Baxter’s neuropathy is a specific condition resulting from the entrapment of a small nerve in the heel area, which is a frequently overlooked cause of chronic heel pain. This entrapment involves the compression of the nerve as it passes through a narrow space beneath the arch of the foot. It is estimated that this condition accounts for up to 20% of cases involving long-term heel pain, often leading to a misdiagnosis of plantar fasciitis. Correct identification is important because its treatment differs significantly from other common causes of heel discomfort.
Defining the Nerve and Entrapment Site
The nerve involved is known medically as the Inferior Calcaneal Nerve, also called the First Branch of the Lateral Plantar Nerve (FBLPN). This small nerve originates from the Lateral Plantar Nerve, a major branch of the tibial nerve that runs through the ankle’s tarsal tunnel. The FBLPN then courses beneath the heel bone, or calcaneus.
The nerve is most commonly compressed at two primary locations along its path under the heel. The first site is between the deep fascia of the abductor hallucis muscle and the quadratus plantae muscle. The second common site is further along its course, where it can be compressed against the heel bone, particularly near the medial calcaneal tuberosity.
The FBLPN is a mixed sensory and motor nerve, supplying sensation to the heel bone’s covering (periosteum) and providing motor control to the abductor digiti minimi muscle. This anatomical position, sandwiched between muscle and bone at a point of high mechanical stress, makes it vulnerable to compression. Entrapment leads to inflammation and dysfunction, manifesting as persistent heel discomfort.
Identifying the Symptoms of Nerve Compression
Patients typically experience a deep, aching, or burning pain concentrated on the inner (medial) side of the heel and extending into the foot’s arch. The discomfort is often sharp and localized to the point of nerve compression. Unlike classic plantar fasciitis, which causes intense pain upon the first steps in the morning, Baxter’s neuropathy pain may not be immediately worse upon rising.
The nerve-specific nature of the problem can also lead to symptoms such as tingling, numbness, or a pins-and-needles sensation in the arch or along the inner heel. Since the nerve supplies the abductor digiti minimi muscle, long-standing compression may lead to weakness or atrophy in that muscle. The pain frequently intensifies after prolonged periods of standing, walking, or physical activity, reflecting the cumulative pressure on the entrapped nerve.
Common Causes and Risk Factors
The primary reason for nerve entrapment is the narrowing of the space through which it travels, often due to biomechanical or structural factors. A frequent contributor is excessive pronation (flat feet), which alters foot mechanics and increases tension on the muscles and ligaments. This change in foot posture can cause the abductor hallucis muscle to enlarge (hypertrophy), effectively squeezing the nerve against adjacent structures.
Structural changes in the foot can also physically crowd the space around the nerve. Bone spurs on the underside of the heel bone, sometimes associated with plantar fasciitis, can directly press upon the FBLPN. Obesity is another significant risk factor, as increased body weight puts greater mechanical stress on the foot’s soft tissues and muscles.
Repetitive strain from high-impact activities (such as running or sports) or occupations requiring extended standing can lead to chronic inflammation and swelling in the foot. This inflammation further reduces the available space and irritates the nerve. Poorly fitting footwear that lacks adequate arch support or is too tight can also contribute to the condition.
Methods for Diagnosis and Management
Diagnosing Baxter’s neuropathy begins with a detailed physical examination, as symptoms closely resemble other common heel issues. A healthcare provider may perform maneuvers like Tinel’s sign, which involves lightly tapping the nerve’s course to see if it reproduces the characteristic tingling or sharp pain. Imaging studies are often employed to rule out other causes and visualize soft tissues.
While X-rays can identify bone spurs that may be compressing the nerve, Magnetic Resonance Imaging (MRI) or high-resolution ultrasound can visualize the nerve and any associated muscle changes, such as swelling or atrophy. The most definitive diagnostic tool is often an ultrasound-guided diagnostic nerve block. A small amount of local anesthetic is precisely injected near the nerve; a temporary cessation of pain strongly indicates FBLPN entrapment.
Initial management focuses on conservative strategies to relieve pressure and inflammation on the nerve. This typically includes activity modification, rest, and the use of customized orthotic devices to correct excessive pronation and redistribute pressure away from the entrapment site. Physical therapy often involves targeted stretching and strengthening exercises to improve foot mechanics.
If conservative methods fail to provide adequate relief, interventional treatments are considered. These include injections of corticosteroids near the nerve to reduce inflammation, or nerve hydrodissection, where fluid is injected to gently separate the nerve from surrounding tissues. For cases that do not respond to non-surgical treatment, surgical decompression (nerve release) may be performed to physically free the entrapped nerve.