suspected ( Figs. 125.5 and 125.6 ). Based on the patient’s clinical presentation, additional testing may be warranted, including a complete blood count, uric acid level, erythrocyte sedimentation rate, and antinuclear antibody testing. The injection technique described later serves as both a diagnostic and a therapeutic maneuver.
