EFFICACY OF THE OPENSIM SIMULATOR AS A TOOL TO DETECT CHANGES IN GAIT: A PERIPHERAL ARTERY DISEASE MODEL

INTRODUCTION Peripheral Artery Disease (PAD) is characterized by atherosclerotic plaques in the leg arteries. A common treatment for PAD is supervised exercise training [1]. However, gait is not fully restored following supervised exercise training (SET). Musculoskeletal simulation may provide insight into how muscle activation changes following SET contributed to persistent gait alterations. METHODS Kinematic and kinetic data from overground walking of patients with PAD (n=12), before and after a 6-month exercise intervention, was used as input for musculoskeletal modeling (OpenSim). The subjects in our sample were subdivided based on the location of ischemic muscle pain, as reported on the San Diego Claudication Questionnaire. Virtual models were scaled to match the anthropometry of the subjects before muscle parameters were derived. Muscle activation was analyzed across the stance phase of gait and the output was analyzed across subjects and conditions. RESULTS AND DISCUSSION The subset of subjects that reported an attenuation of thigh pain as a result of SET (pain-free, n=4) showed a significant increase in late-stance knee flexor force, whereas the group that experienced no difference in thigh pain following SET (pain, n=8) did not demonstrate a significant change in knee flexor force. A significant positive association exists between the difference in absolute claudication distance and the difference in maximum knee flexor force. CONCLUSIONS This study demonstrated that a subset of patients with PAD experienced a significant increase in knee flexor force as a result of SET. Simulations may be an effective tool for understanding gait changes in a PAD model

MUSCLE OXYGENATION IN PATIENTS WITH PERIPHERAL ARTERY DISEASE DURING WALKING WITH AND WITHOUT AN ANKLE FOOT ORTHOSIS

Peripheral artery disease (PAD) is a cardiovascular disease caused by blockages in the arteries that reduce blood flow to the peripheral limbs. Claudication, a prominent symptom of PAD is a condition in which the lack of blood flow causes an inability to meet the metabolic demands of the muscle tissue, causes severe cramping pain. Previous studies have shown muscle oxygenation starts significantly lower and declines faster in patients with PAD compared to healthy controls. An ankle foot orthosis (AFO) can provide walking assistance by absorbing and returning the mechanical force during walking. We hypothesized oxygenation levels would be higher in patients with PAD walking with the AFO. Our research included seven subjects with PAD, patients performed a standardized graded treadmill test until claudication pain made them stop for both the AFO and non-ankle foot orthosis condition (NAF). Muscle oxygenation values were recorded before, during and directly following the trials for both conditions. PAD patients using the AFO significantly improved muscle oxygenation in the calf muscles. Our study only included seven patients, larger trials will be needed to increase the statistical strength

COLLISION WORK PERFORMED BY PATIENTS WITH PERIPHERAL ARTERY DISEASE

The goal of this study was to assess the differences in collision work performed by healthy, aged-matched controls compared to patients with peripheral artery disease (PAD) to provide foundations for an eventual exoskeleton design. Collision work is energy dissipated into the surrounding environment from impact, in this study’s case, upon heel strike. When designing an exoskeleton for patients with PAD, harvesting energy lost to collision work could be a valuable mechanism to improve walking performance. Devices designed to utilize the normally dissipated energy for assisting propulsion to improve walking performance are under-explored [1, 2]. The purpose of this study was to assess the validity of healthy, older individuals as a model for patients with PAD when investigating collision work as a primary exoskeleton design consideration. References [1] Kuo, A., et al. (2005). Exerc. Sport Sci. Rev.,33: 88-97 [2] Li, Q., et al. (2009). J. Neuroeng. Rehabil., 6: 22-22 [3] Donelan, J., et al.(2002). A. D. J. Biomech., 35: 117-12

The effect of pharmacological treatment on gait biomechanics in peripheral arterial disease patients

<p>Abstract</p> <p>Background</p> <p>Pharmacological treatment has been advocated as a first line therapy for Peripheral Arterial Disease (PAD) patients suffering from intermittent claudication. Previous studies document the ability of pharmacological treatment to increase walking distances. However, the effect of pharmacological treatment on gait biomechanics in PAD patients has not been objectively evaluated as is common with other gait abnormalities.</p> <p>Methods</p> <p>Sixteen patients were prescribed an FDA approved drug (Pentoxifylline or Cilostazol) for the treatment of symptomatic PAD. Patients underwent baseline gait testing prior to medication use which consisted of acquisition of ground reaction forces and kinematics while walking in a pain free state. After three months of treatment, patients underwent repeat gait testing.</p> <p>Results</p> <p>Patients with symptomatic PAD had significant gait abnormalities at baseline during pain free walking as compared to healthy controls. However, pharmacological treatment did not produce any identifiable alterations on the biomechanics of gait of the PAD patients as revealed by the statistical comparisons performed between pre and post-treatment and between post-treatment and the healthy controls.</p> <p>Conclusions</p> <p>Pharmacological treatment did not result in statistically significant improvements in the gait biomechanics of patients with symptomatic PAD. Future studies will need to further explore different cohorts of patients that have shown to improve significantly their claudication distances and/or their muscle fiber morphology with the use of pharmacological treatment and determine if this is associated with an improvement in gait biomechanics. Using these methods we may distinguish the patients who benefit from pharmacotherapy and those who do not.</p

Gait variability is altered in patients with peripheral arterial disease

Objective Claudication is the most common presentation of peripheral arterial disease (PAD), producing significant ambulatory compromise. Claudicating patients, most of whom are elderly, have reduced mobility and poor health outcomes, including an increased risk of falls. The gait of elderly fallers is characterized by increased variability. Increase in the variability of the locomotor system makes the gait more noisy and unstable. The purpose of this study is to investigate gait variability in patients with PAD. Methods Nineteen symptomatic PAD patients (age, 63.6 ± 9.8 years; body mass, 82.1 ± 18.5 kg; height, 1.71 ± 0.06 m) walked on a treadmill in the absence of pain or claudication symptoms while joint flexion and extension kinematics were captured. Results were compared with results obtained from 17 matched healthy controls (age, 65.2 ± 12.5 years; body mass, 82.0 ± 25.9.5 kg; height, 1.73 ± 0.08 m). Relative joint angles were calculated for the ankle, knee, and hip flexion/extension, and the stride-to-stride variability of joint flexion and extension was calculated from at least 30 consecutive footfalls. Variability was expressed using the largest Lyapunov exponent, standard deviation, and coefficient of variation. Independent t tests were used to compare gait variability between groups. Results Symptomatic PAD patients had significantly higher largest Lyapunov exponent values and coefficient of variation values for all joints, and higher standard deviation values at the ankle and the hip (P \u3c .05). Conclusion Symptomatic PAD patients have increased gait variability at the ankle, knee, and hip joints at baseline ambulation in the absence of claudication pain. Our findings indicate significant baseline deterioration in the locomotor system of symptomatic PAD patients. This deterioration results in increased noise and instability of gait and is a potential contributing factor to the falls and mobility problems experienced by symptomatic PAD patients