Medical and Surgical Considerations in
the Care of Patients with Insensate
Dysvascular Feet
John H. Bowker, MD
Introduction
Diabetes mellitus is the disease most often
linked in the developed world with damage
to the feet due to loss of protective sensation. In much of the developing world, insensitivity due to Hansen's disease-formerly
known as leprosy-is more frequent. Another fairly common cause of insensate feet,
seen worldwide, is alcoholism.
When studying the causes and prevention
of foot ulceration, one must first consider the
risk factors involved. The primary factor is
peripheral neuropathy, which interferes with
normal transmission of signals in peripheral
nerves. Most healthcare professionals are
now acutely aware of sensory neuropathy, in
which loss of protective sensation results in
damage to the feet.
Other forms of neuropathy, however,
such as motor and autonomic neuropathy,
can also play a significant role. Most commonly, motor neuropathy leads to a paralysis of the foot's intrinsic muscles, resulting in
dorsal subluxation or clawing of the toes. As
the toes subluxate dorsally, the plantar fat
pad, which normally protects the metatarsal
head area moves distally, leaving thinner
skin (which is poorly suited for force dispersion) under the metatarsal heads. Motor
neuropathy may also weaken the foot dorsiflexors, leading to a loss of controlled descent of the forefoot following heelstrike at
the beginning of the stance phase of gait.
Combined with loss of metatarsal head padding, the resultant slapping gait can cause
rapid damage to the skin of the plantar forefoot.
Autonomic neuropathy causes dryness of
the skin due to lack of normal sweat production. This condition may lead to fissuring of
the skin, creating portals of entry for bacteria. Poor management of diabetes, resulting
in chronic hyperglycemia, leads to glycosolation of collagen with diminished capacity to
heal wounds.
Smoking is another risk factor of real significance. In the short term, vessels constrict, and over a longer period of time,
smoking can enhance development of atherosclerosis. On a daily basis, healing is also
impaired by the blood's decreased ability to
deliver oxygen to tissues. (Carbon monoxide
binds sites on hemoglobin, which normally
carry oxygen.)
Development of foot ulceration is also related to the duration of diabetes. In a study
of 119 diabetics in our clinic, those with ulcers had diabetes for an average of 16 years,
while those without ulcers had diabetes only
11 years. The age at which patients developed ulcers was striking, averaging only 54
years. It is a major challenge to restore function to individuals at the height of their productive years. There were no significant differences in age, race or type of diabetes (i.e.,
insulin-dependent or noninsulin-dependent)
among those who developed ulcers and
those who did not.
We used a biothesiometer to obtain the
Vibratory Perception Threshold (VPT) as a
measure of sensory loss. Overall, those with
a VPT greater than the normal upper limit of
25 had a tenfold increased risk of having
ulceration compared with those patients
with readings of less than 25. If the reading
was more than 43, there was a thirty-fold increase in risk. In our series, the average VPT
of patients with ulcers was 40. Those without
ulcers averaged 23.5 (1).
It is sometimes thought ulceration must be
related to lack of circulation. However, we
determined the Doppler ischemic index at
the ankle in 58 patients with ulcers and 42
without and found no significant difference.
Acute Management
To manage any disease process, lesions
should be classified by a method that has
therapeutic significance. For this reason, we
triage our insensate foot lesions by the method of Meggitt and Wagner (2) (see Figure 1
).
Grade 0 is represented by a callused area
over a bony prominence with no evidence of
skin breakdown. Nonetheless, these insensitive feet are at risk. As local pressure builds
up on skin squeezed between a prominent
bone internally and the unyielding floor and
hard callus externally, a superficial ulceration or Grade I lesion occurs. If weight
relief and modified shoewear are not obtained, a Grade 2 lesion will supervene.
Grade 2 ulcers are deep, penetrating to tendon or joint capsule, but do not enter the
joint. The next stage is a Grade 3 lesion in
which the joint has been violated, leading to
septic arthritis and osteomyelitis. Further
progression leads to a Grade 4 lesion or gangrene of the forefoot and to Grade 5, gangrene of the entire foot. Specific protocols
have been developed for each grade of lesion.
As noted above, Grade 0 represents a foot
at risk. Ordinarily, undue localized pressure
can be relieved by custom inserts placed in
shoes that comfortably accommodate both
the foot and the insert. At times, this is not
feasible and a prophylactic osteotomy is
done to reduce or remove the offending
bony prominence. Diligent foot care thereafter should prevent sores.
In Grades 1 and 2, provided that infection
does not supervene, weight relief is necessary until the lesion is firmly healed. There
are a number of non-weightbearing options.
Using crutches or a walker is awkward at
best, and these devices are frequently ignored by the patient because the ulcer causes
no pain. They also make it difficult to carry
objects and, therefore, are a nuisance. A
wheelchair is sometimes useful for patients
with lesions on both feet. Bed rest is to be
condemned for its debilitating effect. Since
their introduction by Brand, healing casts
have been used for the healing of insensate
ulcers in patients with Hansen's disease.
They are extremely effective in distributing
forces during weightbearing over the entire
foot, thus reducing pressure over the prominent area. Recently, shoes have been introduced that bear major weight on the heel
with little or none through the forefoot (see
Figure 2
). These are excellent for forefoot
lesions but healing casts are still the best
option for hindfoot lesions. Once healing has
been achieved, protective shoes as described
above should continue to be used.
Grade 3 and 4 lesions should be cultured
aerobically and anaerobically. Coverage
with broad spectrum antibiotics is given,
pending the results of sensitivity testing, due
to the polymicrobial nature of most diabetic
food infections. Diabetic control should then
be initiated. This may be difficult to accomplish in the presence of infection. Treating
the infection with antibiotics, on the other
hand, will be only partially effective because
of the inhibitory effect of hyperglycemia on
leukocyte functions. The interdependence of
these factors reinforces the case for early
excisional debridement of necrotic and infected tissue.
Determining the circulatory status of the
affected limb will ensure surgery is performed at the appropriate level. Segmental
systolic blood pressure measurement by
Doppler is useful if peripheral vessels have
not become overly stiffened from calcification secondary to diabetes. These values are
compared to the systolic pressure in the brachial artery to obtain the ischemic index.
This should be at least 0.45 to 0.5 in the
affected area if reliable healing is to occur at
that level. Pressures are recorded at the base
of the toes with a cuff around the forefoot, as
well as the ankle, with a supramalleolar cuff
to provide information about the entire foot.
Grade 3 and 4 lesions will require excisional debridement of all infected and necrotic tissue. While the gangrenous tissue in
Grade 4 lesions may be dry, more often it is
wet due to infection. (Gangrenous changes
occur due to thrombosis of local vessels surrounded by purulent material.) The patient
must understand the procedure is somewhat
exploratory in nature; and based on information acquired from the blood flow studies,
the surgeon will be as conservative as possible in removing tissue.
However, the first priority is controlling
the disease. Both the patient and surgeon
must be willing to redebride the lesion as
necessary, either at the bedside or more
formally in the operating room if the patient's loss of sensitivity is not sufficient to
permit this procedure without anesthesia.
Following complete debridement, weightbearing must be limited until the wound is
fully healed, whether it has been closed primarily or allowed to heal by secondary intention.
In instances where the wound can be
closed primarily, the procedure consists of
two parts. These are debridement of all necrotic and infected tissue, including bone,
followed by reconstruction of the foot using
all viable remaining tissue (provided the
wound can be closed primarily according to
criteria discussed later in this article). It is
common to fashion nonstandard flaps using
any residual noninfected viable tissue. In the
case of osteomyelitis of the distal phalanx of
the great toe, if sufficient skin can be salvaged to cover the proximal phalanx, the
patient's gait definitely will be enhanced, as
opposed to removing the toe at the metatarsophalangeal joint (see Figure 3a
and Figure 3b
).
Infection of the distal phalanx of the lesser
toes also can be treated by removing only
that phalanx. Removing the entire great toe
produces some disability that will require
shoe corrections. Removing only the second
toe removes the support needed by the first
toe to prevent bunion formation (see Figure
4
). It is often better, therefore, to remove
the entire second metatarsal down to its
proximal metaphysis to allow the foot to narrow (see Figure 5
). If one of the lateral three
toes is removed, the others tend to shift and
fill in the gap.
As Grade 4 lesions are gangrene of part or
all of the forefoot, they require a partial foot
amputation or Syme ankle disarticulation,
followed by a prosthetic fitting and lifelong
follow-up. Here we need to consider the role
of transverse versus longitudinal amputations. With a longitudinal amputation, such
as a single lesser ray resection, only the
width of the residual foot lever is affected.
Rollover function and overall foot balance
during terminal stance should be minimally
affected.
Ray resections are excellent examples of
conservative forefoot amputations. The best
ray resections, from a functional point of
view, are those of single lesser rays. With
barefoot walking, there is never a good first
ray amputation (see Figure 6
) because an
intact medial column in forward propulsion
is important. If the first metatarsal is infected, the length of the shaft of the first metatarsal should be preserved as much as possible. If sufficient length has been saved, an
adequate custom-molded insert can be made
to support the medial arch of the foot in
proper shoewear. Removing two or more
central rays is not good functionally or cosmetically (see Figure 7
). If necessary, all lateral rays and portions of metatarsals can be
removed in an oblique fashion and still provide a good functional result if the first ray
remains intact (see Figure 8
).
Transmetatarsal Amputation
Transmetatarsal amputation can be performed when all of the distal forefoot is involved transversely, and the blood flow to
the soft tissues is sufficient to support the
flap fashioned from the distal plantar skin.
This procedure provides a reasonably long
foot lever that can be quite functional in a
shoe with a stiff sole or sole plate and rocker.
Some patients, who are not too concerned
about cosmesis, will elect a short shoe.
The Lisfranc and Chopart levels have considerably less to recommend them. If these
are attempted in infected cases and fail, it is
very difficult to salvage a Syme level. Patients also tend to develop equinus deformity
and foot imbalance since insertions of the
foot's extrinsic muscles are disrupted.
Therefore, percutaneous fractional heel
cord lengthening and proper balancing of the
foot by reinsertion of extrinsic foot muscles
should be done at the time of amputation. A
post-operative cast is also helpful in maintaining the proper plantigrade position. In
fitting transmetatarsal, Lisfranc and Chopart
amputations, special care must be exercised
to avoid excessive direct and shear forces at
the interface of the prosthesis and residual
foot.
Following excisional debridement, with or
without partial foot amputation, a decision
must be made regarding primary closure vs.
open management of the wounds created.
Prior to the pioneering work of Kritter, these
wounds were invariably left open. His studies led to a revolution in the management of
these problems (3). By following his principles, primary healing can be achieved in
three to four weeks in virtually all cases; this
avoids lengthy healing by secondary intention that might take four to six months in
many cases. It also avoids skin grafting, resulting in better cosmesis.
This method works well when certain criteria are met. Pus in the presenting wound
must be either absent or minimal. When the
debridement is complete, the wound should
be clean with minimal inflammation of the
remaining tissues. A 14- or 16-gauge polyethylene intravenous catheter, equipped
with its own insertion needle, is passed
through the skin into the depths of the
wound. The needle is withdrawn and the
catheter hub is sutured in place to the skin. A
bag of normal saline is then attached to the
catheter. Once the system has been noted to
be running well, the skin is closed loosely
with a few deep, widely spaced simple cutaneous sutures (see Figure 9
). Widely spaced
sutures let the fluid escape from the wound
to be absorbed in a soft dressing. The wound
is irrigated in this flow-through manner for
three days at a rate of one liter of normal
saline every 24 hours. Intravenous antibiotics are given concomitantly. At the end of
three days, if there is any evidence of purulence, the wound can simply be opened and
packed at the bedside. This rarely occurs,
however, if the criteria described are met.
Long-Term Management
Once healing has been achieved, it is essential patients become involved in an effective
program for the long-term management of
their insensate/dysvascular feet. In general,
the problems related to diabetes have not
been approached from a holistic point of
view, but rather from a fragmented one related to the various organ systems affected.
Therefore, it is important to take a more
organized approach in foot management if
true preventive rehabilitation is to be
achieved. A team dedicated to the prevention of foot loss is ideal and must be both
interdisciplinary and interactive.
In our institution, orthopaedics and diabetology work closely together to ensure the
proper overall care of the patient. The vascular surgeon is ready for consultation, as necessary, in cases where reconstruction or recanalization of vessels might be indicated.
The dietician, physical therapist, psychologist and social worker all have major roles to
play. The pedorthist plays a special role in
providing the proper shoewear and shoe inserts. The patient is probably the most important member of the team because without
his or her compliance, little can be accomplished.
The heart of our system, the Patient-Family Education Clinic, is run by master's-level
nurse educators. In this clinic they try to
instill concepts of foot self-care, arrange pedorthic care, closely monitor foot condition,
trim nails and calluses as necessary and triage foot problems so patients receive the
appropriate services in a timely fashion. The
nurses also operate a hotline that encourages
early reporting of foot lesions. This leads not
only to early effective management, but also
prevents the long emergency department delays commonly seen in large public hospitals
such as ours. Use of the hotline also prevents
inappropriate triage to services not used to
handling these situations. The hotline is operated by the nurse educators at work from 7
a.m. to 3 p.m. Three nurses rotate call from
3 to 9 p.m. at home each evening.
Specific instructions are given on shoewear-specifically avoiding tight, noncompliant materials, high heels and inward-facing seams. Favored features include
roominess for toes and a high, wide toe box,
pliant leather rather than rigid plastics and
proper padding in the form of inserts depending on the individual conformation of
the sole of the foot. We have found that well-fitted indepth shoes with custom-molded inserts meet most patients' foot protection
needs. Patients are encouraged to check
their shoes, socks and feet daily for problems
and are warned to avoid barefoot walking.
Further preventive instructions are given
about avoiding thermal injury, keratolytic
callus removers and "bathroom surgery."
Rational walking programs are stressed to
prevent excessive weightbearing trauma.
Psychological risk factors include denial,
depression and displacement of the locus of
control. These all affect compliance with the
foot care program and are addressed by the
social worker and the psychologist. This
counseling can be done in individual and
group sessions in both inpatient and outpatient phases of care.
Summary
Peripheral neuropathy complicating diabetes mellitus is the leading cause of insensate
foot problems in the developed world. The
risk factors associated with this problem
have been discussed. A systematic approach
to the management of insensate foot lesions,
based on the work of Wagner and Meggitt, is
described. Proper application of the principles noted by all members of the interdisciplinary team, including the patient, should
lead to prevention of major limb loss.
John H. Bowker, MD, is a professor of orthopedics and rehabilitation at the University of Miami
School of Medicine and is Director of Insensate
Foot and Amputation Service, U.M.-Jackson
Memorial Rehabilitation Center, Miami, Fla.
References:
- Boulton AJM, Kubrusly DB, Bowker JH.
Gadia MT, Quintero L, Becker DM, Skyler JS,
Sosenko JM. Impaired vibratory perception and
diabetic foot infection. Diabetic Medicine 1986;
3 :335-337.
- Wagner FW Jr. Orthopaedic rehabilitation
of the dysvascular limb. Orthopaedic Clinics of
North America 1978; 9:325-350.
- Kritter AL. A technique for salvage of the
infected diabetic foot. Orthopaedic Clinics of
North America 1973; 4:21-30.
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