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The primary objective of conservative care for the diabetic foot is to protect the foot from excessive pressures. Pressure reduction and redistribution may be achieved by designing and fabricating orthotic devices based on foot structure, tissue mechanics, and external loads on the diabetic foot. The purpose of this paper is to describe the process used for the development of patient-specific mathematical models of the second and third rays of the foot, their solution by the finite element method, and their sensitivity to model parameters and assumptions. We hypothesized that the least complex model to capture the pressure distribution in the region of the metatarsal heads would include the bony structure segmented as toe, metatarsal and support, with cartilage between the bones, plantar fascia and soft tissue. To check the hypothesis, several models were constructed with different levels of details. The process of numerical simulation is comprised of three constituent parts: model definition, numerical solution and prediction. In this paper the main considerations relating model selection and computation of approximate solutions by the finite element method are considered. The fit of forefoot plantar pressures estimated using the FEA models and those explicitly tested were good as evidenced by high Pearson correlations (r=0.70-0.98) and small bias and dispersion. We concluded that incorporating bone support, metatarsal and toes with linear material properties, tendon and fascia with linear material properties, soft tissue with nonlinear material properties, is sufficient for the determination of the pressure distribution in the metatarsal head region in the push-off position, both barefoot and with shoe and total contact insert. Patient-specific examples are presented. [ABSTRACT FROM AUTHOR]

The paper describes a measurement device for obtaining the kinematic characterisation and isometric loading of ankle joints under different working conditions. Non-invasive, in vivo experiments can be conducted with this experimental apparatus, the potential of which could be usefully exploited in basic biomedical research, prosthesis design, clinical applications, sports medicine and rehabilitation. The device determines the 3D movement of the foot with respect to the shank and evaluates the torques and moments around the three articular axes in relation to any desired angular position of the ankle complex. When integrated with superficial electromyographic techniques and electrical stimulation, it allows the assessment of the functionality of the lower leg in both mechanical and myo-electrical terms. The paper reports the main mechanical and electronic features of the device (high linearity; maximum moment ranges +/- 300 Nm for flexion-extension, +/- 35 Nm for both pronation-supination and internal-external rotation; angular ranges: +/- 100 degrees of dorsi-plantar flexion, +/- 50 degrees of internal-external rotation and prono-supination; linear ranges: +/- 25 mm along each axis). Results from a healthy volunteer, under voluntary or stimulated conditions, helped in testing its operatability, reliability, robustness, repeatability and effectiveness. Preliminary simplified protocols have been also applied to 20 healthy volunteers, and the main results were 80.8 +/- 11.9 degrees of internalexternal rotation, 46.2 +/- 9.1 degrees of prono-supination and 74.6 +/- 13.1 degrees of flexion-extension. Torques and moments were normalised with respect to a body mass index of 30. The maximum plantar flexion moment (57.5 + 21.3 Nm) was measured with the foot at 150 of dorsal flexion; the maximum dorsal flexion moment (50.2 + 20.3 Nm) was measured with the foot at 150 of plantar flexion. [ABSTRACT FROM AUTHOR]

The paper proposes a novel method for an accurate and unobtrusive reconstruction of the upper-limb kinematics of stroke patients during robot-aided rehabilitation tasks with end-effector machines. The method is based on a robust analytic procedure for inverse kinematics that simply uses, in addition to hand pose data provided by the robot, upper arm acceleration measurements for computing a constraint on elbow position; it is exploited for task space augmentation. The proposed method can enable in-depth comprehension of planning strategy of stroke patients in the joint space and, consequently, allow developing therapies tailored for their residual motor capabilities. The experimental validation has a twofold purpose: (1) a comparative analysis with an optoelectronic motion capturing system is used to assess the method capability to reconstruct joint motion; (2) the application of the method to healthy and stroke subjects during circle-drawing tasks with InMotion2 robot is used to evaluate its efficacy in discriminating stroke from healthy behavior. The experimental results have shown that arm angles are reconstructed with a RMSE of 8.3 × 10(-3) rad. Moreover, the comparison between healthy and stroke subjects has revealed different features in the joint space in terms of mean values and standard deviations, which also allow assessing inter- and intra-subject variability. The findings of this study contribute to the investigation of motor performance in the joint space and Cartesian space of stroke patients undergoing robot-aided therapy, thus allowing: (1) evaluating the outcomes of the therapeutic approach, (2) re-planning the robotic treatment based on patient needs, and (3) understanding pathology-related motor strategies. [ABSTRACT FROM AUTHOR]

Task-oriented, repetitive and intensive arm training can enhance arm rehabilitation in patients with paralyzed upper extremities due to lesions of the central nervous system. There is evidence that the training duration is a key factor for the therapy progress. Robot-supported therapy can improve the rehabilitation allowing more intensive training. This paper presents the kinematics, the control and the therapy modes of the arm therapy robot ARMin. It is a haptic display with semi-exoskeleton kinematics with four active and two passive degrees of freedom. Equipped with position, force and torque sensors the device can deliver patient-cooperative arm therapy taking into account the activity of the patient and supporting him/her only as much as needed. The haptic display is combined with an audiovisual display that is used to present the movement and the movement task to the patient. It is assumed that the patient-cooperative therapy approach combined with a multimodal display can increase the patient's motivation and activity and, therefore, the therapeutic progress. [ABSTRACT FROM AUTHOR]

This paper presents a three-dimensional (3D) reconstruction system of the human spine for the routine evaluation of musculoskeletal pathologies like idiopathic scoliosis. The main objective of this 3D reconstruction system is to offer a versatile and robust tool for the 3D analysis of spines in any healthcare centre with standard clinical setup using standard uncalibrated radiographic images. The novel system uses a self-calibration algorithm and a weak-perspective method to reconstruct the 3D coordinates of anatomical landmarks from bi-planar radiographic images of a patient's trunk. Additionally, a small planar object of known dimensions is proposed to warrant an accurately scaled model of the spine. In order to assess the validity of the 3D reconstructions yielded by the proposed system, a clinical study using 60 pairs of digitized X-rays of adolescents was conducted. The subject cohort in the study group was composed of 51 scoliotic and 9 non-scoliotic patients, with an average Cobb angle on the frontal plane of 25 degrees. For each case, a 3D reconstruction of the spine and pelvis was obtained with the previous system used at our hospital (which requires a positioning apparatus and a calibration jacket), and with the proposed method. Results show that 3D reconstructions obtained with the new system using uncalibrated X-ray images yield geometrically accurate models with insignificant differences for 2D and 3D clinical indexes commonly used in the evaluation of spinal deformities. This demonstrates the system to be a viable and accurate tool for clinical studies and biomechanical analysis purposes, with the added advantage of versatility to any clinical setup for routine follow-ups and surgical planning. [ABSTRACT FROM AUTHOR]

The paper presents a theoretical model of the ankle joint, i.e. tibio-talar articulation, which shows how the articular surfaces and the ligaments, acting together as a mechanism, can control the passive kinematics of the joint. The authors had previously shown that, in virtually unloaded conditions, the ankle behaves as a single degree-of-freedom system, and that two ligament fibres remain nearly isometric throughout the flexion arc. Two different equivalent spatial parallel mechanisms together with corresponding kinematic models were formulated. These assumed isometricity of fibres within the calcaneal-fibular and tibio-calcaneal ligaments and rigidity of the articulating surfaces, taken as three sphere-plane contacts in one model, and as a single spherical pair in the other. Geometry parameters for the models were obtained from three specimens. Motion predictions compare quite well with the measured motion of the specimens. The differences are accounted for by the simplifications adopted to represent the complex anatomical structures, and might be reduced by future more realistic representations of the natural articular surfaces. [ABSTRACT FROM AUTHOR]

This paper presents an inertial based sensing system for real-time three-dimensional measurement of human spinal motion, in a portable and non-invasive manner. Applications of the proposed system range from diagnosis of spine injury to postural monitoring, on-field as well as in the lab setting. The system is comprised of three inertial measurement sensors, respectively attached and calibrated to the head, torso and hips, based on the subject's anatomical planes. Sensor output is transformed into meaningful clinical parameters of rotation (twist), flexion-extension and lateral bending of each body segment, with respect to calibrated global reference space. Modeling the spine as a compound flexible pole model allows dynamic measurement of three-dimensional spine motion, which can be animated and monitored in real-time using our interactive GUI. The accuracy of the proposed sensing system has been verified with subject trials using a VICON optical motion measurement system. Experimental results indicate an error of less than 3.1 degrees in segment orientation tracking. [ABSTRACT FROM AUTHOR]

This paper presents a new, simple model to evaluate the instrumental random errors in kinematic analysis of human movements using stereophotogrammetry. By means of equations analogous to that relate linear or angular momentum with linear or angular velocities, a direct measurement of instantaneous motion can be made without previous finite displacement analysis. Single explicit expressions can be obtained to evaluate the influence of instrumental random errors in the accuracy of the kinematic variables. From these expressions, some conclusions about the effect of marker cluster design on the experimental errors are obtained. An experiment has been carried out in order to validate the proposed technique and to assess the experimental errors in linear and angular velocity measurement and its influence in instantaneous helical axis determination. [ABSTRACT FROM AUTHOR]

Very few finite element models on the lumbosacral spine have been reported because of its unique biomechanical characteristics. In addition, most of these lumbosacral spine models have been only validated with rotation at single moment values, ignoring the inherent nonlinear nature of the moment-rotation response of the spine. Because a majority of lumbar spine surgeries are performed between L4 and S1 levels, and the confidence in the stress analysis output depends on the model validation, the objective of the present study was to develop a unique finite element model of the lumbosacral junction. The clinically applicable model was validated throughout the entire nonlinear range. It was developed using computed tomography scans, subjected to flexion and extension, and left and right lateral bending loads, and quantitatively validated with cumulative variance analyses. Validation results for each loading mode and for each motion segment (L4-L5, L5-S1) and bisegment (L4-S1) are presented in the paper. [ABSTRACT FROM AUTHOR]

The paper describes the design, technical characteristics and first results of an adjustable staircase with commercial force plates embedded in the steps and custom force transducers as part of the handrail supports. For the railing assembly, the greatest errors (< 10% of maximum signal) and cross-talk range (0.58-6.74%) were in the medial-lateral direction and were corrected using a calibration matrix. Power spectral density analyses showed free vibration frequency responses for both the railing (15 Hz) and steps (38.6 Hz) that were relatively distinct from lower applied forces recorded during stair ascent. The creation of standardised filtering protocols was therefore possible to provide step reaction force signals identical to the literature and examples of upper-limb reaction forces that have not been shown before. Such a staircase will allow a more complete study of full body contributions to stair walking across various subject populations. [ABSTRACT FROM AUTHOR]

Research has focused on improvement of the quality of life of stroke patients. Gait detection, kinematics and kinetics analysis, home-based rehabilitation and telerehabilitation are the areas where there has been increasing research interest. The paper reviews position-sensing technologies and their application for human movement tracking and stroke rehabilitation. The review suggests that it is feasible to build a home-based telerehabilitation system for sensing and tracking the motion of stroke patients. [ABSTRACT FROM AUTHOR]

In the medical field, there is a need for small ambulatory sensor systems for measuring the kinematics of body segments. Current methods for ambulatory measurement of body orientation have limited accuracy when the body moves. The aim of the paper was to develop and validate a method for accurate measurement of the orientation of human body segments using an inertial measurement unit (IMU). An IMU containing three single-axis accelerometers and three single-axis micromachined gyroscopes was assembled in a rectangular box, sized 20 x 20 x 30 mm. The presented orientation estimation algorithm continuously corrected orientation estimates obtained by mathematical integration of the 3D angular velocity measured using the gyroscopes. The correction was performed using an inclination estimate continuously obtained using the signal of the 3D accelerometer. This reduces the integration drift that originates from errors in the angular velocity signal. In addition, the gyroscope offset was continuously recalibrated. The method was realised using a Kalman filter that took into account the spectra of the signals involved as well as a fluctuating gyroscope offset. The method was tested for movements of the pelvis, trunk and forearm. Although the problem of integration drift around the global vertical continuously increased in the order of 0.50 degrees s(-1), the inclination estimate was accurate within 3 degrees RMS. It was shown that the gyroscope offset could be estimated continuously during a trial. Using an initial offset error of 1 rad s(-1), after 2 min the off-set error was roughly 5% of the original offset error. Using the Kalman filter described, an accurate and robust system for ambulatory motion recording can be realised. [ABSTRACT FROM AUTHOR]

The paper provides a new technique based on a least-squares approach for the accurate estimation of a force platform calibration matrix using simple manual procedures, when the direction of the applied loads cannot be perfectly aligned with the axes of the platform. This new procedure can be applied to all force platforms and allows the combined application of vertical and horizontal forces, both static and time-varying. The robust calibration method includes the angular errors in the least-squares parameter vector, thus reducing the bias in the estimated calibration matrix parameters. The performance of the robust method was compared with the conventional one, using a numerical simulation approach starting from a known calibration matrix. With the conventional approach, in noiseless conditions, the maximum error due to load misalignment (SD = 3 degrees) was 6% for the direct terms and over 10% for the cross-talk terms. With the robust method, these errors reduced to zero and were always below 0.4%, even when realistic noise was superimposed on the measures. With perfectly aligned loads and realistic output noise, the confidence intervals of the calibration matrix parameters were very similar for the two methods, demonstrating that the increased number of parameters did not affect the reliability of the estimate. [ABSTRACT FROM AUTHOR]

A numerical model able to investigate the influence of biomechanical factors on the long-term secondary stability of implants would be extremely useful for the design of new cementless prosthetic devices. A purely biomechanical model of osseo-integration has been developed, formulated as a rule-based adaptation scheme. Due to its complexity, the problem was divided into three steps: preliminary implementation of the model (proof of concept); implementation of the complete model and investigation of the model solution; and model validation. The paper describes the first of these three steps. The model was implemented as a discrete-states machine, and the few parameters required were derived from the literature. It was then applied to a real clinical case. The study was conducted using the frictional contact finite element model of a human femur implanted with a cementless anatomical stem. A stable solution was achieved after between three and 15 iterations for all initial positions considered. Similar initial conditions yielded similar final configurations. The model predicted all initial configurations, with the exception of a partial osseo-integration, ranging between 62% (distal fit) and 78% (proximal fit) of the viable interface. This is in good agreement with the values reported in the literature that never exceed 75%, even in the best conditions, and report better clinical results for proximal fit. For the varus configuration, which lacks cortical support, the algorithm predicted a completed loosening. [ABSTRACT FROM AUTHOR]

The flexibility of the scoliotic spine is an important biomechanical parameter to take into account in the planning of surgical instrumentation. The objective of the paper was to develop a method to characterise in vivo the mechanical properties of the scoliotic spine using a flexible multi-body model. Vertebrae were represented as rigid bodies, and intervertebral elements were defined at every level using a spherical joint and three torsion springs. The initial mechanical properties of motion segments were defined from in vitro experimental data reported in the literature. They were adjusted using an optimisation algorithm to reduce the discrepancy between the simulated and the measured Ferguson angles in lateral bending of three spine segments (major or compensatory left thoracic, right thoracic and left lumbar scoliosis curves). The flexural rigidity of the spine segments was defined in three categories (flexible, nominal, rigid) according to the estimated mechanical factors (alpha). This approach was applied with ten scoliotic patients undergoing spinal correction. Personalisation of the model resulted in an increase of the initial flexural rigidity for seven of the ten lumbar segments (1.38 < or = alpha < or = 10.0) and four of the ten right thoracic segments (1.74 < or = alpha < or = 5.18). The adjustment of the mechanical parameters based on the lateral bending tests improved the model's ability to predict the spine shape change described by the Ferguson angles by up to 50%. The largest differences after personalisation were for the left lumbar segments in left bending (4 degrees +/- 3 degrees). The in vivo identification of the mechanical properties of the scoliotic spine will improve the ability of biomechanical models adequately to predict the surgical correction, which should help clinicians in the planning of surgical instrumentation manoeuvres. [ABSTRACT FROM AUTHOR]

This study focused on the application of real-time Kalman filters to biomechanical data and, in particular, the simulation environment used to compare the performance of modified and standard two-state Kalman filters when estimating displacement and velocity from noisy displacement data. The modification proposed in this paper was the numerical tachometer, augmented by a median smoother. The numerical tachometer integrated the derivative estimates from finite differences of noisy sampled data into the Kalman filter structure; the median smoother acted before differentiation, to protect from grossly erroneous measurements. The numerical tachometer allowed better fits to the simulated data than can be achieved without it: the root mean square errors decreased by 10% in the displacement domain and by 54% in the velocity domain, for sampling frequencies and signal contamination levels that were typical in human movement sciences. The sensitivity to errors in the modelling of the signal and noise characteristics was less than in the standard filter implementation. The use of the median smoother improved the robustness of the filtering algorithm against additive white Gaussian measurement noise and allowed the cancellation of isolated noise spikes. [ABSTRACT FROM AUTHOR]