A Review of the Biomechanics of the Diabetic Foot

Effect of viscoelastic properties of plantar soft tissues on plantar pressures at the first metatarsal head in diabetics with peripheral neuropathy

Diabetic foot ulcers are one of the most serious complications associated with diabetes mellitus. Current research studies have demonstrated that biomechanical alterations of the diabetic foot contribute to the development of foot ulcers. However, the changes of soft tissue biomechanical properties associated with diabetes and its influences on the development of diabetic foot ulcers have not been investigated. The purpose of this study was to investigate the effect of diabetes on the biomechanical properties of plantar soft tissues and the relationship between biomechanical properties and plantar pressure distributions. We used the ultrasound indentation tests to measure force-deformation relationships of plantar soft tissues and calculate the effective Young's modulus and quasi-linear viscoelastic parameters to quantify biomechanical properties of plantar soft tissues. We also measured plantar pressures to calculate peak plantar pressure and plantar pressure gradient. Our results showed that diabetics had a significantly greater effective Young's modulus and initial modulus of quasi-linear viscoelasticity compared to non-diabetics. The plantar pressure gradient and biomechanical properties were significantly correlated. Our findings indicate that diabetes is linked to an increase in viscoelasticity of plantar soft tissues that may contribute to a higher peak plantar pressure and plantar pressure gradient in the diabetic foot.

Effects of a combined strengthening, stretching and functional training program versus usual-care on gait biomechanics and foot function for diabetic neuropathy: a randomized controlled trial

Background

Polyneuropathy is a complication of diabetes mellitus that has been very challenging for clinicians. It results in high public health costs and has a huge impact on patients' quality of life. Preventive interventions are still the most important approach to avoid plantar ulceration and amputation, which is the most devastating endpoint of the disease. Some therapeutic interventions improve gait quality, confidence, and quality of life; however, there is no evidence yet of an effective physical therapy treatment for recovering musculoskeletal function and foot rollover during gait that could potentially redistribute plantar pressure and reduce the risk of ulcer formation.

Methods/Design

A randomised, controlled trial, with blind assessment, was designed to study the effect of a physiotherapy intervention on foot rollover during gait, range of motion, muscle strength and function of the foot and ankle, and balance confidence. The main outcome is plantar pressure during foot rollover, and the secondary outcomes are kinetic and kinematic parameters of gait, neuropathy signs and symptoms, foot and ankle range of motion and function, muscle strength, and balance confidence. The intervention is carried out for 12 weeks, twice a week, for 40-60 min each session. The follow-up period is 24 weeks from the baseline condition.

Discussion

Herein, we present a more comprehensive and specific physiotherapy approach for foot and ankle function, by choosing simple tasks, focusing on recovering range of motion, strength, and functionality of the joints most impaired by diabetic polyneuropathy. In addition, this intervention aims to transfer these peripheral gains to the functional and more complex task of foot rollover during gait, in order to reduce risk of ulceration. If it shows any benefit, this protocol can be used in clinical practice and can be indicated as complementary treatment for this disease.

Trial Registration

ClinicalTrials.gov Identifier: NCT01207284

Effect of insole material on lower limb kinematics and plantar pressures during treadmill walking

BACKGROUND

Currently there is a paucity of research providing recommendations on the type of orthotic or material used in its construction for different patient requirements.

OBJECTIVES

To gain a greater understanding of the characteristics of orthotic materials and how they affect gait so to enhance the clinical decision-making process.

STUDY DESIGN

Repeated measures.

METHODS

Plantar pressures and kinematics were evaluated for 10 participants while walking on a treadmill under various conditions which included, shoes only and shoes with four different flat insoles and custom devices created in each of two densities of two materials.

RESULTS

For the flat insoles, medium density ethyl vinyl acetate was found to produce greater peak pressures than at least one of the other material conditions and low and medium density polyurethane were most effective at increasing average contact area and at reducing pressure time integral. For the custom devices, while no significant differences were evident, when compared to the shoe only condition, medium density polyurethane increased average contact area by a greater percentage than the other materials.

CONCLUSIONS

Results for medium density polyurethane suggest a possible difference in loading characteristics, indicating a potential material suitability for patients with a compromised ability to deal with pressure.

Increased plantar foot pressure in persons affected by leprosy

Although foot pressure has been reported to be increased in people affected by leprosy, studies on foot pressure and its determinants are limited. Therefore, the aim was to assess barefoot plantar foot pressure and to identify clinical determinants of increased plantar foot pressure in leprosy affected persons. Plantar pressure in both feet was assessed using the Novel EMED-X platform in 39 persons affected by leprosy. Peak pressure was determined for the total foot and four regions: hallux, metatarsal heads, midfoot and heel. Potential determinants were: age, weight, nerve function (Neuropathy Disability Score, Pressure Perception Threshold and Vibration Perception Threshold), toe and foot deformities, joint mobility, ankle muscle strength and callus. Increased peak pressure (>600kPa) was observed in 46% of the participants. The highest peak pressure (mean) was found in the metatarsal heads region (right 549 (SD 321)kPa; left 530 (SD 298)kPa). Multilevel regression analysis showed that Neuropathy Disability Score, amputation/absorption of toes and hallux valgus independently contributed to metatarsal heads peak pressure in persons affected with leprosy. To conclude, peak pressure is increased in people affected by leprosy. The highest peak pressure is found in the forefoot region and is significantly associated to Neuropathy Disability Score, toe amputation/absorption and hallux valgus. Screening for clinical characteristics can be used to identify individual persons affected by leprosy at risk of excessive pressure.

Spatial relationships between shearing stresses and pressure on the plantar skin surface during gait

Based on the hypothesis that diabetic foot lesions have a mechanical etiology, extensive efforts have sought to establish a relationship between ulcer occurrence and plantar pressure distribution. However, these factors are still not fully understood. The purpose of this study was to simultaneously record shear and pressure distributions in the heel and forefoot and to answer whether: (i) peak pressure and peak shear for anterior-posterior (AP) and medio-lateral (ML) occur at different locations, and if (ii) peak pressure is always centrally located between sites of maximum AP and ML shear stresses. A custom built system was used to collect shear and pressure data simultaneously on 11 subjects using the 2-step method. The peak pressure was found to be 362 kPa ± 106 in the heel and 527 kPa ± 123 in the forefoot. In addition, the average peak shear values were higher in the forefoot than in the heel. The greatest shear on the plantar surface of the forefoot occurred in the anterior direction (mean and std. dev.: 37.7 ± 7.6 kPa), whereas for the heel, peak shear the foot was in the posterior direction (21.2 ± 5 kPa). The results of this study suggest that the interactions of the shear forces caused greater "spreading" in the forefoot and greater tissue "dragging" in the heel. The results also showed that peak shear stresses do not occur at the same site or time as peak pressure. This may be an important factor in locating where skin breakdown occurs in patients at high-risk for ulceration.

Flexible and rigid casting tape as a novel approach to offloading diabetic foot ulcers

Offloading diabetic ulceration is a key component to the success in healing ulcers on the plantar aspect of the foot. New advances in offloading techniques allow for differing approaches in sometimes complex diabetic foot pathologies with associated ulceration. This case study looks at the use of flexible and rigid casting technique as part of the treatment in offloading plantar foot ulceration.

Electromyography and kinematic changes of gait cycle at different cadences in diabetic neuropathic individuals

INTRODUCTION

Changes in gait cadence caused by challenging situations in daily life might induce higher demand for strength and propulsion in diabetic neuropathic (DN) subjects.

METHODS

Forty-six subjects (healthy and DN) walked at two cadences (self-selected and 25% higher). Kinematic and electromyographic data were obtained from lower limbs and compared across the gait cycle.

RESULTS

DN subjects showed a delayed peak in plantarflexor activity along the whole cycle (irrespective of cadence) compared with healthy subjects. However, during the imposed cadence, DN individuals showed reduced ankle range of motion along the entire cycle compared with the self-selected condition and healthy individuals walking at both cadences (P = 0.002).

CONCLUSIONS

These findings suggest that when diabetic individuals face a new challenging situation that induces a higher demand for muscle strength and propulsion, the necessary range of motion and neuromuscular control around distal joints are insufficient.

Walking speed and peak plantar pressure distribution during barefoot walking in persons with diabetes

BACKGROUND

The impact of walking speed has not been evaluated as a feasible outcome measure associated with peak plantar pressure (PPP) distribution, which may result in tissue damage in persons with diabetic foot complications. The objective of this pilot study was to determine the walking speed and PPP distribution during barefoot walking in persons with diabetes. 

METHODS

 Nine individuals with diabetes and nine age-gender matched individuals without diabetes participated in this study. Each individual was marked at 10 anatomical landmarks for vibration and tactile pressure sensation tests to determine the severity of sensory deficits on the plantar surface of the dominant limb foot. A steady state walking speed, PPP, the fore and rear foot (F/R) PPP ratio and gait variables were measured during barefoot walking. 

RESULTS

 Persons with diabetes had a significantly slower walking speed than the age-gender matched group resulting in a significant reduction of PPP at the F/R foot during barefoot walking (p < 0.05). There was no significant difference in F/R foot PPP ratio in the diabetic group compared with the age-gender matched group during barefoot walking (p > 0.05). There was a significant difference between the diabetic and non-diabetic groups for cadence, step time, toe out angle and the anterior-posterior excursion (APE) for centre of force (p < 0.05). 

CONCLUSION

 Walking speed may be a potential indicator for persons with diabetes to identify PPP distribution during barefoot walking in a diabetic foot. However, the diabetic group demonstrated a more cautious walking pattern than the age-gender matched group by decreasing cadence, step length and APE, and increasing step time and toe in/out angle. People with diabetes may reduce the risk of foot ulcerations as long as they are able to prevent severe foot deformities such as callus, hammer toe or charcot foot.

Dressing plantar wounds with foam dressings, is it too much pressure?

Diabetes and its associated complications have become a major concern locally, nationally and internationally. One such complication is lower extremity amputation, commonly preceded by chronic ulceration. The cause of this tissue breakdown is multi-faceted, but includes an increase in pressure, particularly plantar pressure. As such, the choice of dressing to be applied to a plantar wound should ideally not increase this pressure further. A commonly used and possibly more bulky dressing is the foam dressing. This pilot study investigates the plantar pressures associated with three common foam dressings (Allevyn(®), Lyofoam(®) and Mepilex(®)) compared with a control dressing (Melolin(®)). Twelve healthy males and 19 females [SD] age 36.6 [10.4] were measured using the F-scan plantar pressure measurement system. Substantial variations in individual pressure changes occurred across the foot. No significant differences were identified, once a Bonferroni correction was applied. In healthy adults, it could be concluded that foam dressings do not have any effect on the plantar pressures of the foot. However, the need remains for a robust trial on a pathological population.

The effect of target strain error on plantar tissue stress

Accurate quantification of soft tissue properties, specifically the stress relaxation behavior of viscoelastic tissues such as plantar tissue, requires precise testing under physiologically relevant loading. However, limitations of testing equipment often result in target strain errors that can contribute to large stress errors and confound comparative results to an unknown extent. Previous investigations have modeled this artifact, but they have been unable to obtain empirical data to validate their models. Moreover, there are no studies that address this issue for plantar tissue. The purpose of this research was to directly measure the difference in peak force for a series of small target strain errors within the range of our typical stress relaxation experiments for the subcutaneous plantar soft tissue. Five plantar tissue specimens were tested to seven incremental target strain error levels of -0.9%, -0.6%, -0.3%, 0.0%, 0.3%, 0.6%, and 0.9%, so as to undershoot and overshoot the target displacement in 0.3% increments. The imposed strain errors were accurately attained using a special compensation feature of our materials testing software that can drive the actuator to within 0% (1-2 microm) of the target level for cyclic tests. Since stress relaxation tests are not cyclic, we emulated the ramp portion of our stress relaxation tests with 5 Hz triangle waves. The average total stress variation for all specimens was 25+/-5%, with the highest and lowest stresses corresponding to the largest and smallest strain errors of 0.9% and -0.9%, respectively. A strain overshoot of 0.3%, the target strain error observed in our typical stress relaxation experiments, corresponded to an average stress overshoot of 3+/-1%. Plantar tissue in compression is sensitive to small target strain errors that can result in stress errors that are several fold larger. The extent to which the overshoot may affect the peak stress will likely differ in magnitude for other soft tissues and loading modes.

Surgical off-loading of the diabetic foot

Surgical intervention for chronic deformities and ulcerations has become an important component in the management of patients with diabetes mellitus. These patients are no longer relegated to wearing cumbersome braces or footwear for deformities that might otherwise be easily corrected. Although surgical intervention in these often high-risk individuals is not without risk, the outcomes are fairly predictable when patients are properly selected and evaluated. In this brief review, we discuss the rationale and indications for diabetic foot surgery, focusing on the surgical decompression of deformities that frequently lead to foot ulcers.

A new classification of diabetic gait pattern based on cluster analysis of biomechanical data

BACKGROUND

The diabetic foot, one of the most serious complications of diabetes mellitus and a major risk factor for plantar ulceration, is determined mainly by peripheral neuropathy. Neuropathic patients exhibit decreased stability while standing as well as during dynamic conditions. A new methodology for diabetic gait pattern classification based on cluster analysis has been proposed that aims to identify groups of subjects with similar patterns of gait and verify if three-dimensional gait data are able to distinguish diabetic gait patterns from one of the control subjects.

METHOD

The gait of 20 nondiabetic individuals and 46 diabetes patients with and without peripheral neuropathy was analyzed [mean age 59.0 (2.9) and 61.1(4.4) years, mean body mass index (BMI) 24.0 (2.8), and 26.3 (2.0)]. K-means cluster analysis was applied to classify the subjects' gait patterns through the analysis of their ground reaction forces, joints and segments (trunk, hip, knee, ankle) angles, and moments.

RESULTS

Cluster analysis classification led to definition of four well-separated clusters: one aggregating just neuropathic subjects, one aggregating both neuropathics and non-neuropathics, one including only diabetes patients, and one including either controls or diabetic and neuropathic subjects.

CONCLUSIONS

Cluster analysis was useful in grouping subjects with similar gait patterns and provided evidence that there were subgroups that might otherwise not be observed if a group ensemble was presented for any specific variable. In particular, we observed the presence of neuropathic subjects with a gait similar to the controls and diabetes patients with a long disease duration with a gait as altered as the neuropathic one.

Diabetic foot biomechanics and gait dysfunction

BACKGROUND

Diabetic foot complications represent significant morbidity and precede most of the lower extremity amputations performed. Peripheral neuropathy is a frequent complication of diabetes shown to affect gait. Glycosylation of soft tissues can also affect gait. The purpose of this review article is to highlight the changes in gait for persons with diabetes and highlight the effects of glycosylation on soft tissues at the foot-ground interface.

METHODS

PubMed, the Cochrane Library, and EBSCOhost on-line databases were searched for articles pertaining to diabetes and gait. Bibliographies from relevant manuscripts were also searched.

FINDINGS

Patients with diabetes frequently exhibit a conservative gait strategy where there is slower walking speed, wider base of gait, and prolonged double support time. Glycosylation affects are observed in the lower extremities. Initially, skin thickness decreases and skin hardness increases; tendons thicken; muscles atrophy and exhibit activation delays; bones become less dense; joints have limited mobility; and fat pads are less thick, demonstrate fibrotic atrophy, migrate distally, and may be stiffer.

INTERPRETATION

In conclusion, there do appear to be gait changes in patients with diabetes. These changes, coupled with local soft tissue changes from advanced glycosylated end products, also alter a patient's gait, putting them at risk of foot ulceration. Better elucidation of these changes throughout the entire spectrum of diabetes disease can help design better treatments and potentially reduce the unnecessarily high prevalence of foot ulcers and amputation.

The characterization and optimization of injectable silicone resin particles in conjunction with dermal fibroblasts and growth factors: an in vitro study

Minimally invasive subdermal injection of liquid silicone has been used clinically to augment the soft tissue of the foot to mitigate high pressures that cause diabetic foot ulcers. However, implant migration has been a clinical issue. The objective of this study was to assess the effects of three specific concentrations of silicone resin particles (12 mum average diameter) in conjunction with either platelet-derived growth factor (PDGF-BB) or basic fibroblast growth factor (bFGF) on fibroblast cell proliferation, collagen synthesis, cell morphology, and migration through in vitro assays and a monolayer scratch wound model. PDGF and bFGF enhanced the proliferation of fibroblasts 5.7-fold and fivefold, respectively, while the addition of silicone particles had no significant effect on proliferation. Collagen production was increased approximately twofold with the addition of bFGF and the medium concentration of particles over bFGF without particles and the PDGF groups. The addition of silicone particles had no significant effect on collagen production compared with control groups without particles. Fibroblast migration was enhanced by the addition of both PDGF and bFGF compared to controls, although slower scratch wound closure rates were observed in the presence of particles compared to controls without particles. Cell morphology suggested that particles induced cellular aggregation encircling silicone particles postwounding as well as migration into the wound area. These results suggest that silicone particles in combination with a growth factor might enhance fibroblast aggregation and implant stability, and could promote connective tissue ingrowth and implant encapsulation in the soft tissue of the diabetic foot.

Effect of growth factors in combination with injectable silicone resin particles on the biological activity of dermal fibroblasts: a preliminary in vitro study

Injections of silicone fluid have been clinically evaluated to treat and prevent foot ulcers due to diminished plantar fat-pad in neuropathic diabetics. The objective of this study was to determine preliminary in vitro effects of an injectable form of silicone resin particles in combination with growth factors to determine the suitability of this potential therapy for prevention of diabetic foot ulcers. Basic fibroblast growth factor (bFGF), epidermal growth factor (EGF) and platelet-derived growth factor (PDGF-BB) were added to monolayer culture along with silicone resin particles (12 microm average diameter). Growth factors were also combined as follows: bFGF+PDGF-BB, EGF+PDGF-BB, and bFGF+EGF. Growth factors alone and in combination increased fibroblast proliferation, but the presence of particles did not significantly affect cellular proliferation. The addition of particles significantly increased fibronectin production 117% in the control group and 151% in the PDGF only group. Collagen production was increased with exposure to EGF and growth factor combinations, but the presence of particles did not lead to any significant differences, except an 81% increase in the bFGF group. These preliminary results suggest that a combination of PDGF and bFGF may be effective in stimulating proliferation and matrix production around injectable silicone resin particles to generate a fibrous tissue pad to alleviate the abnormal distribution of high pressures that contribute to diabetic foot ulcer formation.

A comparison of lower limb EMG and ground reaction forces between barefoot and shod gait in participants with diabetic neuropathic and healthy controls

Background

It is known that when barefoot, gait biomechanics of diabetic neuropathic patients differ from non-diabetic individuals. However, it is still unknown whether these biomechanical changes are also present during shod gait which is clinically advised for these patients. This study investigated the effect of the participants own shoes on gait biomechanics in diabetic neuropathic individuals compared to barefoot gait patterns and healthy controls.

Methods

Ground reaction forces and lower limb EMG activities were analyzed in 21 non-diabetic adults (50.9 ± 7.3 yr, 24.3 ± 2.6 kg/m²) and 24 diabetic neuropathic participants (55.2 ± 7.9 yr, 27.0 ± 4.4 kg/m²). EMG patterns of vastus lateralis, lateral gastrocnemius and tibialis anterior, along with the vertical and antero-posterior ground reaction forces were studied during shod and barefoot gait.

Results

Regardless of the disease, walking with shoes promoted an increase in the first peak vertical force and the peak horizontal propulsive force. Diabetic individuals had a delay in the lateral gastrocnemius EMG activity with no delay in the vastus lateralis. They also demonstrated a higher peak horizontal braking force walking with shoes compared to barefoot. Diabetic participants also had a smaller second peak vertical force in shod gait and a delay in the vastus lateralis EMG activity in barefoot gait compared to controls.

Conclusions

The change in plantar sensory information that occurs when wearing shoes revealed a different motor strategy in diabetic individuals. Walking with shoes did not attenuate vertical forces in either group. Though changes in motor strategy were apparent, the biomechanical did not support the argument that the use of shoes contributes to altered motor responses during gait.

Diabetic gait and posture abnormalities: a biomechanical investigation through three dimensional gait analysis

BACKGROUND

Diabetic sensorimotor polyneuropathy is a long-term diabetic complication. It is involved in the pathogenesis of the diabetic foot, which is a major cause of morbidity and mortality. The study aims to investigate the effects of diabetic polyneuropathy on gait and posture.

METHODS

Sixty seven subjects were enrolled: 21 diabetics without polyneuropathy, 26 with polyneuropathy, 20 controls (respectively, mean age 63.8 (SD 5.4), 63.2 (SD 5.6), 59.0 (SD 5.2) years, mean body mass index 26.3 (SD 2.5), 25.6 (SD 3), 24.0 (SD 2.9)). Postural and morphological evaluation and gait analysis were performed. Physical examination, together with a motion capture system synchronized with two force plates and two baropodometric systems were used. We evaluated lower limb mobility, foot deformities, trunk and pelvic posture, knee and heel position, plantar foot arch, three dimensional kinematics and kinetics during gait. The effect of peripheral vascular disease and microangiopathy on trunk and lower limb motion was also evaluated.

FINDINGS

Trunk and lower limb joint mobility (in static and dynamic states) were more reduced in diabetics either with or without polyneuropathy on each plane; however in diabetics with polyneuropathy significantly lower ranges of motion were registered. Furthermore, both groups showed significant reductions in each joint moment and velocity (P0.003) during gait. In presence of both vasculopathy and microangiopathy a further significant reduction (P0.001) was noticed.

INTERPRETATION

Altered gait and posture were found in diabetic patients irrespective of polyneuropathy. This approach may be relevant to predict the risk ulceration before clinically detectable neuropathy.

Characterizing multisegment foot kinematics during gait in diabetic foot patients

BACKGROUND

The prevalence of diabetes mellitus has reached epidemic proportions, this condition may result in multiple and chronic invalidating long term complications. Among these, the diabetic foot, is determined by the simultaneous presence of both peripheral neuropathy and vasculopathy that alter the biomechanics of the foot with the formation of callosity and ulcerations. To diagnose and treat the diabetic foot is crucial to understand the foot complex kinematics. Most of gait analysis protocols represent the entire foot as a rigid body connected to the shank. Nevertheless the existing multisegment models cannot completely decipher the impairments associated with the diabetic foot.

METHODS

A four segment foot and ankle model for assessing the kinematics of the diabetic foot was developed. Ten normal subjects and 10 diabetics gait patterns were collected and major sources of variability were tested. Repeatability analysis was performed both on a normal and on a diabetic subject. Direct skin marker placement was chosen in correspondence of 13 anatomical landmarks and an optoelectronic system was used to collect the data.

RESULTS

Joint rotation normative bands (mean plus/minus one standard deviation) were generated using the data of the control group. Three representative strides per subject were selected. The repeatability analysis on normal and pathological subjects results have been compared with literature and found comparable. Normal and pathological gait have been compared and showed major statistically significant differences in the forefoot and midfoot dorsi-plantarflexion.

CONCLUSION

Even though various biomechanical models have been developed so far to study the properties and behaviour of the foot, the present study focuses on developing a methodology for the functional assessment of the foot-ankle complex and for the definition of a functional model of the diabetic neuropathic foot. It is, of course, important to evaluate the major sources of variation (true variation in the subject's gait and artefacts from the measurement procedure). The repeatability of the protocol was therefore examined, and results showed the suitability of this method both on normal and pathological subjects. Comparison between normal and pathological kinematics analysis confirmed the validity of a similar approach in order to assess neuropathics biomechanics impairment.

Role of ankle mobility in foot rollover during gait in individuals with diabetic neuropathy

BACKGROUND

The purpose of this study was to investigate the ankle range of motion during neuropathic gait and its influence on plantar pressure distribution in two phases during stance: at heel-strike and at push-off.

METHODS

Thirty-one adults participated in this study (control group, n=16; diabetic neuropathic group, n=15). Dynamic ankle range of motion (electrogoniometer) and plantar pressures (PEDAR-X system) were acquired synchronously during walking. Plantar pressures were evaluated at rearfoot, midfoot and forefoot during the two phases of stance. General linear model repeated measures analysis of variance was applied to investigate relationships between groups, areas and stance phases.

FINDINGS

Diabetic neuropathy patients walked using a smaller ankle range of motion in stance phase and smaller ankle flexion at heel-strike (P=0.0005). Peak pressure and pressure-time integral values were higher in the diabetic group in the midfoot at push-off phase when compared to heel-strike phase. On the other hand, the control group showed similar values of peak pressure in midfoot during both stance phases.

INTERPRETATION

The ankle mobility reduction observed could be associated to altered plantar pressure distribution observed in neuropathic subjects. Results demonstrated that midfoot and forefoot play a different role in subjects with neuropathy by receiving higher loads at push-off phase that are probably due to smaller ankle flexion at stance phase. This may explain the higher loads in anterior areas of the foot observed in diabetic neuropathy subjects and confirm an inadequate foot rollover associated to the smaller ankle range of motion at the heel-strike phase.

Accelerated atrophy of lower leg and foot muscles--a follow-up study of long-term diabetic polyneuropathy using magnetic resonance imaging (MRI)

AIMS/HYPOTHESIS

The aim of the study was to determine the loss of muscle volume in the lower leg and foot in long-term diabetic patients in relation to the presence of neuropathy.

METHODS

We re-examined 26 type 1 diabetic patients who had participated in magnetic resonance imaging (MRI) studies on muscle volume in the lower leg and foot 9 to 12 years earlier. Re-examination involved MRI, isokinetic dynamometry, clinical examination, electrophysiological studies and quantitative sensory examinations.

RESULTS

Annual loss of muscle volume of ankle dorsal and plantar flexors was 4.5 (5.5-3.9)% (median [range]) and 5.0 (7.0-4.2)% in neuropathic patients, 1.9 (3.2-1.0)% and 1.8 (2.6-1.3)% in non-neuropathic patients, and 1.7 (2.8-0.8)% and 1.8 (2.4-0.8)% in controls, respectively (p < 0.01). Annual change of volume and strength correlated for ankle dorsal flexors (r (s) = 0.73, p < 0.01) and for ankle plantar flexors (r (s) = 0.63, p < 0.05) in diabetic patients. In addition, annual change of muscle volume for dorsal and plantar flexors was related to the combined score of all measures of neuropathy (r (s) = -0.68, p < 0.02 and r (s) = -0.73, p < 0.01, respectively). Foot muscle volume declined annually by 3.0 (3.4-1.0)% in neuropathic patients and by 1.1 (4.0-0.2)% in non-neuropathic patients, both values being significantly different from controls (0.2 [-2.5 to 2.4]%). Loss of foot muscle volume was related to severity of neuropathy assessed at clinical evaluation (r (s) = -0.6, p < 0.05).

CONCLUSIONS/INTERPRETATION

Muscular atrophy in long-term diabetic neuropathy occurs early in the feet, progresses steadily in the lower legs, relates to severity of neuropathy and leads to weakness at the ankle.

Charcot arthropathy risk elevation in the obese diabetic population

PURPOSE

To examine the association of obesity, peripheral neuropathy, and other risk factors with the Charcot arthropathy incidence rate in a large diabetic population.

METHODS

The Department of Veterans Affairs inpatient and outpatient administrative datasets were used to identify persons with diabetes in 2003. Logistic regressions were used to model the likelihood of a person developing Charcot arthropathy as a function of individual characteristics, obesity, peripheral neuropathy, diabetic control, and comorbidities.

RESULTS

Of Veterans Affairs users with diabetes, 652 (0.12%) were newly diagnosed with Charcot arthropathy in 2003. Compared with persons without obesity or peripheral neuropathy, those with obesity alone were approximately 59% more likely, those with neuropathy alone were 14 times more likely, and those with both obesity and neuropathy were 21 times more likely to develop Charcot arthropathy. Ages 55 to 64 years, diabetes duration 6 years or more, hemoglobin-A1c 7% or more, renal failure, arthritis, and deficiency anemia also were associated with an increased incidence of Charcot arthropathy.

CONCLUSION

Obesity is significantly associated with an increased incidence of Charcot arthropathy independently of other risk factors. When obesity is combined with neuropathy, the Charcot arthropathy incidence rate increases multiplicatively. Prevention and detection of Charcot arthropathy should take the interaction between obesity and neuropathy into consideration.

MR imaging of the diabetic foot

MR imaging can be quite useful in the evaluation of pathologic processes related to the diabetic foot. The diagnosis of soft tissue processes such as callus formation, ulceration, foreign body granuloma, cellulitis, abscess, and gangrene can be made with the assistance of MR imaging. Osseous deformities such as hammertoe, rocker-bottom foot, neuropathic osteoarthropathy, and osteomyelitis can be detected and defined with MR imaging. Finally, although there are some overlapping features of neuropathic osteoarthropathy and osteomyelitis, the differentiation between the two entities is possible in most instances with the aid of MR imaging.

The relationship between passive range of motion and range of motion during gait and plantar pressure measurements

AIMS

To investigate the relationship between limited joint mobility (LJM; measured both passively and during gait) and plantar pressure measurements.

METHODS

A cross-sectional study involving 28 diabetic patients with peripheral neuropathy but no plantar ulceration (DN), 25 diabetic patients with ulceration (DU), 25 diabetic control patients with no ulceration or peripheral neuropathy (DC), and 25 non-diabetic reference subjects (NDR). Movements of the ankle joint complex (AJC) and 1st metatarsophalangeal (MTP) joint were recorded, together with plantar pressures.

RESULTS

The passive range of motion at the AJC was significantly reduced in all the diabetes groups, but the gait range of motion was comparable with non-diabetic subjects. At the AJC, no correlation was found between the passive and gait range of motion (ROM) and these were not correlated with plantar pressure variables. At the 1st MTP, a correlation was found between the passive and gait dorsiflexion ROM and a significant correlation existed between gait dorsiflexion ROM at the 1st MTP joint and peak forefoot pressures in the DU group.

CONCLUSIONS

Despite a significant reduction in the passive ROM at the AJC in the diabetic groups, the gait ROM was indistinguishable from reference subjects and was not correlated with plantar pressure variables. At the 1st MTP joint, a correlation was found between the passive and gait ROM and furthermore the gait ROM was correlated with peak forefoot pressures, suggesting ROM measures at the 1st MTP joint may be preferable to ROM measures at the AJC.

The treatment of diabetic foot ulcers: reviewing the literature and a surgical algorithm

PURPOSE

To provide an overview of the literature related to the treatment of diabetic foot ulcers.

TARGET AUDIENCE

This continuing education activity is intended for physicians and nurses with an interest in wound care.

OBJECTIVES

After reading this article and taking this test, the reader should be able to:

Xerosis and callus formation as a key to the diabetic foot syndrome: Dermatologic view of the problem and its management

The diabetic foot syndrome is a major complication of diabetes mellitus. The two most important pathophysiologic factors are peripheral arterial occlusion and peripheral neuropathy. The cutaneous lesion is a plantar ulcer, often accompanied by soft tissue and bone infections which can require amputation. Triggers include poorly fitting shoes, poor foot care, or overlooked foreign bodies, often coupled with a structural foot deformity. Increased plantar pressure, especially beneath the metatarsal heads, and the resultant callus play an important role. The patients often already have xerosis of the plantar skin with scales, fissures, erosions and impaired barrier function, complicating the situation. Prompt neurologic and vascular diagnostic studies, coupled with routine examination of the feet and primary prophylactic measures are most important. The most important therapeutic goals are optimal control of the diabetes mellitus, relieving pressure points and avoiding or reducing callus formation.

Recent clinical advances in diabetic polyneuropathy

PURPOSE OF REVIEW

Recent dramatic increases in the incidence and prevalence of diabetes make an understanding of chronic symmetric sensorimotor diabetic polyneuropathy, the most common and problematic of chronic diabetic complications, essential for a wide range of medical practitioners.

RECENT FINDINGS

The demonstration of neuropathic dysfunction in patients with prediabetes or impaired glucose tolerance emphasizes the susceptibility of peripheral nerve fibers, especially small A delta fibers and C fibers, to relatively mild, short-duration hyperglycemia. New testing can reveal peripheral nerve dysfunction prior to clinical neuropathic symptoms and signs. In the absence of effective medications to halt or reverse nerve damage or promote nerve regeneration, early diagnosis of diabetic polyneuropathy, followed by tight glycemic control with diet and exercise, offers the best opportunity to prevent progressive symptoms of sensory loss, pain, autonomic dysfunction, ulcerations, and amputations. Some patients with impaired glucose tolerance have a reversal of neuropathic features with tight glycemic control. Nonpharmacologic therapies for neuropathic pain in diabetic polyneuropathy appear promising.

SUMMARY

Tight glycemic control, especially early in diabetes, is the best approach to minimizing the prevalence and severity of diabetic polyneuropathy and makes research into the deleterious effects of even mild hyperglycemia imperative.

Diabetic foot disorders. A clinical practice guideline (2006 revision)

The prevalence of diabetes mellitus is growing at epidemic proportions in the United States and worldwide. Most alarming is the steady increase in type 2 diabetes, especially among young and obese people. An estimated 7% of the US population has diabetes, and because of the increased longevity of this population, diabetes-associated complications are expected to rise in prevalence. Foot ulcerations, infections, Charcot neuroarthropathy, and peripheral arterial disease frequently result in gangrene and lower limb amputation. Consequently, foot disorders are leading causes of hospitalization for persons with diabetes and account for billion-dollar expenditures annually in the US. Although not all foot complications can be prevented, dramatic reductions in frequency have been achieved by taking a multidisciplinary approach to patient management. Using this concept, the authors present a clinical practice guideline for diabetic foot disorders based on currently available evidence, committee consensus, and current clinical practice. The pathophysiology and treatment of diabetic foot ulcers, infections, and the diabetic Charcot foot are reviewed. While these guidelines cannot and should not dictate the care of all affected patients, they provide evidence-based guidance for general patterns of practice. If these concepts are embraced and incorporated into patient management protocols, a major reduction in diabetic limb amputations is certainly an attainable goal.

Postoperative imaging of the ankle and foot

This article describes the relevant surgical detail and MR imaging appearance of common operations performed in the foot and ankle. To evaluate postsurgical patients critically, it is important to understand the primary clinical diagnosis, surgical treatment undergone, the interval since surgery, and patients' current clinical symptoms. Radiography is the most common imaging modality for evaluation of the postoperative ankle and foot. MR imaging may be useful for evaluating the soft tissues and osseous structures in the postsurgical foot and ankle.

Effect of peak pressure and pressure gradient on subsurface shear stresses in the neuropathic foot

The pressure distribution on the plantar surface of the foot may provide insights into the stresses within the subsurface tissues of patients with diabetes mellitus and peripheral neuropathy (PN) who are at risk for skin breakdown. The purposes of this study were to (1) estimate the stress distribution in the subsurface soft tissue from a measured surface pressure distribution and determine any differences between values in the forefoot and rearfoot, and (2) determine the relationship between maximum shear stress (MSS) (magnitude and depth) and characteristics of the pressure distribution. The measured in-shoe pressure distributions during walking characterized by the peak plantar pressure and maximum pressure gradient on the plantar surface of the feet for 20 subjects with diabetes, PN and history of a mid foot or forefoot plantar ulcer were analyzed. The effects of peak pressure and maximum pressure gradient at the peak pressure location on the stress components in the subsurface soft tissue were studied using a potential function method to estimate the subsurface tissue stress. The calculated MSSs are larger in magnitude and located closer to the surface in the forefoot, where most skin breakdown occurs, compared to the rearfoot. In addition, the MSS (magnitude and depth) is highly correlated with the pressure gradient (r=-0.77 & 0.61) and the peak pressure (r=-0.61 & 0.91). The peak pressure and the maximum pressure gradient obtained from the surface pressure distribution appear to be important variables to identify where MSSs are located in the subsurface tissues on the plantar foot that may lead to skin break down.

Muscle weakness: a progressive late complication in diabetic distal symmetric polyneuropathy

The aim of the study was to determine the progression of muscle weakness in long-term diabetes and its relation to the neuropathic condition. Thirty patients were recruited from a cohort of 92 diabetic patients who participated in a study on muscular function 6-8 years earlier. Nine subjects were nonneuropathic, 9 had asymptomatic neuropathy, and 12 had symptomatic neuropathy. Thirty matched control subjects who participated in the initial studies were also included. At follow-up, isokinetic dynamometry at the ankle, electrophysiological studies, vibratory perception thresholds, and clinical examination (neuropathy symptom score and neurological disability score [NDS]) were repeated. The annual decline of strength at the ankle was 0.7 +/- 1.7% in control subjects, 0.9 +/- 1.9% in nonneuropathic patients, 0.7 +/- 3.1% in asymptomatic neuropathic patients, and 3.2 +/- 2.3% in symptomatic neuropathic patients. In the symptomatic patients, the decline of muscle strength at the ankle was significant when compared with matched control subjects (P = 0.002) and with the other diabetic groups (P = 0.023). Also, the annual decline of muscle strength at the ankle was related to the combined score of all measures of neuropathy (r = -0.42, P = 0.03) and to the NDS (r = -0.52, P = 0.01). In patients with symptomatic diabetic neuropathy, weakness of ankle plantar and dorsal flexors is progressive and related to the severity of neuropathy.