Posterior tarsal tunnel syndrome

The posterior tarsal tunnel syndrome, on the other hand, affects the tibial nerve and manifests itself at the inner ankle region. The N. tibialis, the tibial part of the N. ischiadicus, runs in the depth of the calf muscles, the deep flexor box, down to the foot. There, it runs along the inside of the ankle through the medial or posterior tarsal tunnel (=canalis malleolaris) to the sole of the foot.

During the passage through the tarsal tunnel, the tibial nerve is separated into two nerve branches, the lateral and medial plantar nerves. The passage through the tarsal tunnel represents a relevant narrowing, so that a nerve bottleneck syndrome of the tibial nerve is very likely. The posterior tarsal tunnel syndrome also generally occurs more frequently than the anterior tarsal tunnel syndrome.

The anatomical constriction is caused by the compact location of various structures. The retinaculum musculi flexorum, a ligament-like structure between the medial calcaneus and the inner ankle, should be emphasized. As in anterior tarsal tunnel syndrome, injuries, fractures, a ganglion, metabolic disorders (diabetes mellitus, gout, hypothyroidism, etc.)

or tendosynovitis can trigger a space-occupying process that leads to nerve compression. Another risk factor for posterior tarsal tunnel syndrome is the mechanical overload caused by long jogging (“Joggers Foot”).Decisive for the diagnosis is primarily the information provided by the patient during the anamnesis (questioning by the doctor) and the clinical examination. During this examination there is often a pressure pain behind the affected inner ankle, and the Hoffmann-Tinel sign is often positive.

In order to check this sign, the examiner taps the nerve pathways and may cause the patient to experience electrifying pain in the painful area. Electrophysiological methods can be used to measure the nerve conduction velocity of the tibial nerve, which is reduced in this area in tarsal tunnel syndrome. A test of sweat secretion on the sole of the foot using the ninhydrin test can also be informative, as this is often reduced in tarsal tunnel syndrome.

MRI (magnetic resonance imaging) has the decisive advantage of being able to depict soft tissue, such as ligaments and cartilage, very well. This is particularly useful in diagnostics of the ankle joint, where torn ligaments or overstretching and inflammation are particularly common. Magnetic resonance imaging is based on the movement of atoms and since our body is largely made up of water molecules, the movement of these molecules is mainly used for imaging. This also explains why the lungs or bones are not particularly well visible in MRI. There are not many water molecules in these tissues.