Benjamin J. Darter

Reliability and Minimal Detectible Change values for gait kinematics and kinetics in healthy adults.

Computerized assessment of gait is commonly used in both research and clinical settings to quantify gait mechanics and detect change in performance. Minimal Detectable Change values have only recently been reported, are only available for patient populations, and in many cases exceed 10°. Twenty nine healthy individuals underwent two biomechanical gait assessments separated by 5.6 (SD 2.2) days, with two raters for each session. All subjects walked at a self selected pace and three controlled velocities. ICC, SEM and MDC for kinematic and kinetic measures were calculated for interrater-intrasession, intrarater-intersession and interrater-intersession. ICC values were in the good to excellent range (r>0.75) for all kinematic and kinetic variables and all comparisons. MDC values were lower than previously published data for all similar comparisons. The results of the current study suggest that reliability is good to excellent across a range of controlled walking velocities and the introduction of a second rater does not appreciably impact ICC or MDC values. In young healthy adults changes in gait kinematics of greater than approximately 5° can be identified when comparing between sessions.

Gait training with virtual reality-based real-time feedback: improving gait performance following transfemoral amputation.

Background and Purpose Gait training is an important component of rehabilitation after lower-extremity amputation. Abnormal gait performance often persists even for individuals who reacquire a high level of function. This case report describes the use of a virtual reality (VR)–based gait training program that provides real-time feedback in order to improve biomechanical and physiological performance. The aim of this case report is to describe the effects of the training in a person with a transfemoral amputation. Case Description A 24-year-old man with a transfemoral amputation completed a 3-week gait training program. The intervention consisted of 12 sessions of treadmill walking with real-time visual feedback on full-body gait kinematics. A treating therapist directed the patients attention to specific gait deviations as a means to normalize gait biomechanics. Outcomes The patient completed overground biomechanical gait analyses and multiple-speed treadmill tests 3 weeks apart prior to and following the training program. Biomechanical gait analyses indicated the training produced improved frontal-plane hip, pelvis, and trunk motion during overground walking. Improvement in trunk motion was observed at the posttraining test, and improvements in pelvis and hip motion were observed at the 3-week follow-up test. Decreases of up to 23% in oxygen consumption also were demonstrated. Discussion Although the exact contribution of the visual feedback could not be isolated, the training was effective in improving the patients walking performance. Biomechanical data suggest correcting trunk motion and increasing hip abductor strength (force-generating capacity) may be important in facilitating improvements at the pelvis and hip. Observed improvements in oxygen consumption were significantly larger than achieved through previously reported interventions.

Comparison of walking overground and in a Computer Assisted Rehabilitation Environment (CAREN) in individuals with and without transtibial amputation

BackgroundDue to increased interest in treadmill gait training, recent research has focused on the similarities and differences between treadmill and overground walking. Most of these studies have tested healthy, young subjects rather than impaired populations that might benefit from such training. These studies also do not include optic flow, which may change how the individuals integrate sensory information when walking on a treadmill. This study compared overground walking to treadmill walking in a computer assisted virtual reality environment (CAREN) in individuals with and without transtibial amputations (TTA).MethodsSeven individuals with traumatic TTA and 27 unimpaired controls participated. Subjects walked overground and on a treadmill in a CAREN at a normalized speed. The CAREN applied optic flow at the same speed that the subject walked. Temporal-spatial parameters, full body kinematics, and kinematic variability were collected during all trials.ResultsBoth subject groups decreased step time and control subjects decreased step length when walking in the CAREN. Differences in lower extremity kinematics were small (< 2.5○) and did not exceed the minimal detectable change values for these measures. Control subjects exhibited decreased transverse and frontal plane range of motion of the pelvis and trunk when walking in the CAREN, while patients with TTA did not. Both groups exhibited increased step width variability during treadmill walking in the CAREN, but only minor changes in kinematic variability.ConclusionsThe results of this study suggest that treadmill training in a virtual environment should be similar enough to overground that changes should carry over. Caution should be made when comparing step width variability and step time results from studies utilizing a treadmill to those overground.

Test–Retest Reliability and Minimum Detectable Change Using the K4b2: Oxygen Consumption, Gait Efficiency, and Heart Rate for Healthy Adults During Submaximal Walking

Purpose: Oxygen consumption (VO2; mLO2/kg/min), gait efficiency (GE; mlO2/kg/m) and heart rate (HR; beats per minute) are measures of physiological gait performance. However, the collection device, procedures for data normalization, and biological factors can affect measurement variability. The purpose of this study was to determine the test–retest reliability and minimum detectable change (MDC) for VO2, GE, and HR with the K4b2 at submaximal walking speeds in healthy young adults. A second purpose was to determine if net measures improved reproducibility. Method: Twenty-two participants completed 2 identical treadmill tests on separate days at submaximal walking speeds from 0.71 m/s to 1.65 m/s. Results: Intraclass correlation coefficient (ICC) values for gross VO2, gross GE, and HR were greater than .85 for all walking speeds. Associated MDC values were approximately 7% to 10% for gross VO2 and GE, and approximately 9% to 12% for HR. ICC values for resting VO2 were lower, with MDC values approaching 25%. Subtracting out resting values to derive net VO2 and GE values produced ICC values below .76 for the 2 slowest speeds but ICC values greater than .83 for the faster speeds. MDC values for net VO2 and GE were up to 20% for the slowest speeds. Conclusions: The results demonstrate metabolic cost can be assessed reliably using the K4b2 during submaximal walking and that gross measures are more reliable than net measures. Furthermore, changes at self-selected speeds exceeding 1.0 mLO2/kg/min in gross VO2 and 0.01 mLO2/kg/m in gross GE can be considered a true change in walking performance.

Physical Performance Assessment in Military Service Members

&NA; Few established measures allow effective quantification of physical performance in severely injured service members. We sought to establish preliminary normative data in 180 healthy, active‐duty service members for physical performance measures that can be readily implemented in a clinical setting. Interrater and test‐retest reliability and minimal detectable change (MDC) values were also determined. Physical performance testing included self‐selected walking velocity on level and uneven terrain, timed stair ascent, the sit‐to‐stand five times test, the four‐square step test, and the 6‐minute walk test. Data analysis included descriptive statistics, intraclass correlation coefficients, and MDC. Interrater and test‐retest reliability were excellent for all measures (intraclass correlation coefficients >0.75). MDC values for timed measures were <0.3 seconds for interrater comparisons and <1.5 seconds for between‐day comparisons. Physical performance measures had a narrow range of normal performance and were reliable and stable between days.

Energetic consequences of using a prosthesis with adaptive ankle motion during slope walking in persons with a transtibial amputation

Background: Technological advances in prosthetic design include the use of microprocessors that adapt device performance based on user motion. The Proprio ankle unit prepositions the foot to adjust for walking on slopes and increases foot clearance during swing to minimize gait deviations. Study design: Comparative analysis. Objectives: To investigate the effect of a prosthesis with adaptive ankle motion on physiological gait performance during slope walking. Methods: Six persons with a unilateral transtibial amputation completed treadmill walking tests at three slopes (−5°, 0°, and 5°). The participants were tested wearing a customary device, active Proprio (Pon), and an identical inactivated Proprio (Poff). Results: Metabolic energy expenditure, energy cost for walking, and rating of walking difficulty were not statistically different between the Pon and Poff for all tested slopes. However, for slope descent, energy expenditure and energy cost for walking improved significantly by an average of 10%–14% for both the Pon and Poff compared to the customary limb. Rating of walking difficulty also showed an improvement with slope descent for both the Pon and Poff compared to the customary device. An improvement with slope ascent was found for Pon compared to the customary limb only. Conclusions: Adaptive ankle motion provided no meaningful physiological benefit during slope walking. The Proprio was, however, less demanding than the customary device for slope descent. Differences in the mechanical properties of the prosthetic feet likely contributed to the changes. Clinical relevance While the adaptive ankle motion did not affect metabolic energy expenditure or energy cost for walking, the results suggest close attention should be paid to the mechanical properties of the foot component. Assessment of gait on nonlevel surfaces is recommended to better understand the implications of different prosthetic design features.

Home-Based Treadmill Training to Improve Gait Performance in Persons With a Chronic Transfemoral Amputation

OBJECTIVE To investigate the effectiveness of a home-based multiple-speed treadmill training program to improve gait performance in persons with a transfemoral amputation (TFA). DESIGN Repeated measures. SETTING Research laboratory. PARTICIPANTS Individuals with a TFA (N=8) who had undergone a unilateral amputation at least 3 years prior as a result of limb trauma or cancer. INTERVENTION Home-based treadmill walking for a total of 30 minutes a day, 3 days per week for 8 weeks. Each 30-minute training session involved 5 cycles of walking for 2 minutes at 3 speeds. MAIN OUTCOME MEASURES Participants were tested pretraining and after 4 and 8 weeks of training. The primary measures were temporal-spatial gait performance (symmetry ratios for stance phase duration and step length), physiological gait performance (energy expenditure and energy cost), and functional gait performance (self-selected walking speed [SSWS], maximum walking speed [MWS], and 2-minute walk test [2MWT]). RESULTS Eight weeks of home-based training improved temporal-spatial gait symmetry at SSWS but not at MWS. A relative interlimb increase in stance duration for the prosthetic limb and proportionally greater increases in step length for the limb taking shorter steps produced the improved symmetry. The training effect was significant for the step length symmetry ratio within the first 4 weeks of the program. Energy expenditure decreased progressively during the training with nearly 10% improvement observed across the range of walking speeds. SSWS, MWS, and 2MWT all increased by 16% to 20%. CONCLUSIONS Home-based treadmill walking is an effective method to improve gait performance in persons with TFA. The results support the application of training interventions beyond the initial rehabilitation phase, even in individuals considered highly functional.

Axial bone–socket displacement for persons with a traumatic transtibial amputation: The effect of elevated vacuum suspension at progressive body-weight loads:

Background: Elevated vacuum suspension systems use a pump to draw air from the socket with the intent of reducing bone–socket motion as compared to passive suction systems. However, it remains unknown if elevated vacuum suspension systems decrease limb displacement uniformly during transitions from unloaded to full–body–weight support. Objectives: To compare limb–socket motion between elevated vacuum and passive suction suspension sockets using a controlled loading paradigm. Study design: Comparative analysis. Methods: Persons with transtibial amputation were assessed while wearing either an elevated vacuum or passive suction suspension socket. Digital video fluoroscopy was used to measure axial bone–socket motion while the limb was loaded in 20% body-weight increments. An analysis of variance model was used to compare between suspension types. Results: Total axial displacement (0%–100% body weight) was significantly lower using the elevated vacuum (vacuum: 1.3 cm, passive suction: 1.8 cm; p < 0.0001). Total displacement decreased primarily due to decreased motion during initial loading (0%–20%; p < 0.0001). Other body-weight intervals were not significantly different between systems. Conclusion: Elevated vacuum suspension reduced axial limb–socket motion by maintaining position of the limb within the socket during unloaded conditions. Elevated vacuum provided no meaningful improvement in limb–socket motion past initial loading. Clinical relevance Excessive bone–socket motion contributes to poor residual limb health. Our results suggest elevated vacuum suspensions can reduce this axial displacement. Visual assessment of the images suggests that this occurs through the reduction or elimination of the air pocket between the liner and socket wall while the limb is unloaded.

Assessing preparative gait adaptations in persons with transtibial amputation in response to repeated medial-lateral perturbations

Preventing loss of balance in individuals with transtibial amputation is important, as they are susceptible to a high frequency of fall related injuries. In order to validate fall prevention and balance therapies, methods to assess gait stability must be developed. Kinematic, temporal-spatial, and center of mass data from six healthy young participants with transtibial amputation were collected during treadmill walking during exposure to 10 randomly ordered discrete medial-lateral perturbations. The 20 strides prior to each perturbation were assessed for anticipatory changes. The only consistent postural adjustment made as a result of the perturbations was a significantly lowered center of mass height (p=0.016).

Factors Influencing Functional Outcomes and Return-to-Work After Amputation: A Review of the Literature

Purpose Amputation is a life changing event that can significantly impact an individual’s physical and mental well-being. Our objective was to review literature exploring the impact of amputation upon a person’s functioning and inclusion in the workplace. Methods Medline, CINAHL, and PsycINFO were searched using keywords related to amputation, employment and community reintegration. Eligible studies were published since 2000 and one of the following study designs: randomized controlled trial, non-randomized controlled trial, retrospective study, prospective study, concurrent cohort study, or cross sectional study. Studies for civilians with amputation as well as service members and Veterans with amputation were considered for inclusion. Results The search identified 995 articles, 25 of which met inclusion/exclusion criteria and were included in the review. While strong evidence for correlations and predictors of outcomes after amputation were limited, multiple factors were identified as contributing to physical functioning and employment after amputation. Conclusions Outcomes after amputation can vary widely with many potentially inter-related factors contributing. The factors identified may also serve to inform the development of interventions aiming to improve functional performance and reintegration after amputation. Furthermore, the review highlights the need for more high quality prospective studies.