Baxter's Nerve Entrapment

From WikiMSK

Revision as of 20:04, 16 April 2022 by Jeremy (talk | contribs)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

Written by: Dr Jeremy Steinberg – created: 15 April 2022; last modified: 16 April 2022

This article is still missing information. Join WikiMSK to help expand it
Baxter nerve entrapment sites.png
The two common sites of entrapment between the abductor hallucis (AH) and quadratus plantae (QP), and along the medial calcaneal tuberosity under the flexor digitorum brevis (FDB)
Baxter's Nerve Entrapment
Pathophysiology Compression of the Inferior Calcaneal Nerve (Baxter Nerve)
Clinical Features Burning medial heel pain that worsens with standing and walking.
Tests MRI
Treatment Rest, NSAIDs, injections, orthotics, surgery.

Baxter's nerve entrapment, also known as Baxter neuropathy, and inferior calcaneal nerve entrapment, is plantar heel pain arising from compression of the inferior calcaneal nerve (Baxter nerve).

Anatomy

Baxter nerve (Nerve to abductor digiti quinti).[1]
Main article: Inferior Calcaneal Nerve (Baxter Nerve)

The inferior calcaneal nerve (Baxter nerve) is the first branch of the lateral plantar nerve, which is itself a branch of the tibial nerve. The nerve lies in between the abductor hallucis muscle and quadratus plantae.

The Gray's anatomy image and many other anatomy textbook images are incorrect. The Baxter nerve is quite posterior and lies very close to the calcaneus. It was named after Donald Baxter.[1]

Pathophysiology

There are three entrapment points:[2]

  1. Where the nerve runs between the deep fascia of the abductor hallucis and medial plantar margin of the quadratus plantae
  2. More distally along the anterior aspect of the medial calcaneal tuberosity. A calcaneal plantar enthesophyte and/or soft tissue changes of plantar fasciitis may contribute to entrapment at this second location.

Aetiology

The following are some causes of entrapment[3]

  • Repetitive microtrauma. E.g. those with jobs requiring prolonged standing or walking, or avid runners. Plantar fasciitis. Fat pad atrophy.
  • Acute trauma. direct trauma from a fall or stepping on a hard object, scar tissue after plantar fasciotomy.
  • Impingement from bony exostosis, calcaneal spur, neuroma, neurilemmoma
  • Stretch injury from a hypermobile pronating foot, abductor hallucis hypertrophy in runners
  • Diabetic peripheral neuropathy.

Epidemiology

It is estimated that up to 20% of patients with chronic heel pain may be due to Baxter nerve entrapment.[1]

Risk Factors

Obesity, age, diabetes, muscle hypertrophy, hyperpronated foot, pes planus, plantar calcaneal spur, plantar fasciitis, spondyloarthritis.

Clinical Features

Tenderness of the medial calcaneal tubercle (reproduced with permission by Dr A Trescot.)[3]

History

The clinical features may be similar to or coexist with plantar fasciitis. However there may be less morning pain, occasional altered sensation, and intrinsic muscle atrophy. The pain is felt in the medial heel and is often burning. It may worsen with prolonged standing and walking. It typically has a gradual onset.

There are two groups of patients with this condition: keen runners and those involved in everyday living.[1]

Examination

On examination the patient may walk with exaggerated supination to avoid placing weight on the medial heel. They are tender over the medial calcaneal tubercle similar to the location for plantar fasciitis.

Palpate the distal Achilles tendon and retrocalcaneal bursa looking for tenderness. Also squeeze the heel to detect a stress fracture.

Look at active motion of toe abduction and adduction and compare to the other side. Assess strength with resisted abduction and adduction.

Evaluate Tinel's sign by percussing the upper and lower tarsal tunnels, however this is often absent.

Differential Diagnosis

Differential Diagnosis of Heel Pain

Differentiation from plantar fasciitis is not always straight forward. MRI can be helpful.

Differentiating Plantar Fasciitis and Baxter Nerve Entrapment.
Feature Baxter Nerve Entrapment Plantar Fasciitis
Timing Pain worse after activity and night "First step" pain. Worse first thing in the morning and after a period of inactivity
Walking Worse with walking Better with walking
Pain type Neuropathic pain Nociceptive pain
Tenderness Medial calcaneal tuberosity, radiates to medial ankles and/or lateral foot Insertion of plantar fascia at medial calcaneal tuberosity and along the medial edge where the fascia may feel thickened.
Heel pad sensation Equal to contralateral side Equal to contralateral side
Modifed from Trescot et al.[3]

If the patient has back pain then consider L5 or S1 radicular pain and examine for radiculopathy (See Lumbar Radicular Pain).

If the patient has bilateral heel pain then consider a rheumatologic origin.

Baxter nerve has no cutaneous sensation, and so if there is sensory change then medial calcaneal nerve entrapment is more likely.

In tarsal tunnel syndrome the entrapment and tenderness is more proximal.

Investigations

Coronal PD image showing fatty atrophy.[4]

Diagnostic Injection

Injecting the baxter nerve can't differentiate between plantar fasciitis and baxter nerve entrapment.

Imaging

On MRI in the acute phase there is decreased T1 signal intensity and increased T2 signal intensity with fat saturation in the muscles innervated by the Baxter nerve. In the chronic phase there is fatty change of the abductor digiti minimi muscle, and occasionally the Flexor Digitorum Brevis and Quadratus Plantae.

Ultrasound can show a thickened and hypoechoic plantar fascia. This doesn't rule out Baxter nerve entrapment because a thickened plantar fascia can entrap the nerve.

Treatment

The nerve can be injected with corticosteroid and/or hydrodissected under ultrasound guidance.

External Links

Baxter's Nerve (First Branch of the Lateral Plantar Nerve) Impingement - Radsource

References

  1. 1.0 1.1 1.2 1.3 Baxter, D. E.; Thigpen, C. M. (1984-07). "Heel pain--operative results". Foot & Ankle. 5 (1): 16–25. doi:10.1177/107110078400500103. ISSN 0198-0211. PMID 6479759. Check date values in: |date= (help)
  2. Moroni, Simone; Zwierzina, Marit; Starke, Vasco; Moriggl, Bernhard; Montesi, Ferruccio; Konschake, Marko (2019-01). "Clinical-anatomic mapping of the tarsal tunnel with regard to Baxter's neuropathy in recalcitrant heel pain syndrome: part I". Surgical and radiologic anatomy: SRA. 41 (1): 29–41. doi:10.1007/s00276-018-2124-z. ISSN 1279-8517. PMC 6514163. PMID 30368565. no-break space character in |title= at position 123 (help); Check date values in: |date= (help)
  3. 3.0 3.1 3.2 A.M. Trescot (ed.), Peripheral Nerve Entrapments: Clinical Diagnosis and Management, DOI 10.1007/978-3-319-27482-9_76
  4. Bauones, S., Feger, J. Baxter neuropathy. Reference article, Radiopaedia.org. (accessed on 15 Apr 2022) https://doi.org/10.53347/rID-25994
  5. Baxter's nerve Sd. Procedure: corticosteroid injection & orthotics. Good result. @Dr_Ramon_Balius #MSKUltrasound pic.twitter.com/ED9RcmqJnz

Literature Review