Chapter 25: Entrapment Neuropathies in the Foot and Ankle

Objectives

On completion of this chapter, the student/practitioner will be able to:

• Describe the anatomical pathways of the major peripheral nerves in the lower extremity.

• Identify possible sites of entrapment of the major peripheral nerves in the lower leg.

• Discuss the pathogenesis of peripheral nerve injury.

• Discuss the possible etiologies of lower extremity peripheral nerve entrapment.

• Describe the surgical and conservative interventions for each lower extremity nerve entrapment site.

• Include peripheral nerve entrapment as a potential differential diagnosis for lower extremity impairments during the clinical evaluation.

Key Terms

• Entrapment neuropathy

• Neurolysis

• Neuroma

• Peripheral nerve

Introduction

Symptoms of nerve compression in the lower extremities account for a large percentage of patients visiting their primary physician and being referred to a specialist. Because of the myriad symptoms reported by patients with potential lower extremity neuropathy, the list of potential differential diagnoses is long. Lack of proper diagnostic testing and assessment may lead to inappropriate referral, chronic pain, disability, and surgeries that are not helpful or indicated. Complicating the diagnostic process is that low back pain often accompanies tunnel syndromes in the lower extremity through systemic or multiple nerve involvement or as a direct result of gait compensation secondary to lower extremity antalgia. Lower extremity neuropathic symptoms may also be the indirect result of neoplasm, connective tissue disease, infection, peripheral vascular disease, psychiatric disturbances, hormonal imbalances, toxins, overuse, and metabolic illnesses. The diagnostician must have a good understanding of the anatomy of the lower extremity including the nerve paths. In addition, content knowledge of the endocrine, neural, musculoskeletal, integument, renal, gastrointestinal, and cardiopulmonary systems often is relevant to the diagnosis and interventions associated with lower extremity neurological symptoms.

Anatomy

The lower extremity receives sensory and motor innervation from branches of the sciatic nerve along with the saphenous nerve. The sciatic nerve is the only nerve in the lower extremity arising from the lumbar plexus. Branches of the sciatic nerve include the common peroneal nerve and tibial nerve. The common peroneal nerve branches further to form the superficial peroneal nerve and the deep peroneal nerve. The superficial peroneal nerve provides cutaneous innervation to the anterior and anterolateral aspect of the foot and ankle and provides motor innervation to the muscles in the lateral compartment of the leg. The deep peroneal nerve innervates muscles of the anterior compartment of the leg and intrinsic musculature of the dorsal foot and provides cutaneous innervation to the first interspace. The tibial nerve branches into the sural nerve, medial plantar nerve, lateral plantar nerve, and medial calcaneal nerve. The sural nerve provides cutaneous innervation to the lateral aspect of the foot. The medial plantar nerve innervates the plantar intrinsic musculature of the foot. ...