IMPORTANCE Some patients with lower leg amputations may be candidates for motorized prosthetic limbs. Optimal control of such devices requires accurate classification of the patient's ambulation mode (eg, on level ground or ascending stairs) and natural transitions between different ambulation modes.OBJECTIVE To determine the effect of including electromyographic (EMG) data and historical information from prior gait strides in a real-time control system for a powered prosthetic leg capable of level-ground walking, stair ascent and descent, ramp ascent and descent, and natural transitions between these ambulation modes. DESIGN, SETTING, AND PARTICIPANTS Blinded, randomized crossover clinical trial conducted between August 2012 and November 2013 in a research laboratory at the Rehabilitation Institute of Chicago. Participants were 7 patients with unilateral above-knee (n = 6) or knee-disarticulation (n = 1) amputations. All patients were capable of ambulation within their home and community using a passive prosthesis (ie, one that does not provide external power).INTERVENTIONS Electrodes were placed over 9 residual limb muscles and EMG signals were recorded as patients ambulated and completed 20 circuit trials involving level-ground walking, ramp ascent and descent, and stair ascent and descent. Data were acquired simultaneously from 13 mechanical sensors embedded on the prosthesis. Two real-time pattern recognition algorithms, using either (1) mechanical sensor data alone or (2) mechanical sensor data in combination with EMG data and historical information from earlier in the gait cycle, were evaluated. The order in which patients used each configuration was randomized (1:1 blocked randomization) and double-blinded so patients and experimenters did not know which control configuration was being used. MAIN OUTCOMES AND MEASURESThe main outcome of the study was classification error for each real-time control system. Classification error is defined as the percentage of steps incorrectly predicted by the control system. RESULTSIncluding EMG signals and historical information in the real-time control system resulted in significantly lower classification error (mean, 7.9% [95% CI, 6.1%-9.7%]) across a mean of 683 steps (range, 640-756 steps) compared with using mechanical sensor data only (mean, 14.1% [95% CI, 9.3%-18.9%]) across a mean of 692 steps (range, 631-775 steps), with a mean difference between groups of 6.2% (95% CI, 2.7%-9.7%] (P = .01). CONCLUSIONS AND RELEVANCEIn this study of 7 patients with lower limb amputations, inclusion of EMG signals and temporal gait information reduced classification error across ambulation modes and during transitions between ambulation modes. These preliminary findings, if confirmed, have the potential to improve the control of powered leg prostheses.

Abstract-Although physical limitations associated with transfemoral amputation (TFA) have been studied in laboratory settings, little is known about habitual activity within free-living environments. A retrospective analysis of 12 mo of step activity data was performed to quantify activity levels, variations, and patterns in 17 adults with unilateral TFA. Yearly, seasonal, and monthly average daily step counts and coefficients of variation (CoVs) were examined to characterize mobility. Analysis by Medicare Functional Classification Level (MFCL) was performed to explore relationships between clinical classification and performance. Subjects averaged 1,540 prosthetic steps/day, and activity generally increased with MFCL. Activity between MFCL-2 and -3 subjects was not significantly different, suggesting that ability to engage in habitual physical activity may be similar for these groups. Relative variation (CoV) was 0.65 across subjects but was lower for those with higher activity levels. No significant differences in CoV by group were detected. Marked seasonal and monthly patterns in activity were identified. Warmer seasons and months generally promoted higher activity, but peak temperatures and humidity depressed activity. Results suggest that persons with TFA are greatly limited in regards to activity. Further, large variations within and between subjects may challenge the interpretation of step activity gathered over short periods of time.

Patient satisfaction is an abstract and multidimensional concept that is recognized to be an important component of evidence-based health care. Although there have been increased attempts to develop and use standardized, patientreported outcome (PRO) measures for the evaluation of satisfaction with rehabilitation services, analogous efforts in orthotics and prosthetics (O&P) are less common. Measuring satisfaction in O&P may be challenging because patients' satisfaction is derived from their experiences with both the services and the devices provided. Similarly, patients' experiences with orthoses may differ from prostheses, because their motivations for use may be different. The purpose of this literature review is to identify and appraise PRO instruments that have been used to assess satisfaction with orthotic devices and services. A secondary purpose is to advocate for measures that are suitable for an O&P clinical environment. A systematic search of medical databases was conducted using a combination of the terms "satisfaction" and "orthotic" (and related synonyms, such as "orthosis" and "orthoses"). Publications were selected for review if they identified instruments that were administered with a clear and standardized protocol by an orthotist or a pedorthist to patients or participants with a diagnosis indicating orthotic intervention. The reviewed measures were classified as either formal (i.e., had an established history of psychometric development) or ad hoc (i.e., had not undergone formal psychometric testing of any kind). For each reviewed measure, the subdomains (i.e., determining factors of satisfaction) were identified through a review of the measure's items and the body of the associated publication(s). Fourteen publications met the selection criteria and were chosen for review. Publications dates ranged from 1989 to 2009, and studies included a variety of orthotic devices (e.g., ankle-foot orthoses, knee-ankle-foot orthoses, cranial helmets, spinal, etc.). Seven ad hoc and four formal PRO instruments were identified in the review. Formal measures included the Orthotics and Prosthetics Users' Survey (OPUS), the modified SERVQUAL instrument, the Quebec Users' Evaluation of Satisfaction with assistive Technology 2.0, and the Scoliosis Research Society 22/24 questionnaire. Seventeen subdomains of satisfaction were identified within the reviewed outcome measures. Eight subdomains pertained to device satisfaction (e.g., cosmesis or comfort), eight subdomains contributed to satisfaction with services (e.g., competence or communication), and one (i.e., overall satisfaction) was applicable to both device and service domains. The OPUS and SERVQUAL were identified as measures that may be well suited to the assessment of orthotic services (SERQUAL and OPUS) and devices (OPUS) in a clinical environment. Future research is recommended to focus on the use of standardized measures of satisfaction and dissemination of experiences with these instruments. (J Prosthet Orthot. 2011;23:95-105.)

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.

No abstract