Background

Diabetic Foot Pathophysiology 

 

1. Neuropathy

2. Arteriopathy

3. Immunopathy

 

Neuropathy 

 

Most important aetiologic factor in foot disease. Due to : 

- metabolic (glycosylation of nerves)

- ischaemic factors 

 

A.  Sensory Neuropathy

 

Definition

- loss of protective sensation - level of sensory loss allows damage to occur without being “painful”

 

Distribution

- stocking i.e. affects longest fibers first

 

Diagnosis

1) Semmes Weinstein 5.07 monofilament

- applies 10gm of force

- defines the presence & severity of neuropathy 

- tip pressed against skin until starts to bend; patient asked if they can feel it

- no standardized number of testing sites

- 90% of patients who are able to feel won’t ulcerate

 

2) 128 Hz Tuning Fork

- Less predictive of ulceration

 

B.  Autonomic Neuropathy

 

20 – 40% of Diabetics

- skin dry / scaly / Cracked  

- easier access for bacteria

 

C.  Motor Neuropathy

 

Loss of intrinsic muscle balance = claw & hammer toes

- Achilles tendon contraction = MT head pressure 

- Results in IPJ dorsal & MT head plantar ulcers

 

Arteriopathy 

 

50% of diabetic foot ulcers (DFU) have arteriopathy 

- large and small vessel disease 

 

Vascular Foot

 

A.   Large Vessel Disease

 

Different disease pattern to non-DM population:

- younger onset

- more rapidly progressive

- above and below knee (non-DM below knee rare)

- typical location at or just distal to popliteal vessels

- more diffuse with longer occlusions       

           

Symptoms

- vascular claudication

- rest pain

- nonhealing or hindfoot ulcer

  

B.  Small Vessel Disease

 

Microangiopathy

- primarily responsible for retinopathy / nephropathy

- may contribute to delayed ulcer healing

 

Immunopathy

 

Good BSL control improves healing  (less microbial growth;

no impaired chemotaxis)

 

Nutrition affects wound healing; predictive indices 

- total protein > 6 g/dl or 60 g/L

- albumin > 3.5 g/dL or 35 g/L

- lymphocyte count > 1500 /mm3

- transferrin < 200mg/dl

 

Diabetic Foot Complications

1)   Diabetic Foot Ulcers (DFU)

2)   Diabetic Foot Infections

3)   Charcot Arthropathy (refer to separate section)

 

1. Diabetic Foot Ulceration (DFU)

 

Rule of 50s -

50% DM admissions 

50% of all leg amputations

50% involve major level (BKA or AKA)

50% coexisting vascular disease

50% contralateral amputation 5 years

50% mortality 5 years (higher than breast and prostate ca)

 

85% of diabetic amputations involve DFU

 

2. Diabetic Foot Infection

 

Microbiology

 

1) Acute & Mild Infections

- usually monomicrobial

- commonly S Aureus, Strep

- Up to 30% of DFU hospitalized patients MRSA  

 

2) Chronic & Severe

- more likely polymicrobial

- G + Cocci (Staph; Group B Strep)

- G - (E Coli; Pseudomonas)

- Anaerobes –in ischaemic Limbs; Eg Bacteriodes Fragilis

 

Workup of Diabetic Foot 

 

Diabetic Foot History

 

Ulceration 

- duration 

- episodes of infection

- mobility level 

- prior treatments (wound care; shoe-wear) 

 

Diabetic Control

- HbA1c

- end organ disease (vascular; cardiac; retinopathy; neuropathy; nephropathy)  

 

Examination

 

Look 

- shoes – fit, material, wear-pattern

- bony prominences / deformity

- ulcers

   size, depth, granulation tissue, deep structures, cellulitis

- toenails - ingrown, thickened (vascular/ fungal)

 

Feel 

- pulses / capillary refill

- temperature (Charcot)

 

Move 

- anterior and lateral compartment mm power (for balancing transfers)  

 

Special Tests 

- Silfverskiold Test (need for TAL)