Current energy storage and return prosthetic feet only marginally reduce the cost of amputee locomotion compared with basic solid ankle cushioned heel feet, possibly due to their lack of push-off at the end of stance. To the best of our knowledge, a prosthetic ankle that utilizes a hydraulic variable displacement actuator (VDA) to improve push-off performance has not previously been proposed. Therefore, here we report a design optimization and simulation feasibility study for a VDA-based prosthetic ankle. The proposed device stores the eccentric ankle work done from heel strike to maximum dorsiflexion in a hydraulic accumulator and then returns the stored energy to power push-off. Optimization was used to establish the best spring characteristic and gear ratio between ankle and VDA. The corresponding simulations show that, in level walking, normal push-off is achieved and, per gait cycle, the energy stored in the accumulator increases by 22% of the requirements for normal push-off. Although the results are promising, there are many unanswered questions and, for this approach to be a success, a new miniature, low-losses, and lightweight VDA would be required that is half the size of the smallest commercially available device.

Abstract-Energy storage and return (ESR) feet have long been assumed to promote metabolically efficient amputee gait. However, despite being prescribed for approximately 30 yr, there is limited evidence that they achieve this desired function. Here, we report a meta-analysis of data from 10 studies that met our selection criteria to determine whether amputee walking with ESR feet is more efficient than with conventional solid ankle cushioned heel (SACH) feet. Additionally, the data were tested for a relationship with walking speed since it has been suggested ESR feet might perform better at higher speeds. The raw data were highly variable because of differences in study protocols; therefore, we normalized the data and found a statistically significant difference (p < 0.001) between ESR and SACH feet. However, the magnitude of this difference is small, with the cost of transport (COT) with ESR feet being 97.3% of the cost with SACH feet. No relationship between normalized ESR COT and speed was found (p = 0.19). We hypothesize that the small but statistically significant difference between ESR and SACH feet may not constitute a functionally significant improvement in COT, possibly related to the limited push-off power provided by ESR feet compared with nondisabled ankles.

COVID-19 research has relied heavily on convenience-based samples, which—though often necessary—are susceptible to important sampling biases. We begin with a theoretical overview and introduction to the dynamics that underlie sampling bias. We then empirically examine sampling bias in online COVID-19 surveys and evaluate the degree to which common statistical adjustments for demographic covariates successfully attenuate such bias. This registered study analysed responses to identical questions from three convenience and three largely representative samples (total N = 13,731) collected online in Canada within the International COVID-19 Awareness and Responses Evaluation Study ( www.icarestudy.com ). We compared samples on 11 behavioural and psychological outcomes (e.g., adherence to COVID-19 prevention measures, vaccine intentions) across three time points and employed multiverse-style analyses to examine how 512 combinations of demographic covariates (e.g., sex, age, education, income, ethnicity) impacted sampling discrepancies on these outcomes. Significant discrepancies emerged between samples on 73% of outcomes. Participants in the convenience samples held more positive thoughts towards and engaged in more COVID-19 prevention behaviours. Covariates attenuated sampling differences in only 55% of cases and increased differences in 45%. No covariate performed reliably well. Our results suggest that online convenience samples may display more positive dispositions towards COVID-19 prevention behaviours being studied than would samples drawn using more representative means. Adjusting results for demographic covariates frequently increased rather than decreased bias, suggesting that researchers should be cautious when interpreting adjusted findings. Using multiverse-style analyses as extended sensitivity analyses is recommended. Supplementary Information The online version contains supplementary material available at 10.1007/s10654-022-00932-y.

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Objective: To evaluate the amputees’ satisfaction with their prostheses and with the clinical services. Method: The cross-sectional study was conducted at the Medical Rehabilitation Hospital, Madinah, Saudi Arabia, from August 2018 to November 2019, and comprised unilateral, traumatic lower limb amputees. Data was collected using the client satisfaction with the device, and the client satisfaction with service modules of the Orthotics and Prosthetics User's Survey instrument. Data was analysed using SPSS 23. Result: Of the 220 subjects, 43(19.54%) were transfemoral amputees; 37(86%) males with a mean age of 51.9±12.7 years, and 6(14%) females with mean age 51.9±12.7 years. There were 168(76.36%) transtibial amputees; 146(87%) males with mean age 51.7±12.9 years, and 22(13%) females with mean age 54.1±12.7 years. Besides, there were 9(4.09%) female partial-foot amputees with a mean age of 36.0± 6.5 years. Overall, 165(75%) subjects were satisfied with the durability of their prostheses, and 213(97%) were satisfied with the service standard. Conclusion: Most of the participants were generally satisfied with their prostheses, and almost all of them were generally satisfied with the clinical services. Key Words: Amputees, Artificial limb, Lower extremity, Patient satisfaction, Rehabilitation centres, Surveys, Questionnaire.