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Review of Management for Nerve Entrapment Issues in the Foot and Ankle

Posted on: 03/25/2015
While relatively uncommon, nerves can become entrapped in the lower leg and ankle. A recent updated review article touched upon management of these diagnoses. The author stated that itís important to establish an accurate diagnosis through which physicians will rely on a thorough physical examination and must additionally possess a thorough understanding of relevant anatomy. Electrodiagnostic testing, including nerve conduction velocity NVC and electromyography EMGs and advanced imaging such as magnetic resonance imaging MRI and ultrasonography can assist with localizing the area of entrapment and contributing factors.

Tarsal tunnel syndrome occurs when the tibial nerve is entrapped and can be further divided into proximal syndrome and distal syndrome. Proximal tarsal tunnel syndrome is the most common and occurs when the tibial nerve is compressed in the tarsal tunnel proper. Patients will typically present with diffuse pain along the inside of the ankle and bottom of the foot. It is often described as burning, shooting, electric, tingling and numbing. After comprehensive physical examination, radiographs and MRI or ultrasonography may be used to identify soft tissue or bony contributions. Electrodiagnostic studies may be used to confirm entrapment but they cannot be used to exclusively rule in or out tarsal tunnel syndrome. Typically non-surgical management is used first including anti-inflammatory medication, activity modifications, physical therapy, and eliminating use of compressive clothing or footwear. Surgical release is only recommended when these conservative measures have failed. Full release of the flexor retinaculum is recommended. It was also found that early diagnosis and intervention provided improved outcome than those who had more chronic symptoms.

Distal tarsal tunnel syndrome is further divided into entrapment of the terminal branches of the tibial nerve, specifically the medial plantar nerve and lateral plantar nerve otherwise known as joggerís foot and Baxter nerve respectively. Patientís with joggerís foot report pain along the medial plantar side of the foot that is induced with exercise. The pain can radiate to the bottom of the first, second and third toes and can also radiate up into the inside of the heel and ankle. Itís important for physical examination to occur including examining shoe wear for sources of external compression such as excessive or rigid arch support. Imaging can further assist with diagnosing causative deformities. Again initial treatment is non-surgical management and if these fail surgical release may be considered. Patientís with Baxter neuropathy, or compression of the lateral plantar nerve, present with pain along the medial plantar aspect of the heel often similar to distribution of pain from plantar fasciitis. Paresthesias and weakness are not typically reported. If diagnosis is unclear, further diagnostic studies may prove to be beneficial. In this case, surgical intervention is often required.

Soleal sling syndrome occurs with the tibial nerve is entrapped in the calf region by a fibrous sling at the origin of the soleus muscle. Patients may report calf pain and have pain that mimics tarsal tunnel syndrome and may even possess a history of failed tarsal tunnel release. Pain with gentle palpation on the calf approximately 9 cm below the flexion crease of the knee will typically generate pain. Weakness may also be present, specifically the flexor hallucis longus. Electrodiagnostic testing can be difficult to perform secondary to the depth of the nerve at this level. Non-surgical management should include modification of activities and discontinued use of restricted clothing or footwear. Anti-inflammatory and nerve-modulating medications may also proved some benefit. If conservative management fails to provide relief then surgical decompression is recommended.

Morton neuroma occurs when there is entrapment of the interdigital nerve most commonly in the third web space and occasionally in the second web space. Patients will present with burning or electric pain and numbness and tingling in the affected webspace. Women are affected more than men. Symptoms are reproduced with direct pressure on the plantar aspect of the foot between the metatarsal heads upon physical examination. Lidocaine injection can also help confirm diagnosis as patient will receive pain relief. Diagnostic tests are usually reserved for abnormal presentations to confirm the diagnosis. Nonsurgical treatment includes fabrication of custom orthoses, metatarsal pads, accommodative footwear and anti-inflammatory medications and injections. If these treatment modalities fail, surgical management may be warranted. One study reviewed advocated a hybrid intraoperative approach in which the nerve is resected if it is found to be thickened otherwise the authors released only the transverse metatarsal ligament and total relief of symptoms was reported in 96-98 per cent of patients.

Superficial peroneal nerve entrapment occurs when the nerve is compressed or entrapped as it pierces the deep fascia because of thickened fascia tunnel, a fascial defect or soft-tissue mass. Most patients will report pain related to activity in the lower outside leg as well as dysesthesias in the dorsum and lateral aspect of the foot. Chronic exertional compartment syndrome should be considered as differential diagnosis. First line of treatment includes removing external factors that may be causing the compression as well as stabilizing any instability that may be tensioning the nerve. Surgery is rarely required.

Anterior tarsal tunnel syndrome occurs when the deep peroneal nerve is entrapped in the anterior tarsal tunnel. Patientís with entrapment of the lateral branch will report pain along the dorsal foot. Patients with entrapment of the medial nerve branch will report pain and or numbness to the first web space. After thorough physical evaluation, radiologic evaluation can prove critical in the workup as the most common causes of anterior tarsal tunnel syndrome are trauma and impingement of the nerve by bony growths or osteophytes are the talonavicular joint. Non-operative management focuses on reducing external compression, stabilizing ankle laxity and reducing inflammation. Surgical cases should only be reserved for very site specific difficult cases to reduce the risk of scarring from excessive nerve dissection.

Sural nerve entrapment is rare but can occur anywhere in the leg ankle or foot. Patients may report pain, burning, numbness or aching in the back-outside leg, outside part of the ankle or foot. Treatment is dependent on the accurate identification of causative factors and the location of the entrapment. Swelling and underlying instability should be treated first as should any external factors. The authors recommend that if the cause is post traumatic or postoperative then a three to six month period of observation, desentization and neural gliding should occur prior to proceeding to surgery.

Saphenous nerve entrapment is also very rare. Typically it occurs more proximally and patients will present with pain and paresthesias to the foot and ankle. Surgical treatment should be delayed until nonoperative management have failed to provide relief.

In summary, in treatment of entrapment neuropathies of the lower leg, ankle and foot a comprehensive knowledge of relevant anatomy must be possessed followed by thorough physical examination and appropriate treatment. Patientís will often respond to nonoperative treatment, however, when this fails to provide relief surgical involvement will be considered.

Gregory Pomeroy, MD, et al. Entrapment Neuropathy About the Foot and Ankle: An Update. Journal of the American Academy of Orthopaedic Surgeons. Jan 2015. Vol 23. No 1. Pp 58-66.

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