Imaging of nerve entrapment in the foot and ankle

Magnetic Resonance Neurography of the Foot and Ankle

Peripheral neuropathies of the foot and ankle can be challenging to diagnose clinically due to concomitant traumatic and nontraumatic or degenerative orthopedic conditions. Although clinical history, physical examination, and electrodiagnostic testing comprised of nerve conduction velocities and electromyography are used primarily for the identification and classification of peripheral nerve disorders, MR neurography (MRN) can be used to visualize the peripheral nerves as well as the skeletal muscles of the foot and ankle for primary neurogenic pathology and skeletal muscle denervation effect. Proper knowledge of the anatomy and pathophysiology of peripheral nerves is important for an MRN interpretation.

Magnetic Resonance Neurography of the Foot and Ankle

Peripheral neuropathies of the foot and ankle can be challenging to diagnose clinically due to concomitant traumatic and nontraumatic or degenerative orthopedic conditions. Although clinical history, physical examination, and electrodiagnostic testing comprised of nerve conduction velocities and electromyography are used primarily for the identification and classification of peripheral nerve disorders, MR neurography (MRN) can be used to visualize the peripheral nerves as well as the skeletal muscles of the foot and ankle for primary neurogenic pathology and skeletal muscle denervation effect. Proper knowledge of the anatomy and pathophysiology of peripheral nerves is important for an MRN interpretation.

Magnetic Resonance Imaging Findings in Patients with Tarsal Tunnel Syndrome

Tarsal tunnel syndrome (TTS) is a common entrapment syndrome whose diagnosis can be difficult. We compared preoperative magnetic resonance imaging (MRI) and operative findings in 23 consecutive TTS patients (28 sides) whose mean age was 74.5 years. The 1.5T MRI sequence was 3D T2* fat suppression. We compared the MRI findings with surgical records and intraoperative videos to evaluate them. MRI- and surgical findings revealed that a ganglion was involved on one side (3.6%), and the other 27 sides were diagnosed with idiopathic TTS. MRI visualized the nerve compression point on 23 sides (82.1%) but failed to reveal details required for surgical planning. During surgery of the other five sides (17.9%), three involved varices, and on one side each, there was connective tissue entrapment or nerve compression due to small vascular branch strangulation. MRI studies were useful for nerve compression due to a mass lesion or idiopathic factors. Although MRI revealed the compression site, it failed to identify the specific involvement of varices and small vessel branches and the presence of connective tissue entrapment.

The Course of Tarsal Tunnel Syndrome after Ultrasound-Guided Injections

BACKGROUND

Local ultrasound (US)-guided injections of anesthetics with corticosteroids are commonly performed for the conservative treatment of tarsal tunnel syndrome (TTS).

OBJECTIVE

This retrospective study aimed to investigate the outcomes of TTS after US-guided injections.

METHODS

The study included patients who were diagnosed with TTS and received US-guided injections as part of their initial treatment. The pain levels were noted on a scale between zero and ten before and after each injection. The patients were divided into non-surgical and surgical groups. The nonsurgical group included patients who had received US-guided injections and did not proceed to surgical treatment, and the surgical group included those who received US-guided injections and ultimately underwent tarsal tunnel release (TTR). The two groups were compared in terms of age, post-injection follow-up time, and the amount of pain reduction immediately after injection (ΔPN). In the surgical group, outcomes of surgical treatment were also assessed.

RESULTS

A total of 218 patients were diagnosed with TTS and received US-guided injections. After the injections, 169 patients (77.5%) did not go on to TTR (nonsurgical group) and 49 patients (22.5%) underwent TTR (surgical group). The average ages for the nonsurgical and surgical groups were 53.8 and 48.9 years (P = 0.03). The average time between the injection and final follow-up for the nonsurgical group was 339 days. The average time between the injection and TTR for the surgical group was 145 days. There were no differences in pain relief after the injections between the nonsurgical and surgical groups (mean ΔPN: 3.6 and 3.8, respectively). The average post-surgical follow-up time was 117 days. At final follow-up, 41 patients (84%) in the surgical group had complete resolution of pain and neurological symptoms.

CONCLUSION

US-guided injection can be an effective conservative treatment option for patients with TTS. Younger patients may be more likely to proceed to TTR.

Level of Evidence

Level III

Imaging of Entrapment Neuropathies in the Ankle

Entrapment neuropathies of the ankle and foot pose a major diagnostic challenge and thus remain underdiagnosed. Recent advancements in imaging modalities, including magnetic resonance neurography (MRN), have resulted in considerable improvement in the anatomical localization and identification of pathologies leading to nerve entrapment. MRN supplements clinical examination and electrophysiologic studies in the diagnosis of neuropathies, aids in assessing disease severity, and helps formulate management strategies. A comprehensive understanding of the anatomy and imaging features of the ankle is essential to diagnose and manage entrapment neuropathies accurately. Advancements in imaging and their appropriate utilization will ultimately lead to better diagnoses and improved patient outcomes.

Anatomical study and branching point of neurovascular structures at the medial side of the ankle

Nerve entrapment and blood circulation impairment associated with the medial side of the ankle are not uncommon. The purpose of this study was to describe the anatomical basis of neurovascular structures of the medial ankle which comprised the number, origin, branching pattern, and branching point. Forty feet of fresh cadavers were examined by using 2 reference lines: the malleolar-calcaneal (MC) and navicular-calcaneal (NC) axes. We recorded number, origin, length of the 2 axes, the locations and widths of neurovascular structures on MC and NC axes, the branching point of neurovascular structures, and the branching pattern of neurovascular structures was recorded and was separated into 5 types. The posterior tibial nerve (PTN) bifurcated to plantar and calcaneal nerves and branched proximally to the tarsal tunnel (TT). The posterior tibial artery bifurcated to plantar and calcaneal arteries and branched inferiorly to PTN and within the TT. The calcaneal nerves and arteries had more variation of number and origin. The most common branching point of calcaneal nerves and arteries is within the TT, except the medial calcaneal nerve. It branched proximally to the TT. The anatomical knowledge from this study is important for the diagnosis and treatment of clinicians.

Results of ultrasound-guided release of tarsal tunnel syndrome: a review of 81 cases with a minimum follow-up of 18 months

Background

This study aims to analyse the clinical results of ultrasound-guided surgery for the decompression of the tibial nerve, including its distal medial and lateral branches, to treat tarsal tunnel syndrome. These structures are the complete flexor retinaculum and the deep fascia of the abductor hallucis muscle, including individualised release of the medial and lateral plantar nerve tunnels.

Method

This is a retrospective review of 81 patients (36 men and 45 women) with an average age of 41 years old (32–62) and an average clinical course of 31 months (8–96) compatible with idiopathic tarsal tunnel syndrome, who underwent ultrasound-guided decompression of the proximal and distal tarsal tunnel between February 2015 and November 2017 (both months included), with a minimum follow-up of 18 months.

Results

Based on the Takakura et al. scale for the 81 patients, 76.54% obtained excellent results, 13.58% good results, and 9.87% poor results.

The patients with the longest course of symptoms displayed the worst results.

Conclusion

Although 9% of patients did not improve, ultrasound-guided tarsal tunnel release might be a viable alternative to conventional open approaches.

New Techniques in MR Imaging of the Ankle and Foot

Foot and ankle disorders are common in everyday clinical practice. MR imaging is frequently required for diagnosis given the variety and complexity of foot and ankle anatomy. Although conventional MR imaging plays a significant role in diagnosis, contemporary management increasingly relies on advanced imaging for monitoring therapeutic response. There is an expanding need for identification of biomarkers for musculoskeletal tissues. Advanced imaging techniques capable of imaging these tissue substrates will be increasingly used in routine clinical practice. Radiologists should therefore become familiar with these innovative MR techniques. Many such techniques are already widely used in other organ systems.

Normal Anatomy and Compression Areas of Nerves of the Foot and Ankle: US and MR Imaging with Anatomic Correlation

The anatomy of the nerves of the foot and ankle is complex, and familiarity with the normal anatomy and course of these nerves as well as common anatomic variants is essential for correct identification at imaging. Ultrasonography (US) and magnetic resonance (MR) imaging allow visualization of these nerves and may facilitate diagnosis of various compression syndromes, such as "jogger's heel," Baxter neuropathy, and Morton neuroma. It may be difficult to distinguish the nerves from adjacent vasculature at MR imaging, and US can help in differentiation. The authors review the normal anatomy and common variants of the nerves of the foot and ankle, with use of dissected specimens and correlative US and MR imaging findings. In addition, the authors illustrate proper probe positioning, which is essential for visualizing the nerves at US. The authors' discussion focuses on the superficial and deep peroneal, sural, saphenous, tibial, medial and lateral plantar, medial and inferior calcaneal, common digital, and medial proper plantar digital nerves.

Chronic leg pain in athletes

Chronic leg pain is commonly treated by orthopaedic surgeons who take care of athletes. The sources are varied and include the more commonly encountered medial tibial stress syndrome, chronic exertional compartment syndrome, stress fracture, popliteal artery entrapment syndrome, nerve entrapment, Achilles tightness, deep vein thrombosis, and complex regional pain syndrome. Owing to overlapping physical examination findings, an assortment of imaging and other diagnostic modalities are employed to distinguish among the diagnoses to guide the appropriate management. Although most of these chronic problems are treated nonsurgically, some patients require operative intervention. For each condition listed above, the pathophysiology, diagnosis, management option, and outcomes are discussed in turn.

Entrapment neuropathy about the foot and ankle: an update

Occurrences of entrapment neuropathies of the lower extremity are relatively infrequent; therefore, these conditions may be underappreciated and difficult to diagnose. Understanding the anatomy of the peripheral nerves and their potential entrapment sites is essential. A detailed physical examination and judicious use of imaging modalities are also vital when establishing a diagnosis. Once an accurate diagnosis is obtained, treatment is aimed at reducing external pressure, minimizing inflammation, correcting any causative foot and ankle deformities, and ultimately releasing any constrictive tissues.

Recurrent tarsal tunnel syndrome

Recurrence of tarsal tunnel syndrome after surgery may be due to inadequate release, lack of understanding or appreciation of the actual anatomy involved, variations in the anatomy of the nerve(s), failure to execute the release properly, bleeding with subsequent scarring, damage to the nerve and branches, persistent hypersensitivity of the nerves, and preexisting intrinsic damage to the nerve. Approaches include more thorough release, use of barrier materials to decrease adherence of the nerve to surrounding tissues to avoid traction neuritis, excisions of neuromas using conduits, and consideration of nerve stimulators and systemic medications to deal with persistent neural pain.