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Biomechanics of the Diabetic Foot Robert G. Frykberg, DPM, MPH Chief, Podiatry Section Carl T. Hayden VA Medical Center Phoenix, AZ USA.

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Presentation on theme: "Biomechanics of the Diabetic Foot Robert G. Frykberg, DPM, MPH Chief, Podiatry Section Carl T. Hayden VA Medical Center Phoenix, AZ USA."— Presentation transcript:

1 Biomechanics of the Diabetic Foot Robert G. Frykberg, DPM, MPH Chief, Podiatry Section Carl T. Hayden VA Medical Center Phoenix, AZ USA

2 Diabetes Mellitus NeuropathyVascular Disease Trauma MOTOR SENSORY AUTONOMIC MICROVASCULAR MACROVASCULAR Weakness Loss of Protective Anhidrosis Structural: Atherosclerosis Atrophy sensation Dry skin, Fissures Capillary BM Decreased Sympathetic thickening Deformity tone Functional: Ischemia (Altered blood flow A-V shunting Abnormal stress regulation) Increased blood flow Neuropathic edema High plantar pressure Callus formation Reduced nutrient capillary blood flow Osteoarthropathy Amputation DIABETIC FOOT ULCERATION Impaired Response to Infection RGF

3 Causal Pathways to Foot Ulcers From: Reiber et al: Diabetes Care 22: , 1999 Critical Triad in >63% of causal pathways High Plantar Foot Pressures

4 Altered Biomechanics in Diabetes Biomechanical abnormalities / structural deformities are most frequently a consequence of Neuropathy Altered gait patterns can result in unsteady gait with increased plantar foot pressures for longer durations (pressure-time integrals) Combination of foot deformity and neuropathy increases the risk of ulcer Limited Joint Mobility (ankle, STJ, great toe) will also lead to higher plantar pressures and ulcers Van Schie 2005 Cavanagh 1996

5 Contributing Factors to the Abnormal Mechanics of the Diabetic Foot Diabetes Mellitus Neuropathy Structural Deformity Gait Abnormalities LJM Mononeuropathy Primary (idiopathic) Foot drop Collagen glycosylation Polyneuropathy Secondary Equinus reduced mobility Sensory Muscle atrophy Intrinsic muscle reduced shock absorption Motor Equinus atrophy increased pressures Autonomic Amputations Clawtoes Charcot Amputations Abnormal Biomechanics High Plantar Pressures Neuropathic Ulceration Van Schie 2005 Zimny 2004 Frykberg 1995

6 Classification of Diabetic Neuropathy Generalized Symmetric Polyneuropathies –Acute Sensory –Chronic Sensorimotor –Autonomic Focal and multifocal neuropathies –Cranial –Truncal –Focal limb –Proximal motor (amyotrophy –Coexisting CIDP Boulton, Malik et al: Diabetes Care, 2004 Boulton, Vinik, et al: Diabetes Care, 2005

7 Andersen et al: 2004 Intrinsic Muscle Atrophy

8 Bus et al: Diabetes Care, 2002 Intrinsic Muscle Atrophy

9 Common Foot Deformities in Diabetes Hammertoes (Clawtoes) Bunions (hallux valgus) Prominent metatarsal heads (pes cavus) Charcot arthropathy Partial foot amputations Equinus (Achilles contracture) Foot drop

10 STRUCTURAL DEFORMITY Primary (idiopathic) Pes cavus, pes planus, hallux valgus, hammertoes, forefoot deformities Deformities, pressure points, calluses precede neuropathy. Secondary "intrinsic minus foot"- clawtoes, pes cavus, depressed metatarsals. Loss of intrinsic muscle stability with long flexor over-dominance. Anterior crural atrophy (Ant. Tib.,EHL) - weakness, foot drop Equinus deformity- triceps surae dominance, post. tibial, long flexors Charcot deformity - rocker bottom, Lisfranc subluxation, MTP subluxation Iatrogenic Post amputation: digital, ray, TMA, Lisfrancs, Choparts, Symes Frykberg 1995

11 AMPUTATIONS IN THE FOOT CONSEQUENCES  Structural alterations  Reduced contact areas  Increased plantar pressures  Altered function  Altered gait

12 STRUCTURAL DEFORMITY Frykberg et al: J Foot Ankle Surg 2006 Any deformity can lead to high plantar Pressures and subsequent ulceration in the Neuropathic Foot

13 The Role of High Plantar Pressures in Diabetic Foot Ulceration High plantar foot pressures are consistently detected in diabetic pts with neuropathy Boulton 1987, Veves 1992, Stess 1997, Shaw 1998 correlated with Limited Joint Mobility, plantar tissue thickness, and plantar fascia thickness Zimny 2004, Abouaesha 2001, D’Ambrogi 2003 risk factor for foot ulceration Fernando 1991 Lavery 1998 Frykberg 1998 Lavery 2003 Racial variations are evident Veves 1995Frykberg 1998

14 Predictive Value of Foot Pressure Assessment 24 month study of 1666 DM patients Mean age 69 yrs 50% male Mean Duration DM 11.1 yrs Mean Peak Plantar Pressure 86.6 N/cm2 VPT 22.5 volts 263 (15.8%) had or developed ulcer Ulcer group had higher pressures Lavery LA, Armstrong, DG, et al, Diabetes Care 2003

15 Pressure is a factor Lavery LA, Armstrong, DG, et al, Diabetes Care 2003 Deformities IWGDF Foot Risk Categories

16 Progressive Risk of Ulceration No Neuropathy Neuropathy Neuropathy, PVD, And/ or Deformity Hx Ulcer / Amp Peters 2001 IWGDF Foot Risk Classification

17 GAIT DISTURBANCES n Function of neuropathy, deformity, & LJM n Abnormal loading patterns - earlier and longer n Altered cadence - instability and limp n Altered weight bearing sites – n Partial foot amputations - smaller area n Increased plantar pressures n Susceptible to ulceration

18 Proximal muscle atrophy - thigh weakness Anterior crural atrophy - dorsiflexor weakness Intrinsic muscle atrophy - clawtoes; reduced toe loading Foot drop - Anterior tibial, Extensor hallucis longus paresis Equinus - Posterior group dominance; triceps surae Structural deformities - Charcot, post amputations GAIT ABNORMALITIES Contributing Factors

19 A product of Nonenzymatic glycosylation of collagen –Also associated with retinopathy Decreased ankle and hallux motion Restricted subtalar range of motion –reduced shock absorption; –Increased vertical and shear forces –Increased peak plantar pressures Alone does not cause ulceration With neuropathy, contributes to plantar ulceration Limited Joint Mobility Delbridge 1988 Fernando 1991 Zimny 2004

20 The Role of Limited Joint Mobility in Diabetic Patients with an At-Risk Foot Zimny, Schatz, Pfohl: Diabetes Care 27: , 2004

21 Zimny: Diabetes Care, 2004 There is a strong inverse correlation between joint mobility and PTI in diabetic patients At-Risk Neuropathic patients have less joint mobility and higher PTI’s than control DM (non-neuropathic) patients

22 Equinus Deformity Achilles tendon contracture Increases plantar forefoot pressure May increase risk for ulceration Present in ~ 40% of high-risk patients At 3x greater risk for presenting with high plantar pressures Barry DC et al, JAPMA, 1993 Grant WP et al, JFAS, 1997 Lavery, et al, Arch Intern Med, 1998 Lavery, Armstrong, Boulton, JAPMA, 2002

23 Equinus Deformity Diabetic population study San Antonio, TX n= % male Age ~ 69 yrs Duration DM 11.1 yrs VPT ~ 22.5 Equinus Prevalence 10.3% Peak plantar pressure 86.6 N/cm2 Lavery, Armstrong, Boulton, JAPMA, 2002

24 SUMMARY

25 Biomechanics of The Diabetic Foot  Biomechanical alterations are a composite function of neuropathy, structural deformity, LJM, and associated gait disturbances  Neuropathy is a primary determinant  Early recognition, intervention, and prevention of deformity with high plantar pressures are crucial to the avoidance of ulceration

26 You can observe a lot just by watching Yogi Berra American Baseball Player and Philosopher

27 THANK YOU! Robert G. Frykberg, DPM, MPH

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