Baxter neuropathy

Baxter neuropathy is a nerve entrapment syndrome resulting from the compression of the inferior calcaneal nerve (Baxter nerve).

Clinical presentation

• heel pain with maximal tenderness over the course of the inferior calcaneal nerve (on the plantar medial aspect of the foot and anterior to the medial aspect of the calcaneus)
• paraesthesia with motor weakness of the abductor digiti minimi muscle (abductor minimi digiti or abductor digiti quinti)
• no associated cutaneous sensory deficit

Pathology

The inferior calcaneal nerve is the first branch of the lateral plantar nerve which courses in a medial to lateral direction between the abductor hallucis muscle and the medial calcaneal tuberosity.

There are three sites of possible entrapment: 

1. deep to or adjacent to the fascial edge of a hypertrophied abductor hallucis muscle
2. along the medial edge of the quadratus plantae muscle
3. adjacent to the medial calcaneal tuberosity

Predisposing factors include: 

• muscle hypertrophy
• obesity
• hyperpronated foot
• flat foot
• calcaneal enthesophyte: plantar calcaneal spur
• plantar fasciitis
• seronegative spondyloarthropathies

Radiographic features

MRI

Acute phase of muscle denervation

Affected region shows decreased signal intensity on T1 and increased signal intensity on T2 with fat-saturation due to increased extracellular water content and decreased muscle fibre volumes of the involved muscles innervated by the inferior calcaneal nerve.

Chronic phase of muscle denervation

Signs of amyotrophy or fatty degeneration of the abductor digiti minimi muscle and less commonly of the flexor digitorum brevis and the quadratus plantae muscles.

Treatment and prognosis

The treatment is generally via a non-surgical approach (e.g. glucocorticoid injections), however surgery can be performed if refractory to non-surgical approaches.

History and etymology

Baxter neuropathy is named after Donald E Baxter (fl. 2018) an American orthopaedic surgeon ⁵.

See also

• denervation changes in muscles