Diabetes: Insensitive Foot Injury Mechanisms

Objectives

• Learners should be able to describe potential injury mechanisms for the insensitive foot.
• Based on patient characteristics, individuals should be able to choose physical therapy management for an insensitive foot, including footwear prescriptions and examination components.

Diabetes and Diabetic Foot Incidence

• In the US, the CDC reported that in 2015, 30.3 million or 9.4% of the population had diabetes.
• In 2020, that number increased to 34.2 million or 10.5% of the population.
• Twenty-three percent of adults with DM did not know or report they had the disease.
• Foot disease/ulcer is a common problem leading to hospitalization.
• 34% of patients with DM develop an ulcer during their lifetime.
• The annual incidence of foot ulcers in the non-diabetic population is approximately 2%.
• Amputation rates are 10-13 times higher than in controls.
• 50% of lower extremity amputations could be prevented.
• The CDC reports that 45% to 85% of non-traumatic lower extremity amputations in the US attributable to diabetes could have been avoided with proper foot care programs.

Contributing Factors to Foot Breakdown

• Peripheral Arterial Disease (PAD)
• Peripheral Neuropathy
• Joint Deformity (limited joint mobility)
• Physical stresses

Peripheral Arterial Disease (PAD)

• Arteries narrow from fatty plaque deposits, decreasing circulation.
• Muscles require decreased blood supply, especially during activity, which decreases the oxygen supply.
• Ischemia occurs, leading to excessive lactic acid accumulation and pain.
• Patients with more severe PAD may experience earlier onset of Diabetes Mellitus (DM).
• Distal vessels are affected
• There is a greater than 4x incidence in DM.
• Those with a 20-year duration of DM have a 45% prevalence.

PAD Testing

• Common reliability tests include posterior tibial and dorsalis pedis pulses, but these have poor reliability.
• The relative risk is 1.90 if absent or present.
• Ankle Brachial Index (ABI) and Angiogram are more reliable.
• ABI is the ratio of systolic blood pressure at the ankle to the brachial systolic pressure.
• Ankle Systolic Blood Pressure is taken using the posterior tibial artery or dorsalis pedis with a Doppler.
• ABI is the gold standard for diagnosing PAD, with 95% sensitivity and 99% specificity.
• Normal ABI is >0.9 to <1.3
• <.8 is problematic, < .4 may lead to wound healing issues.
• ABI does not work as well in diabetic patients with calcified tibial arteries due to falsely high values of >1.3, which is a problem.
• Angiograms locate and determine how much occlusion from plaques exist in the artery.
• Dye is injected in the artery, and an x-ray of the blood vessels determines the extent and location of the occlusion.

Other Effects of PAD

• Ischemic pain
• Visual changes in the skin such as dry skin, thickened nails, wounds distally, and poor wound healing.
• Rubor of dependency

Neuropathy

• Peripheral neuropathy includes motor, sensory, and autonomic components.
• It involves muscular wasting of intrinsic foot muscles.
• Sensory deficits lead to decreased touch, vibration sense, proprioception, temperature, and pain sensation.
• Pain may worsen at night or at rest, burning, tingling, and progressing to no pain.
• Distal and symmetric polyneuropathy can involve stocking-glove presentation that involves toes and progresses to feet and lower extremities.
• Often, there is no pain or subjective complaints.
• 50% have symptoms after 25 years with DM.
• The Semmes Weinstein Monofilaments test measures peripheral neuropathy.
• A reading of 5.07 indicates a loss of protective sensation (~10 grams).
• 4.17 is intact and >6.10 is essentially absent.
• Patients unable to sense 5.07 SW monofilament were 10 times more likely to develop foot ulcers and 17 times more likely to require amputation.
• The Semmes Weinstein Monofilaments test should be applied for 1 second on and 1 second off, applying enough pressure for the monofilament to bend.
• Deficits in sweating can lead to dry, cracking feet.
• Other symptoms involve deficits in vascular/thermoregulation.
• Fungal infections can develop.
• Lotion is used

Mechanisms of Injury

• Excessive pressures can lead to injury of insensitive skin.
• Low pressures for long durations, high pressures for short durations, or moderate pressures repeated many times can cause injury.
• Dr. Paul Brand researched Hanson's Disease.
• The Physical Stress Theory (MJM et al. 2002) also relates to injury mechanisms.
• Neuropathy and minor trauma can lead to amputation.
• Excessive stress to the plantar foot contributes to injuries.
• High pressure (1,300 PSI) with low duration, low pressure (5-8 psi) with long duration (6-8 hours), and moderate pressure (40-70 PSI) repeated can all cause injury.

Foot Deformities

• Hammer toes and prominent metatarsal heads are associated with high pressures and ulcers at the dorsal Interphalangeal joints and plantar Metatarsophalangeal joints.
• Development of hammer toe deformity involves decreased ankle dorsiflexion, decreased intrinsic muscle function, decreased MTPJ flexion, and increased MTPJ extension movement pattern.
• Claw toes are also considered a foot deformity.

Limited Joint Mobility

• It may indicate a systematic problem and multiple joint involvement, including hands, wrists, shoulders, ankle STJ, and MTPs.
• Positive Prayer Sign
• Advanced Glycated End Products (AGEs)
• The First MTP can cause Hallux limitus and an ulcer on the 1st toe.
• The Subtalar joint can cause a forefoot ulcer.
• The ankle joint leads to a forefoot ulcer.

Acute Charcot Arthropathy

• Neuropathic bone destruction can cause swelling, redness, heat, and may not have pain.
• Immobilization is needed because there is a risk for skin breakdown and deformity.
• Stage 0: Inflammatory period - response to injury, no radiographic changes, onset of erythema, warmth, swelling, pain;
• Stage 1: Fragmentation/destruction period – fragmentation of subchondral bone and cartilage, distension of joint capsule and ligamentous laxity, joint subluxation/dislocation with deformity;
• Stage 2: Coalescence – diminishing inflammation, absorption of cartilaginous and subchondral debris, formation of bone callus, and consolidation of fractures;
• Stage 3: Reconstruction - bony ankylosis, hypertrophic bone formation, fixed deformity, or persistent instability.

Partial Foot Amputation

• Higher pressure is placed on the residuum
• More likely to develop an ulcer on the residuum
• 30% develop a risk for more amputation

Extrinsic Factors of Footwear

• Poor fitting shoes and walking barefoot with insensitive feet are common causes of ulceration

Other Factors

• Diabetic control: HbA1c normal range <6.5% with the current ADA goal is <7.0
• Diet and nutrition consult

Patient Screening

• Check for diabetes or prediabetes history
• Vascular disease: check pulse and look for skin changes.
• Neuropathy: inability to sense the 5.07 monofilament.
• Assess skin changes in the Autonomic Nervous System.
• Foot deformities such as hammer toe, claw toe, prominent metatarsal heads, partial foot amputation, Charcot, and bunions.
• Ulcer: blister, gangrene.

Patient Examination Considerations

• It is vital to examine the wound, including a description of edema, drainage, and the periwound area and wound bed.
• It is vital to look at current wound management.
• Healthcare providers should understand staging of diabetic foot ulcers by Wagner Scale and University of Texas San Antonio Scale.
• The patient history is vital, including past history of ulceration, vascular disease, amputation, Charcot joint, and angioplasty.
• Neuropathic symptoms should also be noted like burning pain, numbness, and the inability to feel the feet.
• Vascular symptoms like claudication, resting pain, and non-healing ulcers
• Additional diabetic complications like retina vision, renal-dialysis, and transplant
• Health management with DM and smoking; hemoglobin A1C, nutrition, tobacco use, and bone density.
• Examine for sensation, specifically if monofilament is >5.07, as this equals a loss of protection.
• Look for ankle reflexes, pinprick, and use a 128 Hz tuning fork, or biothesiometer.
• Check for measures of PAD, including pulses, the posterior tibial, and dorsalis pedis pulses.
• Perform an ABI.
• The functional assessment includes ambulation, transfers, and stairs, as well as quality of motion at the joints of the foot.
• Heel toe raises should be documented.
• Note the current activity level based on step activity monitor.
• Ask if there is a history of vascular disease or claudication pain.
• Ask about fall history, including falls in the past year if patients feel unsteady when standing or walking, or if they worry about falling.
• Balance checks should be performed
• Footwear should be examined

Footwear Assessments

• The current shoes should be examined on both feet. Length, width, depth, shape, material, and construction shall be noted.
• There should be a half inch (1.27 cm) between the longest toe's end and the shoe's front.
• Light-colored materials are preferred to black for cooler temperatures.
• The accommodation of swelling- Velcro, a hook/loop closure, should be adjustable with laces.
• Linings should be soft with no loose edges or prominent seams.
• Insoles should not have wrinkles or curling but provide shock absorption.
• Orthotics should be semi-flexible.
• Materials should be leather, suede, canvas, and breathable synthetics.
• Avoid plastics/vinyl, sandals, thongs, high heels, and open toes.
• Materials should be leather, suede, canvas, and breathable synthetics.
• Shop for shoes at the end of the day when feet tend to be swollen.
• Match the shoe shape to the shape of the foot to avoid pressure on bony prominences.
• Use orthotists to make specialized diabetic footwear for those with foot deformity.
• Change shoes once or twice daily to avoid prolonged pressure over any areas of the foot.
• Making a tracing of the foot may be needed.

National Diabetes Education Program Risk

Categories include

• Low Risk Patients with none of the five high-risk characteristics below. Perform an annual comprehensive foot exam, assess/recommend appropriate footwear, provide the patient with selfcare information for prevention, and perform visual foot inspection.
• High-Risk Patients with one or more of the following: loss of protective sensation, absent pedal pulses, foot deformity, history of foot ulcer, or prior amputation. Perform annual comprehensive foot exam, visual foot inspection at every visit, demonstrate preventative self-care of the feet, and refer to specialists and an educator. Assess and prescribe appropriate footwear and certify Medicare patients for therapeutic shoe benefits while placing a “High-Risk Feet” sticker on the medical record.
• The IWGDF 2019 Risk Stratification System stratifies to determine foot screening frequency. Note the screening frequency is based on expert opinion, since there is no published evidence to support these intervals.

Assessment

• Asses for signs and symptoms consistent with neuropathic ulcers secondary to insensitivity and foot deformities.
• Medical diagnosis: Neuropathic Ulcer
• MSI Diagnosis: Tissue Impairment, Stage 1
• Determine the contributing factors to excessive pressure on the ulcer and how those factors can be modified to reduce the pressure.
• #1 reason for hospitalizations for people with DM.
• What is the most common way to assess lower extremity in clinic?
• Is an ABI of 0.7 okay and what if the ABI is 1.4 and what could be the cause?
• What are the normal ranges of ABI?
• Which monofilament is protective sensation?
• What is the common mechanism of injury to the foot?
• What is a good clinical test of systematic limited joint mobility?
• ADA goals for glucose control.
• Factors contributing to skin breakdown on the diabetic foot.
• Examination components for clients with diabetes and suspected neuropathy.

Interventions

• Patient education
• Footwear
• Wound management
• Surgical

Patient Education:

• Daily foot inspection by family members.
• early detection and treatment.
• Wearing shoes that fit to avoid going barefoot.
• Wash feet daily in warm water and dry.
• Avoid direct heat to desensitize the foot.
• Cut toenails straight across after bathing with nails softened.
• Wear white cotton or synthetic, moisture-wicking socks(soft, padded, not prominent toe seams, tight elastic or holes).
• Apply moisturizer to feet.
• Avoid going barefoot
• Look at current shoes on both feet for length, width, depth, shape, material and construction.
• Allow ½” (1.27 cm) between the end of the longest toe and the front of the shoe.
• Light-colored materials are preferred to black (lower temperatures).
• Swelling can be accommodated with Velcro, a hook or loop closure, or adjustable laces.
• Linings should be soft, without seams.
• Insoles should be free of wrinkles or curling and provide shock absorption.
• Orthotics should be semi-flexible.
• Select materials that are leather, suede, canvas, or breathable synthetics and avoid plastics/vinyl, sandals, thongs, high heels, and open toes
• There is a key to protecting the foot with pressure being the force divided by the area.
• Decrease force or increase the area.

Footwear Guidelines

• It must be the best fitting shoe possible
• Work closely with an orthotist who has shoe-maker experience.
• Accommodate deformity and reduce stress while distributing pressures with a total contact insert.
• The rigid rocker bottom sole should have ADA Consensus, 2008; and IWGDF Guidelines 2019.
• AFO is needed for foot-drop

Main Points

• The contributing factors to skin breakdown on the diabetic foot include peripheral neuropathy, peripheral vascular disease, and joint deformity limited joint mobility due to physical stresses.
• Primary treatment and preventive interventions for neuropathic prevention of skin include protecting the insensitive foot from excessive stress.
• Main important education needed with patients
• Type of intervention needed for each risk

Ulcer Management

• Wound care
• Off-loading
• Remodeling
• Protective footwear

Tissue Impairment Management

• In stage 1, total contact casting is the most effective off-loading method.
• 90% of wounds heal in 42 days.
• There is an 82% pressure reduction at the site of the ulcer.
• Removable pressure relief walkers have comparable pressure reduction, although lower healing rates of 58% vs. 90% have been observed.
• Patients tend to only wear them 25% of the time.

Custom Footwear

• Custom rocker bottom shoes with custom insoles can reduce pressure ~30% and are often fitted with apex proximal to the met heads

Other Findings

• High ulcer recurrence rates such as 34%, 61% and 70% in years 1,3,5 that can be mitigated with Tendo Achilles Lengthening and weakness and with Pressure having been decreased after the procedure with Lin 96, Mueller et al, 2003.
• Walking Goal: 10,000 steps /day (Surgeon General)
• People with Type 2 DM should perform 30 minutes per day of moderate exercise (50% of max heart rate) at least 5x per week or 150 minutes per week of moderate intensity.
• People with DM and PN have historically limited prolonged weight-bearing exercise, with ADA position statements for 2006, 2009, and 2016.
• Surgical causes of amputation are diabetes (at least 90%), peripheral vascular disease, trauma, cancer, and congenital problems.
• Surgical procedures can include toe amputation, transmetatarsal amputation (TMA), below the knee amputation (BKA), and above the knee amputation (AKA).
• Of LEAs, 41% are in DM; 26% in other; Report from Reiber, 2001;
• In TMA, 11% of all occur in DM cases while 6% will result in others.
• In immediate post-op TMA treatment, there should be a heel strike offloader shoe rather than the patient being non-weight bearing (NWB).
• StudIes show there is less peak plantar pressure when incisions are healed in DM patients.
• Key practice includes total contact insert.
• And includes use of rigid rocker-bottom sole is very useful and is included in the (Snacore).

Key Points

• Screen diabetic foot risk
• Protect the sensitive Always
• Reduce excessive Skin (Tissue wound, and limit excessive stress

Review

• Is footwear appropriate for patients with surgery or TMA