Laboratory- and community-based health outcomes in people with transtibial amputation using crossover and energy-storing prosthetic feet: A randomized crossover trial

<div><p>Contemporary prosthetic feet are generally optimized for either daily or high-level activities. Prosthesis users, therefore, often require multiple prostheses to participate in activities that span a range of mobility. Crossover feet (XF) are designed to increase the range of activities that can be performed with a single prosthesis. However, little evidence exists to guide clinical prescription of XF relative to traditional energy storing feet (ESF). The objective of this study was to assess the effects of XF and ESF on health outcomes in people with transtibial amputation. A randomized crossover study was conducted to assess changes in laboratory-based (endurance, perceived exertion, walking performance) and community-based (step activity and self-reported mobility, fatigue, balance confidence, activity restrictions, and satisfaction) outcomes. Twenty-seven participants were fit with XF and ESF prostheses with standardized sockets, interfaces, and suspensions. Participants were not blinded to the intervention, and wore each prosthesis for one month while their steps were counted with an activity monitor. After each accommodation period, participants returned for data collection. Endurance and perceived exertion were measured with the Six-Minute Walk Test and Borg-CR100, respectively. Walking performance was measured using an electronic walkway. Self-reported mobility, fatigue, balance confidence, activity restrictions, and satisfaction were measured with survey instruments. Participants also reported foot preferences upon conclusion of the study. Differences between feet were assessed with a crossover analysis. While using XF, users experienced improvements in most community-based outcomes, including mobility (<i>p</i> = .001), fatigue (<i>p</i> = .001), balance confidence (<i>p</i> = .005), activity restrictions (<i>p</i> = .002), and functional satisfaction (<i>p</i> < .001). Participants also exhibited longer sound side steps in XF compared to ESF (<i>p</i> < .001). Most participants (89%) reported an overall preference for XF; others (11%) reported no preference. Results indicate that XF may be a promising alternative to ESF for people with transtibial amputation who engage in a range of mobility activities.</p><p><b>Trial registration:</b> ClinicalTrials.gov <a href="https://clinicaltrials.gov/ct2/show/NCT02440711" target="_blank">NCT02440711</a></p></div

Activities along the mobility spectrum that ESF, RSF, and XF are estimated to span for most prosthetic limb users.

<p>The black sections of the arrows indicate that the foot is well-designed for these activites, the faded sections indicate that the foot design can be used for these activities, however, performance may be suboptimal.</p

CONSORT participant flow diagram.

<p>CONSORT participant flow diagram.</p

Results of clinical performance and self-report measures (n = 27).

<p>Results of clinical performance and self-report measures (n = 27).</p

Prostheses with an ESF (left) and an XF (right).

<p>Prostheses with an ESF (left) and an XF (right).</p

Participant demographics and characteristics (n = 27).

<p>Participant demographics and characteristics (n = 27).</p

Unrestricted migration favours virulent pathogens in experimental metapopulations: evolutionary genetics of a rapacious life history

Understanding pathogen infectivity and virulence requires combining insights from epidemiology, ecology, evolution and genetics. Although theoretical work in these fields has identified population structure as important for pathogen life-history evolution, experimental tests are scarce. Here, we explore the impact of population structure on life-history evolution in phage T4, a viral pathogen of Escherichia coli. The host–pathogen system is propagated as a metapopulation in which migration between subpopulations is either spatially restricted or unrestricted. Restricted migration favours pathogens with low infectivity and low virulence. Unrestricted migration favours pathogens that enter and exit their hosts quickly, although they are less productive owing to rapid extirpation of the host population. The rise of such ‘rapacious’ phage produces a ‘tragedy of the commons’, in which better competitors lower productivity. We have now identified a genetic basis for a rapacious life history. Mutations at a single locus (rI) cause increased virulence and are sufficient to account for a negative relationship between phage competitive ability and productivity. A higher frequency of rI mutants under unrestricted migration signifies the evolution of rapaciousness in this treatment. Conversely, spatially restricted migration favours a more ‘prudent’ pathogen strategy, in which the tragedy of the commons is averted. As our results illustrate, profound epidemiological and ecological consequences of life-history evolution in a pathogen can have a simple genetic cause