Heel pain is commonly caused by plantar fasciitis, and treated successfully with physiotherapy. But there are times when despite stretching, night splints, manual techniques, orthotics and laser the pain does not go away. Other conditions that can cause heel pain include heel pad atrophy, tarsal tunnel syndrome, heel spurs, calcaneal stress fractures, periosteal inflammation and entrapment of the first branch of the lateral plantar nerve (Baxter’s nerve). The heel pain with all is similar, making it difficult to differentiate between the causes, and they may occur simultaneously with plantar fasciitis.
Research suggests that up to 20% of heel pain is not caused by plantar fasciitis, but by entrapment of Baxter’s nerve. Plantar fasciitis pain is typically worse on the medial aspect of the heel, and is most painful with the first step in the morning or after prolonged sitting as the plantar fascia tightens with non weight bearing and is then forcibly stretched once a step is taken. Baxter’s nerve entrapment typically is most painful on the lateral aspect of the heel, is worse with prolonged weight bearing and often aches even at rest. A feature unique to Baxter’s nerve entrapment is paralysis of the little toe. Baxter’s nerve provides motor function to the abductor digiti minimi, and sometimes also to the flexor digitorum. Involvement of abductor digiti minimi can be detected by attempting to spread the toes, and noticing that the little toe does not move. Because many people cannot do this normally, it is important to compare both sides before the test is considered positive. Involvement of flexor digitorum can be assessed by attempting to hold a playing card on the floor with the 4 toes of the foot (not the big one!) while trying to pull the card away. If one is unable to spread the little toe and hold a card on the floor with the 4 toes, entrapment of Baxter’s nerve should be considered. There may also be lack of sensation to the little toe and half of the fourth toe if the sensory branch of the nerve is affected.
Because Baxter’s nerve entrapment often occurs concurrently with plantar fasciitis, the original treatment approach is the same. A program of manual stretching techniques, home stretches, ice, strengthening foot intrinsics, night splints and laser is initiated. If pain persists, then special nerve tractioning techniques for the lateral plantar nerve and massage of the abductor digiti minimi, flexor digitorum and quadratus plantae are added. A course of anti-inflammatories or corticosteroid injection is often considered. An MRI is valuable in detecting atrophy of the abductor digiti minimi, as without it Baxter’s nerve entrapment often goes undiagnosed. If these conservative techniques fail, then surgical release or block of the nerve is considered.