Introduction 

Tarsal Tunnel Syndrome (TTS) is a compression neuropathy caused by the posterior tibial nerve as it runs down the tarsal tunnel.¹ The posterior tibial nerve is a narrow space located inside the ankle, behind the medial malleolus.² 

Common symptoms associated with include burning or stabbing pain, paresthesia  (the sense of burning and numbness), nighttime dysesthesia, neurological deficits, and trophic changes such as decreased sweating.³

One of the most common causes of TTS is the swelling or the formation of structural abnormalities in the tarsal tunnel. However, environmental factors, such as ankle injuries or fractures, can also lead to TTS.⁴

To avoid long-term consequences such as chronic pain, muscle weakness or permanent nerve damage, effective treatment at the early stages is essential.⁵ In this article, the role of orthotics, a non-invasive treatment option, will be discussed.⁶

Anatomy of the tarsal tunnel 

The tarsal tunnel is a fibro-osseous tunnel located on the inner side of the ankle, behind the medial malleolus.⁷ The tunnel is formed by the flexor retinaculum (roof) and the medial surfaces of the tibia, talus, and calcaneus (floor).  8.

Causes of TTS

Causes of TTS can be classified as either intrinsic, extrinsic or both.

Intrinsic 

Intrinsic factors refer to problems within the tarsal tunnel itself that can put pressure on the nerve, such as ganglion cysts, lipomas, or varicose veins.⁴ Underlying conditions, such as diabetes or neuropathy, can also influence TTS; they can cause nerve inflammation, impaired healing and reduced blood supply. Extrinsic 

Extrinsic factors refer to problems outside the tarsal tunnel, such as traumas or injuries. By spraining, fracturing or dislocating the ankle, swelling or scar tissue may appear. Individuals who have pes planus (flat feet) can also have problems because the trigeminal nerve can be stressed by increased pressure. Furthermore, instability in the ankle can cause conditions such as posterior tibial tendon dysfunction, which can affect the tarsal tunnel. This may result in irritation and discomfort of the tibial nerve.⁴

Combined 

Both intrinsic and extrinsic factors can play a combined role. For instance, individuals who are athletes may apply more pressure to the nerve,  leading to both tendon inflammation (intrinsic) and external compression from swelling or biomechanical imbalances (extrinsic).⁹

Symptoms 

• Sharp, shooting pain
• Numbness
• Tingling, pins and needles
• Burning sensation
• Swelling
• Muscle weakness
• Electric shock sensations 

Diagnosis and medical evaluation

To diagnose TTS, a critical physical examination must be followed to provide the best treatment strategy. 

Here, the clinician will ask you questions about your condition to know more about the onset, duration and progression of the symptoms.¹⁰

It is important to have a medical history to identify any previous conditions or injuries that may be associated with the ankle. This will enable the clinician to understand the causes or influences for TTS. Other underlying conditions may also be questioned, such as diabetes, neuropathy or systemic conditions that can be linked to nerve compression. 

The role of orthotics in foot health 

Orthotics are medical devices such as braces or splints. They provide support to weak or damaged bones, joints, and muscles.¹¹ They can help align and improve the function of your foot and the lower limb. They are placed in shoes to correct biomechanical abnormalities, relieve pain and reduce stress on the foot structures. They can be categorised according to their customisation, material, or function.

• Customisation 

Orthotics can be either custom-made or prefabricated. Customised orthotics are designed for an individual's foot structure.  They are usually made from a 3D scan, cast or impression. They provide personalised correction and support. On the other hand, prefabricated orthotics are mass-produced based on foot sizes.  They are used to provide support and cushioning but lack individual customisation.¹²

• Material

Orthotics can be made of rigid/semi-rigid materials or soft materials.  Those fabricated with rigid/semi-rigid materials are used to correct the abnormal foot motion and improve the biomechanics. However, those made with soft materials are used to provide shock absorption and pressure relief. They are useful for diabetic and arthritis patients.¹³

• Function

There are different types according to the foot condition. Arch support orthotics are designed for flat feet or high arches.¹⁴ Heel cushions and cups are typically used to provide shock absorption. Sport-specific orthotics are designed for athletes and runners.¹⁵

Custom vs over-the-counter orthotics 

An individual can be provided with orthotics over the counter, or they can be customised for them specifically. 

• Customised - individually designed from the foot scan. They provide support and correction, and are characterised by high durability. However, they can be expensive and may take a long time to produce¹⁶
• Over-the-counter mass-produced prefabricated insoles. They provide general support and cushioning. They are more affordable than customised ones and are also easily accessible, as no prescription is required. However, they do not have as much cushioning, are not suitable for severe cases, and they do not last long¹⁷

Choosing the right orthotics for tts 

When choosing the right orthotics, it is important to take a few factors into account, such as the material and design. The first few steps should be to undertake a professional biomechanical assessment. This will help to first evaluate the foot structure and injury to understand which orthotic feature is most effective for the patient.¹⁸

The material and design play an important role. For instance, rigid or semi-rigid materials are beneficial for controlling motion and correcting position. On the other hand, soft orthotics, typically made from gel or EVA foam,  tend to offer greater cushioning and pressure relief, making them one of the best options for diabetic patients and individuals with hypersensitive feet.¹⁹

Limitations and considerations 

Although orthotics provide help and improvement to the TTS condition, they are not always effective.²⁰ In cases where the symptoms do not seem to improve, it is important to find further guidance and medical evaluation. In these cases, additional treatment may be advised, such as corticosteroid injections, physical therapy or even surgery.²¹

Conclusion 

TTS is a condition that occurs when there is a nerve compression at the tibial nerve. It causes symptoms such as burning sensation, swelling, or sharp pain. Early diagnosis is crucial to prevent further complications. 

Orthotics are medical devices that can be used to provide support to the ankle and the arch. Overall, they help to improve the foot alignment and also provide some relief to the tibial nerve. However, they are not a cure. If a patient is in a stage where the condition is severe or the symptoms are not improving, they may be advised to undergo additional treatment such as corticosteroid injection, physical therapy or even surgery.