A. Lee Dellon, MD, Professor of Plastic Surgery and Neurosurgery at
Johns Hopkins University
SELECTION
OF THE PATIENT FOR DECOMPRESSION
Over the past twenty years, an approach to selection of the patient
for decompression of peripheral nerves has been developed. This approach
begins with the measurement of peripheral nerve function in order
to stage the degree of nerve impairment.21 The model developed for
staging the degree of nerve impairment in patients with chronic nerve
compression but without a neuropathy has been found to be valid in
patients with neuropathy too. Since 1989, the approach to this measurement
has been with computer-assisted sensorimotor testing. While vibrometry
is useful for evaluating a single patient and comparing that patient
to a group of patients, vibrometry does not help the surgeon interested
in decompressing a particular nerve. This is because the vibration
travels as a wave. If the vibration is not perceived well in the index
finger, is it because of a lesion of the median or of the radial nerve?
If the vibration is not perceived well in the big toe, is it because
of a lesion of the tibial or of the peroneal nerve? While the Semmes-Weinstein
monofilament number 5.07 (10 gm of force) may be useful in identifying
an individual with diabetes who has lost protective sensation, and
is therefore at risk of ulceration in the foot,22-29 this filament
represents a cutaneous pressure threshold of greater than 90 gm/mm.
At this advanced stage of chronic nerve compression, the patient has
lost two-point discrimination, has severe axonal loss, and is most
often past the point at which surgical intervention to restore sensation
and relieve pain is still possible.
In contrast, we have found that the Pressure-Specified Sensory Device™
can identify the earliest degree of chronic nerve compression by measuring
the pressure required to distinguish one from two points touching the
skin. Normative values for the Pressure-Specified Sensory Device™
(PSSD)(Sensory Management Services, LLC, Baltimore, Maryland) have been
reported for the upper extremity and for patients with carpal and cubital
tunnel syndrome,31 and for the lower extremity and for patients with
tarsal tunnel syndrome.32 The PSSD is at least as sensitive as traditional
electrodiagnostic studies,33 and is not invasive and therefore not painful.
No electric shocks are used.
The American Diabetes Association has indicated for the past seven
years in its annual Standards of Care for the Foot in Diabetes that
even the diabetic at low risk for ulceration should have a yearly somatosensory
(quantitative sensory testing) measurement of the foot.34-36 A guideline,
based upon a cross-sectional study of people with diabetes with and
without foot ulceration,38 is available for application of measurement
with quantitative sensory testing for the diabetic foot. (Figure 2.)
As the cutaneous pressure threshold for the big toe increases above
the 99% confidence limit for normal (but axonal degeneration has not
yet occurred), the patient with diabetes is referred in order first
to a diabetes educator and Podiatrist for evaluation of orthotic use,
and then to the Podiatrist for fabrication of special shoes. Once the
99% confidence limit is exceeded for the distance at which one from
two points can be distinguished, indicating that axonal degeneration
has occurred, then a referral to a surgeon knowledgeable in peripheral
nerve decompression is appropriate to determine whether the patient
would be a candidate for restoration of sensation and relief of pain.
The most valid prognostic sign for a good result from decompression
of a nerve in the diabetic with symptoms of neuropathy is the presence
of a positive “Tinel sign”. This test is done by tapping
the region of known anatomic tightness, like the tarsal tunnel, with
the examiners finger (not with a percussion hammer). A “positive”
test occurs when the patient can feel a radiating sensation, painful
or not, into the territory supplied by that nerve, e.g., the arch of
the foot, the heel, or the big toe when the percussion is done over
the tarsal tunnel. The simple perception by the patient that a thumping
occurred is not a positive sign. Tapping over several “control”
sites, ie. areas of skin without a known anatomic region of compression
beneath them, should be done. For the common peroneal nerve at the fibular
head, often the nerve is just tender, and a distally radiating perception
does not occur. Tenderness of this nerve is sufficient to suggest entrapment
at this location. In my experience with patients with diabetic neuropathy,
when a superimposed nerve compression is identified by a positive Tinel
sign, there is an 80% chance of a good to excellent result, meaning
relief of pain and restoration of sensation to the feet.
RESULTS OF DECOMPRESSION OF PERIPHERAL NERVES IN THE DIABETIC
Since 1992, there have been several studies that have evaluated the
results of decompression of peripheral nerves in the diabetic. These
studies have been reviewed, and their patient populations regrouped
to permit comparison of nerve-specific results. These results are presented
in Table 1 for carpal tunnel decompression, in Table 2 for cubital tunnel
decompression, and in Table 3 for tarsal tunnel decompression.
Table 1
Table 2
Table 3
The results of decompression of the median nerve in the carpal tunnel
in the diabetic gives excellent relief of sensory symptoms in about
95% of patients and good results in the remaining 5%, with 95% of the
patients recovering useful two-point discrimination.38,41 These results
are what one would expect in the non-diabetic having carpal tunnel decompression.7
The results of anterior submuscular transposition of the ulnar nerve
at the elbow, using the musculofascial lengthening technique, in the
diabetic, gives excellent relief of sensory symptoms in about 77% of
patients and good results in the another 22%, with about 95% of the
patients recovering useful two-point discrimination. 38,41 These results
are what one would expect in the non-diabetic having this type of ulnar
nerve surgery for moderate to severe degree of ulnar nerve compression.7
Recovery of motor function is not as good with just 55% of the patients
recovering normal grip strength and 40% recovering normal pinch strength.
The results of decompression of the four medial ankle tunnels, related
to the tibial nerve and its medial and lateral plantar and calcaneal
branches, is determined by restoration of sensation to the sole of the
foot, and relief of pain in the foot. For all four reported groups of
patients, each of whom was decompressed using the same surgical technique,
pain was relieved in 86% of patients and 72% recovered useful two-point
discrimination.38-41 Two studies included patients that had a history
of ulceration, and the percentage of patients having relief of pain
was the same in these patients, however, many of these patients recovered
just protective sensation (no two-point discrimination).39,40 Among
the 62 patients in this combined series that had never had an 10 ulcer
or amputation, none reported an ulceration or an amputation during the
follow-up period of observation. Among the 24 patients in this combined
series that had a previous ulcer or amputation, 1 (4%) reported a recurrent
ulceration during the follow-up period of observation.
The ability to restore sensation to the feet of a diabetic holds the
promise of prevention of ulceration and amputation. Over the period
of time that I have been doing this type of nerve decompression in the
feet of patients with diabetes, there have been a series we have been
able to follow for a mean of 4.5 years who have only had a unilateral
set of peripheral nerves decompressed. Figure 3 is an example of such
a patient who had the right leg decompressed 7 years prior to this photograph.
Sensation had been recovered in this foot. Because of the distance he
lived from our office, he never came back to have his opposite foot
have the nerve decompression surgery. He developed an ulceration in
the contralateral foot, and went on to require amputation of two toes
on that foot. Our series to the present includes 43 patients. None of
these patients have had an ulcer or an amputation in the side that was
decompressed. In contrast, there have been 7 ulcerations and 2 amputations
in their contralateral limbs. The statistical significance of the success
of peripheral nerve decompression in prevention of ulcer and amputation
in this group of 43 patients has a p value of .002.41
DISCUSSION
The realization that the peripheral nerve in the patient with diabetes
is susceptible to compression can offer the patient, who suffers with
unrelieved symptoms of neuropathy, a new source of optimism.18 Over
the past twenty years, progressing from clinical observations38 to basic
science research,19 and then back to clinical treatment of the diabetic
with symptomatic lower extremity neuropathy,42 experience has been gained
that can now be translated into the regular care of the patient with
diabetes. Independent surgical centers have reported essentially the
findings; decompression of the tibial nerve and its branches at the
ankle and foot level can relieve pain and restore sensibility in about
80% of the patients.39,40
As with the treatment of most diseases, the earlier a patient can be
referred for treatment, the better is the chance that the symptoms of
the disease can be helped. With regard to diabetic neuropathy, once
the patient has developed an ulceration, we know that sufficient sensory
axons have degenerated that we may only be able to restore protective
sensation by decompression of the peripheral nerve. By contrast, if
sensibility can be done earlier in the patient with symptoms of neuropathy
in the feet, then the ability to restore sensation can be offered at
an earlier stage in the pathophysiology. The reason that the results
of decompression of the median nerve in the carpal tunnel has a higher
success rate than decompression of the tibial nerve in the tarsal tunnel
is that patient's usually present to their physician earlier with hand
problems than with feet problems.38,41
This earlier presentation of the patient with hand problems than with
feet problems may be related to the general pessimism that accompanies
the teaching the diabetic neuropathy is "progressive and irreversible".
The observation that patients who have had restoration of sensation
to their feet through decompression of peripheral nerves have not developed
ulcers or had an amputation suggests that the natural history of diabetic
neuropathy may be able to be changed. To affect this change, clinicians
responsible for the care of the patient with diabetes will need to measure
sensibility in the foot, evaluate the foot for the presence of a Tinel
sign over known sites of peripheral nerve compression, and refer the
patient to a surgeon trained in lower extremity peripheral nerve decompression
techniques. If this concept can be introduced into clinical practice,
we should see a significant decrease in foot ulcerations and amputations.
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A. Lee Dellon, M.D. is the founder of The Dellon Institutes
for Peripheral Nerve Surgery®. He is an accomplished Plastic Surgeon
as well as a Professor of Plastic Surgery and Neurosurgery at the prestigious
Johns Hopkins University School of Medicine, at the University of Maryland
in Baltimore, Maryland and at the University of Arizona, Tucson, Arizona.
He specializes in the treatment of diabetic neuropathy
as well as other painful peripheral nerve disorders and has trained
many surgeons worldwide in the procedures he has developed to relieve
pain.
Dr. Dellon completed his BS at John Hopkins University
and received hi Medical Degree from Johns Hopkins University School
of Medicine in 1970. He Completed General Surgery, Plastic Surgery and
Hand Surgery Residencies at Columbia Presbyterian Hospital, John Hopkins
Hospital and Union Memorial Hospital respectively. He has been in practice
since 1978 and has been on the faculty of Johns Hopkins since that time.
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