Flexion Cycle Research Articles

NOVEL ROBOTIC TECHNIQUE TO INVESTIGATE TOTAL KNEE ARTHROPLASTY STABILITY

AbstractIntroductionMid-flexion instability may cause poor outcomes following TKA. Surgical technique, patient-specific factors, and implant design could all contribute to it, with modelling and fluoroscopy data suggesting the latter may be the root cause. However, current implants all pass the preclinical stability testing standards, making it difficult to understand the effects of implant design on instability. We hypothesized that a more physiological test, analysing functional stability across the range of knee flexion-extension, could delineate the effects of design, independent of surgical technique and patient-specific factors.MethodsUsing a SIMvitro-controlled six-degree-of-freedom robot, a dynamic stability test was developed, including continuous flexion and reporting data in a trans-epicondylar axis system. 3 femoral geometries were tested: gradually reducing radius, multi-radius and single-radius, with their respective tibial inserts. 710N of compression force (body weight) was applied to the implants as they were flexed from 0–140° with three levels of anterior/posterior (AP) tibial force applied (−90N,0N,90N).ResultsWhile in static tests, the implants performed similarly, functional stability testing revealed different paths of motion and AP laxities throughout the flexion cycle. Some designs exhibited mid-flexion instability, while others did not: the multi-radius design allowed increased AP laxity as it transitioned to each arc of reduced femoral component radius; the single-radius design had low tibial bearing conformity, allowing 16mm difference in the paths of mid-flexion versus extension motion.ConclusionsPreclinical lab testing reveals functional differences between different design philosophies. Implant design impacts kinematics and mid-flexion stability, even before factoring in surgical technique and patient-specific factors.

Scaphoid, lunate and capitate kinematics in the normal and ligament deficient wrist: A bi-plane X-ray fluoroscopy study

The ligamentous structures of the wrist stabilise and constrain the interactions of the carpal bones during active wrist motion; however, the three-dimensional translations and rotations of the scaphoid, lunate and capitate in the normal and ligament deficient wrist during planar and oblique wrist motions remain poorly understood. This study employed a computer-controlled simulator to replicate physiological wrist motion by dynamic muscle force application, while carpal kinematics were simultaneously measured using bi-plane x-ray fluoroscopy. The aim was to quantify carpal kinematics in the native wrist and after sequential sectioning of the scapholunate interosseous ligament (SLIL) and secondary scapholunate ligament structures. Seven fresh-frozen cadaveric wrist specimens were harvested, and cycles of flexion–extension, radial-ulnar deviation and dart-thrower’s motion were simulated. The results showed significant rotational and translational changes to these carpal bones in all stages of disruptions to the supporting ligaments (p < 0.05). Specifically, following the disruption of the dorsal SLIL (Stage II), the scaphoid became significantly more flexed, ulnarly deviated, and pronated relative to the radius, whereas the lunate became more extended, supinated and volarly translated (p < 0.05). Sectioning of the dorsal intercarpal (DIC), dorsal radiocarpal (DRC), and scaphotrapeziotrapezoid (STT) ligaments (Stage IV) caused the scaphoid to collapse further into flexion, ulnar deviation, and pronation. These findings highlight the importance of all the ligamentous attachments that relate to the stability of the scapholunate joint, but more importantly, the dorsal SLIL in maintaining scapholunate stability, and the preservation of the attachments of the DIC and DRC ligaments during dorsal surgical approaches. The findings will be useful in diagnosing wrist pathology and in surgical planning.

Determining the relationship between tibiofemoral geometry and passive motion with partial least squares regression.

Tibiofemoral geometry influences knee passive motion and understanding their relationship can provide insight into knee function and mechanisms of injury. However, the complexity of the geometric constraints has made characterizing the relationship challenging. The aim of this study was to determine the tibiofemoral bone geometries that explain the variation in passive motion using a partial least squares regression (PLSR) model. The PLSR model was developed for 29 healthy cadaver specimens (10 female, 19 male) with femur and tibia geometries retrieved from MRIimages and six degree-of-freedomtibiofemoral kinematics determined during a flexion cycle with minimal medial pressure. The first 13 partial least squares(PLS) components explained 90% of the variation in the kinematics and accounted for 89% of the variation in geometry. The first three PLS components which shared geometric changes to particular surface congruencies of the tibial and femoral condyles explained the most amount of variation in the kinematics, primarily in anterior-posterior translation. Meanwhile, variations in femoral condyle width and the intercondylar space, tibia plateau size and conformity, and tibia eminences heights in PLS2 and 4 explained the greatest amount of variation in internal-external rotation. PLS 4 exhibiting variation in overall size of the knee accounted for greatest amount of variation in geometry (50%) and had the greatest influence on the abduction-adduction motion and some on internal-external rotation but, overall, explained only a small proportion of the kinematics (10%). Elucidating the complex relationship between tibiofemoral bone geometry and passive kinematics may help personalize treatments for improved functional outcomes in patients.

Influence of articular step-off on contact mechanics in fractures of the posterolateral-central tibial plateau - a biomechanical study

BackgroundThe posterior quadrants of the tibial plateau are frequently involved in OTA type C tibial plateau fractures. The biomechanical influence of a residual articular step-off of the posterolateral-central (PLC) segment, which is difficult to visualize intraoperatively, remains unclear.Therefore, aim of this study was to investigate the contact area and stress of the tibial plateau in cases of different articular step-offs of the PLC segment. MethodsSeven human cadaveric knees were used to simulate articular impressions of the PLC segment with step-offs of 1 mm, 3 mm, and 5 mm. The knees were axially loaded up to 150 N during a total of 25 dynamic cycles of knee flexion up to 90°. Pressure mapping sensors were inserted into the medial and lateral joint compartments beneath the menisci to measure articular contact area and stress. ResultsBetween 60° and 90° of knee flexion, increasing PLC segment impressions of the tibial plateau led to increasing contact stress and a significantly reduced contact area. The largest decrease in the contact area was 30 %, with an articular step-off of 5 mm (0.003). An increase in contact stress, especially from a 3-mm step-off, was measured, with a doubling of the mean contact stress at 3-mm and 5-mm step-offs and 90° knee flexion (p = 0.06/0.05). ConclusionFrom a biomechanical point of view, posterior impressions of the PLC segment greater than a 1-mm step-off should be addressed as anatomically as possible, especially in active patients with the need for higher knee flexion angles.

Lower extremity Interlimb coordination associated brain activity in young female athletes: A biomechanically instrumented neuroimaging study.

Bilateral sensorimotor coordination is required for everyday activities, such as walking and sitting down/standing up from a chair. Sensorimotor coordination functional neuroimaging (fMRI) paradigms (e.g., stepping, cycling) increase activity in the sensorimotor cortex, supplementary motor area, insula, and cerebellum. Although these paradigms are designed to assay coordination, performance measures are rarely collected simultaneously with fMRI. Therefore, we aimed to identify neural correlates of lower extremity coordination using a bilateral, in-phase, multi-joint coordination task with concurrent MRI-compatible 3D motion analysis. Seventeen female athletes (15.0 ± 1.4 years) completed a bilateral, multi-joint lower-extremity coordination task during brain fMRI. Interlimb coordination was quantified from kinematic data as the correlation between peak-to-peak knee flexion cycle time between legs. Standard preprocessing and whole-brain analyses for task-based fMRI were completed in FSL, controlling for total movement cycles and neuroanatomical differences, with interlimb coordination as a covariate of interest. A clusterwise multi-comparison correction was applied at z > 3.1 and p < .05. Less interlimb coordination during the task was associated with greater activation in the posterior cingulate and precuneus (zmax =6.41, p < .01) and the lateral occipital cortex (zmax =7.55, p=.02). The inability to maintain interlimb coordination alongside greater activity in attention- and sensory-related brain regions may indicate a failed compensatory neural strategy to execute the task. Alternatively, greater activity could be secondary to reduced afferent acuity that may be elevating central demand to maintain in-phase lower extremity motor coordination. Future research aiming to improve sensorimotor coordination should consider interventional approaches uniquely capable of promoting adaptive neuroplasticity to enhance motor control.

Wearable glove-embedded sensors for therapeutic drug monitoring in sweat for personalized medicine

Wearable sensing technology may fulfill the requirements of precision medicine, but the use of on-body devices for rapid, selective screening of therapeutic drugs is relatively new. In this paper, we report on wearable glove-embedded sensors for non-invasive and selective determination of therapeutic drugs and a biomarker in sweat samples. Electrochemical sensing was made with an array of sensors printed on four fingers of a plastic glove. Uric acid was detected using the index finger functionalized with carbon black with a limit of detection of 1.37 × 10–6 mol L–1. Paracetamol and paroxetine were detected using the middle and ring fingers coated with Printex Carbon with limits of detection of 2.47 × 10–7 and 4.93 × 10–7 mol L–1, respectively. Ethinylestradiol (EE2) detection was performed with a pre-treated screen-printed carbon electrode on the little finger with limit of detection of 9.35 × 10–7 mol L–1. The high sensitivity and selectivity achieved with the glove-embedded sensors were possible due to a judicious choice of sensing layers and optimized working conditions for differential pulse voltammetry. Monitoring of the analytes was carried out in sweat samples with suitable recovery between 90 and 110%. The glove-embedded sensors were robust against multiple flexion cycles, stable and reproducible, with no response to interference from other molecules in sweat. They may be extended to detect other targets for on-site analysis, in addition to applications in environmental and water samples.

Dynamic Mediolateral Patellar Translation Is a Sex- and Size-Independent Parameter of Adult Proximal Patellar Tracking Using Dynamic 3 Tesla Magnetic Resonance Imaging

To provide normal values for physiological patellofemoral tracking in a representative group of healthy individuals, as well as sex differences, using real-time 3T-magnetic resonance imaging (MRI) and to test for the reliability of the presented technique. One hundred knees of healthy individuals with no history of patellofemoral symptoms were scanned with dynamic MRI sequences, during repetitive cycles of flexion (40°) and full extension. Within a 30-seconds time-frame, three simultaneous, transverse slices were acquired. Dynamic mediolateral patellar translation (dMPT) and dynamic patellar tilt (dPT) were measured on two occasions by two independent examiners. Common radiological parameters were measured using static MRI, and correlations were calculated. 100 knees (53 right, 47 left; age: 26.7 ± 4.4 years; BMI: 22.5 ± 3.1) of 57 individuals (27 females, 30 males) were included. Mean height was 170.1 ± 7.7 cm in women and 181.8 ± 6.4 cm in men. Average patella diameter was 37.9 ± 2.7 (95% CI 37.1-38.7) mm in women and 42.4 ± 3.2 (95% CI 41.5-43.3) mm in men. In females, the patellar diameters and intercondylar distances were significantly smaller than in males (P < .001). Radiological parameters for patellar maltracking were within the normal range. During the range of motion, mean dMPT was 1.7 ± 2.4 (95% CI .9-2.5) mm in females and 1.8 ± 2.7 (95% CI 1.1-2.6) mm in males (P= .766). Mean dPT was 1.3 ± 2.9° (95% CI .4-2.1°) in females and-0.2 ± 3.8° (95% CI-1.2-.9°) in males (P= .036). Neither dMPT nor dPT was correlated with height, BMI, or patellar diameter. Intercondylar distance correlated weakly with dPT (r=-.241; P= .041). Intra- and interrater reliability were excellent for dMPT and dPT. Dynamic mediolateral patellar translation is a size- and sex-independent parameter for proximal patellar tracking. In healthy individuals without patellofemoral abnormalities normal dMPT proximal to the trochlea groove was 1.7 ± 2.5 (1.2-2.2) mm, independent of size or sex. Normal dPT showed a dependency on sex and was 1.3±2.9 (.4-2.1)° in women and-0.2 ± 3.8 (-1.2-0.9)° in men. Level II, diagnostic study.

Rehabilitation after flexor tendon repair and others: a safe and efficient protocol.

In this review I detail the protocol that I use after flexor tendon repair and outline my experience regarding how its framework might be used for other disorders. The early passive-active flexion protocol has a sufficient number of cycles of active flexion in each exercise session, which is at least 40, and ideally 60 to 80. The frequency of exercise sessions may range from 4 to 6 a day, distributed in the morning, afternoon and evening. Increasing the number of daily sessions without a sufficient number of runs in each session is ineffective. In the first 2-3 weeks after surgery, active digital flexion should go through only a partial range. In weeks 4-6, the patient gradually moves through the full range. With modifications, I suggest generalization of the partial-range finger motion to therapy after treating other hand injuries. I consider partial-range active flexion a generalizable working principle for different hand disorders.

Metal‐Textile Laser Welding for Wearable Sensors Applications

AbstractElectronic textile (E‐textile), an emerging technology, has the potential to revolutionize consumer electronics by transforming them into wearable devices. Highly conductive, textile conductors, suitable for commercialization, have yet not been developed. Here, a new metal‐textile laser welding method is presented for a rapid one‐step, stable, and cost‐efficient manufacturing of electrically conductive textiles. This method is a direct on‐textile approach for customized 2D nanothick metal coatings with flexible design. Different metals, like palladium, silver, or copper can be welded on functional membranes and textiles containing polymers. As shown by bonding a copper 2D pattern on a polyamide textile, the resistivity does not vary if compared to the bulk material. The generated interlocking bonding ensures strong physical adhesion between the partly molten polyamide fibers and a copper layer, resisting up to 10 000 abrasion cycles using the standardized Martindale test and up to 42 000 flexion cycles using the industrial standardized Schildknecht test. A promising application for textile integrated conductors is body monitoring sensors. The feasibility of a laser welded resistance temperature sensors on a functional membrane is demonstrated without impairing its mechanical stability. This technology presents suitable properties and variabilities for a wide range of application in E‐textiles and its commercialization.

An Isolated Transosseous Flexible Suture Frame in the Treatment of Patellar Tendon Rupture Provides Adequate Mechanical Resistance.

Acute patellar tendon ruptures are frequently observed in patients with metabolic comorbidities, and the benchmark treatment is surgical repair. It is desirable not to harm an already fragile biologic environment with sutures and hardware. We aimed to compare the mechanical requirements of an isolated, flexible, high-strength nonabsorbable transosseous suture frame with that of the Krackow suture technique. A total of 12 cadaveric pieces were randomized into two groups: the isolated flexible frame group (n = 6) and the standard Krackow fixation group (n = 6). A traumatic rupture of the patellar tendon was performed, and a transosseous displacement sensor was installed on a validated biomechanical system. Gap formation was measured during 50 cycles of flexion and extension with traction on the quadriceps (250 N). Subsequently, specimens underwent progressive loading in a fixed flexion position until failure occurred. The data were analyzed using nonparametric statistical tools with a significance level of 5%. The isolated frame group had a smaller gap formation (1.7 mm) than the Krackow group (3.4 mm; P = 0.01). No significant difference existed in the median failure end points of the two groups (676 and 530 N, respectively; P = 0.11). Patellar tendon repair using an isolated, transosseous, flexible, suture frame outperformed using the traditional Krakow repair technique in gap formation. Further studies are needed to determine if this will result in better functional outcomes or fewer clinical failures. Level IV, experimental case series.

Trunk control during repetitive sagittal movements following a real-time tracking task in people with chronic low back pain

Precision of trunk movement has commonly been examined by testing relocation accuracy rather than evaluating accuracy of tracking dynamic movement. In this study we used a 3-D motion capture system to provide a novel real-time tracking task to assess trunk motor control at varying movement speeds between people with and without chronic non-specific low back pain (LBP). Eleven asymptomatic volunteers and 15 participants with chronic non-specific LBP performed 12 continuous cycles of trunk flexion–extension following real time visual feedback, during which, trunk motion was measured using eight optoelectronic infrared cameras. Significant time differences between the feedback and actual trunk motion were found between groups (P = 0.001). Both groups had similar variability of tracking accuracy when following the feedback (P > 0.05). However, tracking variability at a slow speed correlated (P = 0.03; r = 0.55) with the Fear-Avoidance Beliefs Questionnaire (FABQ) scores in those with LBP. This study shows that both asymptomatic people and individuals with LBP displayed anticipatory behaviour, however, the response of those with LBP was consistently delayed in tracking the visual feedback compared to the asymptomatic group. Additionally, the extent of variability of tracking accuracy over repeated tracking cycles was associated with the degree of fear of movement in people with LBP.

Development of a new additive manufacturing platform for direct freeform 3D printing of intrinsically curved flexible membranes

The wearable technology market has been expanding from wearable medical devices for non-invasive continuous monitoring of patient vital signs to wearable devices for tracking fitness activities that any person can access. Regardless of their form or function, desirable characteristics of wearable devices are the ability to be flexible, conformal, and easily attachable to the human body. However, as the human body is intrinsically curved and irregular, flat devices often have poor interfacial adhesion with the human body. This often leads to interfacial delamination and eventual detachment of the device. Therefore, a new additive manufacturing (AM) platform, a direct freeform 3D printing process (DF3DP), is proposed to allow direct construction of intrinsically curved 3D surfaces during the material deposition phase without the need for any pre-shaped supporting molds or templates. This 3D freeform printing process involves a supporting matrix made up of calcium alginate microgels, printing material made from silicone ink, and freeform printing paths derived from customized G-codes that conform exactly to the scanned human surface profile. Curved meshes mimicking the human elbow were used as a demonstration. A static contact stability test showed that the printed 3D silicone mesh was highly conformal to the model elbow surface as compared to a 2D flat mesh. A dynamic contact stability test was also conducted by subjecting both meshes to 100 cycles of mechanical flexion and extension, proving that intrinsically curved surfaces can provide better contact stability for complex human body surfaces undergoing motion than can flat surfaces. These results have proven that intrinsically curved membranes or structures fabricated by DF3DP can reduce the interfacial shear stress and occurrence of cracks and delamination while maintaining structural integrity and stability during use without compromising the comfort of the users. Our approach can resolve interfacial issues in flexible substrates and has great potential for epidermal devices or soft robotics via its long-term sustainable performance.

Implied Evidence of the Functional Role of the Rectus Capitis Posterior Muscles.

Osteopathic physicians often target the rectus capitis posterior minor (RCPm) and rectus capitis posterior major (RCPM) muscles when using muscle energy or soft tissue cervical techniques to treat patients with head and neck pain. The RCPm and RCPM muscles are located deep within the posterior occipitoatlantal and atlantoaxial interspaces, respectively. To characterize the functional role of RCPm and RCPM muscles by comparing electromyographic (EMG) activation patterns of these muscles with EMG activation patterns of specific flexor and extensor muscles of the head and neck, the sternocleidomastoid (SCM), and the splenius capitis (SC) muscles, respectively. Asymptomatic participants were recruited from the Michigan State University College of Osteopathic Medicine student body. Disposable 25-gauge, bipolar fine-wire intramuscular electrodes were used to collect EMG data from the right and left RCPm and RCPM muscles. Surface electrodes were used to collect EMG data from the right and left SCM and SC muscles. Data were collected as participants performed 4 cycles of flexion and extension with an external 4-lb force applied to the back of the head and the forehead. In RCPM muscles, EMG activity was significantly greater (P<.003) during flexion and extension of the head and neck when an external force was applied to the back of the head. EMG activity in SCM muscles was significantly greater (P<.0001) during flexion and extension of the head and neck when an external force was applied to the forehead. The authors observed that EMG activity in SC muscles was significantly greater (P<.015) during flexion and extension of the head and neck when an external force was applied to the back of the head. No significant difference was found in EMG activity in RCPm muscles (P<.834) during flexion and extension of the head and neck, regardless of whether the external force was applied to the back of the head or the forehead. The EMG activation patterns of the RCPm muscles suggest that their functional role may be to stabilize the occipitoatlantal joint by helping maintain congruency of the joint surfaces. In contrast, the EMG activation patterns of the RCPM muscles suggest that their functional role may be to contribute to extension of the head, primarily at the occipitoatlantal and the atlantoaxial joints.

Concurrent validity of a wearable IMU for objective assessments of functional movement quality and control of the lumbar spine

Inertial measurement units (IMUs) are being recognized in clinical and rehabilitation settings for their ability to assess movement-related disorders of the spine for better guidance of treatment-planning and tracking of recovery. This study evaluated the Mbientlab MetaMotionR IMUs, relative to Vicon motion capture equipment in measuring local dynamic stability of the spine (quantified using maximum finite-time Lyapunov exponent; λmax), lumbopelvic coordination (quantified using mean absolute relative phase; MARP), and intersegmental motor variability (quantified using deviation phase; DP) of lumbopelvic segments in 10 participants during 35 cycles of repetitive spine flexion–extension (FE). Intraclass correlations were strong between systems when using both the FE angle time-series and the sum of squares (SS) time-series to measure local dynamic stability (0.807 ≤ICC2,1λmax,FE ≤ 0.919; 0.738 ≤ ICC2,1λmax,SS ≤ 0.868), sagittal-plane lumbopelvic coordination (0.961 ≤ICC2,1MARP ≤ 0.963), and sagittal-plane lumbopelvic variability (0.961 ≤ICC2,1DP ≤ 0.963). It was concluded that the MetaMotionR IMUs can be reliably used for measuring features associated with spine movement quality and motor control during a repetitive FE task. Future work will assess the reliability of sensor placement, performance during multi-directional movements, and ability to discern clinical and healthy populations based on assessment of movement quality and control.

Weight Bearing Activities change the Pivot Position after Total Knee Arthroplasty

The knee joint center of rotation is altered in the absence of the anterior cruciate ligament, which leads to substantially higher variance in kinematic patterns. To overcome this, total knee arthroplasty (TKA) designs with a high congruency in the lateral compartment have been proposed. The purpose of this study was to analyze the influence of a lateral pivot TKA-design on in-vivo knee joint kinematics. Tibiofemoral motion was retrospectively addressed in 10 patients during unloaded flexion-extension and loaded lunge using single plane fluoroscopy. During the unloaded flexion-extension movement, the lateral condyle remained almost stationary with little rollback at maximum flexion. The medial condyle exhibited anterior translation during the whole flexion cycle. During the loaded lunge movement, a higher degree of rollback compared to the unloaded activity was observed on the lateral condyle, whereas the medial condyle remained almost stationary. The results showed a clear lateral pivot during the unloaded activity, reflective of the implant’s geometric characteristics, and a change to a medial pivot and a higher lateral rollback during the weight-bearing conditions, revealing the impact of load and muscle force. It remains unclear if the kinematics with a lateral TKA design could be considered as physiological, due to the limited knowledge available on native knee joint kinematics.

Polymer optical fiber-embedded, 3D-printed instrumented support for microclimate and human-robot interaction forces assessment

This paper presents the fabrication, characterization and applications of a 3D-printed instrumented support for wearable devices. Intensity variation-based polymer optical fiber (POF) sensors were employed in the support instrumentation, in order to obtain a low-cost system. In the proposed instrumented support, two POFs are embedded in a 3D-printed acrylonitrile butadiene styrene (ABS) rigid structure for microclimate assessment (without the influence of the applied force). Additionally, other two POFs are embedded in a thermoplastic polyurethane (TPU) flexible structure for the force assessment, where one sensor measures the applied force in flexion cycles and the other in extension cycles. All four sensors are characterized with respect to temperature and humidity. Both force sensors are also characterized with respect to the force and their cross-sensitivities with respect to the temperature and humidity. The results show the feasibility of the proposed sensor system embedded in the 3D-printed support, where the errors for the force assessment are below 2.8 N, and for temperature and humidity the errors are about 1.1 °C and 2.5%, respectively. The feasibility of the proposed instrumented support in measuring force and microclimate variations was also verified in the application as a shank support for a lower limb exoskeleton for knee rehabilitation and on a passive orthosis for gait assistance.

Wearable Lumbar-Motion Monitoring Device with Stretchable Strain Sensors

Low-back pain is a common affliction. Epidemiological analyses have reported that periodic cycles of lumbar flexion and rotation are major risk factors for low-back pain. To prevent low-back pain, a lumbar-motion monitoring device could help diagnosticians assess patients’ risk for low-back pain. This study proposes such a device that uses lightweight stretchable strain sensors. Six of these strain sensors form a parallel-sensor mechanism that measures rotation angles of lumbar motion in three axes. The parallel-sensor mechanism calculates rotation angles from the lengths of the strain sensors iteratively. Experimental results reveal that the prototype device is effective for lumbar-motion measurement and significantly improves in terms of wearability over comparable devices.

Determination of a sagittal plane axis of rotation for a dynamic office chair

ObjectiveThis study investigated the location of the axis of rotation in sagittal plane movement of the spine in a free sitting condition to adjust the kinematics of a mobile seat for a dynamic chair. BackgroundDynamic office chairs are designed to avoid continuous isometric muscle activity, and to facilitate increased mobility of the back during sitting. However, these chairs incorporate increased upper body movement which could distract office workers from the performance of their tasks. A chair with an axis of rotation above the seat would facilitate a stable upper back during movements of the lower back. The selection of a natural kinematic pattern is of high importance in order to match the properties of the spine. MethodTwenty-one participants performed four cycles of flexion and extension of the spine during an upper arm hang on parallel bars. The location of the axis of rotation relative to the seat was estimated using infrared cameras and reflective skin markers. ResultsThe median axis of rotation across all participants was located 36 cm above the seat for the complete movement and 39 cm for both the flexion and extension phases, each with an interquartile range of 20 cm. ConclusionThere was no significant effect of the movement direction on the location of the axis of rotation and only a weak, non-significant correlation between body height and the location of the axis of rotation. Individual movement patterns explained the majority of the variance. ApplicationThe axis of rotation for a spinal flexion/extension movement is located above the seat. The recommended radius for a guide rail of a mobile seat is between 36 cm and 39 cm.

Design, characterisation and evaluation of a soft robotic sock device on healthy subjects for assisted ankle rehabilitation

Motor impairment is one of the common neurological conditions suffered by stroke patients, where this chronic immobility together with the absence of early limb mobilisation can lead to conditions such as joint contracture with spastic limbs. In this study, a soft robotic sock device was developed, which can provide compliant actuation to the ankle joint in the early stage of stroke recovery. The device is fitted with soft extension actuators and when the actuators are inflated, they extend and guide the foot into plantarflexion; upon deflation, the actuators will resume their initial conformations. Each actuator is linked to a pneumatic pump-valve control system that injects pressurised air into or release air from the system. In this study, the design and characterisation of the soft actuators will be presented, where the theoretical and experimental forces generated by the actuators were compared. The performance of the device was also evaluated on healthy subjects and the results had shown that the device was able to move the subjects’ ankles into cycles of dorsiflexion-plantarflexion, in the absence of voluntary muscle effort. The findings suggested that the soft wearable robotic device was capable of assisting the subjects in performing repeated cycles of ankle flexion.

Flexible High Performance Lithium Ion Battery Electrode Based on Free-Standing TiO2 Nanocrystals/Carbon Cloth Composite

Wearable and flexible electronics is an emerging and popular area of research. However, the availability of flexible energy storage to accompany these devices is lacking. Herein, a flexible electrode based on a composite of TiO2 nanocrystals and carbon cloth was synthesized by a simple drop-casting method followed a post-annealing treatment. The obtained TiO2/carbon cloth electrode shows a reversible capacity of 280-310 mAh g-1 at a current density of 100 mA g-1. The composite electrode also exhibits excellent mechanical stability even after 100 cycles of flexion. A proof-of-concept flexible pouch half-cell was assembled and it was able to power an LED bulb under flexion.