Posterior Tibial Nerve

Introduction

Neuropathic pain is a common type of chronic pain that affects approximately 4.6% of the European population and 17.9% of Canada’s population. The estimated prevalence in the United States is 12.4%. Peripheral nerve stimulation (PNS) is a currently evolving method that is used to treat peripheral neuralgias that are resistant to other therapies. PNS is also used as an alternative to different medical treatments such as opioids. In this context, it can be used to reduce the opioid use, reducing potential addiction problems.

The use of posterior tibial nerve stimulation (PTNS) is one of the most interesting choices we can make when deciding to stimulate a nerve; on one hand, it can be used in cases of tarsal tunnel entrapment, including trauma injuries. On another hand, it can also be used in patients with urologic problems, such as urinary incontinence, hyperactive bladder, and urinary urgency, and even with proctologic problems, such as incontinence and constipation, as well as for chronic pelvic pain. Thus, we can consider it as one of the most promising nerves to target for stimulation.

The US Food and Drug Administration has approved the following indications for PTNS: hyperactive bladder and associated symptoms of urinary frequency, urinary urgency, and urgent incontinence.

Stimulation of the posterior tibial nerve (PTN) improves control of urination. It is believed that the mechanism of action is retrograde stimulation of the lumbosacral nerves (L4–S3) via the PTN located near the medial malleolus. The lumbosacral nerves control the detrusor muscle and the pelvic floor.

Clinical Presentation

When we think about applying PNS to the tibial nerve, two types of patients can be considered: those with pain in the sole of the foot, as well as those with problems in the urologic or proctologic sphere.

When there is damage to the tibial nerve, it is associated with pain in the foot region; pain in the sole of the foot is a common symptom, and the etiology can be difficult to find. The most frequent cause is tibial nerve compression in the tarsal tunnel; however, distal to the tunnel, the posterior tibial nerve gives off three branches that can also be compressed: the lateral and medial plantar branches, as well as the medial calcaneus nerve. Pain, paresthesias, poststatic dyskinesia, and neurologic changes are symptoms of compression. In patients with heel pain of neural origin, the pain usually is characterized as acute, pinching, burning, electric, and located or radiating proximally or distally, and occasionally as a numb pain. In general, the pain worsens during or after activities that involve weightbearing and improves when the weightbearing ends. A common finding in patients with plantar foot pain of neural origin is pain when the patient gets up after resting periods, a phenomenon that is referred to as poststatic dyskinesia. It is recognized as a severe pain in the morning after getting up from bed in a great number of patients with neural plantar heel pain.

Anatomy

The ankle innervation is complex and is determined by the sciatic nerve (L4–S3). The tibial nerve is one of the two terminal branches of the sciatic nerve, which is the largest nerve in the human body. The tibial nerve originates from the spinal nerve roots L4 to S3 and provides motor and sensory innervation to most of the posterior leg and foot. The tibial nerve arrives at the distal part of the leg from the medial side of the Achilles tendon, where it is found behind the posterior tibial artery.

The nerve gives off the calcaneus medial branch (S1–S2) towards the medial aspect of the heel; after that, it divides into two branches in the posterior part of the medial malleolus, at the flexor retinaculum. The medial (L4–L5) and lateral (S1–S2) plantar nerves both travel under the abductor hallucis to innervate each of the toes ( Table 29.1 ).