The development and reliability testing of the Functional Lower-Limb Amputee Gait Assessment.

OBJECTIVE: The study purpose was three-fold: (a) to describe the development of the Functional Lower-Limb Amputee Gait Assessment, (b) to determine its reliability with two groups of raters, physical therapists, and certified prosthetists, and (c) to determine the agreement on its results between the two groups. DESIGN: A reliability study. SETTING: Institution for higher education. PARTICIPANTS: Five physical therapists and five certified prosthetists. INTERVENTION: Not applicable. MAIN MEASURE: The gait of people with unilateral lower limb amputation was evaluated using the Functional Lower-Limb Amputee Gait Assessment. Kappa statistic was used to analyze reliability. RESULTS: The intra-rater reliability of nine gait deviations in the physical therapists' group and eight in the certified prosthetists' group was between moderate and almost perfect agreement (kappa = .41-1). In the physical therapists' group, the inter-rater reliability of four gait deviations was moderate (kappa = .41-.6). In the certified prosthetists' group, the inter-rater reliability of six gait deviations was moderate to substantial (kappa = .41-.8). Three gait deviations achieved moderate agreement in both groups of clinicians (kappa = .41-.6). CONCLUSIONS: Most gait deviations included in the Functional Lower-Limb Amputee Gait Assessment appear stable over time when used by the same clinician. Six gait deviations in the certified prosthetists' group and four in the physical therapists' group may be used by multiple clinicians, and three gait deviations may be used across both professions to assist in communication and collaboration on the best course of treatment for a patient with a unilateral lower limb amputation.

Comparison of Ischial Containment and Subischial Sockets Effect on Gait Biomechanics in People With Transfemoral Amputation: A Randomized Crossover Trial.

OBJECTIVE: To compare gait biomechanics of the Northwestern University Flexible Sub-Ischial Vacuum (NU-FlexSIV) Socket to the ischial containment (IC) socket. DESIGN: Randomized crossover trial with 2, 7-week periods. SETTING: Private prosthetic clinics and university research laboratory. PARTICIPANTS: A total of 30 enrolled (n=30); 25 participants completed the study with full (n=18) or partial data (n=7). INTERVENTIONS: Two custom-fabricated sockets (IC and NU-FlexSIV), worn full-time for 7 weeks, with testing at 1, 4, and 7 weeks after socket delivery. MAIN OUTCOME MEASURES: Gait analyses were conducted at 1, 4, and 7 weeks post socket delivery. Differences between sockets in selected gait variables related to hip motion and coronal plane socket stability were assessed. RESULTS: For participants with data for both sockets at week 7 (n=19), there were no significant differences in any gait variables between sockets at self-selected normal walking speed. However, when all participants and all study time points were assessed (n=25), there was a significant main effect of socket (P=.013), with prosthetic side sagittal plane hip range of motion being significantly greater for the NU-FlexSIV Socket at self-selected normal walking speed. There were no other significant effects. CONCLUSIONS: The results suggest that, compared to the IC socket, the NU-FlexSIV Socket did not alter gait biomechanics related to hip motion and coronal plane socket stability in people with unilateral transfemoral amputation.

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).

Using a Simple Walking Model to Optimize Transfemoral Prostheses for Prosthetic Limb Stability-A Preliminary Study.

The interaction between the prescribed prosthetic knee and foot is critical to the safety of transfemoral prosthesis users primarily during the stance phase of the gait, when knee buckling can result in a fall. Nonetheless, there is still a need for standardized approaches to quantify the effects of prosthetic component interactions and associated mechanical function on user gait biomechanics. A numerical model was defined to simulate sagittal plane prosthetic limb stance based on a single inverted pendulum and predict effects of prosthetic knee alignment and foot stiffness on knee moment to identify optimal solutions. Model validation against laboratory gait data suggests it is appropriate to preliminary simulate prosthetic gait during single-limb support, when prosthetic knee stability may be most at risk given reliance on the prosthetic limb and proximal anatomy, but only for knees with flexion smaller than 4°. Model predictions identify a solution space containing those combinations of knee alignment and foot stiffness (via roll-over shape radius) guaranteeing knee stability in early and mid- single-limb support, whilst facilitating knee break at the end of it. Specifically, a posterior to in-line knee alignment should be combined with low to medium ankle-foot stiffness, whereas anterior knee alignments and rigid feet should likely be avoided. Clinicians can use these solution spaces to optimize transfemoral prostheses including knees with little to no change in stance flexion, ensuring the safety of users. Model prediction can further inform in-vivo investigations on commercial device interactions, providing evidence for future Clinical Practice Guidelines on transfemoral prostheses design.

Rehabilitation Is a Global Health Priority.

Optimizing functioning at all ages is a major global public health goal. Rehabilitation is unique in its contribution to this public health agenda because of its focus on optimizing function. In this editorial, the editors of leading rehabilitation journals make the case for fully integrating rehabilitation into a nation's health system and strengthening it specifically at the primary care level to increase access and achieve its full potential. Authors submitting papers to rehabilitation journals are encouraged to consider the global health policy implications of their research when they prepare their research reports for publication and to make these implications explicit.

Effects of Upper Limb Loss or Absence and Prosthesis Use on Postural Control of Standing Balance.

OBJECTIVE: Persons with upper limb loss or absence experience a high prevalence of falls. Although upper limb prostheses help perform upper limb tasks, fall likelihood increases by six times with prosthesis use. The effects of upper limb loss or absence and prosthesis use on postural control are poorly documented. DESIGN: Static posturography characterized postural control of standing balance between persons with unilateral upper limb loss or absence not wearing a prosthesis and wearing either a customary prosthesis or prosthesis that matched the mass, inertia, and length of their sound limb. Able-bodied controls were also compared to persons with unilateral upper limb loss or absence not wearing a prosthesis. Center-of-pressure anterior-posterior range, medial-lateral range, and sway area, as well as weight-bearing symmetry, were measured. RESULTS: Persons with upper limb loss or absence display greater standing postural sway than controls. Although wearing a prosthesis improved weight-bearing symmetry, this condition increased postural sway, which was pronounced in the medial-lateral direction. CONCLUSIONS: The presence of upper limb loss or absence increased postural control demands than able-bodied individuals as reflected in greater postural sway, which was further exacerbated with the use of prosthesis. Results suggest that upper limb loss or absence and prosthesis use may affect the internal models that guide motor commands to maintain body center-of-mass position equilibrium. The relatively greater postural control demands might help explain the increase fall prevalence in this patient group.

Effects of upper limb loss and prosthesis use on proactive mechanisms of locomotor stability.

Persons with upper limb loss (ULL) experience a high prevalence of falls, with the majority of falls occurring when walking. This issue may be related to altered arm dynamics, which play an important role in proactive mechanisms of locomotor stability. This study investigated effects of ULL and prosthesis use on proactive stability mechanisms, particularly if matching the mass and inertia of the impaired limb to the sound limb would enhance locomotor stability. Gait data were collected on adults with unilateral ULL during level walking while: (1) not wearing a prosthesis, (2) wearing their customary prosthesis, (3) wearing a mock prosthesis that matched the sound limb mass and inertia. Main and interaction effects of limb side and condition on trunk rotations, arm swing, step width, free vertical moment, and margin-of-stability were analyzed. Across conditions, arm swing, free vertical moment, and margin-of-stability were 2.27, 1.13, and 1.20 times greater, respectively, on the sound limb side than the impaired limb side. Persons with ULL display asymmetry in proactive mechanisms of locomotor stability with potentially greater medial-lateral stability on the sound limb side irrespective of prosthesis use, but heavier prostheses reduced the walking base of support. This bias may enhance fall risk on the impaired side if the prosthetic limb is used inappropriately to regain balance following a disturbance. Research is warranted to explore the consequences of this asymmetry on perturbation response.

Does Decreasing Below-Knee Prosthesis Pylon Longitudinal Stiffness Increase Prosthetic Limb Collision and Push-Off Work During Gait?

Investigations have begun to connect leg prosthesis mechanical properties and user outcomes to optimize prosthesis designs for maximizing mobility. To date, parametric studies have focused on prosthetic foot properties, but not explicitly longitudinal stiffness that is uniquely modified through shock-absorbing pylons. The linear spring function of these devices might affect work performed on the body center-of-mass during walking. This study observed the effects of different levels of pylon stiffness on individual limb work of unilateral below-knee prosthesis users walking at customary and fast speeds. Longitudinal stiffness reductions were associated with minimal increase in prosthetic limb collision and push-off work, but inconsistent changes in sound limb work. These small and variable changes in limb work did not suggest an improvement in mechanical economy due to reductions in stiffness. Fast walking generated greater overall center-of-mass work demands across stiffness conditions. Results indicate limb work asymmetry as the prosthetic limb experienced on average 61% and 36% of collision and push-off work, respectively, relative to the sound limb. A series spring model to estimate residuum and pylon stiffness effects on prosthesis energy storage suggested that minimal changes to limb work may be due to influences of the residual limb which dominate the system response.

Do Upper Limb Loss and Prosthesis Use Affect Lower Limb Gait Dynamics?

INTRODUCTION: Intentional interruption of upper and lower limb coordination of able-bodied subjects alters their gait biomechanics. However, the effect of upper-limb loss (ULL) on lower-limb gait biomechanics is not fully understood. The aim of this secondary study was to perform a follow-up analysis of a previous dataset to characterize the spatiotemporal parameters and lower-limb kinematics and kinetics of gait for persons with ULL when wearing and not wearing an upper limb prosthesis (ULP). We were particularly interested in quantifying the effects of matching the mass and inertia of the prosthetic limb to the sound limb. MATERIALS AND METHODS: Ten persons with unilateral ULL walked at a self-selected speed under three randomly presented conditions: 1) not wearing a prosthesis, 2) wearing their customary prosthesis, and 3) wearing a mock prosthesis that can be adjusted to match the length, mass, and inertial properties of each subject's sound limb. Walkway-embedded force plates and a 12-camera digital motion capture system recorded ground reaction forces (GRFs) and retroreflective marker position data, respectively. Average spatiotemporal (walking speed, cadence, stance time, swing time, step length, double support time), lower-limb kinematic (joint angles), and lower-limb kinetic (ground forces, joint moments and powers) data were processed and their statistical significance were analyzed. RESULT: Walking speed for each condition was nearly equivalent (1.20±0.01 m/s) and differences between condition were non-significant (p=0.769). The interaction effect (side× prosthesis) was significant for peak hip extension (p=0.01) and second peak (propulsive) vertical GRF (p=0.028), but separate follow-up analyses of both main effects were not significant (p≥0.099). All other main effect comparisons were not significant (p≥0.102). CONCLUSIONS: Although the sample cohort was small and heterogeneous, the results of this study suggest that persons with unilateral ULL did not display significant limb side asymmetry in lower-limb gait spatiotemporal, kinetic, and kinematic parameters, regardless of ULP use.

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. Quantitative gait data were collected for three alignment conditions: bench alignment, 2 cm anterior knee translation (ANT), and 2 cm posterior knee translation (POST). In response to a destabilizing alignment perturbation (i.e., the ANT condition), participants significantly increased their early-stance hip extension moment, confirming that persons with transfemoral amputation rely on a hip extensor strategy to maintain knee joint stability. However, participants also decreased the rate at which they loaded their prosthesis, decreased their affected-side step length, increased their trunk flexion, and maintained their prosthesis in a more vertical posture at the time of opposite toe off. Collectively, these results suggest that persons with transfemoral amputation rely on a combination of strategies to coordinate stance-phase knee flexion. Further, comparatively few significant changes were observed in response to the POST condition, suggesting that a bias toward posterior alignment may have fewer implications in terms of stance-phase, knee joint control.

Interrater reliability of mechanical tests for functional classification of transtibial prosthesis components distal to the socket.

Substantial evidence suggests that the design and associated mechanical function of lower-limb prostheses affects user health and mobility, supporting common standards of clinical practice for appropriate matching of prosthesis design and user needs. This matching process is dependent on accurate and reliable methods for the functional classification of prosthetic components. The American Orthotic & Prosthetic Association developed a set of tests for L-code characterization of prosthesis mechanical properties to facilitate functional classification of passive below-knee prosthetic components. The mechanical tests require use of test-specific fixtures to be installed in a materials testing machine by a test administrator. Therefore, the purpose of this study was to assess the interrater reliability of test outcomes between two administrators using the same testing facility. Ten prosthetic components (8 feet and 2 pylons) that spanned the range of commercial designs were subjected to all appropriate tests. Tests with scalar outcomes demonstrated high interrater reliability (intraclass correlation coefficient(2,1) >/= 0.935), and there was no discrepancy in observation-based outcomes between administrators, suggesting that between-administrator variability may not present a significant source of error. These results support the integration of these mechanical tests for prosthesis classification, which will help enhance objectivity and optimization of the prosthesis-patient matching process for maximizing rehabilitation outcomes.

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. METHODS: Upper body kinematics were collected on six able-bodied controls and seven myoelectric transradial prosthesis users during execution of goal-oriented tasks. Range-of-motion, absolute kinematic variability (standard deviation), and kinematic repeatability (adjusted coefficient-of-multiple-determination) were quantified for trunk motion in three planes, shoulder flexion/extension, shoulder ab/adduction, and elbow flexion/extension across five trials per task. Linear mixed models analysis assessed between-group differences and correlation analysis evaluated association between prosthesis experience and kinematic repeatability. RESULTS: Across tasks, prosthesis users demonstrated increased trunk motion in all three planes and shoulder abduction compared to controls (p ≤ 0.004). Absolute kinematic variability was greater for prosthesis users for all degrees-of-freedom irrespective of task, but was significant only for degrees-of-freedom that demonstrated increased range-of-motion (p ≤ 0.003). For degrees-of-freedom that did not display increased absolute variability for prosthesis users, able-bodied kinematics were characterized by significantly greater repeatability (p ≤ 0.015). Prosthesis experience had a strong positive relationship with average kinematic repeatability (r = 0.790, p = 0.034). CONCLUSIONS: The use of shoulder and trunk movements by prosthesis users as compensatory motions to execute goal-oriented tasks demonstrates the flexibility and adaptability of the motor system. Increased variability in movement suggests that prosthesis users do not converge on a defined motor strategy to the same degree as able-bodied individuals. Kinematic repeatability may increase with prosthesis experience, or encourage continued device use, and future work is warranted to explore these relationships. As compensatory dynamics may be necessary to improve functionality of transradial prostheses, users may benefit from dedicated training that encourages optimization of these dynamics to facilitate execution of daily living activity, and fosters adaptable but reliable motor strategies.