Bone-to-bone and implant-to-bone impingement : a novel graphical representation for hip replacement planning

Bone-to-bone impingement (BTBI) and implant-to-bone impingement (ITBI) risk assessment is generally performed intra-operatively by surgeons, which is entirely subjective and qualitative, and therefore, lead to sub-optimal results and recurrent dislocation in some cases. Therefore, a method was developed for identifying subject-specific BTBI and ITBI, and subsequently, visualising the impingement area on native bone anatomy to highlight where prominent bone should be resected. Activity definitions and subject-specific bone geometries, with planned implants were used as inputs for the method. The ITBI and BTBI boundary and area were automatically identified using ray intersection and region growing algorithm respectively to retain the same ‘conical clearance angle’ obtained to avoid prosthetic impingement (PI). The ITBI and BTBI area was then presented with different colours to highlight the risk of impingement, and importance of resection. A clinical study with five patients after 2 years of THA was performed to validate the method. The results supported the study hypothesis, in that the predicted highest risk area (red coloured zone) was completely/majorly resected during the surgery. Therefore, this method could potentially be used to examine the effect of different pre-operative plans and hip motions on BTBI, ITBI, and PI, and to guide bony resection during THA surgery

Early, but not late visual distractors affect movement synchronization to a temporal-spatial visual cue

The ease of synchronizing movements to a rhythmic cue is dependent on the modality of the cue presentation: timing accuracy is much higher when synchronizing with discrete auditory rhythms than an equivalent visual stimulus presented through flashes. However, timing accuracy is improved if the visual cue presents spatial as well as temporal information (e.g., a dot following an oscillatory trajectory). Similarly, when synchronizing with an auditory target metronome in the presence of a second visual distracting metronome, the distraction is stronger when the visual cue contains spatial-temporal information rather than temporal only. The present study investigates individuals' ability to synchronize movements to a temporal-spatial visual cue in the presence of same-modality temporal-spatial distractors. Moreover, we investigated how increasing the number of distractor stimuli impacted on maintaining synchrony with the target cue. Participants made oscillatory vertical arm movements in time with a vertically oscillating white target dot centered on a large projection screen. The target dot was surrounded by 2, 8, or 14 distractor dots, which had an identical trajectory to the target but at a phase lead or lag of 0, 100, or 200 ms. We found participants' timing performance was only affected in the phase-lead conditions and when there were large numbers of distractors present (8 and 14). This asymmetry suggests participants still rely on salient events in the stimulus trajectory to synchronize movements. Subsequently, distractions occurring in the window of attention surrounding those events have the maximum impact on timing performance

Timing and correction of stepping movements with a virtual reality avatar

Research into the ability to coordinate one’s movements with external cues has focussed on the use of simple rhythmic, auditory and visual stimuli, or interpersonal coordination with another person. Coordinating movements with a virtual avatar has not been explored, in the context of responses to temporal cues. To determine whether cueing of movements using a virtual avatar is effective, people’s ability to accurately coordinate with the stimuli needs to be investigated. Here we focus on temporal cues, as we know from timing studies that visual cues can be difficult to follow in the timing context. Real stepping movements were mapped onto an avatar using motion capture data. Healthy participants were then motion captured whilst stepping in time with the avatar’s movements, as viewed through a virtual reality headset. The timing of one of the avatar step cycles was accelerated or decelerated by 15% to create a temporal perturbation, for which participants would need to correct to, in order to remain in time. Step onset times of participants relative to the corresponding step-onsets of the avatar were used to measure the timing errors (asynchronies) between them. Participants completed either a visual-only condition, or auditory-visual with footstep sounds included, at two stepping tempo conditions (Fast: 400ms interval, Slow: 800ms interval). Participants’ asynchronies exhibited slow drift in the Visual-Only condition, but became stable in the Auditory-Visual condition. Moreover, we observed a clear corrective response to the phase perturbation in both the fast and slow tempo auditory-visual conditions. We conclude that an avatar’s movements can be used to influence a person’s own motion, but should include relevant auditory cues congruent with the movement to ensure a suitable level of entrainment is achieved. This approach has applications in physiotherapy, where virtual avatars present an opportunity to provide the guidance to assist patients in adhering to prescribed exercises

Shaft mount for data coupler system

A device for mounting a data transmission apparatus to a rotating, tapered, and instrumented shaft is provided. This device permits attachment without interfering with shaft rotation or the accuracy of data output, and prevents both radial and axial slippage of the data transmission apparatus. The mounting device consists of a sleeve assembly which is attached to the shaft by means of clamps that are situated at some distance removed from the instrumented area of the shaft. The data transmission device is secured to the sleeve such that the entire assembly rotates with the shaft. Shim adjustments between sleeve sections assure that a minimum compressive load is transferred to the instrumented area of the shaft and a rubber lining is affixed to a large portion of the interior surface of the sleeve to absorb vibration

Modelling single-person and multi-person event-based synchronisation

A linear phase correction model has been shown to accurately reflect the corrective processes involved in synchronising motor actions to an external rhythmic cue. The model originated from studies of finger tapping to an isochronous metronome beat and is based on the time series of asynchronies between the metronome and corresponding finger tap onsets, along with their associated intervals. Over recent years the model has evolved and been applied to more complex scenarios, including phase perturbed cues, tempo variations and, most recently, timing within groups. Here, we review the studies that have contributed to the development of the linear phase correction model and the associated findings related to human timing performance. The review provides a background to the studies examining single-person timing to simple metronome cues. We then further expand on the more complex analyses of motor timing to phase and tempo shifted cues. Finally, recent studies investigating inter-personal synchronisation between groups of two or more individuals are discussed, along with a brief overview on the implications of these studies for social interactions. We conclude with a discussion on future areas of research that will be important for understanding corrective timing processes between people

Moving in time: Bayesian causal inference explains movement coordination to auditory beats.

Many everyday skilled actions depend on moving in time with signals that are embedded in complex auditory streams (e.g. musical performance, dancing or simply holding a conversation). Such behaviour is apparently effortless; however, it is not known how humans combine auditory signals to support movement production and coordination. Here, we test how participants synchronize their movements when there are potentially conflicting auditory targets to guide their actions. Participants tapped their fingers in time with two simultaneously presented metronomes of equal tempo, but differing in phase and temporal regularity. Synchronization therefore depended on integrating the two timing cues into a single-event estimate or treating the cues as independent and thereby selecting one signal over the other. We show that a Bayesian inference process explains the situations in which participants choose to integrate or separate signals, and predicts motor timing errors. Simulations of this causal inference process demonstrate that this model provides a better description of the data than other plausible models. Our findings suggest that humans exploit a Bayesian inference process to control movement timing in situations where the origin of auditory signals needs to be resolved

Bright spots, physical activity investments that work : sweatcoin : a steps generated virtual currency for sustained physical activity behaviour change

Sweatcoin converts the step count recorded on smartphones into a virtual currency. Using this app, users generate financial rewards through physical activity, with higher levels of activity creating a higher ‘income’. Sweatcoins can subsequently be used to purchase commercially available products from an in-app marketplace

Physical activity behaviour change driven from engagement with an incentive-based app : evaluating the impact of Sweatcoin

Background Now the fourth leading cause of death, physical inactivity is a primary element of non-communicable diseases. Despite a great number of attempts, there is still a lack of effective approaches that can motivate sedentary populations to increase their levels of physical activity over a sustained period. Financial and non-financial incentives for exercise can provide an immediate reward for increasing activity levels, but due to limited funding to provide rewards, previous programmes using this approach have only shown short-term changes in behaviour. Sweatcoin, a UK-based technology company, has developed a digital platform that tracks and verifies physical movement to convert it into virtual currency. The currency can subsequently be exchanged for goods and services on their marketplace, providing a continuous incentive to be active. This study investigates the physical activity behaviour change observed in Sweatcoin users over a 6-month period of app usage. Objective To investigate the change in physical activity (measured using daily step-count) of Sweatcoin users following registration with the app, the longevity of the change and whether this change can be predicted through and driven by demographic and other lifestyle variables. Methods Activity data from a sample of 5,406 Sweatcoin users was used to analyse daily step count. Activity change was measured in terms of the percentage change in average daily step count for each month after registration, relative to that in the 3 months prior to the app being used. A subset of over 800 users completed a questionnaire capturing demographic and activity information. Change in activity behaviour following app download was calculated and users were grouped according to having no/negative, moderate or high activity change. Differences between groups in terms of activity and demographic status were investigated using regression analyses. Seasonal effects were also investigated and accounted for. Results Analyses show an overall average increase in daily step count of 19.5% over the 6-months following registration, in comparison to 3-months prior to registration (P<.001). Of the questionnaire respondents, 678 were valid responses. Of those, 34% were identified to have shown high levels of behaviour change following app registration. The logistic regression identified the key drivers of high activity behaviour change. There was an obvious impact of seasonality, with those registering the app in winter (OR, 6.89, p<.001) or spring (OR, 5.87, p=.002) were more likely to show high activity behaviour change than those registering in summer. More striking were the results identifying those classified as overweight (measured through body mass index (BMI); OR, 2.22, p=.014) and less active (based on self-report scale of physical activity; OR, 0.85, p=.037), being most likely to show high levels of physical activity change following registration with app. Conclusions The results highlight that an incentives-based app can induce significant sustainable physical activity behaviour change. Importantly, the results suggest that those typically lacking motivation to exercise (sedentary and high BMI) are most likely to be incentivised to increase their activity levels

Profiling commenters on mental health-related online forums : a methodological example focusing on eating disorder-related commenters

Background Understanding the characteristics of commenters on mental health-related online forums is vital for the development of effective psychological interventions in these communities. The way in which commenters interact can enhance our understanding of their characteristics. Objective Using eating disorder-related (EDR) forums as an example, this study details a methodology that aimed to determine subtypes of mental health-related forums, and profile their commenters based on the other forums to which they contributed. Methods The researchers identified all public EDR-forums (with ≥500 contributing commenters between March 2017 and February 2018) on a large online discussion platform (Reddit). A mixed-methods approach comprising network analysis with community-detection, text-mining and manual review identified subtypes of EDR-forums. For each subtype, another network analysis with community-detection was conducted using the EDR-forum commenter-overlap between 50 forums on which the commenters also commented. The topics of forums in each detected community were then manually reviewed to identify the shared interests of each subtype of EDR-forum commenters. Results Six subtypes of EDR-forums were identified, to which 14024 commenters had contributed. The results focus on two subtypes – pro-eating disorder, and thinspiration – and communities of commenters within both subtypes. Within the pro-eating disorder subtype, three communities of commenters were detected that related to the body and eating, mental health, and women, appearance and mixed topics. Regarding the thinspiration group, 78% of commenters had also commented on pornographic forums, and 17% had contributed to pro-eating disorder forums. Conclusions The article exemplifies a methodology that provides insight into subtypes of mental health-related forums, and the characteristics of their commenters. The findings have implications for future research, and online psychological interventions. With the publicly available data and code provided, researchers can easily reproduce the analyses, or utilise the methodology to investigate other mental health-related forums