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ABSTRACT: We investigated the parameter identification of a multi-scale physiological model of skeletal muscle, based on Huxley's formulation. We focused particularly on the knee joint controlled by quadriceps muscles under electrical stimulation (ES) in subjects with a complete spinal cord injury. A noninvasive and in vivo identification protocol was thus applied through surface stimulation in nine subjects and through neural stimulation in one ES-implanted subject. The identification protocol included initial identification steps, which are adaptations of existing identification techniques to estimate most of the parameters of our model. Then we applied an original and safer identification protocol in dynamic conditions, which required resolution of a nonlinear programming (NLP) problem to identify the serial element stiffness of quadriceps. Each identification step and cross validation of the estimated model in dynamic condition were evaluated through a quadratic error criterion. The results highlighted good accuracy, the efficiency of the identification protocol and the ability of the estimated model to predict the subject-specific behavior of the musculoskeletal system. From the comparison of parameter values between subjects, we discussed and explored the inter-subject variability of parameters in order to select parameters that have to be identified in each patient.
Medical & Biological Engineering 02/2013; · 1.76 Impact Factor
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Paladyn. Journal of Behavioral Robotics. 01/2012; 3.
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ABSTRACT: In patients with complete spinal cord injury, fatigue occurs rapidly and there is no proprioceptive feedback regarding the current muscle condition. Therefore, it is essential to monitor the muscle state and assess the expected muscle response to improve the current FES system toward adaptive force/torque control in the presence of muscle fatigue. Our team implanted neural and epimysial electrodes in a complete paraplegic patient in 1999. We carried out a case study, in the specific case of implanted stimulation, in order to verify the corresponding torque prediction based on stimulus evoked EMG (eEMG) when muscle fatigue is occurring during electrical stimulation. Indeed, in implanted stimulation, the relationship between stimulation parameters and output torques is more stable than external stimulation in which the electrode location strongly affects the quality of the recruitment. Thus, the assumption that changes in the stimulation-torque relationship would be mainly due to muscle fatigue can be made reasonably. The eEMG was proved to be correlated to the generated torque during the continuous stimulation while the frequency of eEMG also decreased during fatigue. The median frequency showed a similar variation trend to the mean absolute value of eEMG. Torque prediction during fatigue-inducing tests was performed based on eEMG in model cross-validation where the model was identified using recruitment test data. The torque prediction, apart from the potentiation period, showed acceptable tracking performances that would enable us to perform adaptive closed-loop control through implanted neural stimulation in the future.
Journal of Neural Engineering 12/2011; 8(6):064001. · 3.84 Impact Factor
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ABSTRACT: Patients with spinal cord injury exhibit early and acute bone loss with the major functional consequence being a high incidence of pathological fractures. The bone status of these patients is generally investigated by dual-energy x-ray absorptiometry, but this technique does not reveal the pathophysiological mechanism underlying the bone loss. Bone cell activity can be indirectly evaluated by noninvasive techniques, including measurement of specific biochemical markers of bone formation (such as osteocalcin or bone-alkaline phosphatase) and resorption (such as procollagen type I N- or C-terminal propeptide). The bone loss in spinal cord injury is clearly due to an uncoupling of bone remodeling in favor of bone resorption, which starts just after the injury and peaks at about 1 to 4 months. Beyond 6 months, bone resorption activity decreases progressively but remains elevated for many years after injury. Conversely, bone formation is less affected. Antiresorptive treatment induces an early and acute reduction in bone resorption markers. Level of injury and health-related complications do not seem to be implicated in the intensity of bone resorption. During the acute phase, the hypercalcemic status is associated with the suppression of parathyroid hormone and vitamin D metabolites. The high sensitivity of these markers after treatment suggests that they can be used for monitoring treatment efficacy and patient compliance. The concomitant use of bone markers and dual-energy x-ray absorptiometry may improve the physician's ability to detect patients at risk of severe bone loss and subsequent fractures.
Metabolism: clinical and experimental 05/2011; 60(12):1655-63. · 2.59 Impact Factor
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ABSTRACT: To evaluate the vital prognosis of patients with metastatic epidural spinal cord compression (MESCC) to determine the relevance and duration of physical medicine and rehabilitation (PM&R) admission.
Publications from 1980 to January 2010 selected from 3 databases.
Publications reporting data correlated with survival and prognosis factors, highlighting publications with level A scientific evidence (prospective randomized controlled studies with significant casuistry and relevant judgment criteria). The work focused on patients with MESCC below T1.
Standardized reading grid.
Thirty-eight studies met the inclusion criteria. Most were retrospective. For survival rate at 1 year, they reported data ranging from 12% to 58%. The 12-month and median survival rates were the data reported most often in the articles. The median survival rate ranged from 2.4 to 30 months, and 12-month survival rates ranged from 12% to 58%. Of publications that chose this parameter, 95% reported 12-month survival rates less than 55.2% (95th percentile) regardless of patients' functional status and associated risk factors (eg, location of primary cancer, metastases spreading, pretreatment ambulatory status).
Despite major progress in cancer care, patients with MESCC still have a limited vital prognosis. The relevance and duration of PM&R care must be evaluated against the patient's functional need for rehabilitation while making time for family. The hypothesis of a 1-month stay extended only once appears reasonable for patients to adapt to their new functional status without taking precious time away from their loved ones.
Archives of physical medicine and rehabilitation 01/2011; 92(1):125-33. · 2.18 Impact Factor
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ABSTRACT: To identify functional outcomes that could justify the need for a rehabilitation care program for patients with metastatic epidural spinal cord compression (MESCC) and paraplegia.
Publications from 1950 to January 2010 selected from 3 databases.
Original articles dealing with outcome data for functional status, pain, and bladder dysfunction.
Standardized reading grid.
The data are dominated by retrospective studies for even functional-related data, and studies from rehabilitation teams are rare. They report a functional evolution similar to a population with traumatic spinal cord injury for the first 3 months. Patients who were ambulatory before treatment retained their ability to walk, and patients who were nonambulatory before treatment could regain gait abilities. Data also showed a positive impact on pain and bladder and/or bowel dysfunction.
By restricting physical medicine and rehabilitation therapeutic care to a short time (1-2mo), the progression margin is possible in the short term and implies a voluntary and active therapeutic care approach for patients with paraplegia after MESCC on the basis of a codified and standardized program with clinical indicators, as well as patients' comfort indicators.
Archives of physical medicine and rehabilitation 01/2011; 92(1):134-45. · 2.18 Impact Factor
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ABSTRACT: To identify circumstances surrounding the onset of fracture and common risk factors in persons with spinal cord injury (SCI) and to suggest an alternative or complement to the pharmacologic approach by evaluating the need for a prospective study based on the impact of a targeted therapeutic education on risk management of fractures in this population.
Retrospective study.
Hospital and Rehabilitation Center Setting.
Women (n=7) and men (n=25; N=32; with ≥1 fracture after the initial SCI that occurred at home or in a hospital setting; mean ± SD age, 53±12y at the time of clinical review) with bone mineral density (BMD) measurements.
Not applicable.
Demographics, main circumstances of onset, and complications of fractures, as well as transversal bone mineral density evaluation.
Nine patients had more than 1 fracture and 23 patients had only 1 fracture (total, 43 fractures; mean age at onset of fracture, 49±12y; median time since injury, 13.9y; mean delay in diagnosis, 6.5±15d). Fractures occurred mostly in the lower limbs. The circumstances of onset of these fractures were different and very stereotyped. In 3 cases, no trauma was reported. The most frequent mechanisms identified were forced maneuvers by the patient or a third party and falls. In 10 cases, the fracture occurred during a wheelchair transfer with forced maneuver or a fall from the wheelchair. Twenty-five patients were confined to bed after the fracture (mean duration of bed confinement, 18±28d; range, 0-120d). Postfracture follow-up showed that for 43 cases of fractures, 19 had at least 1 orthopedic complication, 15 had local complications, and 23 had general complications. Patients (23 of 32) benefited from dual-energy X-ray absorptiometry to assess BMD a few months or years after the fracture (mean femoral neck BMD, 0.574±0.197g/cm²; mean femoral neck T score, -3.8±1.5).
With this retrospective analysis of common risk factors and circumstances of onset of secondary fractures, there is a clear future for a prospective study to evaluate the impact of targeted therapeutic education on risk factors for secondary fractures in patients with SCI.
Archives of physical medicine and rehabilitation 01/2011; 92(1):59-67. · 2.18 Impact Factor
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CDC-ECC'11: 50th IEEE Conference on Decision and Control and European Control Conference; 01/2011
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01/2011;
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SKILLS Conference 2011; 01/2011
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International Functional Electrical Stimulation Society (IFESS) conference; 01/2011
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FES'11: 16th Annual International FES Society Conference; 01/2011
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ISEK'10: The XVIII Congress of the International Society of Electrophysiology and Kinesiology; 01/2010
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Sciences et Technologie pour le Handicap. 01/2010; Numéro Spécial Handicap et Mouvement.
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ABSTRACT: Muscle fatigue is an unavoidable problem when electrical stimulation is applied to paralyzed muscles. The detection and compensation of muscle fatigue is essential to avoid movement failure and achieve desired trajectory. This work aims to predict ankle plantar-flexion torque using stimulus evoked EMG (eEMG) during different muscle fatigue states. Five spinal cord injured patients were recruited for this study. An intermittent fatigue protocol was delivered to triceps surae muscle to induce muscle fatigue. A hammerstein model was used to capture the muscle contraction dynamics to represent eEMG-torque relationship. The prediction of ankle torque was based on measured eEMG and past measured or past predicted torque. The latter approach makes it possible to use eEMG as a synthetic force sensor when force measurement is not available in daily use. Some previous researches suggested to use eEMG information directly to detect and predict muscle force during fatigue assuming a fixed relationship between eEMG and generated force. However, we found that the prediction became less precise with the increase of muscle fatigue when fixed parameter model was used. Therefore, we carried out the torque prediction with an adaptive parameters using the latest measurement. The prediction of adapted model was improved with 16.7%-50.8% comparing to the fixed model.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:3523-6.
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ABSTRACT: To assess the reproducibility and the effects of the subjects' characteristics on the reproducibility of transcutaneous oxygen pressure (TcPO2) measurements in the sacral area in persons with spinal cord injury during loading in the supine position.
Test-retest study.
Physical medicine and rehabilitation center.
Thirty spinal cord-injured American Spinal Injury Association grade A subjects.
Two TcPO2 monitoring sessions in the sacral area during loading in the supine position were performed at 24-hour intervals, including the measurement of absolute resting sacral and chest TcPO2 values and the calculation of regional perfusion index (RPI) and delta from rest oxygen pressure, taking into account systemic TcPO2 changes.
The intraclass coefficient of the sacral TcPO2 absolute resting value, RPI, and delta from rest oxygen pressure was .787 and .798, .704 and .635, .760 and .465, respectively, at 20 and 40 minutes. The only characteristic with an influence on RPI reproducibility was the subject's smoking status, whereas age, weight, time since injury, lesion level, and presence of pressure ulcer showed no influence.
TcPO2 measurement is a reproducible method for assessing cutaneous microcirculation during loading over 20-minute monitoring sessions, with RPI exhibiting better reproducibility than delta from rest oxygen pressure at 40 minutes.
Archives of physical medicine and rehabilitation 04/2009; 90(3):507-11. · 2.18 Impact Factor
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ABSTRACT: The knowledge and prediction of the behavior of electrically activated muscles are important requisites for the movement restoration by FES in spinal cord injured subjects. The whole parameter's identification of a physiological musculoskeletal model for FES is investigated in this work. The model represents the knee and its associated quadriceps muscle. The identification protocol is noninvasive and based on the in-vivo experiments on paraplegic subjects. The isometric and nonisometric data was obtained by stimulating the quadriceps muscles of 3 paraplegic subjects through surface electrodes. A cross validation has been carried out using nonisometric data set. The normalized RMS errors between the identified model and the measured knee response are presented for each subject.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:6538-41.
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{Journée Nationale de Rééducation de Hauteville - "Le Complexe Lombo-Pelvi-Fémoral & Réé}ducation"; 01/2009
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ISPGR'06: International Society for Posture and Gait Research; 01/2007
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ABSTRACT: In this work a torque assessment approach is presented to estimate FES-induced torque no matter the muscle is fatigued or not in interrupted stimulation. This approach is based on evoked EMG (eEMG) signal and use peak-to-peak (PTP) amplitude and second phase area (SPA) to correlate eEMG and torque. The mapping function is built with pooled data of recruitment test and fatigue test in two complete paraplegic subjects. In this model, PTP is mainly responsible to the effect of recruitment level, SPA is mainly responsible to the muscle fatigue phenomenon. The model is fitted to the measured recruitment curves and measured fatigue curves and shows good fits, with R2 values above 0.95 and 0.93 for each subject. This suggests that it is possible to use processed eEMG signal to change stimulation intensity to obtain desired trajectory even when stimulated muscle is fatigued or to inform the fatigue condition.
