Diabetic Septic Foot
Amer El-Twati Irhuma,*
Diabetes
mellitus is a common endocrine illness in Africa.1-4 As a non
transmissible disease, it is a world-wide epidemic, especially in developing
countries (Africa, Asia). It is obvious that diabetes mellitus and related
cardiovascular complications are gaining more importance in sub-Saharan Africa.5,6
Associated diseases are coronary heart disease, and chronic renal failure due
to diabetic nephropathy.7 Diabetic foot is one of the most severe
and frequent complication of diabetes mellitus. Its cost is among the highest
of the diabetes chronic complications.2
Diabetic
foot gangrene is the commonest surgical complication and is a health burden in
many African countries.1 The spectrum of diabetic foot infections is
broad, ranging from callous and ulcer formation, to septic arthritis, abscess
formation, and osteomyelitis.8 Pedal complications of diabetes have
long presented a challenge for the clinician and radiologist predominately
related to the difficulty in distinguishing infection from neuroarthropathy.
Surgical intervention after the onset of gangrene may be too late to prevent
death. Prevention and control programmes are needed to stem the rising
occurrence of diabetic foot complications in Africa.3
Diabetic patient with a foot wound
Pathogenesis
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Diabetic patient with a foot wound
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No |
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Yes No
Yes
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*) Dean, Faculty of Medicine, Sebha University, Sebha – Libya.
Diabetes
mellitus is a disorder that primarily affects the microvascular circulation. In
the extremities, microvascular disease due to "sugar-coated
capillaries" limits the blood supply to the superficial and deep
structures. Pressure due to ill-fitting shoes or trauma further compromises the
local blood supply at the microvascular level, predisposing the patient to
infection. The infection may involve the skin, soft tissues, bone, or all of
these tissues. Infection in the neuroischemic foot can lead to cellulitis,
which often progresses to necrosis as a result of septic vasculitis.9
Table 1. Pathogens associated with various clinical foot-infection
syndromes.
|
Foot-infection syndrome
|
Pathogens
|
|
Cellulitis without an open skin wound
|
S. aureus and b-hemolytic streptococcusa
|
|
Infected ulcer that is chronic or was previously treated with
antibiotic therapyc
|
S. aureus, B-hemolytic streptococcus, and
Enterobacteriaceae
|
|
Ulcer that is macerated because of soakingc
|
Pseudomonas aeruginosa (often in
combination with other organisms)
|
|
Long duration nonhealing wounds with prolonged, broadspectrum
antibiotic therapyc.d
|
Aerobic
gram-positive cocci (S. aureus, coagulase- negative staphylococci, and enterococci),
diphtheroids, Enterobacteriaceae,
Pseudomonas species, nonfermentative
gramnegative rods, and, possibly, fungi
|
|
"Fetid foot": extensive necrosis or gangrene, malodorousc
|
Mixed
aerobic gram-positive cocci, including enterococci, Enterobacteriaceae,
nonfermentative gram-negative rods, and obligate anaerobes
|
a
Groups A, B, C. and G.
b
Often monomicrobial.
c
Usually polymicrobial.
d
Antibiotic-resistant species (e.g , methicillin-resistant S. aureus,
vancomydn-resistant enterococci, or extended-spectrum b-lactamase producing
gram-negative rods) are common.16
Infections:
Foot
infections are common in the diabetic patient.10 A combination of
surgery and antibiotics is mandatory in virtually all foot infections. The aim
of surgery is 2-fold: first, to control the infection, and second, to attempt
to salvage the leg. The eventual goal is always to preserve a functional limb.
Foot deformities resulting from surgery may cause reulceration and a high
morbidity. The surgical treatment of the infection largely consists of draining
of pus and removal of all necrotic and infected tissue. Frequently,
revascularization of the foot is needed to save the limb; thus, there must be a
close cooperation with the vascular surgical service. The surgeon must have a
thorough knowledge of foot anatomy and must be familiar with the defects in wound
healing that are caused by diabetes. The outcome of surgery mainly depends on
the skill, care, and experience of the surgeon. The best results arc achieved
within a multidisciplinary setting.
Sixty-five
lower-extremity amputations were performed as a result of sepsis in diabetic
patients during a 3-year period. Chronic plantar ulcer was the most frequent
cause of infection. Other causes of infection included ischemic gangrene,
trauma, and web space fissures. Infections were polymicrobial, with 5.8 bacterial
isolates and 2.3 anaerobes recovered per patient. Anaerobic antibiotic
coverage, however, failed to alter outcome. Sepsis, often without advanced
ischemia, is an important cause of limb loss in patients with diabetes. Open
amputations are recommended, with foot salvage possible in many cases.11
Risk factors
The
primary risk factors for plantar ulceration are believed to be loss of
protective sensation and the presence of high plantar pressures.12
It has been shown that in South African Indians there is a high incidence
of Type 2 diabetes, and in this population significant predictors include
higher baseline blood glucose, Body Man Index and obesity.14 Uraemia
and malnutrition may represent important risk factors for foot ulcers in
diabetic patients who need advanced technology to stimulate tissue repair.14
According
to the four-risk categories-scale 46.3% of the patients belonged to the highest
one; peripheral vascular disease, previous amputations, previous ulcers, and
Charcot joints.15
Table 2: Risk factors for foot ulceration and infection.
|
Risk
factor
|
Mechanism
of injury or impairment
|
|
Peripheral
motor neuropathy
|
Abnormal
foot anatomy and biomechanics, with clawing of toes, high arch, and subluxed
metatarsophalangeal joints, leading to excess pressure, callus formation, and
ulcers
|
|
Peripheral
sensory neuropathy
|
Lack
of protective sensation, leading to unattended minor injuries caused by
excess pressure or mechanical or thermal injury
|
|
Peripheral
autonomic neuropathy
|
Deficient
sweating leading to dry, cracking skin
|
|
Neuro-osteoarthropathic
deformities (i.e., Charcot disease) or limited joint mobility
|
Abnormal
anatomy and biomechanics, leading to excess pressure, especially in the
midplantar area
|
|
Vascular
(arterial) insufficiency
|
Impaired
tissue viability, wound healing, and delivery of neutrophils
|
|
Hyperglycemia
and other metabolic derangements
|
Impaired
immunological (especially neutrophil) function and wound healing and excess
collagen cross-linking
|
|
Patient
disabilities
|
Reduced
vision, limited mobility, and previous amputation(s)
|
|
Maladaptive
patient behaviors
|
Inadequate
adherence to precautionary measures and foot inspection and hygiene
procedures, poor compliance with medical care, inappropriate activities,
excessive weightbearing and poor footwear
|
|
Health
care system failures
|
Inadequate
patient education and control and foot care monitoring of glycemic
|
Modified
from Lipsky et al 2004.16
Age and Sex
It
has been concluded that diabetic septic foot is a disease of the older
population.1 The mean age for patients presenting with a diabetic
foot was 57 ± 9 years2 the median age was 61 years.15 In
a series studied by Demirage and his group (2004)7 the mean
age was 63 years; range 50 to 82 years. Onset occured after the patient had
been diabetic for 15 to 20 years, usually at the age of 50 or older. The age
range was 34 to 90 years with a mean of 56±12 years. The mean duration between
diagnoses of diabetes mellitus and development of foot disease was 13 ± 5
years.1 In a large study done in Belgim , it has been found
that diabetic foot was present in 53% women, 47% men.15 Ekere et
al (2005)1 found that the disease had a male female ratio of
3.6:1.
Bacteriology of diabetic septic foot
Infections
of diabetic foot ulcers are usually polymicrobial.4 Cultures showed
multiple microorganisms in 31.3 percent of patients and a single microorganism
in 25% of patients. Of seventeen microorganisms isolated, 58.8% were
Enterobacter species.7 Anaerobic organisms are still a common
cause for infection, although the prevalence is less.17 It
has been found that aerobes and anaerobes constituted 95.4% and 4.6% of the
total bacterial isolates respectively.4 The most common causes of
diabetic foot infections are S. aureus and P. aeruginosa. Group B streptococcal
foot infections often occur in fragile patients with immune depression or
severe arterial disease. Despite intensive antibiotic therapy and adequate
debridement, amputation is often required in diabetic patients because of
severe damage to the tissue and poor vascularization.18
Jean-Martin
Charcot (1825-1893) was the first to describe the disintegration of ligaments
and joint surfaces (Charcot disease, or Charcot joint). Charcot foot
occurs most often in people with diabetes mellitus. According to the American
Diabetes Association, 60%-70% of people with diabetes develop peripheral nerve
damage that can lead to Charcot foot. The disorder occurs at the same rate in
men and women. Calluses and ulcers may form when bony protrusions rub inside
the shoes. Infected pressure ulcers and osteomyelitis (inflamm-ation of the
bone caused by infection) may develop. Septic arthritis may manifest with
malaise and fever. Characteristics of septic arthritis include inflammation
ofsynovial membranes and infected synovial fluid escaping from the joint
capsule into the joint. Compression of blood vessels and nerves are caused by
disorganization of the joint and may not produce symptoms due to loss of
feeling in the foot.20 Infection in the neuroischemic foot
can lead to cellulitis, which often progresses to necrosis as a result of
septic vasculitis.9
In
our region we don't have previous data on the prevalence and morbidity of the
amputation rate with diabetes patients. We observed 3.87% amputations, which is
rather high in comparison with international data (0.44% - 2.4%).16
The general follow-up of diabetic foot problems can be organised in
co-operation with other care providers.15
Twenty
four patients (59.5%) with stages A or B irrespective of the grade had a chance
of limb salvage using appropriate antibiotic, serial wound debridement, regular
dressing and skin grafting where necessary. Of the 24, 3 absconded, 5 died and
16 healed and were discharged. The remaining 17 patients (40.5%) were stages C
and D and were offered ablative surgery irrespective of the grade. Nine
discharged against medical advice, 5 died and 3 were discharged in good
condition. They concluded that this is a disease of the older population. Delay
in accepting ablative surgery affects prognosis. Outcome in management of
diabetic foot disease can be improved by education, early presentation, funding
for establishment of specialized diabetic foot clinics and early decisive
definitive management.1
Diabetic
muscle infarction (DMI) is a rare, painful and potentially serious complication
in patients with poorly controlled diabetes mellitus and frequently
misdiagnosed clinically as abscess, neoplasm, or myositis. Sahin et al
(2005)20 recorded a 36-year-old diabetic woman with severe
pain in the left antero-medial thigh. She had a 15-year history of Type 2
diabetes mellitus. She was complicated by diabetic nephropathy and requiring
hemodialysis. She had first noticed pain and swelling in her left thigh after a
minimal trauma for 2 days prior to presentation. Clinical and laboratory
evaluation, and muscle biopsy revealed the diagnosis of muscle infarctions. She
did not respond to the conservative therapy. Pain and swelling in her thigh
worsened progressively. She underwent surgical debridment and then, her
clinical status improved.20
Acute
idiopathic scrotal oedema was observed in three adult diabetic patients with
septic foot following life saving above knee guillotine amputation. This is a
previously unreported association as far as we know and no clue to the
pathogenesis could be obtained.21
Surgical Treatment
Treatment of the ischemic diabetic foot syndrome
still represents a medical and economic challenge.22 In the
treatment of a septic diabetic foot, you have to differentiate between a septic
foot with and without ischemia.23 Early recognition, proper
assessment, and prompt intervention are vital.10 Clinical and
non-invasive investigations are essential for this differentiation. The initial
treatment is the same: surgical debridement and antibiotics. For foot debridement,
anatomic knowledge is mandatory because massive edema can lead to a compartment
syndrome of the plantar side of the foot. In case of ischemia, aggressive
revascularization procedures, endovascular, surgical, or a combination should
be performed to create adequate blood supply to the foot.
In a
retrospective analysis, Rauwerda (2004)23 found that a two-year
limb-salvage rate was more than 81.1% with a two-year patency of 62%. A primary
amputation should be considered in case of a pre-operative mobility grade 4 or
5 (wheelchair dependency and bedridden, not able to move around). It has been
concluded that with aggressive treatment with or without revascularisation
procedures, limb salvage of>80% can be achieved in the infected diabetic
foot.23
An
opening and a major stage of the diabetic septic foot surgical treatment is the
primary surgical processing that is usually combined with amputation of
separate fingers or with various types of transmetatarsal amputations. In a
study done by Petkove and his colleagues (2004)24 35.7% underwent
amputation of separate fingers, combined with resection of the metatarsal bone
head. Eighteen percent of the patients underwent transmetatarsal amputations by
Sharp with plantar lambo shaping, and 14.9% had oblique resections with
dermatological plastic surgeries. As a result of this treatment the foot
amputations were reduced to 5.7%. The extended use of conservative treatment
combined with primary surgical processing is a major precondition for
restricting the suppurative gangrenous process. Staged surgical treatment
ensures a drastic decrease in the number of foot amputations. The
reconstruction plastic foot operations enable the shaping of an adequate foot
area with good biomechanics.24
Aggressive
management, soft-tissue coverage, and orthotic use can lead to a functional
weight-bearing extremity. Smith. Jacobs. Fuchs (1993)25 studied
fifty consecutive heel ulcers. The management of these cases included three
methods; (a) debridement, (b) split-thickness skin graft (STSG), (c) bypass
procedures, and (d) orthotics. Group I consisted of 24 ulcers in patients with
diabetes and peripheral vascular disease (PVD), 14 patients in Group II with DM
only, and 12 patients with PVD only (Group III). Healing occurred in 56.5%,
64.3%, and 83.3%, respectively. An average of 2.2 procedures were performed per
patient. Follow-up periods were for a minimum of two years or until amputation.
Time for complete healing and the number of amputations performed were similar
in all groups. Of the diabetics (combined from Groups I and II), a subgroup of
27% required partial excision of the os calcis to facilitate closure. After
saline dressing changes, STSG was accomplished over thin granulation tissue.
Forty percent of this subgroup healed, 30% remained open, and 30% were
amputated.25
Surgical
intervention after the onset of gangrene may be too late to prevent death.
Prevention and control programmes are needed to stem the rising occurrence of
diabetic foot complications in Africa.3 Diabetic patients with
limb-threatening foot ulcers often have multiple coexisting medical conditions
that frequently become impediments to the resolution of foot wounds. Each foot
wound is unique and its etiology is multifactorial; therefore, each foot wound
should be managed differently.26 Adequate assessment of the
lower limb circulation should be routinely performed in complicated diabetic
foot. This evaluation can often be made with simple methods. In addition to
clinical examination ankle/brachial pressure index, systolic toe pressure,
plethysmographic pulse volume recordings and simple hand-held Doppler
auscultation are most often sufficient to make a decision as to whether
angiography is needed or not. Duplex examination can give more profound
information on the severity and extent of arterial occlusive disease, but the
method is strongly user-dependent. Early vascular consultation is mandatory in
diabetic foot work-up and should be undertaken within 2 weeks if a new skin
lesion shows no tendency to heal. Long bypass grafting procedures and
microvascular free flap techniques have been shown to achieve excellent results
in relieving critical leg ischaemia, even in the presence of large foot
lesions, and should be used to prevent major amputation.27
The
treatment algorithm presented in this article is divided into three categories:
Algorithm I describes the treatment of septic foot wounds, which may be
considered true podiatric surgical emergencies; Algorithm II describes
the treatment of ischemic foot ulcers or gangrene with or without underlying
osteomyelitis; and Algorithm III describes
the treatment of neuropathic foot ulcers with or without underlying
osteomyelitis.26
Gangrenous
diabetic feet require aggressive management and early surgical intervention.
Early presentation by patients and prompt surgical intervention during less
severe rather than during later stages of an ulcer may improve patients outcome
and reduce mortality rates.3 Early and accurate diagnosis and prompt
surgical treatment may be life-saving in diabetic patients with NF of the lower
cxtremity.7 An opening and a major stage of the diabetic septic foot
surgical treatment is the primary surgical processing that is usually combined
with amputation of separate fingers or with various types of transmetatarsal
amputations. Out of the total of 379 operated patients 35.7% underwent
amputation of separate fingers, combined with resection of the metatarsal bone
head. 18.3% of the patients underwent transmetatarsal amputations by Sharp with
plantar lambo shaping, and 14.9% had oblique resections with dermatological
plastic surgeries. As a result of this treatment the foot amputations were
reduced to 5.7%i. The extended use of conservative treatment combined with
primary surgical processing is a major precondition for restricting the
suppurative gangrenous process. Staged surgical treatment ensures a drastic
decrease in the number of foot amputations. The reconstruction plastic foot
operations enable the shaping of an adequate foot area with good biomechanics.24
It is estimated that up to 85% of lower extremity amputations can be
prevented through programs for preventing and treating foot ulcers, preventing
reoccurrence of ulcers, and educating patients about proper foot care.28
Recommendations:
The
surgeon must have a thorough knowledge of foot anatomy and must be familiar
with the defects in wound healing that are caused by diabetes. The outcome of
surgery mainly depends on the skill, care, and experience of the surgeon. The
best results are achieved within a multidisciplinary setting.10 A
national program therefore is going to start in the next months. We all have to
be aware of the size of the problem to offer the best possible prevention. As
we have seen, the use of inlay soles and podiatrist-made ortheses for example
is very low. We hope that all care providers will participate in this important
project, so that they will acquire a specific attitude towards these patients.
In daily clinical practice there are some key-roles to be respected by all
health care providers. In our opinion the next are of the utmost importance:
take off your diabetic patient's shoes when they visit you; give specific
education if your patient has a foot at risk; if an ulcer is present, careful
follow-up is mandatory and if no good evolution of the ulcer is seen, an early
referral to a diabetic foot clinic is obvious. Together we can lower down the
amputation rate of diabetic foot lesions. That would be a marvelous
implementation of the St Vincent declaration in Belgium.15 It
is important to diagnose infection early. However, the signs and symptoms of
infection are diminished in the neuroischemic foot. Microbiological
investigation is essential. Severe infection needs intravenous antibiotic
therapy and urgent assessment of the need for surgical drainage and
debridement. Infected neuroischemic feet need vascular assessment and
intervention where appropriate. It is important to maintain strict metabolic
control and optimize cardiovascular function. Recent modern approaches based on
multi-disciplinary clinics have resulted in improved results in the management
of infection in the ischemic diabetic foot.9
Conclusion:
This
is a disease of the older population. Delay in accepting ablative surgery
affects prognosis. Outcome in management of diabetic foot disease can be
improved by education, early presentation, funding for establishment of
specialized diabetic foot clinics and early decisive definitive management.1
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Very Nice and Informative Post Diabetic Foot Infection
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