A neuromechanical model characterizing the motor planning and posture control in the voluntary lean in Parkinson's disease.

Parkinson's disease targets patients' cognitive and motor abilities, including postural control. Many studies have been carried out to introduce mathematical models for a better understanding of postural control in such patients and the relation between the model parameters and the clinical assessments. So far, these studies have addressed this connection merely in static tests, such as quiet stance. The aim of this study is to develop a model for voluntary lean, and as such, identify the model parameters for both PD patients and healthy subjects from experimental data. The proposed model comprises planning and control sections. The model parameters for the planning section were extracted from the time response characteristics. Parameters for the control section were identified based on the spatial characteristics of the center-of-pressure (COP) response using an optimization process. 24 PD patients along with 24 matched healthy subjects participated in the study. The results showed a significant difference between the two groups in terms of temporal parameters for the planning section. This difference emphasizes bradykinesia as an essential symptom of PD. Also, differences were found for the postural control section. In all directions, the proportional gain of the feedback controller was significantly larger in PD patients; however, the gain of the feedforward controller was significantly smaller in PD patients. Furthermore, the control gains were strongly correlated with the clinical scales (Functional Reach Test and Unified Parkinson's Disease Rating Scale) in certain directions. In conclusion, the new model helps to better understand and quantify some PD symptoms in voluntary lean tasks.

Margins of postural stability in Parkinson's disease: an application of control theory.

Introduction: Postural instability is a restrictive feature in Parkinson's disease (PD), usually assessed by clinical or laboratory tests. However, the exact quantification of postural stability, using stability theorems that take into account human dynamics, is still lacking. We investigated the feasibility of control theory and the Nyquist stability criterion-gain margin (GM) and phase margin (PM)-in discriminating postural instability in PD, as well as the effects of a balance-training program. Methods: Center-of-pressure (COP) data of 40 PD patients before and after a 4-week balance-training program, and 20 healthy control subjects (HCs) (Study1) as well as COP data of 20 other PD patients at four time points during a 6-week balance-training program (Study2), collected in two earlier studies, were used. COP was recorded in four tasks, two on a rigid surface and two on foam, both with eyes open and eyes closed. A postural control model (an inverted pendulum with a Proportional-integral-derivative (PID) controller and time delay) was fitted to the COP data to subject-specifically identify the model parameters thereby calculating |GM| and PM for each subject in each task. Results: PD patients had a smaller margin of stability (|GM| and PM) compared with HCs. Particularly, patients, unlike HCs, showed a drastic drop in PM on foam. Clinical outcomes and margins of stability improved in patients after balance training. |GM| improved early in week 4, followed by a plateau during the rest of the training. In contrast, PM improved late (week 6) in a relatively continuous-progression form. Conclusion: Using fundamental stability theorems is a promising technique for the standardized quantification of postural stability in various tasks.

Effects of a multi-component virtual reality program on motor skills and functional postural control in children with hemiplegic cerebral palsy.

Background: Pediatric neurorehabilitation has recently employed virtual reality (VR) technologies as a platform to design and implement novel modalities. Aims: To evaluate the feasibility of a multi-component VR-based program on motor skills and functional postural control for children with hemiplegic cerebral palsy (HCP). Methods: A single-case-experimental design was conducted on eight children with HCP (12.33 ± 4.71 years and GMFCS= II, I). The VR-based program consisted of 3 sessions per week for four weeks. Timed Up and Go (TUG) test, Functional Reach Test (FRT), Pediatric Balance Scale (PBS), Activities Scale for Kids (ASK), ABILHAND-Kids, and Box and Block Test (BBT) were used to evaluate functional changes. Outcomes and results: Statistical analysis showed that improvements in functional postural control were significant on at least one balance measure for seven out of eight participants during the intervention phase. For all participants, a significant increase was observed in the BBT scores. Before-after intervention analysis revealed statistically significant improvements in PBS (z = -2.52, p ≤ 0.01), ABILHAND-Kids (z = -2.25, p ≤ 0.01), and ASK (z = -2.38, p ≤ 0.01). Conclusions and implications: This study provided early evidence of the effectiveness of the multi-component VR-based program in children with HCP. However, future studies with randomized controlled trial design are needed to evaluate the long-term effects and compare them with conventional rehabilitation practice.

Verbal Working Memory-Balance program training alters the left fusiform gyrus resting-state functional connectivity: A randomized clinical trial study on children with dyslexia.

Sufficient activation of the left fusiform gyrus is important in reading ability acquisition due to its role in reading and naming, working memory (WM), and balance tasks. Recently, a newly-designed training program, Verbal Working Memory-Balance (VWM-B), has been evaluated on children with dyslexia, and its positive effects were shown on reading ability, WM capacity, and postural control. In the present study, we aimed to estimate the functional connectivity alterations of the left fusiform gyrus following training by the VWM-B. Before and after 15 sessions of training, the fMRI and other tools data were collected on a sample of children with dyslexia, who were allocated into two control and experiment groups. Data analyses showed the increased functional connectivity of the left fusiform gyrus between the left anterior temporal fusiform cortex, left and right Crus II regions of the cerebellum, and the left middle frontal gyrus. Moreover, VWM-B training significantly improved the reading and naming ability, WM capacity, and postural control of participants in the experiment group in comparison to the control. The current study findings emphasize the critical role of the left fusiform gyrus in reading ability. Moreover, it provides evidence to support the existence of cerebellar deficits in dyslexia.

Direction-dependency of the kinematic indices in upper extremities motor assessment of stroke patients.

BACKGROUND: Kinematic indices (KIs) are frequently used as objective measures to assess the upper extremities motor performance in post stroke patients. The clinimetric analysis of these indices has been mostly limited to their averaged values over different directions of reaching movements. Recent studies indicate direction dependencies of such motor performances due to neural and/or biomechanical causes. The direction dependencies of such indices and their clinimetric parameters remains to be investigated. METHODS: An apparatus was built to perform and measure planar point-to-point reaching tasks in 8 directions using a virtual reality environment. 24 stroke and 18 healthy individuals participated in the study. 24 kinematic indices were calculated. Reliability (ICC), construct validity (Spearman correlation), and responsiveness (paired t-test pre and post intervention) were analyzed in each direction. RESULTS: The clinimetric parameters were found highly direction dependent. The reliability of the indices were strongest when moving away and towards the body. The validity (Spearman>0.75) and responsiveness (p<0.05) were most pronounced when moving in the NW-SE direction. These findings are in compliance with some previous neuro-musculoskeletal observations. CONCLUSION: While smoothness parameters are relatively uniform in all directions, speed and accuracy are direction dependent. The clinimetrics of the kinematic indices also depend on the direction and show stronger values in the NW-SE direction which is therefore proposed as the most accurate and responsive direction for kinematic assessment in stroke patients.

The effects of supervised and non-supervised upper limb virtual reality exercises on upper limb sensory-motor functions in patients with idiopathic Parkinson's disease.

BACKGROUND: Impairments of upper limb (UL) sensory-motor functions are common in Parkinson's disease (PD). Virtual reality exercises may improve sensory-motor functions in a safe environment and can be used in tele-rehabilitation. This study aimed to investigate the effects of supervised and non-supervised UL virtual reality exercises (ULVRE) on UL sensory-motor functions in patients with idiopathic PD. METHODS: In this clinical trial study, 45 patients with idiopathic PD (29 male) by mean ± SD age of 58.64 ± 8.69 years were randomly allocated to either the control group (conventional rehabilitation exercises), supervised ULVRE or non-supervised ULVRE. Interventions were 24 sessions, 3 sessions/week. Before/after of interventions and follow-up period all assessment was done. Hand Active Sensation Test and Wrist Position Sense Test were used for assessing UL sensory function. Gross and fine manual dexterity were assessed by Box-Block Test and Nine-Hole Peg Test, respectively. Grip and pinch strength were evaluated by a dynamometer and pinch gauge, respectively. RESULTS: The results showed significant improvement in discriminative sensory function (HAST-weight and HAST-total), wrist proprioception, gross manual dexterity and grip strength of both less and more affected hands as well as fine manual dexterity of the more affected hand in the three groups in patients with idiopathic PD (P < 0.05). CONCLUSION: The results of this study indicated that both supervised and non-supervised ULVRE using the Kinect device might potentially improve some aspects of UL sensory-motor functions in patients with PD. Therefore, ULVRE using the Kinect device can be used in tele-rehabilitation, especially in the current limitations induced by the COVID-19 pandemic, for improving UL functions in patients with PD.

Symmetric and asymmetric bimanual coordination and freezing of gait in Parkinsonian patients in drug phases.

Freezing of gait (FOG) is a debilitating symptom in patients with Parkinson's disease (PD), which may be associated with motor control impairments in tasks other than gait. This study aimed to examine whether symmetric and asymmetric bimanual coordination is impaired in PD with FOG (PD +FOG) patients and whether dual-task and drug phases may affect bimanual coordination in these patients. Twenty PD +FOG patients, 20 PD patients without FOG (PD -FOG) performed symmetric and asymmetric functional bimanual tasks (reach to and pick up a box and open a drawer to press a pushbutton inside it, respectively) under single-task and dual-task conditions. PD patients were evaluated during on- and off-drug phases. Kinematic and coordination measures were calculated for each task. PD +FOG patients demonstrated exacerbated impairments of bimanual coordination while performing goal-directed bimanual tasks, which was more evident in the asymmetric bimanual task and under dual-task conditions, highlighting the need for rehabilitation interventions for bimanual tasks that include different cognitive loads in these patients. Interestingly, 25% and 5% of participants in the PD +FOG and -FOG groups developed upper limb freezing 2 years later, respectively. This study aimed to examine whether symmetric and asymmetric bimanual coordination is impaired in Parkinson's disease with freezing of gait (PD +FOG) patients and whether dual-task and drug phases may affect bimanual coordination in these patients. PD +FOG patients demonstrated exacerbated impairment of bimanual coordination while performing goal-directed bimanual tasks, highlighting the need for rehabilitation interventions for bimanual tasks that include different cognitive loads in these patients.

Evaluating a new verbal working memory-balance program: a double-blind, randomized controlled trial study on Iranian children with dyslexia.

BACKGROUND: It is important to improve verbal Working Memory (WM) in reading disability, as it is a key factor in learning. There are commercial verbal WM training programs, which have some short-term effects only on the verbal WM capacity, not reading. However, because of some weaknesses in current verbal WM training programs, researchers suggested designing and developing newly structured programs that particularly target educational functions such as reading skills. In the current double-blind randomized clinical trial study, we designed a new Verbal Working Memory-Balance (VWM-B) program which was carried out using a portable robotic device. The short-term effects of the VWM-B program, on verbal WM capacity, reading skills, and postural control were investigated in Iranian children with developmental dyslexia. RESULTS: The effectiveness of the VWM-B program was compared with the VWM-program as a traditional verbal WM training. In comparison with VWM-program, the participants who received training by the VWM-B program showed superior performance on verbal WM capacity, reading skills, and postural control after a short-term intervention. CONCLUSIONS: We proposed that the automatized postural control resulting from VWM-B training had a positive impact on improving verbal WM capacity and reading ability. Based on the critical role of the cerebellum in automatizing skills, our findings support the cerebellar deficit theory in dyslexia. TRIAL REGISTRATION: This trial was (retrospectively) registered on 8 February 2018 with the Iranian Registry of Clinical Trials (IRCT20171219037953N1).

Cross-cultural adaptation and psychometric validation of the Persian version of the central sensitization inventory.

BACKGROUND: The Central Sensitization Inventory (CSI) is a patient-reported tool to assess symptoms associated with central sensitization (CS). It consists of two parts: Part A assesses 25 somatic and emotional CS-related health symptoms, and part B asks if one has previously been diagnosed with a list of 10 Central Sensitivity Syndromes and related conditions. OBJECTIVES: The aim of this study was to translate and cross-culturally adapt the CSI into Persian and to evaluate its psychometric properties. DESIGN: Cross-sectional study. METHOD: After completing the Persian translation, the psychometric properties of the Persian CSI (CSI-Per) were evaluated in 256 patients with chronic pain and 46 healthy subjects. RESULTS: A confirmatory factor analysis confirmed a 1-factor model suggested in a large recent comprehensive multicountry study. Test-retest reliability (ICC = 0.934; P < 0.001) and the internal consistency (Cronbach's α = 0.87) were both good. After dividing the patient subjects into severity level subgroups, based on CSI-Per total scores, significant associations were found with the Persian version of the pain catastrophizing scale, pain duration, current pain intensity, maximum, minimum and average pain intensity in the past week and average pain intensity in the past month. In addition, total CSI-Per scores differentiated between patients and healthy subjects. CONCLUSION: The CSI-Per demonstrated good validity and reliability to assess symptoms associated with CS in Persian-speaking patients with chronic pain.

Using robotic mechanical perturbations for enhanced balance assessment.

Balance impairment is critical for many patient groups such as those with neural and musculoskeletal disorders and also the elderly. Accurate and objective assessment of balance performance has led to the development of several indices based on the measurement of the center of pressure. In this study, a robotic device was designed and fabricated to provide controlled and repeatable mechanical perturbations to the standing platform of the user. The device uses servo-controlled actuators and two parallel mechanisms to provide independent rotations in mediolateral and anterior-posterior directions. The device also provides visual feedback of the center of pressure position to the user. Functional tests were run and showed that the device is able to provide an appropriate dynamics (time constant of 0.19 s and bandwidth of 0.85 Hz) for the two motions. The efficacy of the device on the balance assessment was then evaluated experimentally. Ten healthy subjects performed a balance task with and without perturbations and seven center of pressure indices were measured. It was shown that the sensitivity of the indices to the user's performance was statistically increased in all indices particularly in anterior/posterior direction when the mechanical perturbations were present.

A new postural stability-indicator to predict the level of fear of falling in Parkinson's disease patients.

BACKGROUND: Fear of falling (FoF) is defined as a lasting concern about falling that causes a person to limit or even stop the daily activities that he/she is capable of. Seventy percent of Parkinson's disease (PD) patients report activity limitations due to FoF. Timely identification of FoF is critical to prevent its additional adverse effects on the quality of life. Self-report questionnaires are commonly used to evaluate the FoF, which may be prone to human error. OBJECTIVES: In this study, we attempted to identify a new postural stability-indicator to objectively predict the intensity of FoF and its related behavior(s) in PD patients. METHODS: Thirty-eight PD patients participated in the study (mean age, 61.2 years), among whom 10 (26.32%) were identified with low FoF and the rest (73.68%) with high FoF, based on Falls Efficacy Scale-International (FES-I). We used a limit of stability task calibrated to each individual and investigated the postural strategies to predict the intensity of FoF. New parameters (FTRis; functional time ratio) were extracted based on the center of pressure presence pattern in different rectangular areas (i = 1, 2, and 3). The task was performed on two heights to investigate FoF-related behavior(s). RESULTS: FTR1/2 (the ratio between FTR1 and FTR2) was strongly correlated with the FES-I (r = - 0.63, p < 0.001), Pull test (r = - 0.65, p < 0.001), Timed Up and Go test (r = - 0.57, p < 0.001), and Berg Balance Scale (r = 0.62, p < 0.001). The model of FTR1/2 was identified as a best-fitting model to predicting the intensity of FoF in PD participants (sensitivity = 96.43%, specificity = 80%), using a threshold level of ≤ 2.83. CONCLUSIONS: Using the proposed assessment technique, we can accurately predict the intensity of FoF in PD patients. Also, the FTR1/2 index can be potentially considered as a mechanical biomarker to sense the FoF-related postural instability in PD patients.

Postural control learning dynamics in Parkinson's disease: early improvement with plateau in stability, and continuous progression in flexibility and mobility.

BACKGROUND: Balance training improves postural control in Parkinson's disease (PD). However, a systematic approach for the development of individualized, optimal training programs is still lacking, as the learning dynamics of the postural control in PD, over a training program, are poorly understood. OBJECTIVES: We investigated the learning dynamics of the postural control in PD, during a balance-training program, in terms of the clinical, posturographic, and novel model-based measures. METHODS: Twenty patients with PD participated in a balance-training program, 3 days a week, for 6 weeks. Clinical tests assessed functional balance and mobility pre-training, mid-training, and post-training. Center-of-pressure (COP) was recorded at four time-points during the training (pre-, week 2, week 4, and post-training). COP was used to calculate the sway measures and to identify the parameters of a patient-specific postural control model, at each time-point. The posturographic and model-based measures constituted the two sets of stability- and flexibility-related measures. RESULTS: Mobility- and flexibility-related measures showed a continuous improvement during the balance-training program. In particular, mobility improved at mid-training and continued to improve to the end of the training, whereas flexibility-related measures reached significance only at the end. The progression in the balance- and stability-related measures was characterized by early improvements over the first 3 to 4 weeks of training, and reached a plateau for the rest of the training. CONCLUSIONS: The progression in balance and postural stability is achieved earlier and susceptible to plateau out, while mobility and flexibility continue to improve during the balance training.

Pre-planning of intramedullary nailing procedures: A methodology for predicting the position of the distal hole.

Inserting the distal locking screws is a challenging step of the intramedullary nailing procedures due to the nail deformation that makes the proximally mounted targeting systems ineffective. A pre-planning methodology is proposed, based on an analytical model of the nail-bone construct, to predict the nail deformation during surgery using orthogonal preoperative radiographs. Each of the femoral shaft and the nail was modeled as a curved tubular Euler-Bernoulli beam. The unknown positions and forces of the nail-bone interaction were found using a systematic trial and error approach, which minimized the total strain energy of the system while satisfying the force and geometrical constraints. The predictions of the model for the nail deformation were compared with the experimental results of five cadaver specimens in 15 test conditions. Relatively large displacements (up to 13 mm) were found for the distal hole in sagittal plane only. The model predictions were in close agreement with the experimental results, with a root mean square error of 1.2 mm. It was concluded that the proposed pre-planning methodology is promising for practical clinical use in intramedullary nailing operations, in order to provide the compensatory information that is required for tuning of proximally mounted targeting systems.

Disentangling stability and flexibility degrees in Parkinson's disease using a computational postural control model.

BACKGROUND: Impaired postural control in Parkinson's disease (PD) seriously compromises life quality. Although balance training improves mobility and postural stability, lack of quantitative studies on the neurophysiological mechanisms of balance training in PD impedes the development of patient-specific therapies. We evaluated the effects of a balance-training program using functional balance and mobility tests, posturography, and a postural control model. METHODS: Center-of-pressure (COP) data of 40 PD patients before and after a 12-session balance-training program, and 20 healthy control subjects were recorded in four conditions with two tasks on a rigid surface (R-tasks) and two on foam. A postural control model was fitted to describe the posturography data. The model comprises a neuromuscular controller, a time delay, and a gain scaling the internal disturbance torque. RESULTS: Patients' axial rigidity before training resulted in slower COP velocity in R-tasks; which was reflected as lower internal torque gain. Furthermore, patients exhibited poor stability on foam, remarked by abnormal higher sway amplitude. Lower control parameters as well as higher time delay were responsible for patients' abnormal high sway amplitude. Balance training improved all clinical scores on functional balance and mobility. Consistently, improved 'flexibility' appeared as enhanced sway velocity (increased internal torque gain). Balance training also helped patients to develop the 'stability degree' (increase control parameters), and to respond more quickly in unstable condition of stance on foam. CONCLUSIONS: Projection of the common posturography measures on a postural control model provided a quantitative framework for unraveling the neurophysiological factors and different recovery mechanisms in impaired postural control in PD.

A minimally invasive robotic surgery approach to perform totally endoscopic coronary artery bypass on beating hearts.

The currently available robotic systems rely on rigid heart stabilizers to perform totally endoscopic coronary artery bypass (TECAB) surgery on beating hearts. Although such stabilizers facilitate the anastomosis procedure by immobilizing the heart and holding the surgery site steady, they can cause damage to the heart tissue and rupture of the capillary vessels, due to applying relatively large pressures on the epicardium. In this paper, we propose an advanced robotic approach to perform TECAB on a beating heart with minimal invasiveness. The idea comes from the fact that the main pulsations of the heart occur as excursions in normal direction, i.e., perpendicular to the heart surface. We devise a 1-DOF flexible heart stabilizer which eliminates the lateral movements of the heart, and a 1-DOF compensator mechanism which follows the heart trajectory in the normal direction, thus canceling the relative motion between the surgical tool and the heart surface. In fact, we bring a compromise between two radical approaches of operating on a completely immobilized beating heart with no heart motion compensation, and operating on a freely beating heart with full compensation of heart motion, considering the invasiveness of the first and the technical challenges of the second approach. We propose operating on a partially stabilized beating heart with unidirectional compensation of the heart motion; the flexible stabilizer would exert much less holding force to the heart tissue and the robotic system with unidirectional compensator would be technically feasible. In the proposed approach, a motion sensor mounted on the stabilizer measures the heart excursion data and sends it into a control unit. A predictive controller uses this data to generate an automated trajectory. The slave robots follow this trajectory, which is superimposed on the surgeon's tele-operation commands received from a master console. Finally, the tool-activation units in the slave robots actuate the articulated laparoscopic tools to perform the anastomosis procedure. The evaluation of the hypothesis showed that our solution for the robotic TECAB on beating heart is both practical and cost effective. We showed in an in-vivo study that the flexible stabilizer can effectively restrict the heart lateral movements, while allowing for its normal excursion. We found readily available linear motors which could afford the high forces, speeds and accelerations required for following the heart trajectory. Finally, we showed that the tool-activation unit is capable of providing the maneuverability and workspace required for the most challenging task of CABG procedure, i.e., anastomosis suturing.

Improvement of Upper Limb Motor Control and Function After Competitive and Noncompetitive Volleyball Exercises in Chronic Stroke Survivors: A Randomized Clinical Trial.

OBJECTIVES: To investigate the effects of competitive and noncompetitive volleyball exercises on the functional performance and motor control of the upper limbs in chronic stroke survivors. DESIGN: Randomized clinical trial. SETTING: Outpatient rehabilitation center. PARTICIPANTS: Chronic stroke survivors (N=48). INTERVENTIONS: Participants were randomly assigned to competitive (n=16) or noncompetitive (n=16) volleyball exercise groups (60min/d volleyball exercise+30min/d traditional rehabilitation, 3d/wk for 7wk) and control group (n=16). MAIN OUTCOME MEASURES: Reach and grasp motor control measures were evaluated through kinematic analysis. Functional outcomes were assessed via Motor Activity Log, Wolf Motor Function Test (WMFT), Box and Block Test, and Wrist Position Sense Test. RESULTS: Significant improvement of functional performance was observed in both competitive (P<.0001) and noncompetitive volleyball exercise groups (P<.01), but not in the control group (P>.05), with the exception of WMFT score. Volleyball training, in general, resulted in more efficient spatiotemporal control of reach and grasp functions, as well as less dependence on feedback control as compared to the control group. Moreover, the competitive volleyball exercise group exhibited greater improvement in both functional performance and motor control levels. CONCLUSIONS: Volleyball team exercises, especially in a competitive format, resulted in enhancing the efficacy of the preprogramming and execution of reach and grasp movements, as well as a shift from feedback to feedforward control of the affected upper limb in chronic stroke survivors. This may well be a potential underlying mechanism for improving functional performance.

A planar neuro-musculoskeletal arm model in post-stroke patients.

Mathematical modeling of the neuro-musculoskeletal system in healthy subjects has been pursued extensively. In post-stroke patients, however, such models are very primitive. Besides improving our general understanding of how stroke affects the limb motions, they can be used to evaluate rehabilitation strategies by computer simulations before clinical evaluations. A planar neuro-musculoskeletal arm model for post-stroke patients is developed. The main idea is to use a set of new coefficients, Muscle Significance Factors (MSF), to incorporate the effects of stroke in the muscle control performance. The model uses the optimal control theory to mimic the performance of the CNS and a two-link skeletal model with six muscles for the biomechanical part. The model was developed and evaluated using experimental data from six post-stroke patients with Brunnstrom levels of 4-6. The results show that MSFs are relatively distinct and independent from the arm motion which is used to determine their values. Its variation is in the range of 0-2.58% and decreases in higher Brunnstrom levels. The mean error of the model in predicting the path of motion varies from 0.9% in level 6 to 5.58% in level 4 subjects which can be considered a promising level of accuracy. Using the proposed model and the MSF to customize the model for each individual stroke patient seems a promising approach. It shows a reasonable level of robustness, i.e., independence from the type of motions and correlated with the severity of stroke, and accuracy in predicting the shape of the motion path.

A patient specific finite element simulation of intramedullary nailing to predict the displacement of the distal locking hole.

Distal locking is a challenging subtask of intramedullary nailing fracture fixation due to the nail deformation that makes the proximally mounted targeting systems ineffective. A patient specific finite element model was developed, based on the QCT data of a cadaveric femur, to predict the position of the distal hole of the nail postoperatively. The mechanical interactions of femur and nail (of two sizes) during nail insertion was simulated using ABAQUS in two steps of dynamic pushing and static equilibrium, for the intact and distally fractured bone. Experiments were also performed on the same specimen to validate the simulation results. A good agreement was found between the model predictions and the experimental observations. There was a three-point contact pattern between the nail and medullary canal, only on the proximal fragment of the fractured bone. The nail deflection was much larger in the sagittal plane and increased for the larger diameter nail, as well as for more distally fractured or intact femur. The altered position of the distal hole was predicted by the model with an acceptable error (mean: 0.95; max: 1.5 mm, in different tests) to be used as the compensatory information for fine tuning of proximally mounted targeting systems.

The effects of anxiety and external attentional focus on postural control in patients with Parkinson's disease.

BACKGROUND: Although anxiety is a common non-motor outcome of Parkinson's disease (PD) affecting 40% of patients, little attention has been paid so far to its effects on balance impairment and postural control. Improvement of postural control through focusing on the environment (i.e. external focus) has been reported, but the role of anxiety, as a confounding variable, remains unclear. OBJECTIVES: This study aimed to investigate the influence of anxiety and attentional focus instruction on the standing postural control of PD patients. METHODS: Thirty-four patients with PD (17 with high anxiety (HA-PD) and 17 with low anxiety (LA-PD)), as well as 17 gender- and age-matched healthy control subjects (HC) participated in the study. Postural control was evaluated using a combination of two levels of postural difficulty (standing on a rigid force plate surface with open eyes (RO) and standing on a foam surface with open eyes (FO)), as well as three attentional focus instructions (internal, external and no focus). RESULTS: Only the HA-PD group demonstrated significant postural control impairment as compared to the control, as indicated by significantly greater postural sway measures. Moreover, external focus significantly reduced postural sway in all participants especially during the FO condition. CONCLUSION: The results of the current study provide evidence that anxiety influences balance control and postural stability in patients with PD, particularly those with high levels of anxiety. The results also confirmed that external focus is a potential strategy that significantly improves the postural control of these patients. Further investigation of clinical applicability is warranted towards developing effective therapeutic and rehabilitative treatment plans.

A modular force-controlled robotic instrument for minimally invasive surgery - efficacy for being used in autonomous grasping against a variable pull force.

BACKGROUND: Many deficiencies of minimally invasive robotic surgery systems can be eliminated by using automated laparoscopic tools with force measurement and control capability. METHOD: A fully modular, automated laparoscopic instrument with a proximal force sensory system was designed and fabricated. The efficacy of the instrument was evaluated experimentally when functioning in an autonomous force-controlled grasping scheme. RESULTS: The designed instrument was shown to work easily with standard laparoscopic tools, with the whole distal part detachable for autoclave sterilization. The root mean squared error (RMSE) of the actual pinch force from the target ramp was 0.318 N; it was 0.402 N for a sinusoidal pull force, which dropped by 21% using a static friction compensation. A secure grasping condition was achieved, in spite of this error, by applying a sufficiently large margin from the slip boundary. CONCLUSIONS: With a simple and practical design, the instrument enjoys affordability, versatility and autoclave sterilizability for clinical usage, with an acceptable performance for being used in an auto-grasping control scheme. Copyright © 2016 John Wiley & Sons, Ltd.