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The Gravity Recovery and Climate Experiment (GRACE) satellite mission has provided global long-term observations of mass transport in the Earth system with applications in numerous geophysical fields. In this paper, we targeted the in-orbit performance of the GRACE key instruments, the ACCelerometers (ACC) and the MicroWave ranging Instrument (MWI). For the ACC data, we followed a transplant approach analyzing the residual accelerations from transplanted accelerations of one of the two satellites to the other. For the MWI data, we analyzed the post-fit residuals of the monthly GFZ GRACE RL06 solutions with a focus on stationarity. Based on the analyses for the two test years 2007 and 2014, we derived stochastic models for the two instruments and a combined ACC+MWI stochastic model. While all three ACC axes showed worse performance than their preflight specifications, in 2007, a better ACC performance than in 2014 was observed by a factor of 3.6 due to switched-off satellite thermal control. The GRACE MWI noise showed white noise behavior for frequencies above 10 mHz around the level of 1.5×10−6 m/Hz. In the combined ACC+MWI noise model, the ACC part dominated the frequencies below 10 mHz, while the MWI part dominated above 10 mHz. We applied the combined ACC+MWI stochastic models for 2007 and 2014 to the monthly GFZ GRACE RL06 processing. This improved the formal errors and resulted in a comparable noise level of the estimated gravity field parameters. Furthermore, the need for co-estimating empirical parameters was reduced.

Accurate monitoring of the Earth's gravity field is crucial for understanding mass redistribution processes related to climate change, hydrology, and geodynamics. The Gravity Recovery and Climate Experiment (GRACE) and its successor, GRACE Follow‐On (GRACE‐FO), have provided invaluable satellite gravimetry data through low‐low satellite‐to‐satellite tracking (LL‐SST). However, the precision of gravity field recovery is significantly affected not only by data gaps in the accelerometer (ACC) measurements, but also by potential failures or limitations in their performance. To mitigate these issues, accelerometer data transplantation has been employed, leveraging the similarity in non‐gravitational accelerations experienced by both satellites. This study presents an in‐depth assessment of transplant noise and evaluates advanced accelerometer configurations, including Cold Atom Interferometry (CAI) accelerometers and hybrid electrostatic‐quantum accelerometer setups for future satellite gravimetry missions. Through closed‐loop LL‐SST simulations, we compare four different accelerometer configurations, ranging from conventional electrostatic accelerometers (EAs) to fully hybrid CAI‐EA setups. Results indicate that a dual hybrid accelerometer configuration offers the highest accuracy in gravity field recovery, while a transplant‐based hybrid approach significantly enhances the performance of non‐gravitational force modeling without requiring additional instrumentation. The findings underscore the potential of quantum accelerometery and transplant methodologies for future satellite gravimetry missions, offering a cost‐effective solution to improve gravity field recovery, while benefitting from new sensor types. Key Points Hybrid and transplant‐based accelerometer configurations significantly improve Earth's gravity field recovery accuracy Quantum sensor integration (CAI) offers a promising, cost‐effective solution for future satellite gravimetry missions Advanced accelerometer configurations enable robust gravity field recovery under sensor degradation or data gaps

IntroductionMost lung transplant (LTX) recipients do not meet physical activity (PA) guidelines. Interventions are needed as long-term inactivity is related to morbidity and mortality. We investigated the effect of a telecoaching programme on objectively measured PA in LTX recipients.MethodsInactive patients (<7500 steps/day, n=90) were randomised into a light or intensive version of a 1-year PA telecoaching programme. The light intervention consisted of a step counter and a minimal version of the smartphone application. Patients randomised to the intensive intervention discussed PA barriers and goals, received a step counter, a patient-tailored smartphone application and supportive coaching calls. PA (primary outcome, assessed by an accelerometer), physical function, quality of life and symptoms were measured at baseline, after 3 months (primary endpoint) and 1 year. Mixed model analyses were used to investigate the effectiveness of the intervention compared with the light intervention.ResultsBetween-group difference in change after 3 months and 1 year was observed as mean (CI) 750 (−96 to 1596) (p=0.08) and 680 (−244 to 1605) steps per day (p=0.15), 10 (−0.5 to 20) and 10 (−1 to 22) min of total moving time (walking, taking stairs and cycling) (both p=0.07) and −3 (−6 to 0) (p=0.07) and −6 (−10 to −2) (p=0.002) of sedentary time, all in favour of the intervention group. Other outcomes did not differ between groups.ConclusionPA tends to improve in LTX recipients by following an intensive telecoaching programme compared with a light programme.Trial registration numberNCT04122768.

Due to sensor size and supporting circuitry, in-vivo load and deformation measurements are currently restricted to applications within larger orthopaedic implants. The objective of this study is to repurpose a commercially available low-power, miniature, wireless, telemetric, tire-pressure sensor (FXTH87) to measure load and deformation for future use in orthopaedic and biomedical applications. The capacitive transducer membrane was modified, and compressive deformation was applied to the transducer to determine the sensor signal value and the internal resistive force. The sensor package was embedded within a deformable enclosure to illustrate potential applications of the sensor for monitoring load. To reach the maximum output signal value, sensors required compressive deformation of 350 ± 24 µm. The output signal value of the sensor was an effective predictor of the applied load on a calibrated plastic strain member, over a range of 35 N. The FXTH87 sensor can effectively sense and transmit load-induced deformations. The sensor does not have a limit on loads it can measure, as long as deformation resulting from the applied load does not exceed 350 µm. The proposed device presents a sensitive and precise means to monitor deformation and load within small-scale, deformable enclosures.

Orthostatic hypotension is a cardinal feature of multiple-system atrophy. The upright posture provokes syncopal episodes that prevent patients from standing and walking for more than brief periods. We implanted a system to restore regulation of blood pressure and enable a patient with multiple-system atrophy to stand and walk after having lost these abilities because of orthostatic hypotension. This system involved epidural electrical stimulation delivered over the thoracic spinal cord with accelerometers that detected changes in body position. (Funded by the Defitech Foundation.) An implanted device (typically used to treat pain) that stimulates the thoracic spinal cord and sympathetic ganglia was coupled with accelerometers that detect changes in body position. With this device, a patient with multiple-system atrophy regained the ability to stand and walk without syncope (shown in a video).

Background and purpose Tremor is a frequent complaint of solid organ transplant recipients. We report on the largest population investigated with clinical neurophysiological methods. Our aim is to objectively establish the tremor prevalence and syndrome in the largest population of solid organ transplant recipients. Methods Tremor was measured in heart, kidney, liver, and lung recipients, using accelerometers during rest, postural, and weight‐loaded conditions. The 95th percentile of healthy kidney donors' tremor amplitude was used as the cutoff to determine the presence of tremor in transplant recipients. Tremor frequency, frequency variability, and effect of loading were used to investigate enhanced physiological tremor as the likely tremor syndrome. Impact on activities of daily life was assessed, and correlations with tacrolimus blood levels were investigated. Results Tremor was present in 52% of 246 transplant recipients, typically in postural positions. Mean tremor frequency was 6.1 (±2.0) Hz; mean tremor variability was 2.6 (±1.8) Hz. A frequency decrease upon loading was found in 83% of patients with tremor. Sixty‐five percent of patients met formal clinical neurophysiological criteria for enhanced physiological tremor. Tremor‐related impairment was present in 55% and correlated with tremor amplitude (ρ = 0.23, p ≤ 0.001). In a binominal regression analysis, tacrolimus blood levels were independently associated with tremor prevalence (p = 0.009). Conclusions More than half of solid organ transplant recipients experience a tremor that best fits the syndrome of enhanced physiological tremor. This is the first objective study on tremor that has established a better understanding of the neurophysiological mechanisms of tremor in a large population of solid organ transplant recipients.

Cardiovascular diseases are the leading cause of morbidity and mortality after kidney transplantation. Physical inactivity is an important factor for the development of cardiovascular disease (CVD) risk. To evaluate CVD risk and its association with accelerometer-based physical activity (PA) parameters in kidney transplant recipients (KTRs). This cross-sectional study included 43 KTRs. Number of steps, total energy expenditure, average sleep and lying times, average metabolic equivalent (MET), and PA duration were assessed with SenseWear Armband. CVD risk was predicted using a web-based interactive tool (HeartScore program). CVD risk was negatively correlated with number of steps, average MET and PA duration. Average MET and PA duration were significantly higher in KTRs with low CVD risk compared to KTRs with moderate CVD risk ( = 0.004 and = 0.007, respectively). Average MET, PA duration and number of steps were significantly higher in KTRs with low CVD risk compared to KTRs with high CVD risk ( < 0.001, < 0.001 and = 0.009, respectively). Number of steps was higher in KTRs with moderate CVD risk compared to KTRs with high CVD risk ( = 0.010). The linear regression analysis revealed that average MET was a predictor of CVD risk, accounting for 15.9% of the variance. CVD risk is associated with accelerometer-based PA parameters and average MET is a significant predictor of CVD risk after kidney transplantation in KTRs. Wearable technologies can be used to objectively measure PA parameters in order to determine CVD risk and to monitor the efficiency of PA interventions after kidney transplantation.

Implants and fixation in revision total knee arthroplasty (rTKA) are based on intramedullary referencing and mechanical axis (MA) restoration. Alternative alignment strategies to primary MA total knee arthroplasty (TKA) are increasing in popularity and often place implants in positions of joint line obliquity. The deviation in implant position could result in significant bony defects when being revised to MA-based revision reconstructions. The purpose of this study was to analyze the medial and lateral, as well as flexion and extension gaps, following a standardized workflow to revise a kinematically aligned total knee arthroplasty (KA TKA) to an MA rTKA. Seven cadaveric lower extremities that previously underwent caliper-verified KA TKA were converted to MA rTKA utilizing a series of sequential soft tissue releases followed by a tibial osteotomy set perpendicular to the tibial mechanical axis. Gap measurements following each step were recorded using a digital gap-balancing device. After conversion from KA TKA to MA rTKA, statistically significant increases were observed in the medial extension, medial flexion, lateral extension, and lateral flexion spaces of 1.6 mm (p=0.033), 3. 6mm (p<0.001), 5.6 mm (p<0.001) and 6.9 mm (p<0.001), respectively. Release of the posterior cruciate ligament (PCL) resulted in isolated flexion space opening by 2.4 mm (p=0.002) and 2.3 mm (p=0.022), respectively, for the medial and lateral flexion gaps. Soft tissue releases seen in rTKA have minimal effect on the medial laxity in extension. In specimens with only mild deviation from neutral alignment and joint line obliquity, the conversion from caliper-verified KA TKA to MA rTKA still resulted in large increases in the lateral-sided gaps, especially in the flexion space. This may create issues with current implant offerings, and surgeons should anticipate substantial augmentation or joint line adjustments when revising implants that were placed with intentional joint line obliquity.

Accurate detection of implant loosening is crucial for early intervention in total hip replacements, but current imaging methods lack sensitivity and specificity. Vibration methods, already successful in dentistry, represent a promising approach. In order to detect loosening of the total hip replacement, excitation and measurement should be performed intracorporeally to minimize the influence of soft tissue on damping of the signals. However, only implants with a single sensor intracorporeally integrated into the implant for detecting vibrations have been presented in the literature. Considering different mode shapes, the sensor’s position on the implant is assumed to influence the signals. In the work at hand, the influence of the position of the sensor on the recording of the vibrations on the implant was investigated. For this purpose, a simplified test setup was created with a titanium rod implanted in a cylinder of artificial cancellous bone. Mechanical stimulation via an exciter attached to the rod was recorded by three accelerometers at varying positions along the titanium rod. Three states of peri-implant loosening within the bone stock were simulated by extracting the bone material around the titanium rod, and different markers were analyzed to distinguish between these states of loosening. In addition, a modal analysis was performed using the finite element method to analyze the mode shapes. Distinct differences in the signals recorded by the acceleration sensors within defects highlight the influence of sensor position on mode detection and natural frequencies. Thus, using multiple sensors could be advantageous in accurately detecting all modes and determining the implant loosening state more precisely.

Total knee arthroplasty (TKA) is an effective treatment for severe osteoarthritis. Despite good survival rates, up to 20% of TKA patients remain dissatisfied. Recently, promising new technologies have been developed in knee arthroplasty, and could improve the functional outcomes. The aim of this paper was to present some new technologies in TKA, their current concepts, their advantages, and limitations. The patient-specific instrumentations can allow an improvement of implant positioning and limb alignment, but no difference is found for functional outcomes. The customized implants are conceived to reproduce the native knee anatomy and to reproduce its biomechanics. The sensors have to aim to give objective data on ligaments balancing during TKA. Few studies are published on the results at mid-term of these two devices currently. The accelerometers are smart tools developed to improve the TKA alignment. Their benefits remain yet controversial. The robotic-assisted systems allow an accurate and reproducible bone preparation due to a robotic interface, with a 3D surgical planning, based on preoperative 3D imaging or not. This promising system, nevertheless, has some limits. The new technologies in TKA are very attractive and have constantly evolved. Nevertheless, some limitations persist and could be improved by artificial intelligence and predictive modeling.