Carbon fibre prostheses and running in amputees: A …
The goal of this study was to characterize the short term, biomechanical response of persons with transfemoral amputation to perturbations in prosthetic knee joint alignment during a level walking task. To this end, we implemented a single-blinded, pseudorandomized crossover design in which we systematically varied the anterior-posterior position of a single-axis prosthetic knee joint to affect knee joint stability during the stance phase of gait. To fully characterize the user's response to changes in knee joint stability, we investigated a range of spatiotemporal, kinematic, and kinetic parameters that we selected based on previous studies of prosthetic alignment and on an empirical understanding of prosthetic knee joint control. We then compared these parameters between an anterior-posterior alignment condition and a baseline (i.e., bench alignment) condition. We hypothesized that in response to a destabilizing alignment perturbation (i.e., an anterior shift of the knee joint), participants would primarily increase their internal hip extension moment to maintain weight-bearing stability during early stance phase. We hypothesized that in response to a stabilizing alignment perturbation (i.e., a posterior shift of the knee joint), participants would primarily increase their internal hip flexion moment to initiate knee flexion in late stance phase. Given the fact that few studies have investigated transfemoral amputee gait in the context of prosthetic alignment, the results from this study have the potential to provide insight into the mechanisms available to persons with transfemoral amputation for prosthetic knee joint control.
Training techniques for the transfemoral running gait ..
Eleven participants with unilateral transfemoral amputation were recruited from the Northwestern University Prosthetics-Orthotics Center, the Rehabilitation Institute of Chicago, and local prosthetic clinics according to the following inclusion criteria: (1) age 18 to 65 yr; (2) body mass less than 115 kg; (3) no known history of peripheral vascular disease or neurological/musculoskeletal disorders; (4) 3 yr or more of experience with a definitive prosthesis; (5) ability to walk unaided on a treadmill at a constant, comfortable rate without undue fatigue or health risk; and (6) Medicare Functional Classification Level K3 ambulator or higher status (i.e., able to ambulate with variable cadence and able to traverse most environmental barriers). These criteria corresponded to the weight restrictions of the prosthetic components used in this study and the requirement of participants to complete a treadmill walking protocol. In an effort to recruit participants who could detect subtle changes in residual-limb loading associated with the different alignment conditions, participants at risk for sensory deficits (i.e., participants with peripheral vascular disease) were excluded from this study. Participants were also excluded if they reported persistent pain in their residual limb. Each participant was asked to rate his or her prosthetic socket according to a comfort scale described by Hanspal et al. . This scale, which ranges from 0 (least comfortable) to 10 (most comfortable), is highly correlated with clinical assessments of socket fit and was used to screen participants for functional deficits associated with poor socket fit (defined in this study as a comfort score ≤4).
This paper presents an overview of the design and control of a fully self-contained prosthesis, which is intended to improve the mobility of transfemoral amputees. A finite-state based impedance control approach, previously developed by the authors, is used for the control of the prosthesis during walking and standing. The prosthesis was tested on an unilateral amputee subject for over-ground walking. Prosthesis sensor data (joint angles and torques) acquired during level ground walking experiments at a self-selected cadence demonstrates the ability of the device to provide a functional gait similar to normal gait biomechanics. Battery measurements during level ground walking experiments show that the self-contained device provides over 4,500 strides (9.0 km of walking at a speed of 5.1 km/h) between battery charges.
Bracket-fixable running foot for lower limb prosthesis ..
The joint torque specifications required of the knee and ankle joints were based on an 85 kg user for a walking cadence of 80 steps per minute and stair climbing, as derived from body-mass-normalized data [, ]. The joint power specifications were based on data from Winter , also for an 85 kg user. The structural design requirements were based on a user mass of 115 kg and a minimum factor of safety of two (i.e. the structure was designed to accommodate the loads imposed by a 230 kg user). The design specifications are summarized in . The resulting self-contained powered knee and ankle prosthesis is shown in . A detailed discussion of the mechanical, sensor and embedded system design is given in the following sections.
walking and running for transfemoral amputees ..
Despite significant technological advances over the past decade, such as the introduction of microcomputer-modulated damping during swing, commercial transfemoral prostheses remain limited to energetically passive devices. That is, the joints of the prostheses can either store or dissipate energy, but cannot provide net power over a gait cycle. The inability to deliver joint power significantly impairs the ability of these prostheses to restore many locomotive functions, including walking up stairs and up slopes, running, and jumping, all of which require significant net positive power at the knee joint, ankle joint or both (; ; ; ; ; ; ). Furthermore, although less obvious, even biomechanically normal walking requires positive power output at the knee joint and significant net positive power output at the ankle joint (). Transfemoral amputees walking with passive prostheses have been shown to expend up to 60% more metabolic energy relative to healthy subjects during level walking () and exert as much as three times the affected-side hip power and torque (), presumably due to the absence of powered joints. A prosthesis with the capacity to deliver power at the knee and ankle joints would presumably address these deficiencies, and would additionally enable the restoration of biomechanically normal locomotion. Such a prosthesis, however, would require: (i) power generation capabilities comparable to an actual limb; and (ii) a control framework for generating required joint torques for locomotion while ensuring stable and coordinated interaction with the user and the environment. This paper describes the authors’ progress to date in pursuing both of these goals. Specifically: Section 2 presents the current prosthesis prototype design and discusses the means by which the authors intend to convert this to a self-powered version Section 3 describes the control approach; and Section 4 presents experimental results that demonstrate the hardware and control approach.