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