Evaluation of a Prototype Hybrid Vacuum Pump to Provide Vacuum-Assisted Suspension for Above-Knee Prostheses.

Vacuum-assisted suspension (VAS) of prosthetic sockets utilizes a pump to evacuate air from between the prosthetic liner and socket, and are available as mechanical or electric systems. This technical note describes a hybrid pump that benefits from the advantages of mechanical and electric systems, and evaluates a prototype as proof-of-concept. Cyclical bench testing of the hybrid pump mechanical system was performed using a materials testing system to assess the relationship between compression cycles and vacuum pressure.

Impact testing of the residual limb: System response to changes in prosthetic stiffness.

Currently, it is unknown whether changing prosthetic limb stiffness affects the total limb stiffness and influences the shock absorption of an individual with transtibial amputation. The hypotheses tested within this study are that a decrease in longitudinal prosthetic stiffness will produce (1) a reduced total limb stiffness, and (2) reduced magnitude of peak impact forces and increased time delay to peak force. Fourteen subjects with a transtibial amputation participated in this study.

Validity of the iPhone M7 motion co-processor as a pedometer for able-bodied ambulation.

Physical activity benefits for disease prevention are well-established. Smartphones offer a convenient platform for community-based step count estimation to monitor and encourage physical activity. Accuracy is dependent on hardware-software platforms, creating a recurring challenge for validation, but the Apple iPhone® M7 motion co-processor provides a standardised method that helps address this issue.

Shock absorption during transtibial amputee gait: Does longitudinal prosthetic stiffness play a role?

Background: Reduced-stiffness components are often prescribed in lower-limb prostheses, but their efficacy in augmenting shock absorption has been inconclusive.

Objectives: To perform a systematic variation of longitudinal prosthetic stiffness over a wide range of values and to evaluate its effect on shock absorption during gait.

Study Design: Repeated-measures crossover experiment.

The biomechanical response of persons with transfemoral amputation to variations in prosthetic knee alignment during level walking.

Prosthetic alignment is an important factor in the overall fit and performance of a lower-limb prosthesis. However, the association between prosthetic alignment and control strategies used by persons with transfemoral amputation to coordinate the movement of a passive prosthetic knee is poorly understood. This study investigated the biomechanical response of persons with transfemoral amputation to systematic perturbations in knee joint alignment during a level walking task.

The effects of prosthetic ankle stiffness on stability of gait in people with transtibial amputation.

The ability to control balance during walking is a critical precondition for minimizing fall risk, but this ability is compromised in persons with lower-limb absence because of reduced sensory feedback mechanisms and inability to actively modulate prosthesis mechanical function. Consequently, these individuals are at increased fall risk compared with nondisabled individuals. A number of gait parameters, including symmetry and temporal variability in step/stride characteristics, have been used as estimates of gait stability and fall risk.

Pelvic and Spinal Motion During Walking in Persons With Transfemoral Amputation With and Without Low Back Pain.

Objective: Low back pain (LBP) is prevalent in people with transfemoral amputation (TFA), imposing significant disability. Yet, limited data exist describing spine kinematics in people with and without LBP despite the suggestion that gait adaptations required to walk with a prosthesis may be associated or causative of LBP. Hence, the purpose of this study was to determine if there were any differences in pelvic and spinal kinematics in persons with TFA with and without LBP.

Dilatancy-based impression and fabrication technique for custom foot orthoses.

Background And Aim: Current methods used to take impressions for custom foot orthoses include plaster bandage, foam box, fiberglass, and laser-optical scanner. Impressions are converted to positive plaster or foam models. These methods create waste and may not be feasible in resource-limited areas.

Assessing a low-cost accelerometer-based technique to estimate spatial gait parameters of lower-limb prosthesis users.

Background And Aim: Inexpensive methods for characterizing lower-limb prosthetic gait allow clinicians to monitor gait quality. This study assessed an established method for estimating step length using a low-cost accelerometer to estimate distance walked in lower-limb prosthesis users and explore the use of subject-specific correction factors.

Technique: A three-axis accelerometer was attached to participants using straps.

Coronal plane socket stability during gait in persons with transfemoral amputation: Pilot study.

Little research describes which transfemoral socket design features are important for coronal plane stability, socket comfort, and gait. Our study objectives were to (1) relate socket comfort during gait to a rank order of changes in ischial containment (IC) and tissue loading and (2) compare socket comfort during gait when tissue loading and IC were systematically manipulated. Six randomly assigned socket conditions (IC and tissue compression) were assessed: (1) IC and high, (2) IC and medium, (3) IC and low, (4) no IC and high, (5) no IC and medium, and (6) no IC and low.

A novel in vivo impact device for evaluation of sudden limb loading response.

The lower limbs are subjected to large impact forces on a daily basis during gait, and ambulators rely on various mechanisms to protect the musculoskeletal system from these potentially damaging shocks. However, it is difficult to assess the efficacy of anatomical mechanisms and potential clinical interventions on impact forces because of limitations of the testing environment. The current paper describes a new in vivo measurement device (sudden loading evaluation device, or SLED) designed to address shortcomings of previous loading protocols.

Comparison of range-of-motion and variability in upper body movements between transradial prosthesis users and able-bodied controls when executing goal-oriented tasks.

Background: Current upper limb prostheses do not replace the active degrees-of-freedom distal to the elbow inherent to intact physiology. Limited evidence suggests that transradial prosthesis users demonstrate shoulder and trunk movements to compensate for these missing volitional degrees-of-freedom. The purpose of this study was to enhance understanding of the effects of prosthesis use on motor performance by comparing the movement quality of upper body kinematics between transradial prosthesis users and able-bodied controls when executing goal-oriented tasks that reflect activities of daily living.

Modeling effects of sagittal-plane hip joint stiffness on reciprocating gait orthosis-assisted gait.

Upright ambulation is believed to improve quality of life for persons with lower-limb paralysis (LLP). However, ambulatory orthoses for persons with LLP, like reciprocating gait orthoses (RGOs), result in a slow, exhausting gait. Increasing the hip joint stiffness of these devices may improve the efficiency of RGO-assisted gait.

Mediolateral foot placement ability during ambulation in individuals with chronic post-stroke hemiplegia.

Mediolateral (ML) foot placement is an effective way to redirect the lateral trajectory of the body center of mass (BCoM) during ambulation, but has only been partly characterized in the chronic post-stroke population despite their increased risk for falling [1]. During able-bodied gait, the locomotor system coordinates lower limb swing phase kinematics such that an appropriate ML foot placement occurs upon foot contact. Muscle weakness and abnormal motor patterns may impair foot placement ability post-stroke.

Methods for characterization of mechanical and electrical prosthetic vacuum pumps.

Despite increasingly widespread adoption of vacuum-assisted suspension systems in prosthetic clinical practices, there remain gaps in the body of scientific knowledge guiding clinicians' choices of existing products. In this study, we identified important pump-performance metrics and developed techniques to objectively characterize the evacuation performance of prosthetic vacuum pumps. The sensitivity of the proposed techniques was assessed by characterizing the evacuation performance of two electrical (Harmony e-Pulse [Ottobock; Duderstadt, Germany] and LimbLogic VS [Ohio Willow Wood; Mt.

The effect of trunk flexion on lower-limb kinetics of able-bodied gait.

Able-bodied individuals spontaneously adopt crouch gait when walking with induced anterior trunk flexion, but the effect of this adaptation on lower-limb kinetics is unknown. Sustained forward trunk displacement during walking can greatly alter body center-of-mass location and necessitate a motor control response to maintain upright balance. Understanding this response may provide insight into the biomechanical demands on the lower-limb joints of spinal pathology that alter trunk alignment (e.

The effects of prosthetic ankle stiffness on ankle and knee kinematics, prosthetic limb loading, and net metabolic cost of trans-tibial amputee gait.

Background: Previous studies of commercially-available trans-tibial prosthetic components have been unable to provide clear insight into the relationships between prosthetic mechanical properties and user performance (i.e., gait quality and energy expenditure), the understanding of which is key to improving prosthesis design and prescription.

Validity and reliability of the Berg Balance Scale for community-dwelling persons with lower-limb amputation.

Objective: To evaluate the validity and reliability of the Berg Balance Scale (BBS) for use in people with lower-limb amputation.

Design: Cross-sectional study.

Setting: Research laboratory.

The effects of walking speed and prosthetic ankle adapters on upper extremity dynamics and stability-related parameters in bilateral transtibial amputee gait.

Bilateral transtibial amputee (BTA) gait has been investigated less and is not as well understood compared to that of their unilateral counterparts. Relative to able-bodied individuals, BTAs walk with reduced self-selected speeds, increased step width, hip-hiking, and greater metabolic cost. The clinically observed upper body motions of these individuals have not been quantified, but appear substantially different from able-bodied ambulators and may impact upright balance.

Stance phase mechanical characterization of transtibial prostheses distal to the socket: a review.

Achieving the required functionality of a transtibial prosthesis during the stance phase of gait (e.g., shock absorption, close to normal roll-over characteristics, and smooth transition into swing) depends on the Amputee Independent Prosthesis Properties (AIPPs), defined here as the mechanical properties of the prosthesis that directly influence the performance of the amputee.

Assessing the prosthetic needs of farmers and ranchers with amputations.

Purpose: Farmers and ranchers experience disabling injuries each year of which amputations account for 11%. Anecdotal evidence suggests that current prostheses may not be meeting the needs of farmers and ranchers with amputations. To better understand those prosthetic needs, a descriptive qualitative study was used to gather data with an engineering perspective.

Effect of prosthetic gel liner thickness on gait biomechanics and pressure distribution within the transtibial socket.

Prosthetic gel liners are often prescribed for persons with lower-limb amputations to make the prosthetic socket more comfortable. However, their effects on residual limb pressures and gait characteristics have not been thoroughly explored. This study investigated the effects of gel liner thickness on peak socket pressures and gait patterns of persons with unilateral transtibial amputations.

The effects of transverse rotation angle on compression and effective lever arm of prosthetic feet during simulated stance.

Background And Aim: Unlike sagittal plane prosthesis alignment, few studies have observed the effects of transverse plane alignment on gait and prosthesis behaviour. Changes in transverse plane rotation angle will rotate the points of loading on the prosthesis during stance and may alter its mechanical behaviour. This study observed the effects of increasing the external transverse plane rotation angle, or toe-out, on foot compression and effective lever arm of three commonly prescribed prosthetic feet.

Effect of prosthetic ankle units on roll-over shape characteristics during walking in persons with bilateral transtibial amputations.

Some important walking functions are adversely affected or eliminated in prosthesis users because of reduced or absent ankle motion. This retrospective data analysis determined the effect of prosthetic ankle units on the characteristics of the ankle-foot roll-over shape in persons with bilateral transtibial amputations. Seventeen subjects were fitted with Endolite Multiflex Ankles to provide ankle plantar-/dorsiflexion during the stance phase of gait.