Overview of Mechanisms causing Diabetic Foot Ulcers

Arun Bal Raheja Hospital, Mumbai

Fig

Charcot’s Foot with Acute Stage of Destruction

Fig Bilateral Charcot’s Foot in Acute Stage of Destruction

Diabetic Foot Wounds Are Like

ICEBERG

How Does Foot Injury Occur ?

• Tissue ischemia• Rupture of micro & macro anatomic

structures• Irregular interaction between vertical &

shear stress ie pressure differentials• Cellular mechanisms• Neuropathy, trauma, infection

Mechanical Factors

• Repetitive moderate force as in walking• Inflammation• Erythema and warmth• Collection of exudate• Blister formation• Breakdown of skin ie ulcer

Biomechanical Aspects Of Ulcer Formation and Healing

• Structural alteration • Structure & function relationship• Tissue properties• Limited joint mobility• Plantar callus• Fractures

Biomechanical Aspects Of Ulcer Formation and Healing

• Weakness of muscles• Prior ulceration• Shear stress• Body weight• Abnormal posture• Footwear

Biomechanical Aspect Of Ulcer Formation and Healing

• Foot ulceration is mainly a breakdown of skin under pressure beyond the tolerance of skin.

• Other factors may vitiate the progress• Often ulcers occur from within out,• Infection is not really the cause of ulcers,

but a consequence

Biomechanical Aspect Of Ulcer Formation and Healing

• The pressures on foot are evenly distributed on the fore foot lateral longitudinal arch and heel.

• Conditions under which the pressures go beyond tolerance are

• Faster the gait• Longer the stride• Foot deformities - disturb the even distribution

and create areas of abnormal pressures where breakdown occurs

Biomechanical Aspect Of Ulcer Formation and Healing

The break down pressure is between • 500 TO 700 kilo Pascals • Healing thus will occur if we reduce the

pressure below this level• Deformities cause excessive pressures and

callosities.• Callosities in turn raise pressures 30 times

more

Vascular Phenomena

• Peak plantar pressure generated while walking is 600 kilo Pascals

• Systolic blood pressure of 120mm of Hg can be obliterated by 15 kilo Pascals

• Capillary pressure by 6 kilo Pascals• Causes delayed recovery from ischemia• Leading to delayed restoration of normal

tissue oxygen concentration

Neuropathy and development of ulcer

• Sensory Neuropathy leads to Loss of pain, heat and cold sensation, The insensate foot, leads to ignorance of

repeated or damaging trauma of Painful foreign bodies, surfaces that are hot

or cold, leading to the development of ulcer

Neuropathy and development of ulcer

• Motor – Intrinsic small muscle imbalance, foot deformity, abnormal areas of plantar pressures, ulcer

• Autonomic neuropathy – combines tissue ischemia and gross deformities

Component causes of foot ulcers

• Peripheral neuropathy 78%• Minor trauma 77%• Deformity 63%• Edema 37%• Peripheral ischemia 35%• Callus 30%• Infection 01%

RISK FACTORS DIABETIC NEUROPATHY

• MODIFIABLE• Hyperglycemia• Hypertension• Increased cholesterol• Smoking• Alcohol use

• NON MODIFIABLE• Old age• Long duration of

diabetes• HLA DR 3/4 genotype• Greater height

ETIOLOGY OF DIFFUSE NEUROPATHY

• Hyperglycemia• Vasa nervorum closure• Abnormal fatty acid metabolism• Myoinositol deficiency

Tissue properties

• Advanced glycated end products cause either ligamental laxity or hardening

• This results in deformities like Hallux rigidus, loosing elasticity, becomes susceptible to trauma

• Laxity will cause collapse of the arches and raised mid foot pressures

• Displacement of metatarsal cushion distally

Other factors

• Vibration and position sense is carried by same fibers and lost together, results in altered gait

• Foot lands on the walking surface in abnormal or uneven position, pressures get irregularly distributed with high pressure zones leading to ulceration

Psychological Problems Associated With Diabetic Foot

On the rise• Depression• Divorce rate• Alcohol abuse• Disruption in

social,domestic environment

• Negative attitude

On decline• Diabetic self care• Psychological

adjustment to illness• Social/family support• Self esteem• Quality of life• Satisfaction with

treatment

Preventing ulcer formation

• Many common sense advise can be given to prevent ulcer formation

• Careful clinical examination should reveal conditions of foot predisposing it to the ulceration

• That decides what advise is needed

Contraindicated Exercises

• Insensate, deformed foot with previous ulceration or present ulcer contraindicates • Treadmill, jogging, Stairmaster• Prolonged, fast and long stride walking

Common Sense Advise• Educate patients to look at their feet, wash

daily with warm water, soft soap, dry in the interspaces, cut nails square,

• Wide toe box, extra depth shoes• Insole wing pad, enhances ulcer healing rate

to 90%• “Always shoe” policy• Socks – keep feet most