Document 6475838

RECURRENT INTERMETATARSAT NEUROMA
D. Scot Malay, D.P.M.
The majority of our patients, and those reported in the
literature, with recurrent neuroma are females in their
fourth or fifth decade of life. lt is well known that females
are more commonly diagnosed with Morton's neuroma.
This observation is most likely due to pathomechanical
forces focused on the female forefoot secondary to wearing shoe gear with typically higher heels, a narrower toe
box, and a poorly padded sole. The second and third
interspaces are most commonly affected in patients with
recurrent neuromas/ regardless of sex.
The intermetatarsal neuroma is one of the most common afflictions of the human foot. Classically, this lesion
involves the third intermetatarsal space, and is termed
Morton's neuroma. Miller provided a detailed discussion
of the history, signs and symptoms, pathophysiology,
and treatment of the intermetatarsal neuroma (1).
Surgical intervention is often required to alleviate the
symptoms as conservative management is all too frequently (70%-80y" of cases in our experience) unsuccessful at totally eliminating pain and achieving a satisfactory result. Nonetheless, surgical treatment of the
ETIOIOGY OT PAINFUT RECURRENT NEUROMA
painful intermetatarsal neuroma entails as high as a
10%-15% failure rate, failure being defined as no
improvement over the preoperative condition, or
worsening of symptoms (1-3).
Assuming that the original diagnosis of intermetatarsal
neuroma was correct, and that appropriate surgical
intervention was performed, a recurrence of symptoms
could only come about secondary to the development
of a stump neuroma (Fig. 1). The surgeon evaluating the
patient with a recurrent neuroma should always review
the pathology report, if not the actual histologic sections,
from the previous surgery. Moreover, the previous
operative report should be reviewed if it is available'
rrent symptomatology u sual ly becomes apparent
between three and eight weeks postoperative, or it may
develop after months, or even years of a seemingly successf u I su rgical i ntervention. Recu rrent sym ptomatology
is usually due to the development of a traumatic, or amputation stump neuroma affecting the common digital
nerve just proximal to the metatarsophalangeal joint.
Recurrence often entails some degree of entrapment
Recu
within the scar produced during healing of the surrounding tissues following interspace dissection.
PATIENT POPULATION AND RECURRENCE RATES
A number of recent studies have critically evaluated
the results of neurectomy for the treatment of
in-
termetatarsal neuroma (2-4). Retrospective evaluation
reveals that approximately B%-15% of previously
operated patients will elect to undergo a second surgical
intervention in an effort to alleviate recurrent symptomatology (2, 3). This group of patients, obviously, correlates with the previously mentioned overall rate of
surgical failure of up to 10%-15%. This relationship makes
sense when one considers that failed first surgery has
a very small chance of responding to conservative
management. ln general, we have found that if there is
no improvement by three or four months postoperative
(first surgical intervention), well into the collagen
remodeling phase of wound healing, there is probably
little chance of significant improvement with prolonged
conservative care.
Fig. 1. Symptomatic intermetatarsal stump neuroma status post neurec-
tomy for Morton's neuroma.
321
The stump, or traumatic neuroma/ develops as budding neurites in the proximal segment of the transected
nerve trunk proliferate and attempt to bridge the gap and
grow into the endoneurial tubes of the distal segment.
The neurites become entrapped in scar tissue and may
adhere to neighboring anatomic structures, such as the
metatarsophalangeal joint capsule, or periosteum of the
metatarsal shaft, and adjacent tendons, ligaments, and
muscle. Obviously, the intent of the first surgery was to
eliminate the nerve trunk at the level of the deep
transverse intermetatarsal ligament, allowing the proximal stump to retract into the well protected and well
vascularized confines cif the intrinsic musculature and
plantar vault.
Fig.2. Location of maximum tenderness at plantar aspect of left foot
in 48 year old female, 7 months after second surgical intervention via
dorsal approach for recurrent neuroma involving the third inter-
lnadequate nerve trunk resection may be the most likely cause of recurrence. Unfortunately, there is no way
to accurately measure the adequacy of neurectomy at
the time of surgery, and the surgeon can only strive for
a clean, sharp resection, with accurate anatomic dissection, absolute hemostasis, and the avoidance of wound
complications. lt should also be noted that significant
iatrogenic disruption of the plantar fat pad greatly
increases the risk of neuroma recurrence as well as the
risk of hypersensitive plantar skin in this region.
metatarsal space.
digitalweb space and plantar metatarsal region distalto
Symptoms are typically
aggravated by weightbearing and ambulation, and shoe
gear/ especially shoes with high heels, narrow toe box,
and thin soles. The key finding is reproduction of symptoms upon direct, deep palpation of the stump neuroma.
The pain can be very debilitating and, at the least, often
makes the patient alter his/her shoe gear if not lifestyle.
the previous neurectomy.
The intraoperative use of either glucocorticosteroid,
alcohol, or dilute phenol infiltration into the proximal
nerve stump has not been proven to decrease the incidence of traumatic neuroma formation. Nonetheless,
many surgeons use these agents (usually glucocorticosteroid) based on a knowledge of their antiinflammatory and/or fibrolytic properties. Capping the
proximal stump with silicone has also yielded inconsistent results, due primarily to technical difficulty in
establishing the right fit, and very often required reoperation to remove the implant and revise the
neurectomy.
DIFFERENTIAT DIAGNOSIS
The differential diagnosis for a recurrent neuroma is
the same as that for any form of metatarsalgia. Special
emphasis should be directed toward ruling out specific
biomechanical afflictions of the forefoot that may or may
not be directly related to the neuroma recurrence.
Arthritides, namely rheumatoid arthritis, should be
carefully considered. Arthritis affecting the metatarsophalangeal joints is frequently associated with painful articular subluxation, as well as synovitis of tendon
sheaths, which could be mistaken for focal neuroma
pain. Careful palpation should be performed in an
attempt to rule out the presence of a symptomatic
intermetatarsal bursitis, plantar synovial cyst originating
from the adjacent joint, or proliferation of synovium.
Most of these inflammatory conditions will respond
favorably to the use of non-steroidal anti-inflammatory
drugs and/or glucocorticosteroids, whereas stump
neuromas associated with deep, diffuse scarring
usually do not.
SIGNS AND SYMPTOMS OF RECURRENT NEUROMA
The most common symptom associated with recurrent
intermetatarsal neuroma is exquisite local tenderness at
the level of the stump neuroma. This is usually Iocated
one to one and a half centimeters proximal to the plantar sulcus and web space. This proximal location is
secondary to retraction of the proximal segment of the
nerve stump subsequent to the initial neurectomy
(Fig. 2). Occasionall1l, these patients will complain of a
nodule or "lump" in the previously operated interspace
associated with scar tissue or less commonly bursitis.
It is also important, in any case of metatarsalgia, to
establish whether or not radiculopathy (sciatica) exists.
Moreover, the possibility of new neuroma formation in
an adjacent interspace, or of an accessory nerve in the
same interspace, should be entertained. Post-incisional
Tinel's sign may be elicited upon direct dorsal or more
commonly plantar palpation of the recurrent lesion. This
finding, however, need not be present in all cases.
Similarly, hypoesthesia or anesthesia may affect the
322
peripheral nerve surgery is variable, and an accurate
prediction of the outcome is difficult to make. For this
reason/ the surgeon must explain to the patient the
nature of his/her condition and the goal of re-exploration
and revisional neurolysis. lf revisional neurectomy is anticipated, the patient should be informed as to the expected region of postoperative anesthesia and oriented
as to the necessity of daily foot and shoe inspections.
Likewise, the surgeon may arrange appropriate adaptive
insoles (such as soft plastazote).
entrapment of dorsal cutaneous nerves may also develop
secondary to previous surgery if a dorsal approach was
used. One should also carefully consider the possibility
of a painful plantar scar as a cause of the patient's symptoms, if a plantar approach was used. These usually present as slightly hypertrophic, hyperkeratotic lesions, with
palpably indurated subcutaneous tissues' The patient will
often relate a history of immediate postoperative
weightbearing following the first surgery.
Lastly, dystrophy of the plantar metatarsal fat pad with
The overall goals of re-operation are adequate external neurolysis, identification of the neuroma and any
other pathologic structures, and clean sharp neurectomy
as far proximal as possible. Careful inspection must be
loss of shock absorbing capacity is a frequent compli-
cation of poor interspace dissection technique (spacectomy) and may respond to appropriate conservative
treatment.
CONSERVATIVE TREATMENT
Nonsurgical management of the recurrent
intermetatarsal neuroma rarely eliminates symptomatology to a satisfactory level. Cenerally speaking, a
failed first surgery will not respond favorably to conservative treatment. Nonetheless, it is reasonable to try to
avoid re-operation. Non-steroidal anti-inflammatory
drugs are almost universally ineffective in alleviating the
pain of recurrent intermetatarsal neuroma. Modifications
of shoe gear to include a low heel, wide toe box, accommodative insoles and/or orthoses often effect some relief.
ldeally, revisional peripheral nerve surgery should be
performed under general or spinal anesthesia, and with
the aid of thigh tourniquet hemostasis.
incisional approach
is a
the principles of elective incision planning namely:
1. Exposure of target tissues (the stump neuroma)
2. Maintenance of wound vitalitY
3. Knowledge of the direction of relaxed tension
lines
(RSTL)
The stump neuroma and contents of the interspace
constitute the target tissues. These tissues, if located
proximal to the metatarsal head, may be somewhat difiicult to expose from a dorsal approach as the depth of
the wound becomes quite deep and the intrinsic
musculature must be retracted. For this reason, a plantar approach may be beneficial. lt is also interesting to
note ihat in all cases involving re-operation through a
previously dissected dorsal approach, the deep
transverse intermetatarsal ligament had fully regenerated
and in many cases displayed exuberant collagenization
with entrapment of neighboring soft tissue structures'
sal neuroma.)
REVISIONAL SURGERY
Cenerally speaking, the results of a second (or third)
peripheral neurectomy are better than the preoperative
condition about 80% ol the time. This is substantiated
(2,4) and in our own studies.
the prognosis following any form of
literature
Nonetheless,
of
crucial
preoperative consideration. A recurrent intermetatarsal
neuroma can be exposed by means of a dorsal or plantar incision. A dorsal longitudinal interspace incision is
typically used for the first surgical exploration of an intermetatarsal neuroma, and therefore dorsal scarring is
present in most revisional cases. The choice as to which
incisional approach should be used is made based upon
The choice
Similarly local infiltration of a glucocorticosteroid
about the suspected traumatic neuroma may be
beneficial, primarily due to its late stage fibrolytic properties. We suggest two or three local steroid iniections
(1t4to 1/2cc Kenalog 10) over a three to six month period
as long as some improvement is made following each
injection. Steroid infiltration should be combined with
physical therapy in the form of hydrotherapy,followed
by.ultrasound with or without metatarsophalangeal joint
manipulation depending upon the individual patient's
degree of sensitivitY. (We have also had some success
with phonophoretic administration of lidocaine and
dexamethasone ointment in post-surgical nerve entrapment affecting the intermediate dorsal cutaneous and
sural nerves. This technique, however, has not been
adequately effective in cases of recurrent intermetatar-
in the
for any abnormal
accessory nerves, bursae
(especially in the second and third interspaces), synovial
cysts, or localized scar in the interspace. Should there
be any indication of distal nerve stump entrapment, or
lesion in continuity, then a sharp, clean distal neurectomy should also be effected or the lesion in continuity
should be transposed to a well vascularized and well protected soft tissue bed. Caution should be practiced to
avoid over aggressive disruption of the shock absorbing
plantar fat pad.
made
323
Wound vitality is readily preserved by applying the
principles of anatomic dissection, and recognizing poten-
tial dysvascularity secondary to previous surgical intervention and scarring. A review of the previous medical
record should document any dysvascular episode during or after the first surgery. Should marked subcutaneous and dermal sclerosis be present, or if consecutive interspaces require re-exploration, strong consideration should be given to a plantar approach.
Relaxed skin tension lines (RSTL) in the arch area are
oriented perpendicular to the long axis of the foot, hence
transverse linear incisions (dorsal or plantar) take advantage of intrinsic resting skin tension and tend to gape
minimally. More over, a plantar transverse or zigzagantitension line incision (Fig. 3) made proximal to the
metatarsal head avoids direct submetatarsal weightbearing pressure, allows ready access into consecutive
interspaces, and provides easy exposure of the plantar
nerves without the need for deep retraction of the intrinsic musculature. The surgeon should keep in mind
the fact that any plantar approach will damage the plantar fat pad and replace the fat with some amount of scar
tissue. For this reason, three weeks of non-weightbearing
must be maintained postoperatively.
As previously mentioned, the use of intraoperative
gl
ucocorticosteroid or other neu rolytic agents
i
nf
i
ltrated
into the proximal nerve stump following neurectomy
Fig. 3. A. Zig zag antitension Iine plantar incision for exposure of first,
second, and third intermetatarsal spaces in 25 year old female with
recurrent neuromas. B. Severe incarceration of stump neuroma along
metatarsal shaft.
may be beneficial in the prevention of subsequent symptomatology. This recommendation is based upon empiric
findings, and it should be recognized that no statistical-
ly significant study has been performed to prove or
disprove the effectiveness of this technique. As a group
we feel that this may be a useful adjunct to proper
surgical neurectomy.
Ap prop riate postope rative management often
Finally, the patient undergoing surgery for the treatment
of intermetatarsal neuroma, whether it be first time
surgery or revisional, should be fully informed with
respect to the prognosis and risk of recurrence.
i
n cl u d
es
non-weightbearing, compression dressing, and closed-
suction drainage. Care should be taken
to
References
avoid
immobilization for a prolonged period of time, thereby
risking subsequent re-entrapment of nerves that are not
allowed to glide freely in their soft tissue beds. Unless
the nerve trunk had to be transpositioned and anchored
in a new soft tissue bed then range of motion exercises
are initiated immediately postoperative.
1.
Miller
SJ:
Morton's neuroma a syndrome. ln McGlamry
ED (ed): Comprehensive Textbook of Foot Surgery.
Williams & Wilkins, Baltimore, 1987, pp 38-56.
2. Mann RA, Reynolds JC: Interdigital neuroma - a critical
analysis. Foot & Ankle 3:238-243,1983-
3. Bradley N, Miller WA, Evans JP: Plantar neuroma:
analysis of results following surgical excision in 145
patients. South Med J 69:853-854,1976.
SUMMARY
The surgical treatment of painful intermetatarsal
neuromas is successful in approximately 85%-90% ol
cases. Recurrence of symptomatology almost always requires further surgical intervention. Re-operation is
successful in greater than B0% of revisional cases. The
major goals of the surgical treatment of recurrent
4. Beskin JL, Baxter DE: Recurrent pain following interdigital neurectomy - plantar approach. Foot & Ankte
9:34-39, 1988.
5. Malay DS, Mahan KT: Extensile exposure in the foot
and l"g. In McClamry ED (ed): Reconstructive
Surgery of the Foot and Leg - Update 87. Podiatry
Institute, Tucker CA,1987, pp 39-41.
intermetatarsal neuroma are accurate external neurolysis
and clean, sharp neurectomy as proximal as possible.
324