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The Science andUtility
ofOoading theDiabetic Foot
CaitlinS.Zarick, KurtisD.Bertram,
andThomasF.Milisits
7
Introduction toOoading andIts
Utility
Diabetes mellitus affects over 400 million people around the world and over the next 25 years,
it is estimated that more than 700 million people
will be living with diabetes globally [1]. With
this drastic rise in the prevalence of the disease,
diabetic foot problems put an excessive burden
on the healthcare system due to repeated hospitalizations, increased risk of amputation, and
substantial healthcare costs. For people living
with diabetes, the lifetime risk of developing a
diabetic foot ulcer (DFU) is 25% and subsequently a 40% risk of lower extremity amputation [2]. Nearly 70% of amputations in the
United States are reported to be a result of diabetes and its consequences [2]. The harsh reality is
that a large number of ulcerations that lead to
amputation can be prevented and treated with
proper conservative and surgical ofoading
techniques.
Ofoading, an often underutilized tool in dia-
betic foot prevention and management, is a term
C. S. Zarick (*) · K. D. Bertram · T. F. Milisits
MedStar Washington Hospital Center, MedStar
Georgetown University Hospital,
Washington, DC, USA
e-mail: caitlin.s.zarick@medstar.net;
kurtis.bertram@medstar.net;
thomas.milisits@medstar.net
generally used to describe decreasing pressure to
a targeted area of the foot. Ofoading is a crucial
component of the DFU treatment algorithm as it
removes and redistributes forces to other areas of
the foot to prevent and/or treat ulceration [3].
Understanding the etiology of the ulceration will
help determine the best mechanism of ofoading.
One must take into account all deformities, contractures, prior amputations, and global appearance of the foot when prescribing ofoading
devices.
It has been shown that as many as 50% of
patients suffering from diabetes will lose sensation in their feet secondary to peripheral neuropathy [4]. Neuropathy not only removes protective
sensation but also leads to an imbalance of
intrinsic musculature leading to deformity. It is
the combination of deformity and loss of sensation that leads to tissue breakdown and ultimately ulceration [5]. Understanding the
pathological forces and their potential consequences will allow you to properly help choose
the best ofoading mechanism for your patients.
Shear, frictional, compressive, and tensile forces
all play a part in the development of ulcerations
as well as the treatment (See Table7.1). The goal
of ofoading devices is to help counteract the
forces at play.
© Springer Nature Switzerland AG 2023
C. E. Attinger, J. S. Steinberg (eds.), Functional Limb Salvage,
https://doi.org/10.1007/978-3-031-27725-2_7
73
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C. S. Zarick et al.
Table 7.1 Different forces that act on the diabetic foot
and contribute to ulceration [5]
Type of force Denition
Shear force When a material moves in one or
more directions at the same time
Frictional force When a force moves along a material
while in direct contact with it
Compressive
force
Tensile force When a material is stretched by two
When a material is pressed together
between two or more loads
or more opposing forces
Biomechanics oftheDiabetic Foot
The biomechanics of the diabetic foot are different from that of a nondiabetic foot at both a
structural and functional level. On the structural level, there are changes to the soft tissue
of the foot, particularly to the plantar aspect
(i.e., dryness) as well as loss of the plantar fat
pad. On a functional level, a disorganized pattern occurs within diabetic ligaments, capsules,
and tendons leading to signicant decrease in
elasticity and tensile strength. As a result of
these changes, there is increased propensity for
joint instability, overall stiffness, and contractures of the foot and ankle which leads to inefciencies in gait, lack of accommodation with
weight-bearing, and increased areas of local
pressure [6].
The classic example of this in the diabetic
patient is Charcot Neuroarthropathy which is
dened as a chronic destruction of the bones and
joint subluxations in patients with neuropathy [6–
8]. The main deforming force is the Achilles ten-
don which becomes contracted causing an equinus
deformity. During propulsion of a patient with
Charcot, there is an increased upward force of the
Achilles tendon, causing a break or subluxation of
different areas of the foot (most commonly the
midfoot). Additionally, this increased pull leads to
increased pressures on the forefoot. If these issues
are not addressed in a timely manner with proper
ofoading, whether conservative or surgical, this
can lead to devastating consequences on the
patient’s function and quality of life. Increased
plantar foot pressure can occur which leads to
ulceration, infection, or even amputation.
Thorough radiographic and physical examinations are paramount in diabetic patients, particularly in the uncontrolled diabetic. There are
certain areas of the physical exam that are crucial for evaluation as it pertains to ofoading.
Key components of the examination in the diabetic patient as it pertains to ofoading:
– Radiographic Evaluation: Radiographic anal-
ysis should be completed as it can give vital
information on areas of subluxation and bony
prominences. Weight-Bearing lms are crucial
for an accurate assessment of bony
architecture.
– Plantar Callus: Careful examination of the
plantar aspect of the foot for any callus for-
mation will help determine areas that require
ofoading. In a study by Potter et al., they
found that there was a 25% decrease in peak
plantar pressure after callus removal.
However, there was no signicant difference
between the two groups. Callus removal
alone is not sufcient; the area must also be
ofoaded [9].
– Range of Motion: One should assess the
mobility of joints, whether hypermobile or
immobile. This can give you predictors of
potential future areas of pressure, Charcot
breakdown, and ulcer formation.
– Gait Analysis: A gait exam should always be
performed in order to understand the
mechanics of how a patient ambulates and
can give clues to high pressure areas. If one
has access to a gait lab this would add even
further benet to the exam [10]. This should
be done without shoe gear to assess aspects
of gait such as forefoot to rearfoot relation-
ship, collapse of the midfoot, etc. Efcacy of
an ofoading device can then be evaluated
by comparing pedobarometric data before
and after application of an ofoading
mechanism.
– Contractures and deformities: The presence or
absence of both ankle and foot deformities
must be evaluated. Some of the more common
pathologic deformities are equinus, ankle
varus/valgus, rocker bottom deformity, pes
planus, pes cavus, digital contractures, and
7 The Science andUtility ofOoading theDiabetic Foot
75
bunions. It is of utmost importance to assess
all possible underlying issues.
– Prior amputation: Amputations lead to pre-
dictable mechanical imbalances. Prior amputation can help the practitioner prophylactically
ofoad areas that are at high risk for ulceration. When a patient undergoes any kind of
amputation, whether it be a digit amputation
or a transmetatarsal amputation, there is a loss
of tendinous attachments making the mechanics of the foot less optimal. For example, hammertoes often develop after a partial rst ray
amputation while equinus or even equinovarus
can develop after a midfoot amputation.
The importance of understanding the biomechanics in the diabetic patient is so that we can
prevent and treat ulcerations with proper ofoading, whether it be from conservative or surgical
methods.
Conservative (“External”) Methods
ofOoading theDiabetic Foot
Sound ofoading principles are necessary in any
wound care plan, regardless of the etiology of the
wound. The biomechanics are paramount to
choosing a device; however the practitioner cannot forget other key variables such as age, weight,
skin integrity, vascular status, neurological status, presence of infection, and purpose of the
device (i.e., prophylactic or treatment of an open
wound) [11].
In an ideal world, a device that assists with
total non-weight-bearing would be used to
remove pressure from the plantar surface of the
foot. These include crutches, wheel chairs, or
knee walkers. However, these are rarely practical
because of factors such as obesity, social burdens, and debility [11].
There are several different ways that you can
conservatively ofoad the foot. There is often
not a “one size ts all” method in choosing a
device. Each patient will have unique factors
about them that will sway you to one method
over another. The choice also often comes down
to provider preference and what they feel works
best in their own hands as well as what is readily
available in practice. Compliance, or the ability
of a patient to adhere to treatment, must also be
considered.
Felt Padding
Felt padding is one of the oldest methods of
ofoading and often overlooked in today’s practice. It is extremely inexpensive and an easy way
to begin ofoading immediately while waiting
for custom or permanent devices. The premise of
the felt pad is to increase contact area around the
ulcer and redistribute pressure to other parts of
the foot in order to optimize the ulcer’s healing
potential.
In the author’s opinion, this is most effective
for a smaller ulceration (i.e., size of a nickel) on
the plantar forefoot, or medial/lateral aspects of
the foot. For this padding, you would use either ¼
or ½ inche felt, cut as an aperture pad (donut
shape). It would get placed over top of the wound
and would ideally redistribute pressure away
from the ulceration.
This is a method that can be done right away
during the rst ofce visit. It is also a device that
patients typically tolerate very well and compliance will not be much of a concern. A downside
to felt pad ofoading is that it very well may not
ofoad enough pressure or could be placed inaccurately and cause increased pressure to other
areas. Additionally it could create an edge effect
leading to a larger wound if not monitored closely
[12]. This occurs when the healthy epidermis surrounding the wound breaks down due to increased
pressure from the pad. It is more likely to occur
in completely insensate patients.
Custom Accommodative Orthotics
There are two different types of orthoses: functional and accommodative. In the diabetic population, the authors prefer the use of the
accommodative orthotic because they are soft
and aid in accommodating and ofoading the
foot (Fig. 7.1) [13]. There are several different
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c d
e
Fig. 7.1 Custom accommodative orthotics. (a) Plastazote top layer; (b) Side view of plastazote, EVA, and poron; (c–e)
Example of patient with hallux amputation tting a custom accommodative orthotic with toe ller
materials that are used when creating a custom
accommodative orthotic; however in the diabetic
population, they must ofoad the foot and prevent further breakdown.
At our institution, we use a layered device
when designing an accommodative insert as we
believe it provides the most ofoading characteristics. The base of the device should be the most
dense and each layer above that, or towards the
foot, should be less dense, or a decreased durometer. Two durable and easy to work with materials
for the base are Ethylene vinyl acetate (EVA) and
7 The Science andUtility ofOoading theDiabetic Foot
77
Poron. For the top layer, plastazote is a great
option because it is modiable, comes in various
densities, and is typically well tolerated by the
patients.
Custom accommodative orthotics are typically best utilized to prevent ulceration either
from occurring or reoccurring, particularly after a
limb salvage surgery with reconstruction or
amputation. The premise behind custom orthotics is to control the biomechanics of the foot and
to ofoad certain areas of the foot with different
modications made to the device. They also help
to relieve strain on the tendons/muscles of the
lower extremity as the biomechanics are controlled. Several studies have examined the effectiveness of custom orthotics with the use of
F-Scan systems and found that these devices
increase the contact area of the foot and decrease
pressure [14]. The goal is to help prevent future
ulcers from happening by ofoading areas at risk
for ulceration.
Another key point when it comes to custom
orthotics is that they should be checked for durability every 3–6 months. Once the device becomes
thin, they become less effective and are no longer
benecial to the patient. While custom orthotics
can be expensive, numerous insurance companies do cover new prescriptions on a yearly basis
so it is crucial to check the device during each
visit.
Diabetic shoes provide better motion control,
prevent skin breakdown and callus formation,
and reduce high pressure areas of the foot. Due to
the Therapeutic Shoe Bill passed by Congress in
1993, Medicare covers diabetic shoes and should
always be in the back of the provider’s mind
when treating diabetics [16]. Our opinion is that
any patient who has decreased sensation, a deformity, or history of an ulceration or amputation
should get a prescription for diabetic shoes.
Custom Shoes
Custom shoes are designed for patients who cannot get into an extra depth shoe because of a particular deformity, prior amputation, or large foot
size. Patients will typically get a custom shoe
after a large limb salvage attempt with reconstruction to accommodate their deformity and
provide balance and stability. Custom shoes are
t to each specic patient and molded to a specic foot and ankle shape and size (Fig.7.2).
Controlled Ankle Movement (CAM)
Walker
A controlled ankle movement or “CAM” walker
(Fig.7.3) is an adjustable and removable device
which is used for a variety of different clinical
Diabetic Shoes
Diabetic shoes should be made an option for
high-risk diabetic patients particularly if they
have components of neuropathy combined with
deformity. Patients with a history of an ulceration or amputation should also be prescribed
diabetic shoes with accommodative inserts.
Diabetic shoes are made with minimal stitching
to avoid irritation and typically come with extra
depth to accommodate custom orthotics for
added support and protection. Additionally, they
come with a large protective toe box to prevent
extra pressure of the digits as well as a multidensity diabetic insole that prevents shearing
forces [15].
Fig. 7.2 Custom shoe molded specically to patient’s
foot and ankle shape, size, and deformity
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Fig. 7.3 Controlled Ankle Movement (CAM) Walker. CAM walkers are dispensed in short or long form to accommodate specic deformities
circumstances. Indications for a CAM walker
include plantar foot ulcers, Charcot neuroarthropathy, trauma (such as ankle sprain or ankle
fracture), and postoperatively from elective surgery (such as a bunion correction or atfoot/
cavus reconstruction). There are also specic
CAM walkers made for diabetic patients that
come with an accommodative inlay to help
ofoad pressure from the plantar foot even further. Some of the diabetic-specic CAM walkers
have softer outer shells to help prevent rubbing or
new wounds.
Specically when it comes to the diabetic
foot, the CAM walker is particularly helpful in
the patient with a forefoot ulceration. One study
in the noncompliant patient. Some patients will
not adhere to your treatment regimen and take the
walker off once they leave your ofce. In a recent
study, the authors found that patients using a
removable cast walker only used it as prescribed
for 34% of their treatment duration [19]. In a
patient that is noncompliant, a trick you can use
in the ofce is to use a layer of berglass cast
around the CAM walker to make it difcult for
the patient to take off while at home.
The CAM walker is an excellent device to use
for diabetic foot wounds, but the practitioner
must always examine the boot and investigate
whether the patient is actually wearing it as
prescribed.
found that the CAM walker when compared to a
total contact cast had greater reduction in forefoot peak pressure, maximum force, and force-
Total Contact Cast (TCC)
time integral [17, 18].
One of the main advantages of the CAM
walker is the ease of wound inspection in a
patient with this device due to the fact that it is
removable. However, this is also a disadvantage
The Total Contact Cast or TCC (Fig.7.4) is the
gold standard ofoading device for diabetic foot
ulcers. The TCC is made of berglass and can
incorporate different types of ofoading pads
7 The Science andUtility ofOoading theDiabetic Foot
79
Fig. 7.4 Total Contact Cast (TTC); it is important to have
the patient dorsiex ankle and ensure that bony prominences are well padded, particularly medial and lateral
which offer a customized t for each patient. The
cast encases the patient’s entire foot including the
toes and leg. This allows for maximal ofoading
and is best suited for forefoot and midfoot ulcerations. There are numerous high powered studies
in the literature supporting this claim [20, 21].
One randomized controlled trial comparing a cast
shoe, removable cast walker (i.e., CAM boot),
and TCC determined that the TCC healed 90% of
wounds in half the amount of time compared to
the other two groups. Additionally, the TCC
group took half the amount of steps as the other
two groups [20, 21].
There are several advantages to a TCC.The
rst is decreased plantar pressure and weight
transfer to the tibia. It has been shown that
approximately 30% of plantar pressure from the
foot is removed when the patient is in a TCC.This
is likely due to the conical shape of the tibia
which allows this cast to act as an external
ofoading device redistributing weight [21, 22].
The next advantage is the elimination of ankle
joint motion. When properly applied, the ankle
malleoli and heel. Patients can weight bear in the TTC
while utilizing a special brace
should be rmly held in neutral which will
decrease the amount of plantarexion with each
step and, as a result, decrease forefoot pressure
midstance and propulsion. With the decreased
ankle motion comes a shortened stride length
which results in less time on the ground and
fewer ground reactive forces [21]. TCCs are also
a method of “forced compliance” for patients
because they are not easy to take off and also tend
to be heavy for patients, which keeps them minimally weight-bearing. This should be considered
if deciding between a CAM boot and TCC for
treatment.
Another great use of the TCC is with patients
with Charcot Neuroarthropathy. Patients in the
active state of Charcot need proper ofoading to
minimize collapse and to help begin healing and
consolidation. A TCC is an excellent tool for
this and often used in diabetic patients to maximize ofoading during early phases of Charcot.
One must be careful, however, to not place
patients in a TCC until acute swelling is also
managed.
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There are several contraindications to think
about when you are deciding if you should use
a TCC versus another ofoading device. The
rst is active infection. You always want to
eradicate the infection prior to utilizing a
TCC. The reason is twofold: one is that the
patient will not be able to have daily dressing
changes done and second is that they will not be
able to tell if the infection is worsening or
improving (i.e., increased drainage, redness, or
malodor). The next is exposure of deep structures such as tendons. This is a contraindication
because you will not be able to adequately keep
a close eye on the wound and may make the
wound worse if the cast is not applied right. A
heavily draining wound would also be challenging to place into a TCC for fear of this leading to an infection. A relative contraindication
would be a patient with a large amount of swelling or the ability to easily swell. If patients
were to swell into the cast it could cause friction, blistering, or new wounds.
There is a learning curve to applying these
casts. The author recommends that proper training or workshops on TCC application be
employed for anyone utilizing these in their
practice. TCCs are not without their own risks
if improperly applied. Below are some key
points that the authors use when applying these
casts:
1. Apply a dressing to the wound prior to placing
any cast padding. This can be a dry sterile
dressing, medicated dressing, or synthetic graft
on the wound prior to putting on the TCC.
2. Place extra absorbant dressings for any
expected exudate.
3. Take extra care to make sure that the entire
cast is in contact with the foot/leg because
even the smallest amount of movement can
lead to another pressure point leading to a new
ulceration.
4. Pad bony prominences extremely well and
any areas of increased pressure. Pads are
applied directly over the anterior tibial crest,
medial and lateral malleoli, and the heel. The
toes also get protected with felt padding.
TCCs are typically changed weekly but can be
left on for 2 weeks at a time if there is no wound
present at all or a small, minimally exudative
wound. Educating the patients on the risks and
benets of the cast will assist with compliance.
Charcot Restraint Orthotic Walker:
“CROW” Boot
The Charcot Restraint Orthotic Walker or CROW
(Fig.7.5) is a long-term custom device that functions as a custom molded removable TCC for
Fig. 7.5 Charcot restraint orthotic walker: “CROW” Boot; custom walker typically used after total contact cast with a
rocker bottom insole to help alleviate pressure on the plantar foot and aide in gait
7 The Science andUtility ofOoading theDiabetic Foot
81
patients with Charcot Neuroarthropathy. It comes
in two berglass or plastic pieces: one for the
front of the foot/leg and one for the back. The
CROW is typically utilized after a TCC when
swelling has decreased and the patient has proven
to be compliant with weight-bearing restrictions.
A recent study showed that 25.9% of patients
transitioning from a TCC used a life-long CROW
as a way to prevent further Charcot breakdown
[23]. The walker consists of a fully enclosed custom orthotic, typically with a rocker bottom insole
to help alleviate pressure on the plantar aspect of
the foot and to help support the ankle joint.
Long-Term Bracing Options
Arizona Brace
The Arizona Brace is a custom-fabricated ankle
foot orthosis which was originally designed for
posterior tibial tendon dysfunction. However,
this can be used to ofoad the diabetic foot as it
stabilizes the ankle, subtalar, and midtarsal joints
and provides medial and lateral stability to the
foot [24]. In the authors hands, this device is most
effectively used postoperatively after a partial
calcanectomy as the attachment of the Achilles is
lost to give the patient more stabilization through
the gait cycle. It is also benecial after Charcot
reconstructive surgery. It increases ankle stability
and can help provide support and ofoading after
ankle or tibiotalocalcaneal arthrodesis procedures. It is also benecial after midfoot Charcot
reconstruction to help stabilize the ankle and
potentially prevent breakdown or Charcot from
occurring in the ankle joint as well.
Patellar Tendon Bracing
The patellar tendon brace (PTB) was rst
described in the 1960s for the treatment of tibial fractures as it is said to ofoad the tibia,
bula, and bones of the foot by transferring
weight through lateral uprights [25, 26]. The
PTB has been shown to have approximately a
30% reduction in body weight to the foot [27].
They are made either as xed-ankle or nonxed ankle. One study showed that plantar
pressures were signicantly decreased in a
xed-ankle PTB brace [26]. For obvious reasons the PTB can be another great option for
continuously ofoading pressure to the plantar
diabetic foot.
Surgical (“Internal”) Methods
ofOoading theDiabetic Foot
Surgical intervention is indicated when the
patient is getting recurrent calluses or areas of
ulceration, despite other ofoading measures.
Armstrong and Frykberg revised a classication system for diabetic foot surgery mainly
based on the presence of an ulcer and acuity.
Class I surgeries were considered “elective”
and were performed to correct deformity in
patients without neuropathy. Class II procedures were classied as “prophylactic” as they
were performed in patients with neuropathy to
help reduce the risk of ulceration when no
wound was present. Class III procedures were
considered “curative” and were performed
when ulcers were present in order to heal the
ulcer. An example of this would be to perform a
tendoachilles lengthening procedure in order to
cure a plantar forefoot ulceration. The nal
Class IV procedures were those considered
“emergent” and performed when there was
presence of severe infection [28].
Soft Tissue Procedures
Percutaneous Flexor Tenotomy
Flexible deformity of the digits can be treated
with a percutaneous exor tenotomy (Fig.7.6).
This will help alleviate pressure at the top or tip
of the digit to heal or prevent an ulceration.
This procedure can be done in the ofce with
or without local anesthesia. The authors have
found that in the presence of complete neuropathy local anesthesia is not needed. To get maximal effect from the procedure, the provider
should maximally dorsiex the toe while the
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Fig. 7.6 Example of exor tenotomy being performed with an 18 gauge needle for distal toe wound with associated
hammertoe deformity
patient exes the toe to cause a “bowstring”
effect of the exor tendon. Utilizing a beaver
blade or 18-gauge needle, puncture the skin midline at the base of the middle phalanx and carefully move medial and lateral until you feel the
tendon release. You will notice an immediate difference in the motion of the toe. The puncture site
can be dressed with a band aid and the patient is
weight-bearing as tolerated. In a patient who
needs a partial rst ray there should be a low
threshold to prophylactically perform this procedure on the lesser digits.
Tendoachilles Lengthening
Normal gait requires 10–15 degrees of ankle
dorsiflexion which is determined by the flexibility of the gastroc-soleus complex. Below 10
degrees, there is a significant increase in plantar pressure of the forefoot which poses a
problem for diabetics, particularly ones with a
forefoot ulcer [29]. While degrees of dorsiflexion is important the surgeon should consider an Achilles tendon lengthening anytime
there is a forefoot ulceration. An additional
indication is when the biomechanics are
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