What are the symptoms of tarsal tunnel syndrome?
Tarsal tunnel syndrome is an underdiagnosed pathology, it is an ailment that occurs in the foot and is very difficult to diagnose, because we do not have any test sensitive enough to confirm the diagnosis of tarsal tunnel syndrome. For this reason, a great part of the patients that suffer this pathology are diagnosed of plantar fasciitis, without being really a plantar fasciitis, but a compression of the tibial nerve and its branches, that is to say a syndrome of the tarsal tunnel.
The symptoms of tarsal tunnel syndrome are pain in the heel and/or in the plantar region of the feet, causing a burning sensation, paresthesia in the toes, heaviness in the sole of the foot. Prolonged walking or prolonged static standing often exacerbates symptoms.
Occasionally, patients describe a tight band around the foot, and yet, in certain cases, there are no clear neuropathic symptoms associated, simply an irritation of the sole of the foot. Rarely, in chronic and advanced conditions, there is loss of strength and atrophy of the foot muscles.
What are the causes of this pathology?
A specific cause of compression of the tibial nerve and its branches can only be identified in 60-80% of patients. These causes are generally classified as extrinsic, intrinsic or both.
Extrinsic causes include the sequelae of fractures, ankle sprains, overweight, flat feet, valgus foot, among others; intrinsic causes include any injury that causes a decrease in space in the proximal or distal tarsal tunnel such as: osteophytes, hypertrophic retinaculum, or accessory or hypertrophic muscles, venous varicosities, lower limb edema, inflammatory arthropathies, diabetes and iatrogenic causes such as repeated microtrauma that happens in soccer or runners.
Hyperpronation has been postulated as a predisposing factor to the development of idiopathic TTS, being the eversion position in which the greatest pressure is produced within the proximal and distal tarsal tunnel.
How is tarsal tunnel syndrome diagnosed?
One of the main problems in the treatment of tarsal tunnel syndrome (TTS) is the diagnostic difficulty. The examinations and complementary tests used to diagnose nerve entrapment have poor sensitivity and, therefore, there is controversy about the prevalence of the condition. Currently, there is no reliable test available for the diagnosis of STT, so the diagnosis is a correlation between clinical history and examination and complementary tests, such as MRI and EMG.
MRI could have a diagnostic value, but it depends on the expertise of the physician, being able to detect indirect signs of TTS such as plantar muscle atrophy. Electromyographic and nerve conduction studies may show abnormal results and false negatives are frequent.
A newer diagnostic tool is computer-assisted quantitative sensory testing, also known as pressure-specific sensory device or PSSD. This test has shown that the PSSD provides greater sensitivity in the appreciation of peripheral nerve involvement and can confirm an early diagnosis in the progression of TTS. Measurement of proximal and distal tarsal tunnel pressure may be helpful in establishing a diagnosis of nerve compression in the case of idiopathic TTS syndrome.
Currently, the Hoffman-Tinel test is the major indicator of TTS, being positive in more than half of the patients with involvement. Sustained pressure on the nerve can produce proximal irradiation with tingling and numbness and is known as the Valleix phenomenon. It is positive in about one third of cases.
What treatments are currently available?
The treatments currently used as a first option are conservative, which include corticosteroid infiltrations, radiofrequency guided by ultrasound and antineuritic medication.
When the symptoms do not subside, surgery should be performed, which can be done by open surgery, endoscopic surgery or ultrasound-guided surgery.
Ultrasound-guided surgery is currently the most advanced technique to decompress the nerve, since by means of 1 millimeter incisions and the assistance of a high resolution ultrasound scanner we are able to release the nerve. Drs. Alvaro Iborra and Manuel Villanueva have been performing this technique since 2014, with extensive experience in this field, being pioneers in ultrasound-guided surgery, with awards in the American Academy of Orthopaedic Surgeons and multiple international scientific publications.