Dimitrios Katsavelis

Cyborg beast: a low-cost 3d-printed prosthetic hand for children with upper-limb differences

BackgroundThere is an increasing number of children with traumatic and congenital hand amputations or reductions. Childrens prosthetic needs are complex due to their small size, constant growth, and psychosocial development. Families’ financial resources play a crucial role in the prescription of prostheses for their children, especially when private insurance and public funding are insufficient. Electric-powered (i.e., myoelectric) and body-powered (i.e., mechanical) devices have been developed to accommodate children’s needs, but the cost of maintenance and replacement represents an obstacle for many families. Due to the complexity and high cost of these prosthetic hands, they are not accessible to children from low-income, uninsured families or to children from developing countries. Advancements in computer-aided design (CAD) programs, additive manufacturing, and image editing software offer the possibility of designing, printing, and fitting prosthetic hands devices at a distance and at very low cost. The purpose of this preliminary investigation was to describe a low-cost three-dimensional (3D)-printed prosthetic hand for children with upper-limb reductions and to propose a prosthesis fitting methodology that can be performed at a distance.ResultsNo significant mean differences were found between the anthropometric and range of motion measurements taken directly from the upper limbs of subjects versus those extracted from photographs. The Bland and Altman plots show no major bias and narrow limits of agreements for lengths and widths and small bias and wider limits of agreements for the range of motion measurements. The main finding of the survey was that our prosthetic device may have a significant potential to positively impact quality of life and daily usage, and can be incorporated in several activities at home and in school.ConclusionsThis investigation describes a low-cost 3D-printed prosthetic hand for children and proposes a distance fitting procedure. The Cyborg Beast prosthetic hand and the proposed distance-fitting procedures may represent a possible low-cost alternative for children in developing countries and those who have limited access to health care providers. Further studies should examine the functionality, validity, durability, benefits, and rejection rate of this type of low-cost 3D-printed prosthetic device.

Validated robotic laparoscopic surgical training in a virtual-reality environment

BackgroundA robotic virtual-reality (VR) simulator has been developed to improve robot-assisted training for laparoscopic surgery and to enhance surgical performance in laparoscopic skills. The simulated VR training environment provides an effective approach to evaluate and improve surgical performance. This study presents our findings of the VR training environment for robotic laparoscopy.MethodsEight volunteers performed two inanimate tasks in both the VR and the actual training environment. The tasks were bimanual carrying (BC) and needle passing (NP). For the BC task, the volunteers simultaneously transferred two plastic pieces in opposite directions five times consecutively. The same volunteers passed a surgical needle through six pairs of holes in the NP task. Both tasks require significant bimanual coordination that mimics actual laparoscopic skills. Data analysis included time to task completion, speed and distance traveled of the instrument tip, as well as range of motion of the subject’s wrist and elbow of the right arm. Electromyography of the right wrist flexor and extensor were also analyzed. Paired t-tests and Pearson’s r were used to explore the differences and correlations between the two environments.ResultsThere were no significant differences between the actual and the simulated VR environment with respect to the BC task, while there were significant differences in almost all dependent parameters for the NP task. Moderate to high correlations for most dependent parameters were revealed for both tasks.ConclusionsOur data shows that the VR environment adequately simulated the BC task. The significant differences found for the NP task may be attributed to an oversimplification in the VR environment. However, they do point to the need for improvements in the complexity of our VR simulation. Further research work is needed to develop effective and reliable VR environments for robotic laparoscopic training.

An open source 3D-printed transitional hand prosthesis for children

Introduction Advancements in computer-aided design programs, additive manufacturing, and open-source image editing software offer the possibility of designing, printing, and fitting transitional prosthetic hands and other prosthetic devices at very low cost. The development and use of 3D-printed transitional prosthetic devices to increase range of motion (ROM), strength, and other relevant variables would have a significant clinical impact for children with upper-limb deficiencies. Thus, the purpose of this study was to identify anthropometric, active ROM, and strength changes after 6 months of using a wrist-driven 3D-printed transitional prosthetic hand for children with upper-limb deficiencies. Materials and Methods Anthropometric, active ROM, and strength measurements were assessed before and after 6 months of using a 3D-printed transitional hand prosthesis. Five children (two girls and three boys, 3–10 years of age) with absent digits (one traumatic and four congenital) participated in this study and were fitted with a 3D-printed transitional hand prosthesis. Results There were significant hand × time interactions for the forearm circumference (p = 0.02), active ROM for flexion (p = 0.02), and extension values (p = 0.04). There were no significant hand × time interactions, however, for wrist flexion strength (p = 0.29), wrist extension strength (p = 0.84), active ROM for ulnar deviation (p = 0.5), active ROM for radial deviation (p = 0.25), and forearm skinfold values (p = 0.11). Conclusion Although durability, environment, and lack of printing standards for the manufacturing of 3D-printed prostheses are factors to consider when using these types of devices, the practicality and cost-effectiveness represent a promising new option for clinicians and those patients with upper-limb deficiencies living in developing countries. Thus, the Cyborg Beast transitional prosthetic hand represents a low-cost prosthetic solution for those in need of a transitional device to increase ROM and forearm circumference.

Quantifying thigh muscle co-activation during isometric knee extension contractions: Within- and between-session reliability

Muscle co-activation around the knee is important during ambulation and balance. The wide range of methodological approaches for the quantification of co-activation index (CI) makes comparisons across studies and populations difficult. The present study determined within- and between-session reliability of different methodological approaches for the quantification of the CI of the knee extensor and flexor muscles during maximum voluntary isometric contractions (MVICs). Eight healthy volunteers participated in two repeated testing sessions. A series of knee extension MVICs of the dominant leg with concomitant torque and electromyographic (EMG) recordings were captured. CI was calculated utilizing different analytical approaches. Intraclass correlation coefficient (ICC) showed that within-session measures displayed higher reliability (ICC>0.861) and lower variability (Coefficient of variation; CV<21.8%) than between-session measures (ICC<0.645; CV>24.2%). A selection of a 500ms or larger window of RMS EMG activity around the PT delivered more reliable and less variable results than other approaches. Our findings suggest that the CI can provide a reliable measure for comparisons among conditions and is best utilized for within-session experimental designs.

The Influence of Visual Perception of Self-Motion on Locomotor Adaptation to Unilateral Limb Loading

ABSTRACT Self-perception of motion through visual stimulation may be important for adapting to locomotor conditions. Unilateral limb loading is a locomotor condition that can improve stability and reduce abnormal limb movement. In the present study, the authors investigated the effect of self-perception of motion through virtual reality (VR) on adaptation to unilateral limb loading. Healthy young adults, assigned to either a VR or a non-VR group, walked on a treadmill in the following 3 locomotor task periods—no load, loaded, and load removed. Subjects in the VR group viewed a virtual corridor during treadmill walking. Exposure to VR reduced cadence and muscle activity. During the loaded period, the swing time of the unloaded limb showed a larger increase in the VR group. When the load was removed, the swing time of the previously loaded limb and the stance time of the previously unloaded limb showed larger decrease and the swing time of the previously unloaded limb showed a smaller increase in the VR group. Lack of visual cues may cause the adoption of cautious strategies (higher muscle activity, shorter and more frequent steps, changes in the swing and stance times) when faced with situations that require adaptations. VR technology, providing such perceptual cues, has an important role in enhancing locomotor adaptation.

Common carotid artery peak systolic velocity ratio predicts high-grade common carotid stenosis

OBJECTIVE Screening for common carotid artery (CCA) stenosis with duplex ultrasound (DUS) velocity criteria alone can be limited by within-patient and between-patients hemodynamic variability. This study aimed to evaluate inter-CCA velocity ratio criteria to predict high-grade CCA stenosis. METHODS This was a retrospective review of consecutive patients who underwent computed tomography angiography and DUS peak systolic velocity (PSV) measurements of bilateral CCAs, independently recorded, between 2008 and 2014. Patients with dampened CCA waveforms on DUS composed group B. The remainder without dampened waveforms constituted group A. Inter-CCA PSV ratios were calculated by dividing the higher CCA PSV by the lower one of the other side, so the ratios would always be ≥1. Ratios were subsequently paired with each respective unilateral CCA diameter stenosis and differential bilateral CCA diameter stenosis. A quadratic regression model was fitted to predict unilateral and differential stenosis. Receiver operating characteristic curve was used to determine optimal ratios for ≥50% and ≥80% CCA stenosis. The study excluded patients with carotid artery occlusion. RESULTS From a total of 201 patients, 193 patients were included in group A and 8 in group B. Within group A, 31 patients had ≥50% unilateral stenosis and 17 had ≥50% differential stenosis. All stenoses ≥50% were identified on the same side with the higher PSV. Inter-CCA PSV ratio predicted ≥50% unilateral (r(2) = 0.536; P < .001) and differential stenosis (r(2) = 0.581; P < .001). In group B, all patients had ≥60% stenosis that was near or involved the vessel origin. An increasing inter-CCA PSV ratio showed a trend toward contralateral high-grade stenosis (r(2) = 0.596; P = .1). Receiver operating characteristic curves showed an optimal threshold CCA ratio ≥2.16 for ≥50% unilateral stenosis with 92% accuracy, 62% sensitivity, and 98% specificity (area under curve = 0.854; 95% confidence interval, 0.759-0.948) and a ratio ≥2.62 for ≥50% differential stenosis with 97% accuracy, 83% sensitivity, and 98% specificity (area under curve = 0.94; 95% confidence interval, 0.835-1). CONCLUSIONS DUS-based CCA PSV ratio can accurately predict unilateral and differential high-grade CCA stenosis. Also, in patients with unilateral dampened waveforms, it implied contralateral severe proximal stenosis. This parameter should be further validated in prospective studies and may serve as an adjunct screening tool to detect high-grade CCA stenosis.

Electromyographic Activity Determines Task Difficulty for Robotic Laparoscopic Training Programs

INTRODUCTION In 2003 there were approximately 770,000 inguinal hernia repairs in the United States [1]. Over 75% of those hernia repairs were completed using mesh-based methodologies, and only 14% were completed laparoscopically. Hernia repair using the da Vinci® Surgical System (Intuitive Surgical Inc) has been gaining popularity due to motion scaling, greater range-of-motion and enhanced dexterity. Since hernia repair is a common procedure performed by general surgeons [2], incorporating a similar training task will help improve robotic training programs and the growth of robotic laparoscopy. In the present study such a novel task, mesh alignment, was developed and compared with two well-known and valid surgical tasks, needle passing (Fig.1a) and suture tying (Fig.1b) [3]. We assessed difficulty of these tasks using electromyography (EMG). We hypothesized that the task difficulty of the novel mesh alignment task would be similar to the other two.

THE MINIMUM NUMBER OF DATA POINTS REQUIRED TO COMPUTE APPROXIMATE ENTROPY FOR GAIT DATA

Approximate Entropy (ApEn) is a widely used nonlinear tool to analyze biological data. ApEn quantifies the predictability or regularity of the fluctuations present in a time series, with smaller values indicating greater regularity, and larger values indicate more randomness or irregularity [Pincus, 1991; Pincus et al., 1991]. ApEn is robust with relatively short and noisy data unlike many other nonlinear tools, and the range of data point requirement is rather wide. It can be from 10 to 30, where parameter m is usually set to 2. In addition, since data length N is another parameter for ApEn, ApEn must be calculated for data sets with the same N to ensure appropriate comparisons.