Kinematic analysis of males with transtibial amputation carrying military loads

Influence of prosthetic foot selection on walking performance during various load carriage conditions

BACKGROUND

Ambulatory individuals with lower limb amputations often face challenges with body support, body propulsion, and balance control. Carrying an infant, toddler, backpack, or other load can exacerbate these challenges and highlights the importance of prescribing the most suitable prosthetic foot. The aim of this study was to examine the influence of five different prosthetic feet on walking performance during various load carriage conditions.

METHODS

Biomechanical data were collected from twelve participants wearing five different prosthetic feet (four passive, one powered) while walking with no added load and carrying a load of 13.6 kg in four different positions: posterior, anterior, prosthetic side, and intact side.

FINDINGS

Based on our study population, a powered-ankle-foot offers additional body support when a load is carried posteriorly. If additional forward propulsion is needed while carrying a load anteriorly, a heel wedge is better than a stiffer foot. For individuals who may need additional sagittal plane balance control, no study foot was advantageous regardless of how the load was carried. For those who need additional frontal plane balance control during posterior load carriage, a heel wedge is better than a stiffer or powered foot. Lastly, the standard-of-care, heel wedge, and dual keel feet provided more frontal plane balance control than a powered foot when a load was carried anteriorly.

INTERPRETATION

For individuals with lower limb amputation who carry loads, consideration of their preferred load carrying method may help select an appropriate prosthetic foot for body support, propulsion, and balance control.

Should individuals with unilateral transtibial amputation carry a load on their intact or prosthetic side?

Carrying side loads often occurs during activities of daily living. As walking is most unstable mediolaterally, side load carriage may further compromise gait biomechanics, especially for transtibial amputees (TTAs). This study investigated the effects of side load carriage on gait kinetics during steady-state walking to determine which side, intact or prosthetic, TTAs should carry a load. Twelve unilateral TTAs wore a passive-elastic foot and carried a side load of 13.6 kg while walking at their self-selected speed. Kinetic metrics, including ground reaction force peaks and impulses, loading and unloading rates, and joint moments and powers, were analyzed. TTAs had smaller propulsive forces on their intact limb during the prosthetic side load condition. During the intact side load condition, they had smaller hip flexor moment in late stance and smaller knee flexor moment at the end of swing on their intact limb. They had higher hip and knee abductor moments on their intact limb and prosthetic limb in early and late stance during the contralateral side load condition. TTAs generated higher hip extensor power at weight acceptance during the ipsilateral side load. Significant interactions were observed in hip extensor power and abductor moment, suggesting strong associations between hip extensor power generation and the ipsilateral side load and between hip abductor moment and the contralateral side load. These mixed results demonstrate some kinetic changes due to side load carriage and suggest that the side TTAs should carry a load depends on the desired effects, primarily on their intact limb.

The influence of load carriage and prosthetic foot type on individual muscle and prosthetic foot contributions to body support and propulsion

Individuals with transtibial amputation (TTA) experience altered gait mechanics, which are primarily attributed to the functional loss of the ankle plantarflexors. The plantarflexors contribute to body support and propulsion and play an important role in adapting to different load carriage conditions. However, how muscle function is altered across different prosthetic foot types and load carriage scenarios for individuals with TTA remains unclear. This study used musculoskeletal modeling and simulation of human movement in OpenSim to investigate the effects of a range of prosthetic feet and load conditions on individual muscle and prosthetic foot contributions to body support and propulsion. Twenty walking trials were collected from five individuals with TTA, consisting of five loading conditions (no-load; 30 lbs (13.6 kg) carried as a front-load, back-load, intact-side-load and residual-side-load) while wearing four prosthetic feet (their passive standard of care (SOC) foot, their SOC foot one category stiffer, their SOC foot with a heel stiffening wedge, and a dual-keel foot). Two participants also wore a powered ankle-foot prosthesis, thus completing an additional five trials each. The results indicated that the front-load condition may be more challenging because it required overall increased muscle contributions to body support and propulsion. However, the front- and residual-side-loads required reduced intact-side plantarflexor contributions to support and propulsion, and thus may be advantageous for individuals with plantarflexor weakness. Further, the large variability across contributions suggests that individuals with TTA may rely on a variety of compensatory mechanisms depending on the load condition and prosthetic foot used.

Comparison of static balance and pressure distribution in individuals with unilateral lower limb amputation: The role of barefoot, heel support, and vision

BACKGROUND

In some cultures, shoes are not worn indoors. Prosthesis use barefoot can lead to pressure injuries and loss of balance due to abnormal residual limb loading.

OBJECTIVE

This study aimed to compare the effect of wearing standard alignment prostheses using barefoot at home and visual alteration on static balance and pressure distribution in individuals with unilateral transfemoral amputations (TFAs) or transtibial amputations (TTAs).

STUDY DESIGN

Prospective parallel experimental study.

METHODS

Participants with unilateral TTAs (n = 44) and TFAs (n = 37) were included. Balance and load distribution were assessed using MatScan pressure platforms, both with a heel (3 × 2 cm2 area; 1.8 cm height) support (the use of shoes with a heel is mimicked) and barefoot.

RESULTS

Balance parameters were disrupted in all groups when eyes closed position (p < 0.05). Using heels reduced anterior-posterior and medial-lateral sway in TTA group during eyes closed (p < 0.05). When standing barefoot with the eye open position, TFA group had more load on the rear foot of the prosthetic foot and less load on the forefoot than TTA group (p < 0.05). The opposite pattern was observed in the intact foot (p < 0.05). Using heels in TTA group increased the load on the front of the intact side and the rear of the prosthetic side (p < 0.05).

CONCLUSION

The balance parameters were impaired in both groups while standing barefoot in the absence of vision. However, using heel supports improved static balance in the TTA but not in the TFA group. Using heel support changed this load distribution in both groups, especially in the TTAs, and created positive changes.

A Review of Natural Fiber-Reinforced Composites for Lower-Limb Prosthetic Designs

This paper presents a comprehensive review of natural fiber-reinforced composites (NFRCs) for lower-limb prosthetic designs. It covers the characteristics, types, and properties of natural fiber-reinforced composites as well as their advantages and drawbacks in prosthetic designs. This review also discusses successful prosthetic designs that incorporate NFRCs and the factors that make them effective. Additionally, this study explores the use of computational biomechanical models to evaluate the effectiveness of prosthetic devices and the key factors that are considered. Overall, this document provides a valuable resource for anyone interested in using NFRCs for lower-limb prosthetic designs.

Reducing stiffness of shock-absorbing pylon amplifies prosthesis energy loss and redistributes joint mechanical work during walking

BACKGROUND

A shock-absorbing pylon (SAP) is a modular prosthetic component designed to attenuate impact forces, which unlike traditional pylons that are rigid, can compress to absorb, return, or dissipate energy. Previous studies found that walking with a SAP improved lower-limb prosthesis users' comfort and residual limb pain. While longitudinal stiffness of a SAP has been shown to affect gait kinematics, kinetics, and work done by the entire lower limb, the energetic contributions from the prosthesis and the intact joints have not been examined. The purpose of this study was to determine the effects of SAP stiffness and walking speed on the mechanical work contributions of the prosthesis (i.e., all components distal to socket), knee, and hip in individuals with a transtibial amputation.

METHODS

Twelve participants with unilateral transtibial amputation walked overground at their customary (1.22 ± 0.18 ms^-1) and fast speeds (1.53 ± 0.29 ms^-1) under four different levels of SAP stiffness. Power and mechanical work profiles of the leg joints and components distal to the socket were quantified. The effects of SAP stiffness and walking speed on positive and negative work were analyzed using two-factor (stiffness and speed) repeated-measure ANOVAs (α = 0.05).

RESULTS

Faster walking significantly increased mechanical work from the SAP-integrated prosthesis (p < 0.001). Reducing SAP stiffness increased the magnitude of prosthesis negative work (energy absorption) during early stance (p = 0.045) by as much as 0.027 Jkg^-1, without affecting the positive work (energy return) during late stance (p = 0.159), suggesting a damping effect. This energy loss was partially offset by an increase in residual hip positive work (as much as 0.012 Jkg^-1) during late stance (p = 0.045). Reducing SAP stiffness also reduced the magnitude of negative work on the contralateral sound limb during early stance by 11-17% (p = 0.001).

CONCLUSIONS

Reducing SAP stiffness and faster walking amplified the prostheses damping effect, which redistributed the mechanical work, both in magnitude and timing, within the residual joints and sound limb. With its capacity to absorb and dissipate energy, future studies are warranted to determine whether SAPs can provide additional user benefit for locomotor tasks that require greater attenuation of impact forces (e.g., load carriage) or energy dissipation (e.g., downhill walking).

Automatic Control of Prosthetic Socket Size for People WithTranstibial Amputation: Implementation and Evaluation

OBJECTIVE

The purpose was to design, implement, and test a control system for a motor-actuated, cable-panel prosthetic socket that automatically maintains socket fit by continuous adjustment of the socket size.

METHODS

Sockets with motor-driven adjustable panels were fabricated for participants with transtibial amputation. A proportional-integral control system was implemented to adjust socket size based on Socket Fit Metric (SFM) data collected by an inductive sensor embedded within the socket wall. The sensed distance was representative of limb-to-socket distance. Testing was conducted with participants walking on a treadmill to characterize the system's capability to maintain a set point and to respond to a change in the set point.

RESULTS

Test results from 10 participants with transtibial amputation showed that the Integral of Absolute Error (IAE) to maintain a set point ranged from 0.001 to 0.046 mm with a median of 0.003 mm. When the set point was changed, IAE errors ranged from 0.001 to 0.005 mm, with a median of 0.003 mm. An IAE of 0.003 mm corresponded to approximately a 0.08% socket volume error, which was considered clinically acceptable.

CONCLUSION

The capability of the control system to maintain and respond to a change in set point indicates that it is ready for evaluation outside of the laboratory.

SIGNIFICANCE

Integration of the developed control system into everyday prostheses may improve quality of life of prosthesis users by relieving them of the burden of continually adjusting socket size to maintain fit.

A more compliant prosthetic foot better accommodates added load while walking among Servicemembers with transtibial limb loss

Selecting an optimal prosthetic foot is particularly challenging for highly active individuals with limb loss, such as military personnel, who need to seamlessly perform a variety of demanding activities/tasks (often with and without external loads) while minimizing risk of musculoskeletal injuries over the longer term. Here, we expand on prior work by comparing biomechanical and functional outcomes in two prosthetic feet with the largest differences in mechanical response to added load (i.e., consistently "Compliant" and "Stiff" forefoot properties). In each foot, fourteen male Servicemembers with unilateral transtibial limb loss (from trauma) completed instrumented gait analyses in all combinations of two loading conditions (with and without 22 kg weighted vest) and two walking speeds (1.34 and 1.52 m/s), as well as the Prosthesis Evaluation Questionnaire. With the Stiff foot, sound limb peak loading was 2% smaller (p = 0.043) in the loaded versus unloaded condition, but similar between loading conditions in the Compliant foot (note, the Stiff foot was associated with larger loads, overall). Independent of load or walking speed, the Compliant (versus Stiff) foot provided 67.9% larger (p < 0.001) prosthetic push-off, 17.7% larger (p = 0.01) roll-over shape radii, and was subjectively favored by 10 participants. A more Compliant versus Stiff prosthetic foot therefore appears to better accommodate walking with and without added load, and reinforce the notion that mechanical properties of prosthetic feet should be considered for near-term performance and longer-term (joint) health.

Mechanical and dynamic characterization of prosthetic feet for high activity users during weighted and unweighted walking

Many Service members and Veterans with lower-limb amputations have the potential for high function and the desire to resume physically demanding occupations that require them to carry heavy loads (e.g., military service, firefighters, farmers, ranchers, construction workers). However, it is currently unclear which prosthetic feet best accommodate heavy load carriage while also providing good overall function and mobility during unweighted activities. The main objective of this study was to investigate the ability of currently available prosthetic ankle-foot systems to accommodate weighted walking by examining the mechanical characteristics (i.e., forefoot stiffness) and dynamic function (i.e., rocker radius, effective foot length ratio, and late-stance energy return) of prosthetic feet designed for high activity users. Load versus deflection curves were obtained for nine prosthetic ankle-foot systems using a servohydraulic test frame and load cell. Effective roll-over shape characteristics and late-stance energy return measures were then obtained using quantitative gait analysis for three users with unilateral, transtibial amputation. Results from mechanical and dynamic testing showed that although forefoot stiffness varied across the nine feet investigated in this study, changes measured in roll-over shape radius and effective foot length ratio were relatively small in response to weighted walking. At the same time, prosthetic feet with more compliant forefoot keel structures appeared to provide more late-stance energy return compared to feet with stiffer forefoot keel structures. These results suggest that prosthetic ankle-foot systems with compliant forefoot keel structures may better accommodate weighted walking by reducing the metabolic cost of physically demanding activities. However, to more fully understand the biomechanical and functional implications of these results, other factors, such as the residual-limb strength of the user and the overall stiffness profile of the prosthetic foot, should also be considered.

Center of pressure and total force analyses for amputees walking with a backpack load over four surfaces

Understanding how load carriage affects walking is important for people with a lower extremity amputation who may use different strategies to accommodate to the additional weight. Nine unilateral traumatic transtibial amputees (K4-level) walked over four surfaces (level-ground, uneven ground, incline, decline) with and without a 24.5 kg backpack. Center of pressure (COP) and total force were analyzed from F-Scan insole pressure sensor data. COP parameters were greater on the intact limb than on the prosthetic limb, which was likely a compensation for the loss of ankle control. Double support time (DST) was greater when walking with a backpack. Although longer DST is often considered a strategy to enhance stability and/or reduce loading forces, changes in DST were only moderately correlated with changes in peak force. High functioning transtibial amputees were able to accommodate to a standard backpack load and to maintain COP progression, even when walking over different surfaces.

Changes to transtibial amputee gait with a weighted backpack on multiple surfaces

BACKGROUND

Modern prosthetic technology and rehabilitation practices have enabled people with lower extremity amputations to participate in almost all occupations and physical activities. Carrying backpack loads can be an essential component for many of these jobs and activities; however, amputee gait with backpack loads is poorly understood. This knowledge gap must be addressed in order to further improve an individual's quality of living through changes in rehabilitation programs and prosthesis development.

METHODS

Ten male, unilateral, K4-level (ability or potential for prosthetic ambulation that exceeds basic ambulation skills, exhibiting high impact, stress, or energy levels), transtibial amputees completed ten walking trials at a self-selected pace on simulated uneven ground, ramp ascent, and ramp descent. Five trials were with a 24.5 kg backpack load and five trials without. Temporal-spatial parameters and kinematic peak values for the ankle, knee, hip, pelvis, and trunk were collected and analyzed for differences between backpack conditions.

FINDINGS

Each surface had novel findings not found on the other surfaces. However differences in temporal-spatial parameters were congruent with the literature on able bodied individuals. Pelvis and trunk angular velocities decreased with the backpack. Hip flexion on both limbs increased during weight acceptance while wearing the backpack, a common adaptation seen in able-bodied individuals on level ground.

INTERPRETATION

A 24.5 kg backpack load can be accommodated by transtibial amputees at the K4 functional level. Future studies on load carriage and gait training programs should include incline and descent due to the increased difficulty. Rehabilitation programs should verify hip and knee flexor strength and work to reduce intact limb reliance.