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Tarsal tunnel syndrome

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Description

 

Tarsal tunnel syndrome (TTS) refers , the lower extremity analog of the far more common carpal tunnel syndrome in the wrist, is a condition that causes pain in the foot due to compression of the posterior tibial nerve in with the tarsal tunnel. This can be due to many etiologies, including masses, trauma, and peripheral neuropathies. Tenderness of the tarsal tunnel, shooting pain, numbness, and tingling or burning sensations in the foot are common signs of TTS.The tarsal tunnel is located in the ankle behind the medial malleolus, superficial to the bones (calcaneus and talus) and covered by the flexor retinaculum.  When the posterior tibial nerve is compressed, presenting symptoms include pain, numbness and paresthesias. Tarsal tunnel syndrome can caused by space occupying lesions (such as a ganglion cyst); it may also be caused by deformities of the foot and ankle that decrease the volume of the tarsal tunnel, or stretch the nerve itself.  

Structure and function

The tarsal tunnel is the space located posterior and inferior to the medial malleolus, ; lateral to the calcaneus and talus, and medial to the flexor retinaculum. Many structures run through

The contents of the tarsal tunnel, including, from anterior to posterior, include the tibialis posterior tendon, the flexor digitorum longus tendon, the posterior tibial artery, tibial nerve, and flexor hallucis longus (Figure 1)The pain occurs because The tibial nerve divides within the tarsal tunnel syndrome affects into the tibial nerve or its branches as they course under tight structures with limited space along the inner aspect of the ankle and down along the inner aspect of the heel and turning into the sole.There is some question as to whether this condition exists as an isolated entity as it is commonly seen in conjunction with other conditions such as plantar fasciitis and acquired adult flatfoot deformity. In all of these conditions, the posterior medial structures of the ankle structures on the inside of the ankle are placed under repetitive stress.  Repetitive injury to the tibial nerve can be due to a repetitive traction on the nerve, which creates some recurrent injury to the nerve and nerve sheath. This can lead to scarring of the nerve with resulting painful symptoms.  While the majority of diagnoses of tarsal tunnel syndrome are related to traction on the nerve, there are also cases where a physical mass, such as a bone spur or a ganglion, can press and injure the tibial nerve or its branches. Rarely the structures around the nerve are swollen or diseased such as inflamed tendons coursing along the tibial nerve and can also affect the nerves similarlycalcaneal nerve coursing towards the heel and the medial and lateral plantar nerves which supply the bottom of the foot.

The flexor retinaculum covering the tunnel ensures that the contents of the tunnel remain within it, but may be a source of abnormal compression if the anatomy is disturbed.

Tarsal tunnel is thought to be caused by repetitive traction on the nerve leading to scarring. Of course, extrinsic compression from a bone spur or a ganglion, or synovial proliferation from a tendon disorder can be a cause as well. 

As pressure increases with the tarsal tunnel, blood flow decreases and the nerve becomes ischemic. Malfunction of the nerve, in turn, yield the presenting symptoms of tingling and numbness.

Patient presentation

Patients with TTS tarsal tunnel syndrome typically complain of numbness in the foot radiating to the the big toe  and and the first 3 toes,   pain, burning, electrical sensations, and tingling over the base of the foot and the heel.   If the A broader area of symptoms suggests either nerve entrapment is more proximal , the entire foot can be affected as varying branches of the tibial nerve can become involved. Ankle pain is also present in patients who have high level entrapments. Inflammation or swelling can occur within this tunnel for a number of reasons. The flexor retinaculum has a limited ability to stretch, so increased pressure will eventually cause compression on the nerve within the tunnel. As pressure increases on the nerves, the blood flow decreases. Nerves respond with altered sensations like tingling and numbness. Fluid collects in the foot when standing and walking and this makes the condition worse. As small muscles lose their nerve supply they can create a cramping feeling. 

 Patients with this condition present with pain in the inside of the ankle or heel region that radiates into the sole of their foot. This pain can have a sharp, shooting, dull, or burning feeling and may be associated with numbness. The pain is often worse with activity and towards the evening. Excessive walking and increased body weight can exacerbate the patient’s symptoms.

Image Removed
Figure 1: Location of pain in patient presenting with tarsal tunnel syndrome.(from footeducation.com http://www.footeducation.com/wp-content/uploads/2010/08/tarsal-tunnel-syndrome-Figure-1-300x235.png)

Objective evidence

Physical Exam

to the tarsal tunnel, or a generalized neuropathy.

Because even slight amounts of increased fluid in the tarsal tunnel (edema) can cause a critical decrease in blood flow (perfusion), patients may report that prolonged standing and walking, causing a gravity-related accumulation of fluid, makes their symptoms worse.

Compression of the tibial artery may cause ischemia to the intrinsic muscles of the foot with painful cramping accordingly.

 

Objective evidence

On physical examination, patients will often have a flatfoot type. Direct palpation over the inside of the ankle (posteromedial) will often reveal a localized area of pain with symptoms radiating flat foot.

Palpation over the tarsal tunnel will produce localized pain (tenderness) as well as a radiation into the sole of the foot. If direct pressure or tapping on the nerve reproduces patient symptoms and is described as an electric shock sensation, it   This latter sensation is called a “Tinel’s sign”, though this is not a true objective sign but a vocalized subjective symptom.  (Specific, provoked symptoms on testing may be designated by the neologism wigns”–a whined sign, so to speak.   See www.ncbi.nlm.nih.gov/pubmed/19557488)

Sensory examination of the foot may reveal some decreased sensation on the sole of the foot, although in most patients this is not the case.

Muscle atrophy and claw-toe deformities suggest chronic compression.

Nerve conduction studies will often show a decrease decreases in conduction of electrical pulses over the course of the tibial nerve.

Radiological evidence

Weightbearing velocity in the tibial nerve precisely as it courses under the flexor retinaculum.

Weight-bearing x-rays of the foot should be assessed to review for any obvious pathology in the hindfoot. X-rays can rule out fractures, CT scan or MRI is sometimes indicated to rule out a mass that may be irritating the nerve, and ultrasound can be used to assess for synovitis or ganglia.

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Figure 3: MRI showing fluid-filled ganglion (arrow) that is compressing the posterior tibial nerve. (from footeducation.com http://www.footeducation.com/wp-content/uploads/2010/08/Figure-3-Tarsal-Tunnel-Syndrome-Ganglion-Panchbhavi-04-19-2014.png)

Epidemiology

Though TTS is rare in commonality, causality can usually be determined in 70% of reported cases. According to a May 2014 OSHA report, in the workplace, TTS is considered a musculoskeletal disorder and accounts for 1.8 million cases a year, which accumulates to about $15–$20 billion a year ( Jeffress, Charles N. "Work-related Musculoskeletal Disorders (MSDs)." Work-related Musculoskeletal Disorders (MSDs). Occupational Safety & Health Administration, n.d. Web. 11 May 2014).  TTS occurs more dominantly in active adults, with a higher pervasiveness among women.

Differential diagnosis

 

It is important to attempt to determine the source of the problem.

  • Trauma
  • Space occupying lesion: ganglion cyst, benign tumors, swollen tendon, varicose veins
  • Ankle deformities: pes planus (flat foot)
  • Peripheral neuropathy: diabetes (if pain follows "stocking distribution")
  • Herniated lumbar disk: back pain in L4, L5, S1 regions, leg/thigh pain, "double crush"–one nerve pinch in the lower back, and the second in the tarsal tunnel.
  • Complex regional pain syndrome: if regional discoloration, swelling, temperature changes, allodynia, hyperesthesia
  • Neurofibromatosis: formation of pigmented, cutaneous neurofibromas can invade tarsal tunnel and create pressure.

Red flags

It is important to rule out nerve compression in the low back area. There is a fairly high correlation between nerve compression in the spine region (ex from a disk or spinal stenosis) and tarsal tunnel-type symptoms. If this is the case, then local treatments may not be effective if the real problem is at the level of the low back.

Treatment options and outcomes

Non-operative treatment

The exclude fractures and bone spurs, as well as malalignment (for example, hindfoot varus or valgus) that can alter the geometry of the tarsal tunnel.

CT scans, ultrasound or MRI might be needed to rule out space-occupying lesions within the tarsal tunnel.  These include ganglions, lipomas, or (rarely) accessory muscles within the tarsal tunnel. Detection of a mass is critical, as unless and until it is removed, the patient is unlikely to improve. (By contrast, without a mass, surgery is rarely indicated.)

Epidemiology

 The National Institutes of Health’s website on rare diseases says “The incidence and prevalence of tarsal tunnel syndrome is unknown.” (https://rarediseases.info.nih.gov/diseases/7733/tarsal-tunnel-syndrome). The very fact that tarsal tunnel syndrome is included by the NIH on its list of “rare” conditions means that it affects fewer than 200,000 people in the United States.

Differential diagnosis

The differential diagnosis of tarsal tunnel syndrome can be consider to have two components. The first is the true differential diagnosis–that is, the list of condition that may instead be responsible for a presentation similar to that of tarsal tunnel syndrome. Beyond that, once the diagnosis is established, there is a second differential diagnosis list to consider, namely, the other conditions that may be responsible for causing the tarsal tunnel syndrome itself.

In the first category, the main considerations are lumbar radiculopathy and peripheral neuropathy (most often caused by diabetes). A complex regional pain syndrome (formerly known as Reflex Sympathetic Dystrophy) could be responsible as well, though the findings in complex regional pain syndrome would almost certainly would extend beyond the distribution of th etibial nerve.

Conditions that may be the cause of tarsal tunnel syndrome include trauma (fracture fragments causing compression or ligament injury causing instability and traction on the nerve); space occupying lesions such as ganglion cyst, benign tumors, swollen tendons or varicose veins; ankle deformities such as pes planus (flat foot).

Red flags

There are no true “red flags” with tarsal tunnel syndrome, though the presentation of tarsal tunnel syndrome-like complaints may be the first clue of an otherwise undetected diagnosis of diabetes, peripheral artery disease or disc herniation/spinal stenosis.

 

Treatment options and outcomes

If the patient has confirmed tarsal tunnel syndrome caused by a space-occupying lesion, that offending structure should be removed. Beyond that, the vast majority of patients with tarsal tunnel syndrome can (and should) be treated nonoperatively. The primary approach to treating this condition non-operatively. Only with a prolonged failure of non-operative treatment in a patient with positive nerve conduction studies and severe symptoms should surgical release be considered.

The primary non-operative treatment approach to treating tarsal tunnel syndrome is to attempt to decrease the repetitive traction injury across the nerve and the other structures in this area of the foot. In this regard, treatment is quite similar to that for for acquired adult flatfoot deformity  and plantar fasciitis. In fact, these three conditions (tarsal tunnel, acquired adult flatfoot, and plantar fasciitis) together have been labeled as the terrible triad and it is not uncommon to see them all together in one patient. This patient is typically someone with a flattened arch of the foot who is overweight.

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Comfort shoes designed to disperse the force more evenly across the foot can be very helpful. Weight loss should be recommended to patients who need it, though the futility of weight loss programs to effect enduring change should temper the enthusiasm (and scolding tone) of those who make this recommendation.

A prefabricated

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orthotic with a supportive arch will help to disperse the force more evenly across the foot may also be helpful.

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Phystherapy with stretching exercises designed to stretch the calf

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muscle and thereby indirectly decrease the load through this area of the foot may also be helpful.

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Limiting the patients walking can reduce symptoms but may impede weight loss (and be impractical for other reasons). Advice to limit standing, an activity which can produce symptoms with fewer health benefits than those involving motion, may be more apt. 

Corticosteroid injections may help to decrease the swelling around the nerve in the short and intermediate term. However, it is unclear what effect they have in the long term. In addition it is possible to injure the nerve during the injection process.

Operative treatment

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Tarsal tunnel release has been proposed as a surgical option for treating tarsal tunnel syndrome. Additionally, operative treatment should also address the underlying reason for the repetitive or compressive injury to the nerve. Tarsal tunnel release (Figure 4) involves a neurolysis of the tibial nerve, which requires identifying and freeing up the tibial nerve as it passes the inside of the ankle and hindfoot. This is done by releasing any tight structures and removing any obvious scar on the outer aspect of the nerve. If there is a positive Tinel sign, then there is an 80% chance that decompressing the tarsal tunnel will relieve the symptoms of pain and numbness in a diabetic with TTS. It has been suggested that TTS in conjunction with a mass effect, such as a bone spur or ganglion cyst, may do better. In theory, removing the mass should help the patient’s symptoms. In practice, this is not always proven to be the case, because scarring can occur around the nerve during surgery, which may unfortunately also cause compression. Furthermore, by operating around the nerve, any postoperative bleeding will have a tendency to scar the nerve further. Thus the main potential surgical complication specific to tarsal tunnel release is hypersensitivity in the area of surgery, due to failure to eradicate the symptoms and in some cases, making the symptoms worse. Other potential complications that are not specific to tarsal tunnel surgery include wound healing problems, infection, deep vein thrombosis (DVT), pulmonary embolism (PE), and complex regional pain syndrome. 

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Figure 4: Schematic of tarsal tunnel release (from Wikipedia: Tarsal tunnel syndrome)

can be considered in rare cases.  Primary resection of space occupying lesions causing isolated tarsal tunnel syndrome can relieve symptoms reliably, provided that the nerve is neither scarred nor damaged prior to surgery. Beyond that, operative treatment includes tarsal tunnel release and other procedures to correct deformity causing compression may be used.

Tarsal tunnel release comprises release of the flexor retinaculum and neurolysis of the tibial nerve and its branches. The latter includes removal of scar tissue, if any, as well as fascial releases.

There is limited evidence that surgery is effective.  One study in the Journal of Bone and Joint Surgery [https://www.ncbi.nlm.nih.gov/pubmed/8056802] reported  a 38% incidence of patients “clearly dissatisfied with the result and had no long-term relief of the pain.” Complications were seen in 13% of patients as well, including three wound infections.

 

Risk factors and prevention

Tarsal tunnel syndrome is known to affect both athletes and individuals that stand a lot.  Strenuous activities involved in athletic activities put extra strain on the ankle and therefore can lead to the compression of the tibial nerve. Activities that especially involve sprinting and jumping have a greater risk of developing TTS. This is due to the ankle being put in Strenuous activities involving repetitive eversion, inversion, and plantarflexion at high velocities . Examples of sports that can lead to TTS include basketball, track, soccer, lacrosse, and volleyball.

Neuropathy can occur in the lower limb through many modalities, some of which include obesity and inflammation around the joints. By association, this includes risk factors such as RA, compressed shoes, pregnancy, diabetes and thyroid diseases.

Miscellany

Tarsal tunnel is quite different than carpal tunnel syndrome. Carpal tunnel syndrome is seen in the wrist, where direct compression of the nerve produces the chronic injury and subsequent symptoms. 

Mnemonic for can produce the symptoms of tarsal tunnel syndrome.

Obesity is a double risk factor in that weight alone can cause mechanical overload, but it is also associated with diabetes (which causes a neuropathy that may make the nerve less tolerant of even mild compression).

Rheumatoid arthritis, hypothyroidism and gout are thought to be associated with tarsal tunnel syndrome.

Miscellany

 

The anterior to posterior arrangement of the structures coursing through the tarsal tunnel (from anterior to posterior): Tom, Dick, and very nervous Harry. (Tnamely: the tibialis posterior tendon, the flexor D digitorum longus tendon, the posterior tibial Artery, posterior tibial V artery and vein, the tibial N nerve, and the flexor H hallucis longus tendon) can be recalled with this mnemonic: “Tom, Dick, And Very Nervous Harry.” 


 

Key terms

Tarsal tunnel, posterior tibial nerve, Tinel's sign, terrible triad, adult acquired flatfoot deformity, pes planus, plantar fasciitis, tarsal tunnel release

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Recognize the Tinel's sign

 

Skills 

Perform a comprehensive history and physical that can identify tarsal tunnel syndrome as well as rival conditions on the differential diagnosis list. Recognize the deformities of the foot and ankle that may place undue traction on the posterior tibial nerve.

 

 figures

 

  1. need a nice, simplified view of the anatomy of the TT

Image Added
Figure 2: Location of pain in patient presenting with tarsal tunnel syndrome.(from footeducation.com http://www.footeducation.com/wp-content/uploads/2010/08/tarsal-tunnel-syndrome-Figure-1-300x235.png)

 

Image Added
Figure 3: MRI showing fluid-filled ganglion (arrow) that is compressing the posterior tibial nerve. (from footeducation.com http://www.footeducation.com/wp-content/uploads/2010/08/Figure-3-Tarsal-Tunnel-Syndrome-Ganglion-Panchbhavi-04-19-2014.png)