Correlation between musculoskeletal structure of the hand and primate locomotion: Morphometric and mechanical analysis in prehension using the cross- and triple-ratios.

Biometric ratios of the relative length of the rays in the hand have been analyzed between primate species in the light of their hand function or phylogeny. However, how relative lengths among phalanges are mechanically linked to the grasping function of primates with different locomotor behaviors remains unclear. To clarify this, we calculated cross and triple-ratios, which are related to the torque distribution, and the torque generation mode at different joint angles using the lengths of the phalanges and metacarpal bones in 52 primates belonging to 25 species. The torque exerted on the finger joint and traction force of the flexor tendons necessary for a cylindrical grip and a suspensory hand posture were calculated using the moment arm of flexor tendons measured on magnetic resonance images, and were compared among Hylobates spp., Ateles sp., and Papio hamadryas. Finally, the torques calculated from the model were validated by a mechanical study detecting the force exerted on the phalanx by pulling the digital flexor muscles during suspension in these three species. Canonical discriminant analysis of cross and triple-ratios classified primates almost in accordance with their current classification based on locomotor behavior. The traction force was markedly reduced with flexion of the MCP joint parallel to the torque in brachiating primates; this was notably lower in the terrestrial quadrupedal primates than in the arboreal primates at mild flexion. Our mechanical study supported these features in the torque and traction force generation efficiencies. Our results suggest that suspensory or terrestrial quadrupedal primates have hand structures that can exert more torque at a suspensory posture, or palmigrade and digitigrade locomotion, respectively. Furthermore, our study suggests availability of the cross and triple-ratios as one of the indicators to estimate the hand function from the skeletal structure.

Two-Year Survival After First-Ever Stroke in a General Population of 1.4 Million Japanese　- Shiga Stroke Registry.

BACKGROUND: Stroke is one of the leading causes of disability and mortality in Japan. The aim of the present analysis was to determine the non-acute survival rate after first-ever stroke using data from a large-scale population-based stroke registry in Japan. Methods and Results: Shiga Stroke Registry is an ongoing population-based registry of stroke, which covers approximately 1.4 million residents of Shiga Prefecture in central Japan. A total of 2,176 first-ever stroke patients, who were registered in 2011, were followed up until December 2013. The 2-year cumulative survival rates were estimated using Kaplan-Meier method according to index stroke subtype. Cox proportional hazards models were used to assess predictors of all-cause death. During a 2-year follow-up period, 663 patients (30.5%) died. The 2-year cumulative survival rate after first-ever stroke was 69.5%. There was heterogeneity in 2-year cumulative survival according to stroke subtype: lacunar infarction, 87.2%; large artery infarction, 76.1%; cardioembolic infarction, 55.4%; intracerebral hemorrhage, 65.9%; and subarachnoid hemorrhage, 56.7%. Older age, male sex, medical history, higher Japan coma scale score on admission, and stroke subtype were associated with risk of all-cause death in ≤2 years. CONCLUSIONS: In the present population-based stroke registry with a real-world setting in Japan, 2-year cumulative mortality after first-ever stroke is still high (>30%), particularly for cardioembolic infarction, subarachnoid hemorrhage and intracerebral hemorrhage.

The JAGUAR Score Predicts 1-Month Disability/Death in Ischemic Stroke Patient Ineligible for Recanalization Therapy.

BACKGROUND AND PURPOSE: Most available scoring system to predict outcome after acute ischemic stroke (AIS) were established in Western countries. We aimed to develop a simple prediction score of 1-month severe disability/death after onset in AIS patients ineligible for recanalization therapy based on readily and widely obtainable on-admission clinical, laboratory and radiological examinations in Asian developing countries. METHODS: Using the Shiga Stroke Registry, a large population-based registry in Japan, multivariable logistic regression analysis was conducted in 1617 AIS patients ineligible for recanalization therapy to yield ß-coefficients of significant predictors of 1-month modified Rankin Scale score of 5-6, which were then multiplied by a specific constant and rounded to nearest integer to develop 0-10 points system. Model discrimination and calibration were evaluated in the original and bootstrapped population. RESULTS: Japan Coma Scale score (J), age (A), random glucose (G), untimely onset-to-arrival time (U), atrial fibrillation (A), and preadmission dependency status according to the modified Rankin Scale score (R), were recognized as independent predictors of outcome. Each of their ß-coefficients was multiplied by 1.3 creating the JAGUAR score. Its area under the curve (95% confidence interval) was .901 (.880- .922) and .901 (.900- .901) in the original and bootstrapped population, respectively. It was found to have good calibration in both study population (P = .27). CONCLUSIONS: The JAGUAR score can be an important prediction tool of severe disability/death in AIS patients ineligible for recanalization therapy that can be applied on admission with no complicated calculation and multimodal neuroimaging necessary, thus suitable for Asian developing countries.

The Association between Glomerular Filtration Rate Estimated on Admission and Acute Stroke Outcome: The Shiga Stroke Registry.

AIM: Although renal dysfunction has been identified as a novel risk factor affecting stroke prognosis, few have analyzed the association within large-scale population-based setting, using wide-range estimated glomerular filtration rate (eGFR) category. We aimed to determine the association of admission eGFR with acute stroke outcomes using data from a registry established in Shiga Prefecture, Japan. METHODS: Following exclusion of patients younger than 18 years, with missing serum creatinine data, and with onset more than 7 days prior to admission, 2,813 acute stroke patients registered in the Shiga Stroke Registry year 2011 were included in the final analysis. The Japanese Society of Nephrology equation was used to estimate GFR. Multivariable logistic regression was performed to analyze the association of eGFR with all-cause in-hospital death (modified Rankin Scale [mRS] 6), and at-discharge death/disability (mRS 2-6). Separate analyses were conducted within stroke subtypes. RESULTS: Compared to eGFR 60-89 mL/min/1.73 m2, adjusted odds ratios (ORs) and 95% confidence interval [95% CI] for in-hospital death (in the order of eGFR ＜45, 45-59, and ≥90 mL/min/1.73 m2) were 1.54 [1.04-2.27], 1.07 [0.72-1.58], and 1.04 [0.67-1.59]. Likewise, adjusted ORs [95% CI] for at-discharge death/disability were 1.54 [1.02-2.32], 0.97 [0.73-1.31], and 1.48 [1.06-2.05]. Similar pattern was further evident in the eGFR ＜45 mL/min/1.73 m2 group for both outcomes within acute ischemic stroke patients. CONCLUSIONS: Our study has ascertained that in acute stroke, particularly ischemic stroke, low eGFR was significantly associated with in-hospital death and at-discharge death/disability. Additionally, high eGFR was found to be associated with at-discharge death/disability.

Incidence, Management and Short-Term Outcome of Stroke in a General Population of 1.4 Million Japanese　- Shiga Stroke Registry.

BACKGROUND: This study determined the current status of the incidence, management, and prognosis of stroke in Japan using a population-based stroke registry.Methods and Results:Shiga Stroke Registry is an ongoing population-based registry that covers approximately 1.4 million residents of Shiga Prefecture. Cases of acute stroke were identified using standard definitions through surveillance of both all acute-care hospitals with neurology/neurosurgery facilities and death certificates in 2011. A total of 2,956 stroke cases and 2,176 first-ever stroke cases were identified. The age- and sex-adjusted incidence rate for first-ever stroke using the 2013 European Standard Population as standard was per 100,000 person-years: 91.3 for ischemic stroke, 36.4 for intracerebral hemorrhage, and 13.7 for subarachnoid hemorrhage. It was estimated that approximately 220,000 new strokes occurred in 2011 in Japan. Among the 2,956 cases, most stroke patients underwent neuroimaging, 268 received surgical or endovascular treatment, and 2,158 had rehabilitation therapy; 78 patients received intravenous thrombolysis. A total of 1,846 stroke patients had died or were dependent at hospital discharge, and 390 died within 28 days of onset. CONCLUSIONS: Incidence rates of stroke by subtypes were clarified and the total number of new strokes in Japan was estimated. More than half of stroke patients die or become dependent after a stroke. This study re-emphasized the importance of public health measures in reducing the burden of stroke in Japan.

Active and Passive Haptic Training Approaches in VR Laparoscopic Surgery Training.

Laparoscopic surgery has become a widely performed surgery as it is one of the most common minimally invasive surgeries. Doctors perform the surgery by manipulating thin and long surgical instruments precisely with the assistance of laparoscopic video with limited field of view. The power control of the instruments' tip is especially very important, because excessive power may damage internal organs. The training of this surgical technique is mainly supervised by an expert in hands-on coaching program. However, it is difficult for the experts to spend sufficient time for coaching. Therefore, we aim to teach the expert's hand movements in laparoscopic surgery to trainees using VR-based simulator, which is equipped with a guidance force display device. To realize the system, we propose two haptic training approaches for transferring the expert's hand movements to the trainee. One is active training, and the other is passive training. The former approach shows the expert's movements only when the trainee makes large errors while the latter shows the expert's movements continuously. In this study, we validate the applicability of these approaches through tasks in VR laparoscopic surgery training simulator, and identify the differences between these approaches.

Evaluation of Network-Based Minimally Invasive VR Surgery Simulator.

In this paper, we report a result of an experiment of a field trial of our network-based minimally invasive surgery simulator. In our previous paper, we proposed a network-based visuohaptic surgery training system for laparoscopic surgery. In addition, we proposed a volume-based haptic communication approach, which allows participants at remote sites on the network to simultaneously interact with the same target object in virtual environments presented by multi-level computer performance systems, by only exchanging a small set of manipulation parameters for the target object and additional packet for synchronization of status of binary tree and deformation of shared volume model. We implemented the approach into our network-based surgery simulator, and field trial of the simulator at three locations was performed.

Evaluation of haptic teaching approaches for laparoscopic surgery training.

Laparoscopic surgery, one type of minimally invasive surgery (MIS) is a very important surgery technique which requires advanced surgical technique. At present, expert one-on-one teaching mainly supports the training of these advanced surgical techniques. However, time constraints prevent experts spending the amount of time desired for this training. Therefore, we aim to support training using a VR-based laparoscopic surgery simulator equipped with a guidance force display. This increases the amount of training a trainee can avail of while at the same time allow the expert and the trainee to increase the quality of the limited one-to-one time together. The first step of our research is to investigate approaches that displays the guidance force to teach experts hand movements. In this study, we used two guidance force-display approaches: Instrument-guiding approach and Hand-guiding approach. Through evaluative experiments, we found that the Hand-guiding approach is more suitable for skill transfer than the Instrument-guiding approach in particular tasks. The results are described below.

Laparoscopic surgery simulator using first person view and guidance force.

In general, minimally invasive surgery is seen as the most difficult surgery because there is limited field of view with an endoscope and force sensation from surgical instruments such as forceps is poor. Especially in early clinical education for medical students, a virtual reality surgical simulator would be an effective tool. In this paper, we propose a visuohaptic surgery training system for laparoscopical techniques. We recorded a video from a first person point of view of the instructor (expert). And we also recorded operation information (i.e. trajectory) of surgical instruments of the instructor. Then, we displayed the recorded video and the guidance force to trainees. We constructed a prototype surgery training system and the effectiveness of our approach was confirmed.

A proposal of speculative operation on distributed system for FEM-based ablation simulator.

This study aims to provide physics-based force feedback system on distributed system for simulating invasive operation such as ablation. conventional PC-based VR surgical simulators with haptic interaction are hard to provide sufficient computational resources for the simulation of physics-based soft tissue fracture. For proper presentation of force feedback as real operations, physics-based simulation is inevitable. At the same time finite element method requires huge computational complexites. In this paper, the authors propose server-side speculative operation method on application layer for hiding the calculation latencies. The proposed method would achieve the response acceleration without the decomposition of conventional simulation process. The theoritical estimates of speculation parameters are mentioned.

Interaction model between elastic objects for haptic feedback considering collisions of soft tissue.

The simulation of organ-organ interaction is indispensable for practical and advanced medical VR simulator such as open surgery and indirect palpation. This paper describes a method to represent real-time interaction between elastic objects for accurate force feedback in medical VR simulation. The proposed model defines boundary deformation of colliding elements based on temporary surface forces calculated by temporary deformation. The model produces accurate deformation and force feedback considering collisions of objects as well as prevents unrealistic overlap of objects. A prototype simulator of rectal palpation is constructed on general desktop PC with a haptic device, PHANToM. The system allows users to feel different stiffness of a rear elastic object located behind another elastic object. The results of experiments confirmed the method expresses organ-organ interaction in real-time and produces realistic and perceivable force feedback.

FEM-based soft tissue destruction model for ablation simulator.

In surgical procedures, ablation is one of the most difficult skills to train and acquire. For the risk of ablation failure, ablation training environments are desired. This paper proposes FEM-based deformation and destruction soft tissue model for ablation training simulator. The proposed model employs shearing stress hypothesis. The result of simulation experiments shows that the model can express different destruction progression by manipulation.

FEM-based interaction model between elastic objects for indirect palpation simulator.

Indirect palpation is required to examine lots of cases like breast cancer and prostate malignance. This paper proposes interaction model between elastic objects to simulate indirect palpation. The interaction is simulated by displacement of colliding elements based on normal stress derived from temporary displacement. The physics-based approach represents the difference of physical properties such as stiffness of colliding objects. Deformation and haptic reproduction is possible to be carried out in real time with two organ models consisting of roughly 200 nodal points. As an example, we developed a rectal palpation simulator based on the proposed method. The experiment using rectal palpation simulator confirmed that the method enables a user to perceive difference of stiffness of prostate model located behind rectum model indirectly.

Physics-based preoperative approach planning using hybrid virtual bodies.

This paper proposes a hybrid model mixing geometry and volume data to improve representation of virtual bodies. This model applies object-oriented data models and rendering techniques to virtual organs, and enables both interactive VR simulation and detailed volume visualization of tissue of interest (e.g. coronary). Also, a physics-based framework interactively simulates estimated surgical fields which are used in preoperative discussion. Based on the proposed methods, a VR-based strategic planning system is developed. The system does not need high cost manual segmentation of patient dataset and efficiently supports planning of surgical approaches in cardiovascular surgery.

Measurement of in vivo local shear modulus using MR elastography multiple-phase patchwork offsets.

Magnetic resonance elastography (MRE) is a method that can visualize the propagating and standing shear waves in an object being measured. The quantitative value of a shear modulus can be calculated by estimating the local shear wavelength. Low-frequency mechanical motion must be used for soft, tissue-like objects because a propagating shear wave rapidly attenuates at a higher frequency. Moreover, a propagating shear wave is distorted by reflections from the boundaries of objects. However, the distortions are minimal around the wave front of the propagating shear wave. Therefore, we can avoid the effect of reflection on a region of interest (ROI) by adjusting the duration of mechanical vibrations. Thus, the ROI is often shorter than the propagating shear wavelength. In the MRE sequence, a motion-sensitizing gradient (MSG) is synchronized with mechanical cyclic motion. MRE images with multiple initial phase offsets can be generated with increasing delays between the MSG and mechanical vibrations. This paper proposes a method for measuring the local shear wavelength using MRE multiple initial phase patchwork offsets that can be used when the size of the object being measured is shorter than the local wavelength. To confirm the reliability of the proposed method, computer simulations, a simulated tissue study and in vitro and in vivo studies were performed.