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Chapter 10
Данная книга находится в списке для перевода на русский язык сайта https://meduniver.com/
Amputation Below theAnkle: How
toEnsure theBest Outcome forthePatient
HaniSlim andVenuKavarthapu
Since limb function following a minor amputation is often dictated by the level of
tissue loss in the foot, care should be taken to preserve the remaining viable foot and
achieve good stump healing in order to provide the patient with optimal standing
balance in comfortable footwear. This in turn results in a reduced risk of foot ulceration and a better quality of life. Therefore, careful assessment on the extent of tissue
loss and its effect on foot mechanics, and planning of the procedure are required,
while taking into consideration the patient’s expectations and functional requirements.
Contrary to a major lower extremity amputation where the resection levels are
agreed, minor amputation levels vary widely depending on the clinical presentation.
Even though, there is a wide spectrum of presentations that warrant a minor amputation, a standard set of principles are applicable that help the clinician chose the correct
level and technique. Minor amputations, dened as amputations below the ankle level,
are important surgical procedures when indicated, as they can prevent a major limb
loss and provide the patients with the best functional outcome to maintain their independence. Minor amputations carry less post-operative mortality in comparison to a
major amputation. Contrary to a major amputation that carries a high 30-day mortality
in the elderly population of up to 17.5% [1] and 1 year mortality rate of 66% [2], minor
amputations, especially when done under local anesthesia have a signicantly low
mortality level. In this chapter we focus on the presentations, assessment and principles
of surgical treatment when performing a diabetic foot minor amputation procedure.
H. Slim
Departments of Vascular Surgery, King’s College Hospital, London, United Kingdom
e-mail: hani.slim@nhs.net
V. Kavarthapu (*)
Departments of Vascular Surgery, King’s College Hospital, London, United Kingdom
Department of Trauma and Orthopaedic Surgery, King’s College Hospital, London, United Kingdom
e-mail: venu.kavarthapu@nhs.net
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023
C. P. Shearman, P. Chong (eds.), Management of Diabetic Foot Complications,
https://doi.org/10.1007/978-3-031-05832-5_10
117
118
H. Slim and V. Kavarthapu
Common Causes ofMinor Amputation inDiabetic Foot
The incidence of minor foot amputations is 10–15 times higher in people with diabetes mellitus (DM) compared to those without [3]. Although the leading causes of
minor amputation are related to neuropathy and ischaemia, other presentations
include infected ulcer, non-healing ulcer, osteomyelitis, diabetic foot attack, severe
toe deformities, Charcot neuroarthropathy (CN) resulting in deformity and or instability, deformed forefoot not amenable to ofoading, severely infected ingrown toenail, burn injuries (common in winter in patients with diabetic neuropathy) and
chronic fungal infection of toenails. Patients with such pathologies often present late
to the treating clinician, frequently due to the lack of adequate primary care or access
to specialised units with multi- disciplinary teams (MDT). An MDT is ideally placed
to perform a detailed assessment, determine the cause behind the tissue loss, plan
management and consider the degree of urgency needed for the intervention.
Most minor foot amputations are performed on patients with a diabetic foot
problem [4]. Although a regional variation is noted, most of these procedures are
done by general, vascular, or orthopedic surgeons (particularly those sub- specialising
in foot and ankle surgery); in some countries, physicians, podiatrists and podiatric
surgeons deliver this treatment. There are three broad categories of indications for
amputation of any body part, as described below [5].
1. Dead
2. Deadly
3. Dead loss
A “dead” distal part of the foot is directly related to completely infarcted tissue
which results in dry gangrene. This is a common complication of diabetic foot syndrome due to a combination of macrovascular and microvascular disease [6].
The “deadly” category generally refers to a process that can result in lifethreatening systemic sequelae if untreated in a timely manner. As such, this constitute a true surgical and medical emergency and dealing with it should be prompt due
to a potential limb and life-threatening situation. The presentations in “deadly” category include:
– Diabetic foot attack
– Wet Gangrene
– Gas Gangrene
– Necrotising fasciitis
– Foot Abscess
A “dead loss” is when the foot part is diseased to the point where the tissue is irreparable due to sepsis (as with chronic osteomyelitis) or ischaemia [7], if it ceases to be
functional (as with signicant trauma or severe bone loss), or it impedes the function of the limb (as with neuropathic pain).
Before any amputation, the clinician should ensure that the patient’s medical
comorbidities have been optimised, with a particular emphasis on glycaemic control, cardiovascular support, infection control and revascularization (in the presence
of ischaemia).
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Minor amputation involves resection of distal part of foot by performing a disarticulation through a joint or osteotomy of a bone. The method of resection and the
level of amputation depends on the extent of the disease and the anatomy involved.
As such the degree of postoperative functional loss is generally proportional to the
amount of tissue taken. The great toe is considered the most important of the toes in
functional terms. Nevertheless, great-toe amputation can still be performed with
little resulting functional decit [7, 8] if certain principles are adhered to.
History
Detailed present and past medial history with an emphasis on the acuity of presentation, duration, progression, and any rapid deterioration is taken. Previous surgeries,
especially revascularisation or orthopaedic foot reconstruction procedures should
also be noted.
Specic history of vascular ischaemic symptoms such as claudication or rest
pain should be carefully excluded. Emphasis should be made to distinguish acute
limb ischaemia from the infected and chronically ischaemic foot. Acute ischaemia
(pain, pulselessness, perishing cold, paresthesia, paralysis and pallor) should prompt
immediate referral to a vascular unit for emergency revascularisation. Where there
is tissue loss secondary to chronic foot ischaemia with symptoms of progressive
claudication and rest pain and clinical signs of extensive atrophic skin and nail
changes such as shiny dry skin, thickening of the toenails, open sores, skin infections, long standing ulcers and dry gangrene, it is indicative of a slow deterioration
due to occlusive arterial disease that requires a planned revascularisation rather than
an emergency procedure. In such cases the minor amputation can be delayed, if the
clinical presentation allows, until after the revascularisation to ensure adequate tissue healing response following the amputation procedure.
Any history of fever or rigors and clinical signs of spreading redness, swelling
and tenderness, along with evidence of local tissue loss or purulent discharge should
raise the possibility of a diabetic foot attack. On the other hand, a history of change
in foot shape is indicative of loss of mechanical integrity of the bone and joints in
the foot. The foot shape can change acutely due active CN or trauma, or slowly and
progressively due to muscle imbalance from motor neuropathy or tendon
contractures.
Medical Assessment
Patients with DM presenting with complicated foot infection often present with
challenging medical comorbidities. The prevalence of ischaemic heart disease in
patients with diabetic foot ulcer (DFU) ranged from 6.83 to 60.61% with a pooled
mean of 25.85% (95% CI, 24.28–27.32%) [9]. In addition, up to 40% of patients
with DM are expected to develop chronic kidney disease (CKD), with 19–34%
120
expected to suffer from DFU during their lifetimes [10]. A thorough and detailed
medical assessment in an MDT set up is conducted to identify, assess and optimise
the medical comorbidities, where possible, prior to the surgical procedure.
H. Slim and V. Kavarthapu
Foot Examination
General foot examination includes the assessment of the tissue loss,infection, foot
deformities, neuropathy and vascular status. Care should be taken to identify any
deadly pathologies. In the presence of spreading cellulitis, the erythematous area
with swelling usually feels rm to touch indicating reactive tissue oedema or deepseated abscess. This can be associated with skin crepitus, scolding of tissues, dark
blotches on the skin that turn into uid-lled blisters and malodor. The foot infection often spreads proximally along the tendon sheaths. The clinical examination
should include palpation along the course of tendons for tenderness and swelling.
The presence of spreading cellulitis, swelling and tenderness along the course of
tendons may be indicative of a ‘deadly’ category and warrant prompt and thorough
assessment for possible emergency surgical exploration, debridement, and a minor
or major amputation. The MDT team foot assessment should include adequate
examination of vascular status, peripheral nerves including motor function and tendon contractures, and associated foot deformity, including features consistent
with a CN.
Investigations
In addition to performing a full set of observations, the following clinical investigations are routinely performed:
Capillary blood glucose
HbA1c
Full blood count
Renal and liver function tests
C-reactive protein
Blood cultures
Wound tissue specimens of Ultrasound guided aspirates from the infected area for
microbiology analysis.
Imaging: Foot radiographs are routinely obtained in the dorso-plantar and
oblique views. However, if possible, weight bearing dorso-plantar, weight bearing
lateral and non-weight bearing oblique views of the foot are performed in all patients
for a more detailed mechanical assessment of the foot. The foot radiographs will
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reveal the presence of bone destruction, soft tissue swelling, foot deformity and gas
in the soft tissues. If deep soft tissue collection is suspected, ultrasound examination
will not only identify this, but also allow aspiration of the uid for microbiological
analysis. If time permits, an MRI imaging of the foot and ankle can identify the
presence and spread of infection in the soft tissues and the underlying bone parts.
Vascular investigations: All patients with a history of diabetes presenting with
tissue loss, even with palpable foot pulses should undergo an urgent formal vascular
assessment such as arterial duplex ultrasound scan, to rule out peripheral arterial
disease (PAD). CT/MR angiogram will only be required in certain individual cases
where arterial duplex scan cannot be done. We do not recommend the use of ankle
brachial pressure measurement (ABPI) in these group of patients as it has been
shown that APBI is often falsely raised due to heavily calcied crural vessels, particularly in those with diabetes and chronic kidney disease [11, 12]. Another reason
is that a high proportion of patients with such presentations suffer from inframalleolar level ultra-distal arterial occlusive disease that otherwise cannot be
detected with ABPI but can be revealed on a duplex scan.
Medical Management
It’s important to realise that most patients with diabetes have an underlying plethora
of medical comorbidities. The prevalence of diabetic kidney disease particularly, in
type 2 diabetes mellitus (T2DM) ranges between 25% in patients younger than
65years old to nearly 50% with age older than 65years [13]. Globally, overall cardiovascular disease (CVD) affects approximately 32.2% of all persons with T2DM
[14]. To complicate things further a signicant number of geriatric patients with
diabetes have underlying malnutrition [15]. Associated medical comorbidities contribute to poor outcomes following minor amputations and need to be optimised to
reduce surgical complications and ensure quick post-operative recovery.
Timing ofMinor Amputation
The timing of the surgical procedure is crucial for not only ensuring successful
outcome, but also rapid healing and recovery.
There are two basic categories that determine the speed of intervention.
(a) The deadly category conditions that present with tissue loss and spreading foot
sepsis. Such presentation in the background of diabetes is labelled as ‘diabetic
foot attack’ [16]. This is a true surgical and medical emergency where aggressive foot debridement should be done promptly due to the potential limb and
122
life-threatening situation. Diabetic foot attack should be considered during the
following clinical presentations:
– Foot abscess
– Wet gangrene
– Gas gangrene
– Necrotising fasciitis.
(b) The dead or dead loss categories often present with slow deterioration of tissue
loss with or without a background ischaemia. In such cases the minor amputation
can be done as a planned urgent procedure after reversing or improving the
underlying ischaemia.
H. Slim and V. Kavarthapu
Technical Considerations
Foot Anatomy andBiomechanics
Based on its anatomy and function, the foot is divided to hindfoot, midfoot and forefoot. The hindfoot include talus and calcaneus, and the joint between these bones is
the subtalar joint. This joint contributes to the inversion and eversion movements of
the foot. Midfoot includes the navicular, cuneiforms and cuboid, and these contribute
to the transverse plantar arch of the midfoot. Midfoot articulations work with the
subtalar joint and contribute to the midfoot and hindfoot exibility during wright
bearing and parts of the gait cycle. The forefoot includes the metatarsals and phalanges. The shape of the body of proximal phalanx is similar to the metatarsals in being
convex dorsally and concave on the plantar side. The articular surface of the base of
proximal phalanx is concave for articulation with the metatarsal head, whereas the
distal part has a trochlear surface for articulation with the phalanx distal to it.
The foot mechanically is divided into three columns. The medial column includes
the rst metatarsal, medial cuneiform, and navicular. This column is a slightly exible unit and takes most of the weight while standing. The middle column is rigid
and includes the second and third metatarsals, middle cuneiform and lateral cuneiform. The fourth and fth metatarsals articulate with cuboid to form the lateral
column which is very mobile and allows for exibility when walking on uneven
ground. The medial column is the main contributor of the medial longitudinal arch.
The load bearing in the foot is through the heel posteriorly and the balls of the
large and little toes anteriorly, forming a tripod that provides better stability and
load distribution [17].
As such some important anatomical and biomechanical points need to be considered during minor amputations as given below:
• The ankle Joint. Utmost care should be taken not to expose the ankle joint while
performing debridement for foot infection, as any possible infection spread to
the ankle as a result can lead to a major amputation.
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• The Heel. It plays a very important role in load bearing, as the rst contact point
to the ground during the gait with the foot landing on the posterolateral aspect of
the heel. In addition, the plantar heel pad has a key role in weight transmission
and load dissipation. Hence, it is extremely important to protect the heel to main-
tain the integrity and functionality of the foot.
• The big toe with the rst metatarso phalangeal joint is important for foot stability
and forefoot function. The main function of the big toe is to direct body weight
through the foot in the direction of travel [18]
• The peroneus brevis tendon is attached at the base of the fth metatarsal that
provides forefoot abduction movement and resists foot supination. A minor
amputation that includes the base of the fth metatarsal bone defunctions pero-
neus brevis leading to a progressive forefoot adduction deformity. Hence, it is
recommended to perform a peroneus brevis tendon transfer in such situations,
where the tendon is inserted into cuboid or base of fourth metatarsal, in an effort
to provide continued balance between the supinatory and pronatory muscle
forces [19]
• Achilles tendon tightness is noted in some chronic presentations. It is important
that the tendon lengthening is performed at the time of minor amputation proce-
dure to improve the foot alignment and reduce forefoot overload.
Preprocedural Planning
The minor foot amputation should be performed at a level that makes an anatomic
sense, preserves load bearing ability of the foot and minimises the risk of further
surgical interventions. Each minor amputation should be planned individually
according with the location and extent of the tissue loss. The following principles
are followed in all cases,
Equipment
The materials required for toe amputation include the following:
– Skin marker pen
– Povidone-iodine, chlorhexidine, or a similar surgical disinfectant
– Scalpel with No. 15 blade for toe amputation and 10 blade for larger minor
amputations such as transmetatarsal amputations
– Heavy toothed forceps
– Bone cutter, such as Jacobson or Liston bone cutter that comes with sharp edges
and small blade.
– Bone nibbler
– Curette
124
– Diathermy
– Absorbable and non-absorbable suture materials such as vicryl and Nylon for
wound closure
– Needle holder
– Dressings (including gauze, bandages)
H. Slim and V. Kavarthapu
Patient Preparation
• Informed consent is obtained for the planned debridement and minor amputation.
• Antibiotic should be considered for each individual case. For cases requiring intra-
venous (IV) antibiotics, and when prior microbiology culture sensitivities are not
available, we recommend empirical antibiotic therapy of IV Tazocin 4.5g 8hourly
for patients with diabetes with normal kidney function or 12 hourly when it is
impaired. Alternatively, the local hospital guidelines for such clinical presentations
can be followed when available. When microbiological culture and sensitivities are
available from the intraoperative specimens, the antibiotics can be adjusted accord-
ingly. After an appropriate period of intraoperative antibiotic therapy, the patient
can be discharged on oral antibiotics, usually on Augmentin 625 mg 8 hourly.
Suitable alternative antibiotics are chosen for patients with Penicillin allergy.
• Anaesthesia: It is understood that there is a wide variation on the choice of anaes-
thesia used for minor foot amputations. From our experience, the majority of
minor amputations can be safely done under local anaesthetic ankle block. As
most of the patients present with DM and associated comorbidities, avoidance of
general anaesthesia is preferable whenever possible. However, even under local
anaesthetic, patients should be monitored during the procedure and in post-opera-
tive recovery for any adverse effects such as bleeding from the amputation site.
Those patients with suspected severe infections such as necrotising fasciitis or gas
gangrene may require extensive debridement that requires extension to or above
ankle level, and in these situations general anaesthesia may be a more appropriate.
• The patient is positioned supine, and a sandbag is placed under the ipsilateral hip
for lateral column surgery. In the absence of proximal peripheral arterial disease,
or any other contra-indication, the surgeon can choose to use a high thigh tourni-
quet during the procedure. Intra-operative uoroscopy is useful for more proxi-
mal minor amputations.
The sterile eld is set up so that the surgeon has access to the entire lower leg and
foot on the affected side.
Surgical Techniques
Following the minor amputation procedure if the wound is clean, primary skin
closure using interrupted nylon suture will achieve a quick and predictable healing
and prevent further wound infection. Tension free skin and soft tissue coverage can
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be obtained by removing an adequate amount of bone. Small case series have
shown that primary closure following aggressive debridement and wound irrigation is better than leaving the wound open, even in the presence of infection
[20, 21].
However, in actively infected cases, the wound can either be partially closed or
left open. In such cases many dressing options are available. Small wounds are commonly managed with loosely packed alginate dressing, brillar hemostat agents,
parafn gauze or with dressing gauze soaked in saline or povidone-iodine. Cotton
wool wrapping with or without crepe bandage can be applied. However, care should
be taken for any adjacent bypass grafts so the dressings will not cause compression
of the grafts and result in occlusion. Larger wounds are ideally managed with negative pressure wound therapy (NPWT).
Amputation ofToe
Incision lines are marked on the skin as appropriate for the planned amputation. In
partial toe amputations, different types of skin aps can be raised to help with the
wound coverage. These include plantar-based ap (Fig.10.1), dorsal ap, side-toside ap, sh-mouth ap and occasionally a toe lleting ap from a healthy distal
part of the toe or the adjacent toe that might help cover a larger defect. It is critical
to ensure that the ap is viable before closure and perform a tension-free closure.
For a disarticulation or a transmetatarsal amputation, a long plantar ap is the
best choice.
All necrotic tissue should be debrided back to healthy bleeding surfaces. If infection is present, the tendon sheaths must be drained from any possible purulent material and thoroughly washed with normal saline or 50% diluted iodine solution.
Samples should be sent for microbiology culture and sensitivity testing.
Dissection is carried down to the periosteum, and a bone cutter or pneumatic saw
is used to perform the osteotomy at the appropriate level. It is important to be mindful of tendon insertions and to consider the biomechanical effects that sacricing
these will have.
Disarticulation ofToe
Dissection is carried down to the joint capsule, the capsule is completely incised,
and the distal segment is removed. For amputation of one of the medial two toes,
preservation of the base of the proximal phalanx is benecial, but for different reasons in each toe. In amputation of the big toe (hallux) toe, preservation of the base
of the phalanx preserves the exor hallucis brevis insertion and function, and this
helps to maintain stability during terminal gait phase [22]. In a second-toe
126
Fig. 10.1 A clinical photograph
showing a partial amputation of hallux
with primary wound closure done using
a plantar ap
H. Slim and V. Kavarthapu
amputation, the retained segment helps maintain the position of the hallux and prevent the development of secondary hallux valgus.
For the lateral three toes, virtually no functional loss is experienced with either
partial amputation or disarticulation, and foot architecture is minimally disturbed [23].
Classically a bone nibbler is then used to smoothen the surface of the remaining
bone and remove any sharp edges. It is the common practice of the authors to excise
the hyaline cartilage of the metatarsal head since the cartilage is avascular and its
presence may delay wound healing. However, we acknowledge that some authors
prefer not to remove the hyaline cartilage.
Neurovascular bundles are ligated or cauterised as they are dissected. Before
closure care should be taken to remove any devitalized or foreign material such as
bone wax, bone chips, excessive amounts of suture material, fascia or tendon to
improve stump healing and prevent wound infection.
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