Foot and Ankle cases 23

A 29-year-old woman presents to you with pain on the medial aspect of the ankle and numbness and tingling on the plantar aspect of the foot. She reports no trauma and describes an insidious onset of symptoms over the past month. On physical examination she has neutral hindfoot alignment and no palpable masses. She has a positive Tinnel’s sign just posterior to her medial malleolus which worsens the paresthesias on her plantar foot. Plain radiographs of the ankle demonstrate no masses, no fractures, and no significant arthritis.

You are concerned that the patient has tarsal tunnel syndrome, your next step is:

1. Corticosteroid injection into the tarsal tunnel

2. Tibial nerve decompression

3. Lateral posting orthotics

4. MRI

 

Discussion

The correct answer is (D). A subset of patients with tarsal tunnel syndrome will have a space occupying mass located in or adjacent to the tarsal tunnel causing tibial nerve compression. This space-occupying lesion may be tenosynovitis, a ganglion cyst, varicosities, lipoma, or tumor. Although at some point a single corticosteroid injection may be considered, there is concern about injecting steroid into weight-bearing tendons of the foot. A lateral posting orthotic would likely increase tension on the medial structures and provide no benefit to a patient with a neutral hindfoot alignment. An MRI is performed (Fig. 5–49).

 

 

 

Figure 5–49 Axial MRI demonstrating tenosynovitis along the course of the flexor digitorum longus and flexor hallucis longus.

 

Based on the imaging you now recommend which of the following?

1. Soft tissue rest and anti-inflammatory medications

2. Tarsal tunnel release

3. Tenosynovectomy

4. Flatfoot reconstruction

 

Discussion

The correct answer is (A). The MRI demonstrates tenosynovitis of the flexor hallucis longus. The initial treatment of this will include soft tissue rest, anti-inflammatories, and activity modifications. For the majority of patients, tarsal tunnel syndrome resolves with nonoperative treatment. A period of nonoperative management should be attempted prior to surgical treatment of tarsal tunnel

syndrome. A flatfoot reconstruction would typically address pathology associated with the posterior tibial tendon.

Following the MRI and approximately 12 weeks of conservative treatment, it is noted that the patient is still having symptoms. A repeat MRI demonstrates resolution of the tenosynovitis along the FHL and FDL. An EMG/nerve conduction study is ordered which demonstrates nerve compression within the tarsal tunnel. At this point you discuss the risks and benefits of a tarsal tunnel release and the patient requests to proceed with the surgery. During the release, a thickened region of fascia is identified before entering the tarsal tunnel. This is labeled with an arrow in Figure 5–50.

 

 

 

Figure 5–50 Clinical photograph of the completed tarsal tunnel release demonstrating complete release of the fascia overlying the tarsal tunnel.

 

What is the name of the tissue marked with the black arrow?

1. Extensor retinaculum

2. Laciniate ligament

3. Epineurium

4. Retrocalcaneal bursa

 

Discussion

The correct answer is (B). The laciniate ligament is also known as the flexor retinaculum and is a thickening of the fascia overlying the posterior medial ankle. Additional structures located in this region are anteriorly the posterior tibial tendon and flexor digitorum longus. Posterior and lateral to the neurovascular bundle is the flexor hallucis longus. The extensor retinaculum lies on the anterior aspect of the ankle joint. The epineurium directly overlies nerves. The retrocalcaneal bursa is

located behind the calcaneus and anterior to the Achilles.

While exploring the tibial nerve, a branch of the posterior tibial nerve that passes deep to the abductor hallucis is noted. This nerve is released and the fascia of the abductor hallucis is incised and the muscle belly of the abductor hallucis mobilized.

Which nerve was just released?

1. Medial plantar nerve

2. Calcaneal branch of the tibial nerve

3. First branch of the lateral plantar nerve

4. Second branch of the lateral plantar nerve

 

Discussion

The correct answer is (C). This nerve, also known as Baxter’s nerve, can be a source of medial heel pain. The course of the nerve is from the tibial nerve distally where it crosses deep to the abductor hallucis muscle belly, a common location of compression. Following this, it courses between the flexor digitorum brevis and quadratus plantae before innervating the abductor digiti quinti. The medial plantar nerve runs toward the knot of Henry and innervates the medial three toes. The calcaneal branch of the tibial nerve comes directly off the tibial nerve and is directed posteriorly to the calcaneus.

 

Objectives: Did you learn...?

 

Initially treat tarsal tunnel syndrome?

 

Describe the role of an MRI in the diagnosis of a mass causing tarsal tunnel syndrome?

 

Anatomy of the posteromedial ankle?