In this section Cypress Foot and Ankle specialist Dr. Christopher Correa discusses Baxter's nerve entrapment. The term “Heel Spur” is a common phase used when describing plantar heel pain and is one that often invokes an image of a sharp needle like projection extending from the heel which cuts the patient with every step. While heel spurs can be impressive on X-ray, in most cases of plantar heel pain caused by plantar fasciitis the spur is not usually a major source of pain. This is exemplified by the thousands of X-Rays podiatrist take each year where an inferior calcaneal spur is found without any pain or other symptoms. The exception to this is when the spur either fractures or impinges on Baxter's nerve. When patients refer to heel spurs they typically are referring to a condition called plantar fasciitis. Generally speaking, the cause of plantar fasciitis is the repetitive micro tearing and degeneration of the plantar fascia from repetitive healing and tearing cycles, not typically the spur. While the vast majority of the time the cause of plantar heel pain is plantar fasciitis and the presence of a heel spur is irrelevant, there is a form of heel pain where a nerve becomes entrapped on the calcaneal spur.
What is Baxter's Nerve Entrapment
The first branch of the lateral calcaneal nerve is known as Baxter’s nerve. This nerve runs between two muscle bellies known as the abductor hallucis and quadratus plantae on the instep of the foot. As the nerve passes under the Abductor Hallucis it pierces the fascia and travels just superficial to the plantar heel bone first innervating the bottom surface of the heel and then continuing on to innervate the abductor digiti minimi on the plantar lateral portion of the foot. Classically Baxter’s nerve impingements can occur in 2 locations. The first location is where the nerve passes through the fascia between the abductor hallucis and qudratus plantae muscle bellies. The second is by the spur at the inferior aspect of the heel bone when it is present. The pain created by a Baxter’s nerve entrapment is described to be very similar as plantar fasciitis by patients and is often initially misdiagnosed as such. Fortunately, the initial treatment regime is nearly identical for both. Your physician will likely recommend calf stretching, non-steroidal anti inflammatories, steroid injection, arch supports, compression socks, supportive shoes, physical therapy and a reduction in activity. In many cases symptoms resolve without the real underlying cause every being elucidated. In cases where symptoms do not improve there are certain signs and symptoms that may clue the doctor into a Baxter’s nerve entrapment.
1. The pain is more of a burning and tends to linger for a few minutes when getting off of the foot instead of going away immediately.
2. There is a burning character to the pain and may actually involve the rim of the heel instead of the plantar surface. Additionally, the pain may linger for a few minutes when the patient sits down or proper the foot up.
3. Pain is not worse with the first step out of bed in the morning but rather gets progressively worse throughout the day with weight bearing.
4. The pain is not actually at the plantar medial heel but rather more medially in a soft spot known as the Porta Pedis.
Diagnosis can be aided with advanced imaging modalities such as MRI. In the presence of an entrapped nerve an MRI can show changes and atrophy of the Abductor digiti minimi muscle which occur in response to relative denervation from nerve damage.
Treatment of Baxter's Nerve Entrapment
As mentioned earlier conservative care for Baxter’s nerve entrapment is similar to plantar fasciitis however the surgical treatment is not. Often times in recalcitrant plantar fasciitis the plantar fascia itself is damaged and torn and requires a partial release. In Baxter’s nerve entrapment on the other hand is a form of lower tarsal tunnel syndrome where the nerve is impinged somewhere along its course similar to a carpel tunnel syndrome but in the foot. Neurolysis or release of the nerve from surrounding impingements is necessary to improve symptoms. This usually means freeing the nerve from its scar tissue constrictions as it passes through the fascia deep to the abductor hallux muscle or removal of the heel spur when present. The take home message is that plantar heel pain has a few different possible causes. The presence of a heel spur does not automatically mean that you have plantar fasciitis and the absence of one doesn’t automatically mean that you do not have it. If you have persistent heel pain with will not resolve, call the experts at Select Foot and Ankle Specialists today for a foot and ankle evaluation and take the first step towards recovery today!
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