Plantar Fasciitis with Chronic Baxter's Neuropathy Causing Hindfoot Pain - A Case Report

The main differentials of non-traumatic heel pain are plantar fasciitis (PF), plantar heel fat pad atrophy, worn-out footwear, especially asymmetric wear and tear, hyperuricemia, corns, callosities, tumors of the calcaneum, osteomyelitis, calcaneal stress fractures due to overweight or unaccustomed over usage, radiating pain from S1 nerve root compression, and seronegative spondyloarthropathies. Compression of the tibial nerve or the medial calcaneal nerve at or around the flexor retinaculum is the other possibility. In this case report, we want to highlight a sparsely known pathology, caused due to the entrapment of the first branch of the lateral plantar nerve or inferior calcaneal nerve, also known as Baxter's nerve that may present independently or accompany the common PF. Non-steroidal anti-inflammatory medications or injections of local steroids are typically used for conservative management. However, hydro-dissection or surgical release may be needed in non-responsive cases.

We present the case of a 57-year-old female with complaints of chronic pain and tenderness in the middle of the heel radiating laterally. She underwent magnetic resonance imaging that revealed chronic denervation changes in the form of marked atrophy and near complete fatty replacement of abductor digiti minimi muscle suggesting chronic Baxter neuropathy. A mildly thickened and hyperintense plantar fascia adjacent to the calcaneal spur and significant heel fat pad edema were seen too. The patient responded well to a local steroid injection and remains pain-free at the 1-year follow-up.

When heel pain is present, Baxter's nerve impingement presents as a challenging clinical diagnosis that may accompany the common PF and is often overlooked. MRI can be used to assess the denervation effects of both the acute and chronic stages of Baxter's nerve impingement by identifying abnormalities of the abductor digiti minimi muscle belly.