Hip Joint Angles and Moments during Stair Ascent Using Neural Networks and Wearable Sensors

End-stage hip joint osteoarthritis treatment, known as total hip arthroplasty (THA), improves satisfaction, life quality, and activities of daily living (ADL) function. Postoperatively, evaluating how patients move (i.e., their kinematics/kinetics) during ADL often requires visits to clinics or specialized biomechanics laboratories. Prior work in our lab and others have leveraged wearables and machine learning approaches such as artificial neural networks (ANNs) to quantify hip angles/moments during simple ADL such as walking. Although level-ground ambulation is necessary for patient satisfaction and post-THA function, other tasks such as stair ascent may be more critical for improvement. This study utilized wearable sensors/ANNs to quantify sagittal/frontal plane angles and moments of the hip joint during stair ascent from 17 healthy subjects. Shin/thigh-mounted inertial measurement units and force insole data were inputted to an ANN (2 hidden layers, 10 total nodes). These results were compared to gold-standard optical motion capture and force-measuring insoles. The wearable-ANN approach performed well, achieving rRMSE = 17.7% and R2 = 0.77 (sagittal angle/moment: rRMSE = 17.7 ± 1.2%/14.1 ± 0.80%, R2 = 0.80 ± 0.02/0.77 ± 0.02; frontal angle/moment: rRMSE = 26.4 ± 1.4%/12.7 ± 1.1%, R2 = 0.59 ± 0.02/0.93 ± 0.01). While we only evaluated healthy subjects herein, this approach is simple and human-centered and could provide portable technology for quantifying patient hip biomechanics in future investigations

Is clinically measured knee range of motion after total knee arthroplasty ‘good enough?’: A feasibility study using wearable inertial measurement units to compare knee range of motion captured during physical therapy versus at home

Total knee arthroplasty is highly successful, in part due to range of motion (RoM) recovery. This is typically estimated goniometrically/visually by physical therapists (PTs) in the clinic, which is imprecise. Accordingly, a validated inertial measurement unit (IMU) method for capturing knee RoM was deployed assessing postoperative RoM both in and outside of the clinical setting. The study\u27s objectives were to evaluate the feasibility of continuously capturing knee RoM pre-/post-op via IMUs, dividing data into PT/non-PT portions of each day, and comparing PT/non-PT metrics. We hypothesized IMU-based clinical knee RoM would differ from IMU-based knee RoM captured outside clinical settings. 10 patients (3 M, 69 ± 13 years) completed informed consent documents following ethics board approval. A validated IMU method captured long duration (8–12 h/day, ~50 days) knee RoM pre-/post-op. Post-op metrics were subdivided (PT versus non-PT). Clinical RoM and patient reported outcome measures were also captured. Compliance and clinical disruption were evaluated. ANOVA compared post-op PT and non-PT means and change scores. Maximum flexion during PT was less than outside PT. PT stance/swing RoM and activity level were greater than outside PT. No temporal variable differences were found PT versus non-PT. IMU RoM measurements capture richer information than clinical measures. Maximum PT flexion was likely less than non-PT due to the exercises completed (i.e. high passive RoM vs. low RoM gait). PT gait flexion likely exceed non-PT because of ‘white coat effects’ wherein patients are closely monitored clinically. This implies data captured clinically represents optimum performance whereas data captured non-clinically represents realistic performance

Developing a method for quantifying hip joint angles and moments during walking using neural networks and wearables

Quantifying hip angles/moments during gait is critical for improving hip pathology diagnostic and treatment methods. Recent work has validated approaches combining wearables with artificial neural networks (ANNs) for cheaper, portable hip joint angle/moment computation. This study developed a Wearable-ANN approach for calculating hip joint angles/moments during walking in the sagittal/frontal planes with data from 17 healthy subjects, leveraging one shin-mounted inertial measurement unit (IMU) and a force-measuring insole for data capture. Compared to the benchmark approach, a two hidden layer ANN (n = 5 nodes per layer) achieved an average rRMSE = 15% and R2=0.85 across outputs, subjects and training rounds

Herb-Layer Dynamics in an Old-Growth Forest: Vegetation–Environment Relationships and Response to Invasion-Related Perturbations

Temperate forests of eastern North America are subject to multiple invasions from non-native species that have the potential to drive long-term dynamics in biodiversity. Garlic mustard (Alliaria petiolata (M. Bieb.) Cavara and Grande) is an invasive plant in many deciduous forests, and management efforts often focus on removing this species to initiate native species restoration. Agrilus planipennis Fairmaire (emerald ash borer; Coleoptera: Buprestidae) is a non-native insect pest that has caused substantial loss of ash trees (Fraxinus spp. L.) in North America. Our goal was to understand how the herbaceous layer in an old-growth forest responded to the removal of a significant invasion of A. petiolata and the loss of Fraxinus spp. due to A. planipennis. Herbaceous diversity and environmental parameters were measured in 32 permanent plots (1 m2 each) from 2012 to 2020 in an old-growth forest remnant that had experienced A. petiolata invasion and subsequent removal as well as mortality of Fraxinus spp. due to A. planipennis. Near-total loss of Fraxinus spp. as a canopy tree was not associated with changes in the understory light environment, possibly due to rapid canopy closure by adjacent trees not susceptible to the insect. Alliaria petiolata removal was associated with changes in herbaceous species richness and possibly shifts in individual species importance. Vegetation–environment relationships remained stable throughout the sampling period, suggesting that resource-related factors that structure the herb layer prevailed throughout the changes associated with Fraxinus spp. mortality and A. petiolata management. From a natural area management perspective, our data offer support for the idea that A. petiolata removal influences herb-layer diversity and indicate that in stands with a diverse tree community, the loss of Fraxinus spp. may not directly influence understory biodiversity

Using inertial measurement units to quantify shoulder elevation after reverse total shoulder arthroplasty: a pilot study comparing goniometric measures captured clinically to inertial measures captured ‘in-the-wild’

Background: Reverse total shoulder arthroplasty (rTSA) is utilized for a variety of indications, but most commonly for patients with rotator cuff arthropathy. This procedure reduces pain, improves satisfaction, and increases clinically measured range of motion (ROM). However, traditional clinical ROM measurements captured via goniometer may not accurately represent ‘real-world’ utilization of ROM. In contrast, inertial measurement units (IMUs) are useful for establishing ROM outside the clinical setting. We sought to measure ‘real-world’ ROM after rTSA using IMUs. Methods: A previously validated IMU-based method for continuously capturing shoulder elevation was used to assess 10 individuals receiving rTSA (1M, 82 ± 5 years) and compared to a previously captured 10 healthy individuals (4M, 69 ± 20 years) without shoulder dysfunction. Control subject data were previously collected over 1 week of continuous use. Patients undergoing rTSA donned sensors for 1 week pre-rTSA, 6 weeks at 3 months post-rTSA following clearance to perform active-independent ROM, and 1 week at 1 year and 2 years post-rTSA. Shoulder elevation was computed continuously each day. Daily continuous elevation was broken into 5° angle ‘bins’ (eg, 0-5°, 5-10°, etc.) and converted to percentage of the total day. IMU-based outcome measures were ROM binned percent (as described previously) and maximum/average elevation each week. Clinical goniometric ROM and patient-reported outcome measures were also captured. Results: No differences existed between patient and healthy control demographics. While patients showed improvement in American Shoulder and Elbow Surgeon (ASES) score, pain score, and goniometric ROM, IMU-based average and maximum elevation were equal between control subjects and patients both pre- and post-rTSA. The percent of time spent above 90° was equal between cohorts pre-rTSA, rose significantly at 3 months post-rTSA, and returned to preoperative levels thereafter. Discussion: Although pain, satisfaction, and ROM measured clinically may improve following rTSA, real-world utilization of improved ROM was not seen herein. Improvements during the acute rehabilitation phase may be transient, indicating longer or more specific rehabilitation protocols are necessary to see chronic improvements in post-rTSA movement patterns

A gyroscope-based system for intraoperative measurement of tibia coronal plane alignment in total knee arthroplasty

Coronal plane alignment in total knee arthroplasty (TKA) is an important predictor of clinical outcomes including patient satisfaction and device longevity. Radiography and computer assisted navigation are the two primary technologies currently available to surgeons for intraoperative assessment of alignment; however, neither is particularly well-suited for use in this increasingly high volume procedure. Herein we propose a novel gyroscope-based instrument for intraoperative validation of tibia coronal plane alignment, and provide initial analytical and experimental performance assessments. The gyroscope-based alignment estimate is derived from simplified joint geometry and verified experimentally using a custom tibial trial insert containing a consumer-grade inertial measurement unit (IMU). Average accuracy of the gyroscope-based tibia coronal angle estimate was found to be within ±1° in mechanical leg jig and cadaver testing. These results indicate that the proposed gyroscope-based method shows promise for low cost, accurate intraoperative validation of limb alignment in TKA patients. Integrating IMU technology into the TKA surgical workflow via low-cost instrumentation will enable surgeons to easily validate implant alignment in real time, thereby reducing cost, operating room time, and future revision burden

Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) User's Guide

The Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) software package is an open source, MATLABSimulink toolbox (plug in) that can be used by industry professionals and academics for the development of thermodynamic and controls simulations

Propulsion System Simulation Using the Toolbox for the Modeling and Analysis of Thermodynamic System T-MATS

A simulation toolbox has been developed for the creation of both steady-state and dynamic thermodynamic software models. This paper describes the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS), which combines generic thermodynamic and controls modeling libraries with a numerical iterative solver to create a framework for the development of thermodynamic system simulations, such as gas turbine engines. The objective of this paper is to present an overview of T-MATS, the theory used in the creation of the module sets, and a possible propulsion simulation architecture. A model comparison was conducted by matching steady-state performance results from a T-MATS developed gas turbine simulation to a well-documented steady-state simulation. Transient modeling capabilities are then demonstrated when the steady-state T-MATS model is updated to run dynamically

Effect of resonant magnetic perturbations on low collisionality discharges in MAST and a comparison with ASDEX Upgrade

Sustained ELM mitigation has been achieved on MAST and AUG using RMPs with a range of toroidal mode numbers over a wide region of low to medium collisionality discharges. The ELM energy loss and peak heat loads at the divertor targets have been reduced. The ELM mitigation phase is typically associated with a drop in plasma density and overall stored energy. In one particular scenario on MAST, by carefully adjusting the fuelling it has been possible to counteract the drop in density and to produce plasmas with mitigated ELMs, reduced peak divertor heat flux and with minimal degradation in pedestal height and confined energy. While the applied resonant magnetic perturbation field can be a good indicator for the onset of ELM mitigation on MAST and AUG there are some cases where this is not the case and which clearly emphasise the need to take into account the plasma response to the applied perturbations. The plasma response calculations show that the increase in ELM frequency is correlated with the size of the edge peeling-tearing like response of the plasma and the distortions of the plasma boundary in the X-point region.Comment: 31 pages, 28 figures. This is an author-created, un-copyedited version of an article submitted for publication in Nuclear Fusion. IoP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i

Effect of head size and rotation on taper corrosion in a hip simulator

Aims This study investigates head-neck taper corrosion with varying head size in a novel hip simulator instrumented to measure corrosion related electrical activity under torsional loads. Methods In all, six 28 mm and six 36 mm titanium stem-cobalt chrome head pairs with polyethylene sockets were tested in a novel instrumented hip simulator. Samples were tested using simulated gait data with incremental increasing loads to determine corrosion onset load and electrochemical activity. Half of each head size group were then cycled with simulated gait and the other half with gait compression only. Damage was measured by area and maximum linear wear depth. Results Overall, 36 mm heads had lower corrosion onset load (p = 0.009) and change in open circuit potential (OCP) during simulated gait with (p = 0.006) and without joint movement (p = 0.004). Discontinuing gait’s joint movement decreased corrosion currents (p = 0.042); however, wear testing showed no significant effect of joint movement on taper damage. In addition, 36 mm heads had greater corrosion area (p = 0.050), but no significant difference was found for maximum linear wear depth (p = 0.155). Conclusion Larger heads are more susceptible to taper corrosion; however, not due to frictional torque as hypothesized. An alternative hypothesis of taper flexural rigidity differential is proposed. Further studies are necessary to investigate the clinical significance and underlying mechanism of this finding