Radiofrequency Thermo-Ablation of Morton’s Neuroma: A Valid Minimally Invasive Treatment Procedure in Patients Resistant to Conservative Treatment

doi:10.4236/ojo.2013.38060

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Open Journal of Orthopedics, 2013, 3, 325-330

Published Online December 2013 (http://www.scirp.org/journal/ojo)

http://dx.doi.org/10.4236/ojo.2013.38060

Open Access OJO

325

Radiofrequency Thermo-Ablation of Morton’s Neuroma:

A Valid Minimally Invasive Treatment Procedure in

Patients Resistant to Conservative Treatment

Ronconi Paolo1, Arcioni Roberto2, Baleanu Petre Mihai1

1Foot Medical Hospital, Rome, Italy; 2Pain Unit Sant’Andrea Hospital, University of Rome “La Sapienza”, Rome, Italy.

Email: [email protected]

Received October 8th, 2013; revised November 15th, 2013; accepted November 25th, 2013

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In accor-

ABSTRACT

Background: The authors present the personal results of the review of a group of cases treated for Morton’s neuroma

with continuous radiofrequency (CRF) thermo-ablation of the plantar intermetatarsal nerve. Methods: This retrospec-

tive review consisted of 29 patients treated between January 2008 and December 2011, with a minimum 1 year follow-

up. Three patients underwent bilateral treatment and 10 patients underwent concomitant treatment procedures for asso-

ciated foot disorders: hallux valgus (7), tailor’s bunion (2) and hammertoe (5). The procedure was performed in a day

hospital setting und er direct fluoroscopic control. Results: The follow-up protocol used a visual analog scale (VAS) for

pain (0 = no pain, 10 = worst pain) and a visual analog scale (VAS) for patient satisfaction (0 = no satisfaction, 10 =

complete satisfaction). Success was defined by a decrease of 5 points in pain at 1 year after the treatment procedure.

From these 29 ca se s, w it h a VA S p ai n sc or e be t we en severe and worst pain ever, treatment with CRF thermo-ablation at

one year follow-up yielded these results: 14 cases with no pain (48%), 7 cases with mild pain (24%), 5 cases with mod-

erate pain (17%), 3 cases still with severe pain (10%). The overall b enefit was that 88% of the pa tients had significant

pain improvements. From another point of view, 26 cases (89.6%) had a decrease of the VAS score between 5 and 10

points and in only 3 cases (10.3%) severe pain was reported, even though it was slightly diminished after the procedure.

Conclusion: Continuous radiofrequency (CRF) thermo-ablation of Morton’s neuroma (Entrapment) was a safe and

minimally invasive surgical procedure whi ch gave these pat ients great sati sfactions and a rapid ret urn to no rmal activit y.

Keywords: Morton’s Neuroma; Continuous Radiofrequency (CRF) Thermo-Ablation

1. Introduction

Today, most physicians recognize that Morton’s neuroma

[1] is a nerve entrapment syndrome. This condition is

exacerbated by the wearing of narrow shoes or the use of

compressive support stockings. The ch aracteristic pain is

often described by the patient as: acute, intense, radiating

into the toes, leg an d often with strong burning sensation

or local paresthesia. Local paresthesia of the 3rd and 4th

toes is also common. The painful condition is frequently

found in the third intermetatarsal space, less often in the

second, rarely in the fourth and extremely rarely in the

first intermetatarsal space [2]. The incidence of female:

male ratio is 9:1 in our statistics, and it represents 25% -

30% of overall forefoot complaints in our office [3].

The mean age of the patients was 45 years, with most

cases diagnosed between the third and the sixth decade of

life. The presence of the symptoms at rest or during the

night should increase the suspicion of a neuropathy,

prompting further clinical investigation . It is important to

keep in mind that the Morton’s neuroma could be an ex-

pression of a metabolic degenerative condition of the

peripheral nerve, presenting as a clinical sign of a more

complex neuropathy [2].

General diagnostic methods for Morton’s neuroma in-

clude: a clinical exam which often reveals a positive

Mulder’s click [4], pain and digital paresthesia during the

maneuver of placing medial to lateral compression on the

forefoot while simultaneously applying plantar pres- sure

Radiofrequency Thermo-Ablation of Morton’s Neuroma: A Valid Minimally Invasive

Treatment Procedure in Patients Resistant to Conservative Treatment

326

on the affected intermetatarsal space (“squeeze test”), a

high-resolution sonogram exam or MRI exam to visual-

ize and confirm the presence of Morton’s neuroma, and a

gait analysis with the electronic baropodometric exam.

2. Material and Methods

We reviewed 32 feet in 29 patients affected by symptom-

matic entrapment, which did not respond to conservative

treatment, between January 2008 and December 2011, in

order to evaluate the efficacy of continuous radiofre-

quency (CRF) thermo-ablation—a minimally-invasive

treatment of the plantar intermetatarsal nerve. The pro-

cedure was performed in a day hospital setting, and un-

der direct fluoroscopic control. The follow-up was of

minimum 12 months.

The diagnostic criterion for Morton’s neuroma is

clinical, with the very common description of the pain as:

acute and extremely intense, with a burning sensation or

“knife puncture” at the level of the third and fourth toe,

radiating to the leg, and with the urgent necessity to lib-

erate the foot from shoe compression. Our study fol-

lowed best medical practices which included a clinical

exam which revealed a positive Mulder’s click [4], the

“squeeze test”, a high-resolution sonogram exam or MRI

exam to visualize and confirm the presence of Morton’s

neuroma, and a gait analysis with the electronic baropo-

dometric exam. All patients presented with clinical signs

and underwent this evaluation. Differential diagnosis

was made with other metatarsalgias, radiculopathies,

tarsal tunnel and peripheral neuropathies because the

subjects’ symptoms did not correspond to the pathology

of Morton’s neuroma and they did not enter into the

study group .

We hypothesized that the metatarsophalangeal pain

with neuralgic characteristics frequently is caused by the

compression of the branches of the plantar digital nerves

on their course through the intermetatarsal space.

Once the correct diagnosis of Morton’s neuroma was

established, we proceeded with the following five-step

therapeutic algorith m:

First step therapy: larger shoes, orthoses, local ice,

massage and physical therapy, nonsteroid anti-inflam-

matory drugs (NSAIDs). Depending on the outcome for

the patient, this step can last from 15 days to 2 months.

Second step therapy: corticosteroids plus local anes-

thetic injection (40 mg/ml. methylprednisolone acetate

with 2 cc of 2% mepivacaine), 1 injection, eventually

repeated after two weeks if the response is good after the

first injection. This step is followed for 30 or 40 days to

see if the injections are beneficial.

Third step therapy: Continuous radiofrequency (CRF)

thermo-ablation of the intermetatarsal branches of the

plantar nerve. After the intervention, a minimum of 4 - 6

months must pass in order to determine a successful out-

come. If the intervention is not successful, it is attempted

again or the fourth step is undertaken.

Fourth step therapy: surgical endoscopic decompres-

sion of the TIML (EDIN-Barrett technique) [5]. This

surgery requires a minimum of 6 months in order to

evaluate success.

Fifth step therapy: neuroma amputation with a dorsal

longitudinal intermetatarsal approach.

Pain relief after local radiofrequency nerve ablation is

thought to result from an increase in local temperature at

the site of application around the electrode to the point of

disruption of the tissue protein chains, which subse-

quently destroys the peripheral nerve endings, and the

myelin sheaths, blocking only nociceptive input [6,7].

Other authors have hypothesized that pain relief after RF

neurotomy results are not from the actual destruction of

nerve tissue, but rather from strong electric fields induc-

ed by voltage fluctuations in the area of treatment [8,9].

In this study we only considered patients treated with

continuous radiofr equency (CRF). Continuous RF (CRF)

describes a process whereby RF current is used to pro-

duce a thermal lesion in a target nerv e, resulting in inter-

ruption of nociceptive afferent pathways [8]. The CRF

produces a real nerve thermo-ablation in situ at a tem-

perature of 75˚C for 2 minutes with the probe positioned

parallel and linear with the nerve, providing the destruc-

tion of the nerve fibers. Pulsed RF (PRF) delivers short

bursts to a target nerve producing effects on signal

transduction to reduce pain. These procedures do not

produce a permanent nerve lesion [10]. The PRF, which

reaches 42˚C, is applied perpendicular to the nerve and

determines a partial and reversible lesion of the nerve

fibers with the risk of recidivism in our experience. Even

though these procedures are equally minimally invasive,

we preferred a stable result as we obtained with the CRF

method.

In our study we considered a group of 29 patients di-

agnosed with refractory Morton’s neuroma who had un-

dergone steps one and two of our treatment algorithm,

between January 2008 and December 2011, with con-

tinuous radiofrequency (CRF) thermo-ablation of the

intermetatarsal branches of the plantar nerve. Among the

29 patients, 27 were female and 2 were male. 3 patients

were treated bilaterally. 4 patients were treated for 2nd

and 3rd spaces at the same operative time. Patients’ age

ranged from 27 to 72 years, with the minimum follow-up

period being 12 months.

All the patients were informed about the other surgical

treatment options and they freely chose to attempt con-

tinuous radiofrequency thermo-ablation (CRF) therapy.

Open Access OJO

Radiofrequency Thermo-Ablation of Morton’s Neuroma: A Valid Minimally Invasive

Treatment Procedure in Patients Resistant to Conservative Treatment 327

2.1. Surgical Technique

In the operating room with the patient supine on the op-

erating table the painful intermetatarsal area was marked

and the sterile operating field was prepared. Under direct

fluoroscopic control (Figures 1 and 2) the radiofre-

quency probe was introduced in th e intermetatarsal space

and under the transverse intermetatarsal ligament from an

inter-digital approach and linear to the plantar intermeta-

tarsal nerve (Figure 3). The motor stimulation through

the probe was useful to control and avoid muscle lesion

during the radiofrequency application. The application

started when the patients informed the surgeon that the

pain induced by the sensorial probe test was similar to

the pain usually felt as a symptom. When the patient’s

answer was positive 1cc of 2% of mepivacaine was in-

jected through the probe and the radiofrequency applica-

tion started at a impedance value of 450 Ohms and 4.5

watts, for 2.5 minutes, producing a local increase in

temperature to 75˚C. The procedure was repeated in 3

distinct points along the course of the intermetatarsal

branch of the plantar nerve. Once the procedure was fin-

ished the probe was removed and the patient was dis-

charged with a small bandage. Walking was permitted

with a sport shoe with weight-bearing as tolerated. Rest

at home for 24 - 48 hours prior to returning to work was

Figure 1. Anteroposterior radiograph showing probe insert-

ed in the correct interspace.

Figure 2. Lateral view.

Figure 3. Probe inserted in the 3˚ interspace.

recommended. During the first 1 - 3 days postoperatively

the patient could use the NSAID of their choice for pain

management. The routine follow-up was done at 24 - 48

hours after the p roced ure, at 10 days, 20 d ays, 4 we eks, 3

months, 6 months and 12 months.

2.2. Outcome Surveys

Patient self-evaluation for pain and function was made

by a linear VAS score for pain ranging from 0 (no pain)

to 10 (worst pain) (Table 1).

Patient self-evaluation of satisfaction was made with

VAS in linear fashion from 0 (completely unsatisfied) to

10 (completely satisfied).

2.3. Final Results

From the 29 cases with a VAS pain score between severe

and worst pain ever, at one year follow-up after the treat-

ment with CRF thermo-ab lation of Morton’s n euroma we

obtained: 14 cases with no pain (48%), 7 cases with mild

pain (24%), 5 cases with moderate pain (17%), 3 cases

ith severe pain (10%). These 5 cases with moderate w

Open Access OJO

Radiofrequency Thermo-Ablation of Morton’s Neuroma: A Valid Minimally Invasive

Treatment Procedure in Patients Resistant to Conservative Treatment

Open Access OJO

328

Table 1. Vas pain score.

After treatment 1year follow-up Before treatment

Final results: from 29 cases (100%) with s evere to worst pain ever, at one year followup after the tr eatment with CRF thermo-ablation of t h e Morton’s

neuroma we obtained: 14 cases no pain (48%), 7 cases mild pain (24%), 5 cases moderate pain (17%), 3 cases severe pain (10%). The overall benefit

was 88% sensible improvement with a decrease of the VAS score between 5 to 10 points in 26 cases (89,6%) and only 3 cases with severe pain but

slightly diminishe d af te r the procedure.

No pain Mild pain Moderate pain (discomforting)Severe pain (distressing)Very severe (horrible) Worst pain ever

SCORE 0 1 2 3 4 5 6 7 8 9 10

CASE

1 0 8

2 1 9

3 4 10

4 0 7

5 3 10

6 0 8

7 1 9

8 6 10

9 1 10

10 0 9

11 0 9

12 1 8

13 3 10

14 4 10

15 0 9

16 0 9

17 0 9

18 1 10

19 3 10

20 2 10

21 0 9

22 0 9

23 1 9

24 0 7

25 0 8

26 0 8

27 8 9

28 7 9

29 0 10

total 14 6 1 3 2 1 1/2 1/5 12 10

Radiofrequency Thermo-Ablation of Morton’s Neuroma: A Valid Minimally Invasive

Treatment Procedure in Patients Resistant to Conservative Treatment 329

pain and 3 cases with severe pain can be explained by an

imperfect application of the technique. 88% of the pa-

tients treated had an overall benefit of pain improve-

ment. 26 patients (89.6%) had a decrease of the VAS

score between 5 to 10 po ints and in only 3 (10.3%) cases

was there severe pain reported, even though slightly di-

minished, after the procedure, as showed in Graphs 1

and 2.

The 10 patients who underwent interventions for hal-

lux valgus (7), Tailor’s bunion (2) and hammertoe (5) in

conjunction with CRF had a better overall result due to

the improvement in biomechanical function. They had a

total improvement as compared to the patients who un-

derwent CRF only.

At the end of the study we also noticed that 40% of the

patients still had some degree of footwear restriction,

90% had plantar and digital numbness at 3 months fol-

low-up, corresponding to the treated intermetatarsal

space and to the 3rd - 4th toes, but most patients were

unaware of the sensory loss at 6 months follow-up.

Wearing fashionable shoes for a long time during the day

(6 to 8 hours) remained a problem for most patients even

though they were happy with the treatment received.

20%

40%

60%

80%

100%

preop

wo rst

ve rysevere

severe

moderate

mild

nopain

Graph 1. VAS pain score before treatment.

20%

40%

60%

80%

100%

postop

wo rst

ver ysevere

severe

moderate

mildpain

nopain

Graph 2. VAS pain score after treatment. No significant

complications were encountered.

With comfortable shoes, overall satisfaction was excel-

lent in 26 patients (89%).

3. Conclusion

The results of our retrospective study indicate that the

continuous radiofrequency (CRF) thermo-ablation of the

intermetatarsal branches of the plantar nerve is a mini-

mally-invasive day surgery procedure, effective and safe

for the patient affected by symptomatic neuroma, and a

third step therapy prior to other surgical and more inva-

sive procedures because the resected nerve is always

exposed to mechanical stress and it can be involved in a

scar between skin and subcutaneous tissue, leading to

formation of painful neuroma.

4. Discussion

Many treatments have been proposed for the treatment of

neuromas, often conservative in nature and focusing on

the inflammatory aspect of neuromas.

CRF is an innovative and rapid technique that can be

done in ambulatory conditions without sutures and it

gives the same percentage of positive outcomes as more

invasive procedures and without serious complications.

The procedure has minimal to no side effects or disability

and is a very good third step therapy for patients hoping

to avoid open surgery.

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Treatment Procedure in Patients Resistant to Conservative Treatment

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