Quantifying accommodation to prosthesis interventions in persons with lower limb loss

Functional Performance Outcomes of a Powered Knee-Ankle Prosthesis in Service Members With Unilateral Transfemoral Limb Loss

INTRODUCTION

Clinical knowledge surrounding functional outcomes of a powered knee-ankle (PKA) device is limited, particularly among younger and active populations with limb loss. Here, three service members (SM) with unilateral transfemoral limb loss received an optimally tuned PKA prosthesis and device-specific training.

MATERIALS AND METHODS

Once proficiency with the PKA device was demonstrated on benchmark activities, and outcomes with the PKA and standard-of-care (SoC) prostheses were obtained via a modified graded treadmill test, 6-minute walk test, and overground gait assessment.

RESULTS

All SM demonstrated proficiency with the PKA prosthesis within the minimum three training sessions. With the PKA versus SoC prosthesis, cost of transport during the modified graded treadmill test was 4.0% ± 5.2% lower at slower speeds (i.e., 0.6-1.2 m/s), but 7.0% ± 5.1% greater at the faster walking speeds (i.e., ≥1.4 m/s). For the 6-minute walk test, SM walked 83.9 ± 13.2 m shorter with the PKA versus SoC prosthesis. From the overground gait assessment, SM walked with 20.6% ± 10.5% greater trunk lateral flexion and 31.8% ± 12.8% greater trunk axial rotation ranges of motion, with the PKA versus SoC prosthesis.

CONCLUSIONS

Compared to prior work with the PKA in a civilian cohort, although SM demonstrated faster device proficiency (3 versus 12 sessions), SM walked with greater compensatory motions compared to their SoC prostheses (contrary to the civilian cohort). As such, it is important to understand patient-specific factors among various populations with limb loss for optimizing device-specific training and setting functional goals for occupational and/or community reintegration, as well as reducing the risk for secondary complications over the long term.

Gait Performance of Friction-Based Prosthetic Knee Joint Swing-Phase Controllers in Under-Resourced Settings

Gait quality can influence walking ability and mobility outcomes making it an important part of prosthetic rehabilitation. Prosthetic knee joint designs can influence gait quality, and limited data exists to guide component selection in under-resourced settings. This study compared spatiotemporal and kinematic gait parameters for two common types of friction-based swing-phase controlled prosthetic knee joints. Two-dimensional optical gait analysis was conducted as part of a cross-over study design involving 17 individuals with unilateral transfemoral amputations. Two prosthetic knee joints were compared. One utilized constant-friction (CF) and the other a variable cadence controller (VCC) for swing-phase control. Gait was analyzed at normal and fast walking speeds. Primary gait parameters included swing-phase time, step length, and knee flexion. Swing-phase time and peak knee flexion angles, as well as their related symmetry indices, were lower for the VCC compared to the CF (p < 0.01), by 11.1 to 94.1%. The VCC resulted in faster walking speeds by approximately 15% compared to the CF (p = 0.002). Friction-based swing-phase knee control mechanisms can facilitate an appropriate and cost-effective prosthetic knee joint solution in under-resourced settings. The findings suggest that friction-based mechanism can be designed to improve gait quality, and in turn overall walking performance.

Measuring Balance Abilities of Transtibial Amputees Using Multiattribute Utility Theory

Background

Berg Balance Scale (BBS) can be considered the standard for assessment of functional balance but has a noted ceiling effect in active transtibial amputees (TTAs). Development of ceiling-free measures based on quantitative measurement techniques that is suitable for patients in any experience levels, yet sensitive enough to capture improvements in any stage of prosthetic rehabilitation, is needed. Research Question. Does a scoring scheme based on Multiattribute Utility (MAU) theory assess balance abilities of multileveled TTAs comparable to BBS?

Methods

A case-control study including 28 participants (8 novice TTAs, 10 experienced TTAs, and 10 healthy controls) was conducted. Guided by MAU theory, a novel balance model was developed and initially validated by Spearman correlation between index-generated scores and expert assigned scores, providing preliminary evidence of validity. Floor/ceiling effects were tested, and between-group comparisons of static/dynamic balance were conducted by paired t-test or Wilcoxon signed-rank test depending on data distribution normality.

Results

BBS score was correlated with computed balance index (r = 0.847, p < 0.001). The BBS score of novice/experienced TTAs was 39/54, and the computed balance index was 38/75. A ceiling effect of BBS (30%) was observed in the experienced TTA group, whereas no ceiling effects were found for the computed index in any combination of TTA groups. Group differences between novice and experienced TTAs were observed in center of pressure (COP) ellipse shift area, COP path length, COP average velocity, gait speed, and cadence (all p < 0.05). Significance. Evidence from first stage validation of the proposed MAU balance model indicated that the model performed well. This proposed method can monitor the progress of balance for varied experience-leveled TTAs and provide clinicians with useful information for assessing the rehabilitation training.

Functional outcomes and user preferences of individuals with transfemoral amputations using two types of knee joints in under-resourced settings

BACKGROUND

Information relating to prosthetic performance can inform clinical practice and improve patient outcomes in under-resourced countries.

OBJECTIVES

The main goal of this study was to compare functional outcomes and user preferences of individuals with transfemoral amputations using common types of knee joints in an under-resourced country.

STUDY DESIGN

Prospective, longitudinal, before and after trial.

METHODS

Twenty individuals with unilateral transfemoral amputations from a center in Cambodia transitioned from a commonly used single-axis manually locking knee International Committee of the Red Cross (ICRC) to a more advanced multiaxis knee joint with stance control All-Terrain Knee (ATK). Data were collected for the ICRC knee joint and the ATK immediately after fitting, after acclimation, and as part of a long-term follow-up. A timed walk test assessed walking distance and efficiency. Mobility and user-preferences were evaluated through questionnaires.

RESULTS

Distance during the timed walk test was significantly higher for the ATK compared with ICRC (P < 0.001), with functional gains retained at follow-up. No differences were found for gait efficiency and the mobility questionnaires. All participants, except one, preferred the ATK prosthesis. Benefits included greater knee stability and fewer perceived knee collapses; however, some disliked the appearance of the ATK.

CONCLUSIONS

The findings suggest positive outcomes with prosthetic services in under-resourced regions and the ICRC system, as well as the potential for improved functional outcomes with more advanced multiaxis knee components.

Knee Swing Phase Flexion Resistance Affects Several Key Features of Leg Swing Important to Safe Transfemoral Prosthetic Gait

We systematically investigate in-vivo the effect of increasing prosthetic knee flexion damping on key features of the swing phase of individuals with transfemoral amputation during walking. Five experienced prosthesis users walked using a prototype device in a motion capture laboratory. A range of interchangeable hydraulic rotary dampers was used to progressively modify swing phase flexion resistance in isolation. Toe clearance (TC; vertical distance toe to floor), effective leg length (ELL; distance hip to toe), and knee flexion angle during swing phase were computed, alongside the sensitivities of vertical toe position to angular displacements at the hip, knee and ankle. Key features of these profiles were compared across 5 damping conditions. With higher damping, knee extension occurred earlier in swing phase, promoting greater symmetry. However, with implications for toe catch, minimum TC reduced, and minimum TC and maximum ELL occurred earlier; temporally closer to mid-swing, when the limb must pass the stance limb. Further, TC became less sensitive to changes in hip flexion, suggesting a lesser ability to control toe clearance without employing proximal or contralateralcompensations.Thereisatrade-offbetweenkeyfeaturesrelated to gait safety when selecting an appropriate resistance for a mechanical prosthetic knee. In addition to highlighting broader implications surrounding swing phase damping selection for the optimization of mechanical knees, this work reveals design considerations that may be of utility in the formulation of control strategies for computerized devices.

Evaluation of Gait Variable Change over Time as Transtibial Amputees Adapt to a New Prosthesis Foot

A variety of prescribed accommodation periods have been used in published prosthesis intervention studies that have examined biomechanical outcomes. Few investigators included repeated measurements in their study design, leaving questions as to how measured outcomes change as amputees acclimate to a new prosthesis. This paper is the product of our investigation as to whether measured gait variables were affected by the duration of accommodation period, and to assess the relationship between measured outcomes and the subjective perception of the participants. A sample of transtibial amputees were recruited for this study. Gait data was collected by wearable sensor repeatedly, starting immediately after fitting the interventional foot and extending over a subsequent four days. Participants indicated their perceived accommodation quality on a visual analog scale (VAS). A total of twelve commonly used spatiotemporal gait parameters were analyzed. Friedman tests were used to determine overall differences across time points in both early (one hour) and late (day two through five) accommodation phases, for each gait variable. Statistically significant changes across the early phase were found for variables gait speed χ²(2)=8.000, p=0.018, cadence χ²(2)=7.185, p=0.028, and double support time on the sound side χ²(2)=8.615, p=0.013. Across days two through five, no gait variable significantly changed. VAS scores correlated strongly with step count (r=1.000, p<0.001) and cadence (r=0.857, p=0.014). Longer accommodation periods resulted in less deviations of gait variables for the clinical assessment in the process of prosthetic rehabilitation. Trying out prosthetic interventions for less than one hour has yielded unreliable outcomes.