Optimizing 3D printed ankle-foot orthoses for patients with stroke: Importance of effective elastic modulus and finite element simulation.

Patients with stroke often use ankle-foot orthoses (AFOs) for gait improvement. 3D printing technology has become a popular tool in recent years for the production of AFOs due to its strengths on customization and rapid manufacturing. However, the porosity of the 3D printed materials affects the kinetic features of these orthoses, leading to its lower-strength than solid ones. The effective elastic modulus of 3D printed material was measured following standard test method to obtain the kinetic features precisely in a finite element simulation. This study demonstrated that the porosity of 3D printed samples using 100% fill density was 11% for PLA and 16% for Nylon. As a result, their effective elastic modulus was reduced to 1/3 and 1/12 of fully solid objects, respectively, leading to a lower stiffness of 3D printed orthoses. A fatigue testing platform was built to verify our finite element model, and the findings of the fatigue test were consistent with the analysis of the finite element model. Further, our AFO has been proven to have a lifespan exceeding 200 thousand steps. Our study highlights the significance of determining the actual porosity of 3D printed samples by calculating the effective elastic modulus, which leads to a more precise finite element simulation and enables reliable prediction of the kinetic features of the AFO. Overall, this study provides valuable insights into the production and optimization of 3D printed AFOs for patients with stroke.

A Tenodesis-Induced-Grip exoskeleton robot (TIGER) for assisting upper extremity functions in stroke patients: a randomized control study.

PURPOSE: This study was aimed toward developing a lightweight assisting tenodesis-induced-grip exoskeleton robot (TIGER) and to examine the performance of the TIGER in stroke patients with hemiplegia. METHODS: This was a single-blinded, randomized control trial with pre-treatment, immediate post-treatment, and 12-week follow-up assessments. Thirty-four stroke patients were recruited and randomized to either an experimental or control group, where each participant in both groups underwent 40 min of training. In addition to a 20-min bout of regular task-specific motor training, each participant in the experimental group received 20 min of TIGER training, and the controls received 20 min of traditional occupational therapy in each treatment session. Primary outcomes based on the Fugl-Meyer Motor Assessment of Upper Extremity (FMA-UE) were recorded. RESULTS: Thirty-two patients (94.1%) completed the study: 17 and 15 patients in the experimental and control groups, respectively. Significant beneficial effects were found on the total score (ANCOVA, p = 0.006), the wrist score (ANCOVA, p = 0.037), and the hand score (ANCOVA, p = 0.006) for the FMA-UE in the immediate post-treatment assessment of the participants receiving the TIGER training. CONCLUSION: The TIGER has beneficial effects on remediating upper limb impairments in chronic stroke patients. Clinical trial registration: ClinicalTrials.gov; identifier NCT03713476Implications for rehabilitationBased on use-dependent plasticity concepts, robot training with the more distal segments of the upper extremities has a beneficial effect in patients with chronic stroke.A novel lightweight assisting tenodesis-induced-grip exoskeleton robot (TIGER) system using a mechanism involving musculotendinous coordination of the wrist and hand was proposed in this study.Between-group differences in changes in the upper limb motor performance were observed in the experimental group as compared to patients in the control group. For patients with chronic stroke, receiving 20 min of TIGER training in conjunction with 20 min of task-specific motor training led to clinically important changes in motor control and functioning of the affected upper limb.

Can Parameters Other than Minimal Axial Diameter in MRI and PET/CT Further Improve Diagnostic Accuracy for Equivocal Retropharyngeal Lymph Nodes in Nasopharyngeal Carcinoma?

PURPOSE: Minimal axial diameter (MIAD) in magnetic resonance imaging (MRI) was recognized as the most useful parameter in diagnosing lateral retropharyngeal lymph (LRPL) nodes in nasopharyngeal carcinoma (NPC). This study aims to explore the additional nodal parameters in MRI and positron emission tomography-computed tomography for increasing the prediction accuracy. MATERIALS AND METHODS: A total of 663 LRPL nodes were retrospectively collected from 335 patients with NPC. The LRPL nodes ascertained on follow-up MRI were considered positive for metastases. First, the optimal cutoff value of each parameter was derived for each parameter. In addition, neural network (NN) nodal evaluation was tested for all combinations of three parameters, namely MIAD, maximal axial diameter (MAAD), and maximal coronal diameter (MACD). The optimal approach was determined through brute force attack, and the results of two methods were compared using a bootstrap sampling method. Second, the mean standard uptake value (NSUVmean) was added as the fourth parameter and tested in the same manner for 410 nodes in 219 patients. RESULTS: In first and second analysis, the accuracy rate (percentage) for the MIAD was 89.0% (590/663) and 89.0% (365/410), with the optimal cutoff values being 6.1 mm and 6.0 mm, respectively. With the combination of all three and four parameters, the accuracy rate of the NN was 89% (288/332) and 88.8% (182/205), respectively. In prediction, the optimal combinations of the three and four parameters resulted in correct identification of three (accuracy: 593/663, 89.4%) and six additional nodes (371/410, 90.5%), representing 4% (3/73) and 13.3% (6/45) decreases in incorrect prediction, respectively. CONCLUSION: NPC LRPL nodes with an MIAD ≥ 6.1 mm are positive. Among nodes with an MIAD < 6.1 mm, if the NSUVmean ≥ 2.6 or MACD ≥ 25 mm and MAAD ≥ 8 mm, the nodes are positive; otherwise, they are negative.

Experimental and numerical estimations into the force distribution on an occlusal surface utilizing a flexible force sensor array.

This study presents a novel flexible force sensor array for measuring the distribution of the force distribution over the first molar. The developed force sensor array is composed of a flexible polyimide electrode and barium-titanate-based multilayer ceramic capacitors (MLCCs). The piezoelectric and material properties of industrial-grade MLCCs are ideal for measuring large-force loadings. The sensors are cheap and easy to integrate with automated manufacturing processes. Prior to experimental measurements, the force responses for the MLCC sensor cells were systematically measured and evaluated, confirming their high fracture strength and good sensing properties. Finite element (FE) simulations were used to calculate the force distribution over the tooth crown from the measurement results of the 3×3 force sensor array. Results indicate that the sensor has great sensitivity and linearity under a high-speed cycle loading of 500 N/s conducted to simulate normal chewing. The total force measured using the developed sensor array within the artificial tooth had an error of less than 5%. In addition, the force distributions over the molar crown obtained using a numerical method of FE analysis agree well with those obtained from experiments. The developed flexible force sensor array thus has potential for in-situ bite force measurements that are low-cost and reliable.