The tendency towards using inertial sensors for remote monitoring of the patients at home is increasing. One of the most important characteristics of the sensors is sampling rate. Higher sampling rate results in higher resolution of the sampled signal and lower amount of noise. However, higher sampling frequency comes with a cost. The main aim of our study was to determine the validity of measurements performed by low sampling frequency (12.5 Hz) accelerometers (SENS) in patients with knee osteoarthritis compared to standard sensor-based motion capture system (Xsens). We also determined the test-retest reliability of SENS accelerometers. Participants were patients with unilateral knee osteoarthritis. Gait analysis was performed simultaneously by using Xsens and SENS sensors during two repetitions of over-ground walking at a self-selected speed. Gait data from Xsens were used as an input for AnyBody musculoskeletal modeling software to measure the accelerations at the exact location of two defined virtual sensors in the model (VirtualSENS). After preprocessing, the signals from SENS and VirtualSENS were compared in different coordinate axes in time and frequency domains. ICC for SENS data from first and second trials were calculated to assess the repeatability of the measurements. We included 32 patients (18 females) with median age 70.1[48.1 – 85.4]. Mean height and weight of the patients were 173.2 ± 9.6 cm and 84.2 ± 14.7 kg respectively. The correlation between accelerations in time domain measured by SENS and VirtualSENS in different axes was r = 0.94 in y-axis (anteroposterior), r = 0.91 in x-axis (vertical), r = 0.83 in z-axis (mediolateral), and r = 0.89 for the magnitude vector. In frequency domain, the value and the power of fundamental frequencies (F. 0. ) of SENS and VirtualSENS signals demonstrated strong correlation (r = 0.98 and r = 0.99 respectively). The result of test-retest evaluation showed excellent repeatability for acceleration measurement by SENS sensors. ICC was between 0.89 to 0.94 for different coordinate axes. Low sampling frequency accelerometers can provide valid and reliable measurements especially for home monitoring of the patients, in which handling big data and sensors cost and battery lifetime are among important issues

Summary. Upper extremity activity was similar in patients and healthy subjects, showing no significant asymmetry between arms within subjects. Further improvements (e.g. thresholds, filters, inclinometer function) are needed to show the clinical value of AM for patients suffering shoulder complaints. Introduction. Activity monitoring is becoming a popular outcome tool especially in orthopaedics. The suitability of a single 3D acceleration-based activity monitor (AM) for patients with lower-extremity problems has been shown. However less is known about its feasibility to monitor upper-extremity activity. Insight into the amount and intensity of upper-extremity activity of the affected and non-affected arm (asymmetry) may be of added value for diagnostics, therapy choice and evaluating treatment effects. This study investigates the feasibility of a single AM to evaluate (asymmetry in) upper-extremity activity in daily life. Methods. Upper-extremity activity was measured in 12 patients with subacromial impingent syndrome (59±12yr) and 10 healthy subjects (29±11yrs). Subjects wore a single 3D accelerometer at both arms, just above the base of the Hueter triangle, for one day (min. 8 hours). Specific algorithms were used to derive quantity (activity duration, rest periods) and intensity (low-high) activity parameters (% of the day). The ratio in % activity between non-affected (dominant) and affected (non-dominant) arm was calculated. Asymmetry was expressed as the %-difference in activity between arms with regards to the non-affected (dominant) arm. Also popular PROMs were completed: DASH score (range 0–100;0=best) and SST score (range 0–12; 0=best). Independent t-test, Mann-Whitney U test, Pearson's r correlations were performed. Results. No significant differences in activity duration (Healthy: 50%, patients: 57% of the day) and intensity of upper-extremity activity were found between patients and healthy subjects, although PROMs were significantly worse in patients. Patients and healthy subjects use both arms in similar amounts of time per day. This corresponds to the ratio which almost equals 1 and the low asymmetry values (<10%) in both groups. Also the amount activity in low and high intensity was comparable between affected (non-dominant) and non-affected (dominant) arm. No correlations were found between AM data and PROMs. Discussion and Conclusion. Patients and healthy subjects move their upper arms approximately 53% of the day. No differences in amount and intensity of upper-extremity activity were found between healthy subjects and patients, neither between both arms. This suggests that subjects perform daily activities independent of pain, complaints or arm dominance. It could also hint at the algorithm operating with a too low activity threshold to include shuffling or misclassifying excitations from walking as intense arm movement. Both issues can be adjusted by adjusting thresholds and filter settings. The asymmetry in upper-extremity activity of healthy subjects (9.1%) assumes that a 10% asymmetry in arm activity seems natural, which coincides with similar values reported for functional shoulder tests (Koerver et al. CORS 2010). The lack of correlations between AM and PROMs suggests that both measure different outcome dimensions. The AM has some limitations which should be considered when improving the clinical feasibility of upper-extremity activity monitoring. The AM only allows to measure acceleration-related activities (speed, intensity), while upper-extremity activity often involves static force-related activities. However, the inclinometer capacity of accelerometers allows to measure upper-extremity activity at different elevations (upper arm above/below shoulder). This may add qualitative information, relevant for clinical purposes

Summary. A single 3D accelerometer is accurate in measuring upper-extremity activity durations, rest periods and intensities, suggesting its feasibility for daily life measurements with patients. Further enhancements are feasible to reduce residual false classifications of intensity from certain activities. Introduction. Physical activity is an important outcome measure in orthopaedics as it reflects how surgically restored functional capacity is used in daily life. Accelerometer-based activity monitors (AM) are objective, reliable and valid to determine lower extremity activity in orthopaedic patients. However the suitability of a single AM to monitor upper-extremity activity, in terms of quantity and intensity, has not been investigated. This study investigates the suitability and validity of a single AM to measure quantity and intensity of upper-extremity activity. Method. Five healthy young subjects (25 ± 3 yrs) were included. Subjects underwent a standardised protocol consisting of walking, combing hair, cleaning a desk while standing, brushing teeth and cleaning a window. All one-handed activities were performed with the right arm, as all subjects were right handed. The activities were performed in a fixed order, at self selected speed, for at least 30s. Between the activities, subjects stood still for 10s with their arms next to the body. A light-weight (18g) 3D-accelerometer (f=40Hz) was taped to the right elbow, just above the base of the Hueter triangle, using double sided tape. During the measurement, patients were recorded by a video camera analyzed by an independent human observer as validation reference. AM data and video-recordings were analyzed per second. The time being active (% of time) was determined over the whole measurement and for every activity separately, the percentage of the active time spend in high and low intensity was determined. Video-recording and AM-output were compared by determining Mean Percentage Error (MPE) and the accuracy (100-MPE). Results. High agreement in measuring upper-extremity (in-) activity was found between AM and video-recordings, showing an accuracy of 93%. Except for walking and combing hair, high agreement between AM and video-recordings was found in measuring activity intensity (accuracy range: 83–100%). 97% of walking was misclassified: video-recordings classify walking as low intensity, the AM as high intensity. Low agreement (58% agreement) for intensity was also found for combing hair. Discussion and Conclusion. A single AM is accurate in measuring the duration of upper-extremity activity and rest periods in healthy subjects under controlled circumstances. This suggests the suitability of AM to monitor real life upper-extremity activity, which can serve as objective clinical outcome in patients with shoulder complaints. Beyond durations, the AM seems also suitable for measuring activity intensity, showing high accuracy for most activities. The low accuracy in intensity classification of walking and combing hair can be explained by the different interpretations of intensity by observer and AM. For the observer, intensity classification may be force-related (feeling a resistance may refer to high intensity), while intensity classification is acceleration-related for the AM. The false classification of shoulder movement during walking as intense can be resolved by dedicated filters in the detection algorithms. Future algorithms will allow measurement of arm elevations (elbow below/above shoulder) which may be another relevant outcome parameter. However, already this basic AM application validated here may help e.g. in therapeutic decision making, in evaluating therapy effects or providing biofeedback

Physiotherapy is a critical element in successful conservative management of low back pain (LBP). The aim of this study was to develop and evaluate a system with wearable inertial sensors to objectively detect sitting postures and performance of unsupervised exercises containing movement in multiple planes (flexion, extension, rotation). A set of 8 inertial sensors were placed on 19 healthy adult subjects. Data was acquired as they performed 7 McKenzie low-back exercises and 3 sitting posture positions. This data was used to train two models (Random Forest (RF) and XGBoost (XGB)) using engineered time series features. In addition, a convolutional neural network (CNN) was trained directly on the time series data. A feature importance analysis was performed to identify sensor locations and channels that contributed most to the models. Finally, a subset of sensor locations and channels was included in a hyperparameter grid search to identify the optimal sensor configuration and the best performing algorithm(s) for exercise classification. Models were evaluated using F1-score in a 10-fold cross validation approach. The optimal hardware configuration was identified as a 3-sensor setup using lower back, left thigh, and right ankle sensors with acceleration, gyroscope, and magnetometer channels. The XBG model achieved the highest exercise (F1=0.94±0.03) and posture (F1=0.90±0.11) classification scores. The CNN achieved similar results with the same sensor locations, using only the accelerometer and gyroscope channels for exercise classification (F1=0.94±0.02) and the accelerometer channel alone for posture classification (F1=0.91±0.03). This study demonstrates the potential of a 3-sensor lower body wearable solution (e.g. smart pants) that can identify proper sitting postures and exercises in multiple planes, suitable for low back pain. This technology has the potential to improve the effectiveness of LBP rehabilitation by facilitating quantitative feedback, early problem diagnosis, and possible remote monitoring

Gait measurements can vary due to various intrinsic and extrinsic factors, and this variability becomes more pronounced using inertial sensors in a free-living environment. Therefore, identifying and quantifying the sources of variability is essential to ensure measurement reliability and maintain data quality. This study aimed to determine the variability of daily accelerations recorded by an inertial sensor in a group of healthy individuals. Ten participants, four males and six females, with a mean age of 50 years (range: 29–61) and BMI of 26.9 kg/m. 2. (range: 21.4–36.8), were included. A single accelerometer continuously recorded lower limb accelerations over two weeks. We extracted and analyzed the accelerations of three consecutive strides within walking bouts if the time difference between the bouts was more than two hours. Multivariate mixed-effects modeling was performed on both the discretized acceleration waveforms at 101 points (0–100) and the harmonics of the signals in the frequency domain to determine the variance components for different subjects, days, bouts, and steps as the random effect variables. Intraclass correlation coefficients (ICCs) were calculated for between-day, between-bout, and between-step comparisons. The results showed that the ICCs for the between-day, between-bout, and between-step comparisons were 0.73, 0.82, 0.99 for the vertical axis; 0.64, 0.75, 0.99 for the anteroposterior axis; and 0.55, 0.96, 0.97 for the mediolateral axis. For the signal harmonics, the respective ICCs were 0.98, 0.98, 0.99 for the vertical axis; 0.54, 0.93, 0.98 for the anteroposterior axis; and 0.69, 0.78, 0.95 for the mediolateral axis. Overall, this study demonstrated that accelerations recorded continuously for multiple days in a free-living environment exhibit high variability, mainly between days, and some variability arising from differences between walking bouts during different times within days. However, reliable and repeatable gait measurements can be obtained by identifying and quantifying the sources of variability

In this work, we propose a new quantitative way of evaluating acute compartment syndrome (ACS) by dynamic mechanical assessment of soft tissue changes. First, we have developed an animal model of ACS to replicate the physiological changes during the condition. Secondly, we have developed a mechanical assessment tool for quantitative pre-clinical assessment of ACS. Our hand-held indentation device provides an accurate method for investigations into the local dynamic mechanical properties of soft tissue and for in-situ non-invasive assessment and monitoring of ACS. Our compartment syndrome model was developed on the cranial tibial and the peroneus tertius muscles of a pig's leg (postmortem). The compartment syndrome pressure values were obtained by injecting blood from the bone through the muscle. To enable ACS assessment by a hand-held indentation device we combined three main components: a load cell, a linear actuator and a 3-axis accelerometer. Dynamic tests were performed at a frequency of 0.5 Hz and by applying an amplitude of 0.5 mm. Another method used to observe the differences in the mechanical properties inside the leg was a 3D Digital Image Correlation (3D-DIC). Videos were taken from two different positions of the pig's leg at different pressure values: 0 mmHg, 15 mmHg and 40 mmHg. Two strains along the x axis (Exx) and y axis (Eyy) were measured. Between the two pressure cases (15 mmHg and 40 mmHg) a clear deformation of the model is visible. In fact, the bigger the pressure, the more visible the increase in strain is. In our animal model, local muscle pressures reached values higher than 40 mmHg, which correlate with observed human physiology in ACS. In our presentation we will share our dynamic indentation results on this model to demonstrate the sensitivity of our measurement techniques. Compartment syndrome is recognised as needing improved clinical management tools. Our approach provides both a model that reflects physiological behaviour of ACS, and a method for in-situ non-invasive assessment and monitoring

Wearable inertial sensors can detect abnormal gait associated with knee or hip osteoarthritis (OA). However, few studies have compared sensor-derived gait parameters between patients with hip and knee OA or evaluated the efficacy of sensors suitable for remote monitoring in distinguishing between the two. Hence, our study seeks to examine the differences in accelerations captured by low-frequency wearable sensors in patients with knee and hip OA and classify their gait patterns. We included patients with unilateral hip and knee OA. Gait analysis was conducted using an accelerometer ipsilateral with the affected joint on the lateral distal thighs. Statistical parametric mapping (SPM) was used to compare acceleration signals. The k-Nearest Neighbor (k-NN) algorithm was trained on 80% of the signals' Fourier coefficients and validated on the remaining 20% using 10-fold cross-validation to classify the gait patterns into hip and knee OA. We included 42 hip OA patients (19 females, age 70 [63–78], BMI of 28.3 [24.8–30.9]) and 59 knee OA patients (31 females, age 68 [62–74], BMI of 29.7 [26.3–32.6]). The SPM results indicated that one cluster (12–20%) along the vertical axis had accelerations exceeding the critical threshold of 2.956 (p=0.024). For the anteroposterior axis, three clusters were observed exceeding the threshold of 3.031 at 5–19% (p = 0.0001), 39–54% (p=0.00005), and 88–96% (p = 0.01). Regarding the mediolateral axis, four clusters were identified exceeding the threshold of 2.875 at 0–9% (p = 0.02), 14–20% (p=0.04), 28–68% (p < 0.00001), and 84–100% (p = 0.004). The k-NN model achieved an AUC of 0.79, an accuracy of 80%, and a precision of 85%. In conclusion, the Fourier coefficients of the signals recorded by wearable sensors can effectively discriminate the gait patterns of knee and hip OA. In addition, the most remarkable differences in the time domain were observed along the mediolateral axis

Falls in adults are a major problem and can lead to injuries and death. In order to better understand falls and successful recoveries, identifying kinematics, kinetics, and muscle forces during recovery from loss of balance is crucial. To obtain reactive gait patterns, participants must be subjected to unexpected perturbations such as trips and slips. Previous researchers have reported kinetics recovery data following stumbling; however, the muscle force recovery patterns remain unknown. To better target exercises to reduce the risk of falls, we must first understand which muscles, their magnitude, and their coordination patterns, play a role in a successful recovery from a trip and a slip. Additionally, knowing the successful patterns of lower limb function can help with the diagnosis of faulty movements. A total of 20 healthy adults in their twenties with similar athletic backgrounds were perturbed on a split-belt treadmill using Computer-Assisted Rehabilitation Environment (Motkforce Link) at a preset speed of 1.1m/s. Two kinds of perturbations were administered: slip and trip. Slips were simulated by accelerating one belt, whereas trips were simulated by decelerating one belt. Both perturbations had similar intensity and only differed in the direction. Computational modeling was used to obtain lower-limb function during the compensatory step. SPM paired t-test was used to compare differences in recovery strategies between slip and trip through magnitude and patterns of joints. There were no significant differences in joint angles post tripping vs post-slipping. Results of net joint moments showed that compensating for the loss of balance due to tripping required a higher ankle plantarflexion moment than slipping (at 22-52%; 1.2± 0.3vs0.4±0.2, p<0.001). Additionally, larger gluteus maximus (at 40-50%;8.7±3.8vs2.7±1.1N/kg, p=0.001), gluteus medius (at23~33%; 22.6±5.7vs6.8±3.6N/kg, p<0.001) were generated than post-slipping, respectively. These findings suggested that greater GMAX and GMED forces are required post-trip recovery than slip. Future analysis of trip recovery showed the importance of ankle joint in recovering from forward and backward fall. These results can be used as references in remote diagnosis of joint and muscle weakness and assessment of the risk of falls with the use of accelerometers

Abstract. Objectives. The aim of this study was to investigate whether mechanical loading induced by physical activity can reduce risk of sarcopenia in middle-aged adults. Methods. This was a longitudinal study based on a subset of UK Biobank data consisting of 1,918 participants (902 men and 1,016 women, mean age 56 years) who had no sarcopenia at baseline (assessed between 2006 and 2010). The participants were assessed again after 6 years at follow-up, and were categorized into no sarcopenia, probable sarcopenia, or sarcopenia according to the definition and algorithm developed in 2018 by European Working Group on Sarcopenia in Older People (EWGSOP). Physical activity was assessed at a time between baseline and follow-up using 7-day acceleration data obtained from wrist worn accelerometers. Raw acceleration data were then analysed to study the mechanical loading of physical activity at different intensities (i.e. very light, light, moderate-to-vigorous). Multinominal logistic regression was employed to examine the association between the incidence of sarcopenia and physical activity loading, between baseline and follow up, controlled for other factors at baseline including age, gender, BMI, smoking status, intake of alcohol, vitamin D and calcium, history of rheumatoid arthritis, osteoarthritis, secondary osteoporosis, and type 2 diabetes. Results. Among the 1918 participants with no sarcopenia at baseline, 230 (69 men and 161 women) developed probable sarcopenia and 37 (14 men and 23 women) developed sarcopenia at follow-up. Physical activity loading at moderate-to-vigorous intensity was higher in men (p<0.05), while women had higher physical activity loading at very light intensity (p<0.05). No significant difference was found in physical activity loading at light intensity between men and women (p>0.05). Logistic regression models showed that increase in physical activity loading at moderate-to-vigorous intensity significantly reduced the risk of sarcopenia (odds ratio = 0.368, p<0.05), but not probable sarcopenia (odds ratio = 0.974, p>0.05), while loading at light or very light activity intensity were not associated with the risk of sarcopenia or probable sarcopenia (p>0.05). Conclusion. Loading of physical activity at moderate-to-vigorous intensity could reduce risk of sarcopenia in middle-aged adults. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. Aseptic loosening of the acetabular cup in total hip replacement (THR) remains a major problem. Current diagnostic imaging techniques are ineffective at detecting early loosening, especially for the acetabular component. The aim of this preliminary study was to assess the viability of using a vibration analysis technique to accurately detect acetabular component loosening. Methods. A simplified acetabular model was constructed using a Sawbones foam block into which an acetabular cup was fitted. Different levels of loosening were simulated by the interposition of thin layer of silicon between the acetabular component and the Sawbones block. This included a simulation of a secure (stable) fixation and various combinations of cup zone loosening. A constant amplitude sinusoidal excitation with a sweep range of 100–1500 Hz was used. Output vibration from the model was measured using an accelerometer and an ultrasound probe. Loosening was determined from output signal features such as the number and relative strength of the observed harmonic frequencies. Results. Both measurement methods were capable of measuring the output vibration. Preliminary findings show different patterns in the output signal spectra were visible when comparing the stable cup with the 1mm of simulated spherical loosening at driving frequencies 1050 Hz, 1100 Hz and 1150 Hz (p < 0.05) using the accelerometer, whereas for ultrasound at frequencies 950 Hz and 1350 Hz (p < 0.05). Conclusions. Experimental testing showed that vibration analysis could be used as a potential detection method for acetabular cup component loosening using either an accelerometer or ultrasound probe to detect the vibration. However, the capacity of ultrasound to overcome the attenuating effect of the surrounding soft tissues and its high signal to noise ratio suggest it has the best potential for clinical use

Capturing objective data of the postoperative changes in the mobility of patients is expected to generate a better understanding of the effect of postoperative treatment. Until recently, the collection of gait-related data was limited to controlled clinical environments. The emergence of accurate wearable accelerometers with sufficient runtime, however, enables the long-term measurement and extraction of mobility parameters, such as “real-world walking speed”. An interim analysis of 1967 hours of actibelt data (3D accelerometer, 100 Hz) from 5 patients (planned total 20) with a femur fracture and 5 patients (planned total 20) with a humerus fracture from a geriatric population at two different sites of the university hospital of the Ludwigs-Maximilian-University in Munich was performed. Mobility data was captured during several days of stationary treatment starting directly after surgery and during a short follow-up visit six weeks after the surgery. Preliminary results show an increase of the mean walking speed between the two visits independent of the type of fracture. Patients with a humerus fracture tended to walk faster than patients with a femur fracture during both visits. The data also reveals an unexpected low level of mobility during the stationary stay. Mobile accelerometry can be used to evaluate different postoperative mobilisation strategies and even provide near-time feedback in geriatric trauma patients

The Pivot-shift phenomenon (PS) is known to be one of the essential signs of functional insufficiency of the anterior cruciate ligament (ACL). To evaluate the dynamic knee laxity is very important to accurately diagnose ACL injury, to assess surgical reconstructive techniques, and to evaluate treatment approaches. However, the pivot-shift test remains a subjective clinical examination difficult to quantify. The aim of the present study is to validate the use of an innovative non-invasive device based on the use of an inertial sensor to quantify PS test. The validation was based on comparison with data acquired by a surgical navigation system. The surgeon intraoperatively performed the PS tests on 15 patients just before fixing the graft required for the ACL reconstruction. A single accelerometer and a navigation system simultaneously acquired the joint kinematics. An additional optical tracker set to the accelerometer has allowed to quantify the movement of the sensor. The tibial anteroposterior acceleration obtained with the navigation system was compared with the acceleration acquired by the accelerometer. It is therefore estimated the presence of any artifacts due to the soft tissue as the test-retest repositioning error in the positioning of the sensor. It was also examined, the repeatability of the acceleration parameters necessary for the diagnosis of a possible ACL lesion and the waveform of the output signal obtained during the test. Finally it has been evaluated the correlation between the two acceleration measurements obtained by the two sensors. The RMS (root mean square) of the error of test-retest positioning has reported a good value of 5.5 ± 2.9 mm. While the amounts related to the presence of soft tissue artifacts was equal to 4.9 ± 2.6 mm. It was also given a good intra-tester repeatability (Cronbach's alpha = 0.86). The inter-patient similarity analysis showed a high correlation in the acceleration waveform of 0.88 ± 0.14. Finally the measurements obtained between the two systems showed a good correlation (rs = 0.72, p<0.05). This study showed good reliability of the proposed scheme and a good correlation with the results of the navigation system. The proposed device is therefore to be considered a valid method for evaluating dynamic joint laxity

Mobility plays an important role, in particular for patients with osteoporosis and after trauma surgery, both as an outcome and as treatment. Mobility is closely linked to the patient”s quality of life and exercise is a powerful additional treatment option. In order to be able to generate an evidence base to evaluate various surgical and non-surgical treatment options, objective measurements of patient mobility and exercise over a certain time period are needed. Wearables are a promising candidate, with obvious advantages compared to questionnaires and/or PROs. However, when extracting parameters with wearables, one often faces the problem of algorithms not performing well enough for special cases like slow gait speeds or impaired gait, as they typically appear in this patient group. We plan to further extend the applicability of the actibelt system (3D accelerometer, 100Hz), in particular to improve the measurement precision of real-world walking speed in slow and impaired walking. We are using a special measurement wheel including a rotating 3D accelerometer that allows to capture high quality real-world walking speed and distance measurements, and a mobile high resolution camera system. In a first block 20 patients with osteoporosis were included in the study at the Ludwigs-Maximilians-University”s Department of General, Trauma and Reconstructive Surgery in Munich, Germany and equipped with an actibelt. Patients were asked to walk as “normal” as possible, while wearing their usual apparel, in the building and outside the building. They climbed stairs and had to deal with all unexpected “stop and go” events that appear in real-world walking. Various gait parameters will be extracted from the recorded data and compared to the gold standard. We will then tune the existing algorithms as well as new algorithms (e.g. step detection based on continuous wavelet transformation) to explore potential improvements of both step detection and speed estimation algorithms. Further refinement and validation using real world data is warranted

Objectives. Temperature is known to influence muscle physiology, with the velocity of shortening, relaxation and propagation all increasing with temperature. Scant data are available, however, regarding thermal influences on energy required to induce muscle damage. Methods. Gastrocnemius and soleus muscles were harvested from 36 male rat limbs and exposed to increasing impact energy in a mechanical test rig. Muscle temperature was varied in 5°C increments, from 17°C to 42°C (to encompass the in vivo range). The energy causing non-recoverable deformation was recorded for each temperature. A measure of tissue elasticity was determined via accelerometer data, smoothed by low-pass fifth order Butterworth filter (10 kHz). Data were analysed using one-way analysis of variance (ANOVA) and significance was accepted at p = 0.05. Results. The energy required to induce muscle failure was significantly lower at muscle temperatures of 17°C to 32°C compared with muscle at core temperature, i.e., 37°C (p < 0.01). During low-energy impacts there were no differences in muscle elasticity between cold and warm muscles (p = 0.18). Differences in elasticity were, however, seen at higher impact energies (p < 0.02). Conclusion. Our findings are of particular clinical relevance, as when muscle temperature drops below 32°C, less energy is required to cause muscle tears. Muscle temperatures of 32°C are reported in ambient conditions, suggesting that it would be beneficial, particularly in colder environments, to ensure that peripheral muscle temperature is raised close to core levels prior to high-velocity exercise. Thus, this work stresses the importance of not only ensuring that the muscle groups are well stretched, but also that all muscle groups are warmed to core temperature in pre-exercise routines. Cite this article: Professor A. H. R. W. Simpson. Increased risk of muscle tears below physiological temperature ranges. Bone Joint Res 2016;5:61–65. doi: 10.1302/2046-3758.52.2000484

Introduction. Limited physical activity (PA) is one indication for orthopaedic intervention and restoration of PA a treatment goal. However, the objective assessment of PA is not routinely performed and in particular the effect of spinal pathology on PA is hardly known. It is the purpose of this study using wearable accelerometers to measure if, by how much and in what manner spinal stenosis affects PA compared to age-matched healthy controls. Patients & Methods. Nine patients (m/f= 5/4, avg. age: 67.4 ±7.7 years, avg. BMI: 29.2 ±3.5) diagnosed with spinal stenosis but without decompressive surgery or other musculoskeletal complaints were measured. These patients were compared to 28 age-matched healthy controls (m/f= 17/11, avg. age: 67.4 ±7.6 years, avg. BMI: 25.3±2.9). PA was measured using a wearable accelerometer (GCDC X8M-3) worn during waking hours on the lateral side of the right leg for 4 consecutive days. Data was analyzed using previously validated activity classification algorithms in MATLAB to identify the type, duration and event counts of postures or PA like standing, sitting, walking or cycling. In addition, VAS pain and OSWESTRY scores were taken. Groups were compared using the t-test or Mann-Whitney U-test where applicable. Correlations between PA and clinical scores were tested using Pearson”s r. Results. Spinal stenosis patients showed much lower PA than healthy controls regarding all parameters like e.g. daily step count (2946 vs 8039, −63%, p<0.01) or the relative daily time-on-feet (%) (8.6% vs 28.3%, −70%, p<0.01) which is matched with increased sitting durations (80.3% vs 58.8%, p<0.01). Also qualitative parameters such as walking cadence was reduced in stenosis patients (83.7 vs 97.8 steps/min). With stenosis no patient ever walked >1000 steps without interruption. Also the number of walking bouts between 250–1000 steps was 4.5 times lower than in healthy controls (p<0.01). When the relative distribution of walking bout length was calculated, it became visible that stenosis patients showed more short walking bouts of 10–50 steps (p<0.05). There were no strong and significant correlations between the clinical scores and PA parameters. Discussion & Conclusions. Spinal stenosis greatly reduced physical activity to levels below WHO guidelines (e.g. <5000 steps= sedentary lifestyle) where the risk for general health (overall mortality), cardiovascular or endocrinological health is significantly increased. Activity levels are lower than reported for end-stage hip or knee osteoarthritis. Therefore, spinal stenosis patients should not only receive pain medication, but be made aware of their limited PA and its detrimental health effects, participate in activation programs, or be considered for surgical intervention. The absence of long walking bouts and the relatively more frequent short walking bouts seem indicative of intermittent claudication as typical in spinal stenosis

The relevance of physical activity (PA) for general health and the value of assessing PA in the free-living environment especially for assessing orthopaedic conditions and outcome are discussed. Available methods for assessing PA such as self-reports, trackers, phone apps and clinical grade monitors are introduced. An overview of devices such as accelerometers for research quality assessments is given and aspects for choosing them such as wear location, usability or study population are reviewed. Basic principles to derive mobility parameters from the PA related sensor signals are presented. The symposium explains mobility parameters, their types, definitions, validity, analysis and those with particular relevance to assess orthopaedic conditions. The application of activity monitors is orthopaedic patient studies is demonstrated in various examples such as knee and hop osteoarthritis and total joint arthroplasty, in frail elderly subjects at fall risk or patients with shoulder pathologies

Lower limb fractures are commonly treated with cast immobilization, and as a main consequence of strict immobilization this typically leads to loss in muscle mass, decrease of bone density and decline in functional abilities. Body-worn sensors are increasingly used to assess outcome in clinical trials by providing objective mobility parameters in a real-world environment. The aim of this study is to investigate the usability aspects and potential changes in mobility parameters in partial-immobilization patients in real-world conditions. Six healthy young males (age 22.2 ± 1.2 years; weight 76.5 ± 6.7 kg, height 185.8 ± 6.1 cm. Mean ± standard deviation) wore a leg cylinder cast with walker boot to immobilize their dominant leg for two consecutive weeks. Subjects were asked to continuously wear a tri-axial accelerometer on the waist (actibelt) during waking hours for 6 weeks including 2 weeks before, during and after cast immobilisation. The total amount of days of continuous recording was 339 days with a total wearing time of 120 days. Software packages which allow to detect steps and to estimate real-world walking speed were used to analyse the accelerometry data. It was suspected that knee immobilization would affect strongly the wave form of the signal with an impact on the accuracy of the speed algorithm, whereas the step detection should be more robust. This effect was confirmed in a preliminary study performed to quantify the accuracy under immobilization conditions. On the other hand, step numbers are known to be sensitive to fluctuations in wearing time which was not uniform throughout the entire study. We concluded that in this setting step frequency is the most reliable parameter. Step frequency showed a systematic decrease in the values during the immobilization period which recovered to pre-immobilisation values after cast removal. This confirms the usability of accelerometry and sensitivity of its mobility parameters for clinical outcome assessment

Introduction. Knee osteoarthritis (KOA) causes impairment through pain, stiffness and malalignment and knee joint replacement (KJR) may be necessary to alleviate such symptoms. There is disagreement whether patients with KJR increases their level of physical activity after surgery. The aim of this study is to investigate whether patients with KJR have a higher level of physical activity than patients with KOA, as measured by accelerometer-based method. Furthermore, to investigate whether patients achieve the same level of activity as healthy subjects five years post TJR. Material and method. 54 patients with KOA (29 women, mean age 62±8.6, mean BMI 27±5), 53 patients who had KJR five years earlier (26 women, mean age 66±7.2, mean BMI 30±5) and 171 healthy subjects (76 women, mean age 64±9.7, mean BMI 26±5) were included in this cross sectional study. The level of physical activity was measured over a mean of 5.5 days with a tri-axial accelerometer mounted on the thigh. Number of daily short walking bouts of. Results. Patients with KJR had 10.1 fewer short walking bouts (p=0.04), 745 fewer steps (p=0.19) and 6.2 fewer transfers (p=0.09) per day than patients with KOA. In addition, patients with KJR performed 21.7 fewer short walking bouts (p=0.001), 281 fewer steps (p=0.60) and 3.2 fewer transfers (p=0.32) per day than healthy subjects. Conclusion. Patients with KJR do not seem to be more physically active than patients with KOA. Neither do the seem to be as active as healthy subjects, However, the results may suffer from selection bias and thus the results ought to be confirmed in a bigger cohort study

Background. Shoulder pain limits range of motion (ROM) and reduces performing activities of daily living (ADL). Objective assessment of shoulder function could be of interest for diagnosing shoulder pathology or functional assessment of the shoulder after therapy. The feasibility of 2 wearable inertial sensors for functional assessment to differentiate between healthy subjects and patients with unilateral shoulder pathology is investigated using parameters as asymmetry. Methods. 75 subjects were recruited into this study and were measured for at least 8 h a day with the human activity monitor (HAM) sensor. In addition, patients completed the Disability of the Arm, Should and Hand (DASH) score and the Simple Shoulder Test (SST) score. From 39 patients with a variety of shoulder pathologies 24 (Age: 53.3 ± 10.5;% male: 62.5%) complete datasets were successfully collected. From the 36 age-matched healthy controls 28 (Age: 54.9 ± 5.8;% male = 57.1%) full datasets could be retrieved. Activity parameters were obtained using a self-developed algorithm (Matlab). Outcome parameters were gyroscope and accelerometry-based relative and absolute asymmetry scores (affected/unaffected; dominant/non-dominant) of movement intensity. Results & Discussion. The absolute and relative asymmetry scores of the accelerometry-based intensity results for a threshold of > 0.1 g (AUC 0.821 and AUC 0.827) proved to be slightly more distinctive to the gyroscope-based intensity results for a threshold of > 10 deg/s (AUC 0.807 and 0.795) to distinguish between the healthy group and the shoulder group. Asymmetry (< 1%) was nearly absent in healthy controls (5/56 subjects) using the accelerometry-based intensity (> 0.1g) results but common in patients (29/48 subjects). A moderate, significant correlation was found between the asymmetry scores and the DASH score, thus complementary use is advised. The asymmetry scores had no correlation to the SST score. Conclusion. Ambulant assessment of shoulder activity using human activity monitors, containing a gyroscope and accelerometer, during ADL is feasible. The accelerometry-based and gyroscope-based absolute and relative asymmetry scores are promising parameters to diagnose or assess function of the shoulder. A moderate correlation was found between the DASH score and the activity monitor parameters, suggesting both could be used complementary to assess function

The significance of physical activity (PA) assessment is widely acknowledged as it can aid in the understanding of pathologies. PA of knee osteoarthritis (KOA) patients has been assessed with varying methods, as it is a disease that is known to impair physical function and activity during daily life. Differences between methods have been described for general outcomes (sport participation or sedentary time), yet failed to describe common activities such as stair locomotion or sit-to-stand (STS) transfers. This study therefore aimed to determine the comparability of various methods to assess daily-life activities in KOA patients. Sixty-one clinically diagnosed KOA patients wore a tri-axial accelerometer (AX3, Axivity, UK) for one week during waking hours. Furthermore, they performed three physical function tests: a 40-m fast-paced walk test (WT), a timed up-and-go test (TUGT) and a 15 stair-climb test (SCT). Patients were also asked to fill out the Knee Osteoarthritis Outcome Score (KOOS), a KOA-specific questionnaire. Patients were slightly overweight (average BMI: 27.3±4.8 kg/m2), 60 (±10) years old and predominantly female (53%). The amount of daily level walking bouts was only weakly correlated with the WT performance, representing patients” walking capacity, (ρ=−0.33, p=0.01). Similarly, level-walking bouts during daily life correlated weakly with self-perceived walking capacity addressed by the KOOS (ρ=−0.36, p=0.01). For stair locomotion, a slightly different trend was seen. A moderate correlation was found (ρ=0.65, p<0.001), between the amount of ascending bouts and the objective functional test performance (SCT). However, the subjective assessment of stair ascending limitations (via the KOOS) correlated only weakly with both the functional test performance and the measured level of activity (ρ=−0.30 and −0.35, resp.). Comparable results were found for descending motions. STS transfers during daily life correlated moderately at best with the time to complete the TUGT (ρ=−0.43, p<0.01) and only weakly with the self-perceived effort of STS transfers (ρ=−0.26, p=0.04). Only weak correlations existed between subjective measures and objective parameters (for both functional tests and daily living activities), indicating that they assess different domains (e.g. self-perceived function vs. actual physical function). Furthermore, when comparing the two objective measures, correlation coefficients increased compared to the subjective methods, yet did not reach strong agreement. These findings suggest that addressing common activities of daily life either subjectively or objectively will result in different patient-related outcomes of a study. Assessment methods should therefore be chosen with caution and compared carefully with other studies