Physiotherapy for Morton's Neuroma

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Introduction

Civinini Morton’s Syndrome (CMS) is more commonly known as Morton’s neuroma. Interdigital neuritis is another term that was proposed by Weinfield and Myerson which more correctly describes the pathology of this condition. The presence of inflammatory tissue in histological examination justifies description of Morton's neuroma as perineurial fibrosis. Pain and abnormal forefoot sensation are clinical symptoms that helps with the diagnosis. Conservative treatment including lifestyle adjustment may not always be effective and patient can choose surgery or various types of ultrasound guided percutaneous injections as an option.

Clinically Relevant Anatomy

Magnetic resonance imaging (MRI) shows the medial and lateral plantar nerves arising from the posterior tibial nerve. The tibial nerve terminates in the foot by giving branches to medial and lateral plantar nerves. This bifurcation occurs inside the retinaculum or proximal to the flexor retinaculum. The two plantar nerves penetrate the tunnel made of the deep fascia of the abductor hallucis muscle and the fibrous septum connecting the fascia to the bone.

The medial plantar nerve (MPN) is the larger of the two plantar nerves. It originates under the laminate ligament, passes between abductor hallucis muscle and flexor digitorum brevis. Upon reaching the bases of the metatarsal, it divides into three common digital plantar nerves.MPN innervates the abductor hallucis, flexor hallucis brevis, flexor digitorum brevis and the first lumbrical.

The lateral plantar nerve (LPN) innervates abductor digiti minimi muscle, flexor digiti minimi brevis muscle, quadratus plantae, 3 lateral lumbricals of the foot, adductor hallucis muscle, plantar interossei muscles, and dorsal interossei muscles.

The common plantar digital (CPD) nerves pass under the intermetatarsal ligaments, go through the plantar aponeurosis and divide into 2 branches supplying the plantar skin of the toes. Smaller portions of the CPD nerves innervate the adjacent metatarsals, metatarsophalangeal joints and plantar skin, under the metatarsal heads. The third common digital nerve begins as the medial plantar nerve and receives a communicating branch from the lateral plantar nerve. Because it passes in the narrow space deep to the transverse metatarsal ligament it becomes less mobile, especially during weight bearing activities.

The branches of the common digital nerve in the third planter webspace are most commonly affected. The location of this nerve near the narrow space of the transverse metatarsal ligament may be a possible explanation for the development of the Morton's Neuroma pathology within the third intermetatarsal space.

Neuroma

Neuroma is also referred as pinched nerve. Morton's neuroma is a compressive neuropathy of the common plantar digital nerve caused by an entrapment of the nerve between the intermetatarsal ligaments.

Aetiology

There are several aetiopathogenetic theories behind the development of Morton's neuroma. It include:

• chronic traction damage
• chronic, repetitive trauma
• ischemia of vasa nervorum
• entrapment or mechanical compression
• inflammation due to intermetatarsal bursitis

One of the theory explaining the occurrence of Morton's neuroma is based on the notion that the third common digital nerve is thicker than the others as the result of an anastomosis between two nerve trunks. The inflammation theory is explained by the increased mobility of the fourth ray compared to the third.The compression theory is based on the finding that the plantar nerve is compressed by the distal metatarsal transverse ligament.

Epidemiology

Morton's neuroma is characterised by female predominance, with a female to male ratio of 5:1. It affects about 30% of the population, an average patient's age is 50, the pathology affects both feet, in most cases the third intermetatarsal space is involved, followed by the second (Hauser’s neuroma). Multiple locations are very rare.

Mechanism of Injury / Pathological Process

The most frequently mechanism of injury supported by the literature is nerve entrapment. The third common digital nerve is thicker as a consequence of fusion between the medial and lateral plantar nerves. This leads to its entrapment by the surrounded ligament. Entrapment neuropathy is causing perineural fibrosis and nerve degeneration. The thickening of the nerve progresses as a result of vascular hyalinisation which causes more trauma to the nerve and more entrapment. Adding to the pathological process is the use of high heel shoes forcing the excessive forefoot weight bearing.

Clinical Presentation

There are two types of clinical presentation in Morton's neuroma: clinically symptomatic and clinically asymptomatic.

Clinically symptomatic Morton's neuroma presents with the following symptoms:

• Pain or paresthesias in the intermetatarsal region. Pain is worsened by weight-bearing or the use of high-heeled shoes. Removing shoes and gentle massaging the forefoot usually relief the pain.
• Pain is usually sharp
• Patient can complain of burning sensation in the intermetatarsal spaces
• Mass can be palpated
• Symptoms can be present as a result of trauma
• Altered sensation described as “pebble in the shoe”
• Pain is worsen with walking or running

Presence of the hallux valgus is considered a predisposing factor in development of Morton's neuroma

no visual cues to the presence of a neuroma. Any deformity of the foot specially hallux valgus can lead to overcrowding of the toes and increased pressure on the lesser toes, and is therefore an important predisposing factor.

describe abnormal forefoot sensations such as a burning or ache . Pain localisation is most common in the plantar aspect of the forefoot, followed by the toe(s) and then the dorsal web space. Diagnosis can reliably be made based on clinical presentation and testing with ultrasound proposed as an accurate and cost-effective imaging method to confirm the diagnosis, especially in cases where the clinical diagnosis is equivocal . Ultrasound without a clinical diagnosis may lead to a false diagnosis of MN for asymptomatic interdigital nerve enlargements

he typical symptom is a burning pain between the metatarsal heads, often radiating to the two corresponding toes, with cramps and hyperesthesia/dysesthesia (26). The pain is intense and so debilitating that the patients become afraid and anxious about walking or even putting their foot to the ground. The disorder is that of a severe, sharp, sometimes piercing pain that occurs abruptly while walking. At onset, relief of pain can be obtained by massaging the foot or manipulating the toes. In the worst cases, pain becomes debilitating and patients are timorous about walking. In other cases, patients describe milder symptoms of burning or tingling sensations

Diagnostic Tests

a positive web space compression test or a painful palpable click (Mulder's sign) was considered suggestive of Morton's neuroma.

Diagnostic Procedures

Ultrasound has high diagnostic accuracy for Morton's neuromas, and is frequently used to guide corticosteroid with local anaesthetic injection following the diagnostic scan. However, ultrasound is a highly operator-dependent imaging method, thus technique and experience are extremely important.
if there is any doubt of the diagnosis, an MRI scan is the gold standard investigation to identify a neuroma,

A positive digital nerve stretch test 1 and a positive Mulder’s click test

X-rays appears to be essential as a first line imaging approach, to investigate other possible causes of metatarsalgia such as (36): tarsal–metatarsal joint stiffness, metatarsal hypermetria, Frieberg’s disease, toe deformities and MTP instabilities. However, in order to eliminate possible doubts, sonographic (US) confirmation is usually the instrumental investigation mostly utilized (14), certainly reliable and easy to prescribe, as it is fast and inexpensive for the patient. The imaging must be carried out with plantar and back, transversal and longitudinal US scans with a 7.5 MHz high frequency probe. The neuroma appears as homogeneously hypoechoic mass, well recognizable by the adjacent hyperechoic fat and by the shadow of the metatarsal cortex. Shapiro (37) and Quinn (38) state a diagnostic reliability around 95% for lesions larger than 5 mm, being 2 mm the maximum limit of the normal nerve.

MRI is superior in the differential diagnosis, for its sensitivity on pathologies such as stress fractures, capsulo-synovitis of the MTP, synovial articular forms, or other pathologies of the soft tissues such as lipomas, angiomas, tendon ganglia or connective malignancies of the forefoot (43). Main indications for MRI are unclear clinical assessment and cases when more than one IMS is affected (1). Finally, it must be bear in mind that a negative result does not exclude the diagnosis (false negative 17%)

Outcome Measures

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Management / Interventions

Footwear

staged care approach from wider, low heeled footwear and metatarsal paddingProperly fitted footwear with a wide toe box, low heel and a metatarsal pad

The first approach in the early stages of this condition usually begins with shoe modifications and orthotics, designed to limit the nerve compression. In order to prevent or delay the development of CMS, shoes should be sufficiently long, comfortable, broad toe-boxed, should bear a flat heel and a sufficiently thick external sole which should not be excessively flexible. Most authors suggested that an insole with medial arch support and a retrocapital bar or pad, just proximal to the metatarsal heads, displaces the pressure sites and can be beneficial to relieve the pain from the pinched nerve. A threshold period of 4.5 months appears to emerge from the results of the analysed studies, indicating that, beyond this period and in neuromas larger than 5-6 mm, orthotics and/or shoes modifications do not seem to give convincing results, proving to be more a palliation for the clinical condition to allow an acceptable life with pain rather than a real treatment.

Thus, the first approach in CMS should consist in patients’ education to avoid narrow and high-heeled shoes (4). The objective of shoes modifications is to deliver the pressures uniformly over the sole of foot. Shoes should be sufficiently long, comfortable, broad toe-boxed, flat heeled and should bear a sufficiently thick external sole, not excessively flexible (Figure 2) (2). A rocker-bottom sole may be helpful. Some authors showed that footwear and padding may be successful in relieving symptoms in 32% of cases after a mean of 4.5 months (17, 49) but they seem to achieve lower satisfaction rates when compared with other more invasive methods such as steroid injections .

A threshold period of 4.5 months appears to emerge from the results of the studies, indicating that beyond this period and in larger neuromas than 5-6 mm, orthotics and/or shoes modification do not seem to give convincing results, proving to be more a clinical condition for living acceptably with pain than a real treatment.

Orthotics

The commonest form of treatment (initially) is the Metatarsal Bar. This insole, made by orthotists spreads the heads of the metatarsals to relieve pressure on the neuroma and thus improve symptoms. However, this does require the patient to wear broad toe box shoes and use the inserts so a degree of compliance is required. There is no evidence to support the use of inversion or eversion insoles, with studies demonstrating no significant improvement in patient reported outcomes

de Oliveira HAV et al The study demonstrated that customized insole with metatarsal and arch support relieved walking pain and improved patient-reported measures of function in patients with Morton’s neuroma.

Varus/valgus foot wedge a cobra style hard compressed felt padding adhered to the plantar surface of a fibreboard insole to supinate or pronate the foot. These were worn in the participant’s usual footwear (low heeled lace-up or loose fitting slip on shoes)

In the case of CMS, some authors prefers a custom orthotics through foam impression methods, in a neutral subtalar position, with a prolonged longitudinal vault to support the first metatarsal, with a flat metatarsal support (without olive or bar), in order to favor the physiological pattern of the metatarsal weight bearing, from lateral to medial, before the pressure on the big toe

Other authors suggested that a retrocapital bar or pad, just proximal to the metatarsal heads displaces the pressure sites and can be beneficial for symptoms (Figure 3). Metatarsal padding helps to spread and cushion metatarsal heads to relieve the pain from the pinched nerve. If needed, a cup can be added beneath the painful metatarsal head or heads. Custom-made toe inserts modeled in silicone rubber can be added in patients having associated claw-toe deformity

Steroid Injections

The use of therapeutic injections is very common in the management of Morton’s neuroma, and multiple therapies have been used. The injection can be guided by USS or done using a landmark technique. A randomised trial by Mahadevan et al did not show any statistical difference in patient outcomes after a steroid injection using USS or without.12 Santiago et al. noted that short term improvement in visual analogue scale (VAS) over 3 months in the group of patients having USS guided injections wa

Modality

extracorporeal shockwave therapy ESWT may reduce pain in patients with Morton's neuroma.

Manipulation/Mobilisation

Manipulation/mobilisation (involving distraction and plantarflexion of the metatarsophalangeal joints and mobilisation of other foot and ankle joints as required)

Study by Cashley and Cochrane once a week for 4 weeks followed by 2 further visits at 14-day intervals

Differential Diagnosis

The differential diagnosis includes intermetatarsal bursitis, true neuroma, inflammatory arthritis, pigmented villonodular synovitis, osteomyelitis, foreign body granuloma, stress fracture, Freiberg's infraction, and metatarsophalangeal joint dislocation.

Surgery

In any cases, when modifications fail or if affected individuals are no longer willing to make adjustments to their lifestyle or shoe wear (64, 65), patients may always choose to undergo surgery or other non-operative treatments such as US guided percutaneous radiofrequency (66), alcohol or corticosteroids injection and percutaneous electrostimulation-guided alcoholization with phenol Needle-electrode guided percutaneous alcoholization is an outpatient, minimally invasive procedure with low rate of complications. Better results of those obtained with traditional conservative treatments and comparable with those reported with other alcohols injections or surgical nerve excision were observed.

Operative management options primarily involve either nerve decompression or neurectomy.

Resources

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