A mental workload and biomechanical assessment during split-belt locomotor adaptation with and without optic flow.

Adaptive human performance relies on the central nervous system to regulate the engagement of cognitive-motor resources as task demands vary. Despite numerous studies which employed a split-belt induced perturbation to examine biomechanical outcomes during locomotor adaptation, none concurrently examined the cerebral cortical dynamics to assess changes in mental workload. Additionally, while prior work suggests that optic flow provides critical information for walking regulation, a few studies have manipulated visual inputs during adaption to split-belt walking. This study aimed to examine the concurrent modulation of gait and Electroencephalography (EEG) cortical dynamics underlying mental workload during split-belt locomotor adaptation, with and without optic flow. Thirteen uninjured participants with minimal inherent walking asymmetries at baseline underwent adaptation, while temporal-spatial gait and EEG spectral metrics were recorded. The results revealed a reduction in step length and time asymmetry from early to late adaptation, accompanied by an elevated frontal and temporal theta power; the former being well corelated to biomechanical changes. While the absence of optic flow during adaptation did not affect temporal-spatial gait metrics, it led to an increase of theta and low-alpha power. Thus, as individuals adapt their locomotor patterns, the cognitive-motor resources underlying the encoding and consolidation processes of the procedural memory were recruited to acquire a new internal model of the perturbation. Also, when adaption occurs without optic flow, a further reduction of arousal is accompanied with an elevation of attentional engagement due to enhanced neurocognitive resources likely to maintain adaptive walking patterns.

Pre-neuromusculoskeletal injury Risk factor Evaluation and Post-neuromusculoskeletal injury Assessment for Return-to-duty/activity Enhancement (PREPARE) in military service members: a prospective, observational study protocol.

BACKGROUND: Non-battle related musculoskeletal injuries (MSKI) are one of the primary medical issues diminishing Service member medical readiness. The MSKI problem is challenging because it is difficult to assess all of the factors that increase MSKI risk and influence post-MSKI outcomes. Currently, there are no high-throughput, clinically-feasible, and comprehensive assessments to generate patient-centric data for informing pre- and post-MSKI risk assessment and mitigation strategies. The objective of the "Pre-neuromusculoskeletal injury Risk factor Evaluation and Post-neuromusculoskeletal injury Assessment for Return-to-duty/activity Enhancement (PREPARE)" study is to develop a comprehensive suite of clinical assessments to identify the patient-specific factors contributing to MSKI risks and undesired post-MSKI outcomes. METHODS: This is a phased approach, multi-center prospective, observational study (ClinicalTrials.gov number: NCT05111925) to identify physical and psychosocial factors contributing to greater MSKI risk and undesired post-MSKI outcomes, and to identify and validate a minimal set of assessments to personalize risk mitigation and rehabilitation strategies. In Phase I, one cohort (n = 560) will identify the physical and psychosocial factors contributing to greater MSKI risks (single assessment), while a second cohort (n = 780) will identify the post-MSKI physical and psychosocial factors contributing to undesired post-MSKI outcomes (serial assessments at enrollment, 4 weeks post-enrollment, 12 weeks post-enrollment). All participants will complete comprehensive movement assessments captured via a semi-automated markerless motion capture system and instrumented walkway, joint range of motion assessments, psychosocial measures, and self-reported physical fitness performance and MSKI history. We will follow participants for 6 months. We will identify the minimum set of clinical assessments that provide requisite data to personalize MSKI risk mitigation and rehabilitation strategies, and in Phase II validate our optimized assessments in new cohorts. DISCUSSION: The results of this investigation will provide clinically relevant data to efficiently inform MSKI risk mitigation and rehabilitation programs, thereby helping to advance medical care and retain Service members on active duty status. TRIAL REGISTRATION: PREPARE was prospectively registered on ClinicalTrials.gov (NCT05111925) on 5 NOV 2021, prior to study commencement.

A Biomechanical Comparison of High-Tensile Strength Tape Versus High-Tensile Strength Suture for Tendon Fixation Under Cyclic Loading.

PURPOSE: To compare the biomechanical properties of high-tensile strength tape and high-tensile strength suture across 2 selected stitch techniques, the Krackow and whip stitch, in securing tendinous tissue during 5,000 cycles of nondestructive loading followed by a load to failure. METHODS: Fourteen matched pairs each of cadaveric Achilles, quadriceps, and patellar tendons (n = 84) were randomly assigned to either Krackow or whip stitch and sutured with either 2-mm high-tensile strength tape or No. 2 high-tensile strength suture. Specimens were preloaded to 20 N, cyclically loaded from 20 to 200 N for 5,000 cycles at 2 Hz, and then loaded to failure at 200 mm/min. Linear mixed models evaluated the effects of suture material and stitch technique on cyclic normalized tendon-suture elongation, total normalized tendon-suture elongation at 5,000 cycles, and maximum load at failure. RESULTS: Across all suture constructs, normalized elongation was greater during the initial 10 cycles, compared with all subsequent cycling intervals (all P < .001). There was less total normalized elongation (ß = -0.239; P = .007) and greater maximum load at failure in tape (ß = 163.71; P = .014) when used in the Krackow stitch compared with the whip stitch. CONCLUSIONS: Our findings indicate that tape used in the Krackow stitch maintains the most favorable fixation strength after enduring cyclic loading, with greater maximum load at failure. In addition, overall normalized elongation during long-term cyclic loading was predominately affected by the stitch technique used, regardless of the suture material; however, tape allowed less normalized elongation during the initial loading cycles, especially when placed in the whip stitch. CLINICAL RELEVANCE: Understanding the potential short- and long-term outcomes of suture material and stitch technique on securing tendinous tissue under repetitive stresses can help inform clinicians on optimal tendon fixation techniques for early postoperative activities.

The Relationships Between Self-reported Pain Intensity, Pain Interference, and Quality of Life Among Injured U.S. Service Members With and Without Low Back Pain.

Low back pain is a prevalent military and veteran health problem and individuals injured on deployment may be at particularly high risk of pain conditions. Given that increasing numbers of active duty and veteran military personnel are seeking care in community settings, it is critical that health care providers are aware of military health issues. The current study examined the prevalence of low back pain among individuals with deployment-related injuries, compared their self-reported pain intensity and interference ratings, and assessed the relationship between low back pain, self-reported pain ratings, and quality of life. Almost half of participants had low back pain diagnoses, and individuals with low back pain reported significantly higher intensity and interference due to their pain than individuals without low back pain. Finally, the relationship between low back pain and quality of life was explained by self-reported pain indices, underscoring the importance of patient-centered metrics in pain treatment.

Trunk Postural Control Strategies Among Persons With Lower-Limb Amputation While Walking and Performing a Concurrent Task.

Altered trunk movements during gait in persons with lower-limb amputation are often associated with an increased risk for secondary health conditions; however, the postural control strategies underlying such alterations remain unclear. In this secondary analysis, the authors employed nonlinear measures of triplanar trunk accelerations via short-term Lyapunov exponents to investigate trunk local stability as well as spatiotemporal gait parameters to describe gait mechanics. The authors also evaluated the influence of a concurrent task on trunk local stability and gait mechanics to explore if competition for neuromuscular processing resources can assist in identifying unique strategies to control kinematic variability. Sixteen males with amputation-8 transtibial and 8 transfemoral-and 8 uninjured males (controls) walked on a treadmill at their self-selected speed (mean = 1.2 m/s ±10%) in 5 experimental conditions (8 min each): 4 while performing a concurrent task (2 walking and 2 seated) and 1 with no concurrent task. Individuals with amputation demonstrated significantly smaller Lyapunov exponents than controls in all 3 planes of motion, regardless of concurrent task or level of amputation (P < .0001). Individuals with transfemoral amputation walked with wider strides compared with individuals with transtibial amputation and controls (P < .0001). Individuals with amputation demonstrated more trunk kinematic variability in the presence of wider strides compared with individuals without amputation, and it appears that performing a concurrent cognitive task while walking did not change trunk or gait mechanics.

Overall Greater Demands on the Musculoskeletal System at Multiple Walking Speeds in Service Members With Lower Limb Loss.

Individuals with lower limb loss often walk with altered/asymmetric movement mechanics, postulated as a catalyst for development of low back and knee pain. Here, the authors simultaneously investigated trunk-pelvic movement patterns and lower limb joint kinematics and kinetics among 38 males with traumatic, unilateral lower limb loss (23 transtibial and 15 transfemoral), and 15 males without limb loss, at a self-selected and 2 standardized (1.0 and 1.6 m/s) speeds. Individuals with versus without lower limb loss walked with greater trunk range of motion in the frontal and transverse planes at all speeds (despite ∼10% slower self-selected speeds). At all speeds, individuals with versus without limb loss exhibited +29% larger medial ground reaction forces, and at 1.6 m/s also exhibited +50% to 110% larger vertical hip power generation, +27% to 80% larger vertical hip power absorption, and +21% to 90% larger medial-lateral hip power absorption. Moreover, pervasive biomechanical differences between transtibial versus transfemoral limb loss identify amputation-level movement strategies. Overall, greater demands on the musculoskeletal system across walking speeds, particularly at the hip, knee, and low back, highlight potential risk factors for the development/recurrence of prevalent secondary musculoskeletal conditions (eg, joint degeneration and pain) following limb loss.

Characterizing and Understanding the Low Back Pain Experience Among Persons with Lower Limb Loss.

OBJECTIVE: This study preliminarily characterizes and compares the impact of lower limb loss and development of chronic low back pain (cLBP) on psychosocial factors, as well as the relationship between these factors and low back pain-related functional disability. DESIGN: Cross-sectional study. METHODS: Participants were adults, active duty or retired military, with traumatic lower limb loss with and without chronic low back pain. Psychosocial factors and low back pain-related functional disability were measured using common clinical self-report questionnaires. The presence of psychosocial factors was compared between those with and without cLBP using multivariate analysis of covariance (P < 0.05), and correlations determined relationships between psychosocial factors and cLBP-related functional disability. RESULTS: There were no statistically significant differences among psychosocial factors between those with vs without cLBP (F(4, 13) = 0.81, P = 0.54, η2= 0.19). Employment status (ρ = 0.43, P = 0.02), anxiety (ρ = 0.45, P = 0.04), and kinesiophobia (ρ = 0.47, P = 0.04) were moderately associated with low back pain-related disability. CONCLUSIONS: Psychological (i.e., anxiety) and social (i.e., employment status) factors may influence how persons with traumatic lower limb loss respond to self-reported measures of low back pain-related disability. The findings suggest that the Modified Oswestry Disability Index identifies cLBP-related functional disability in the context of lower limb loss. These results support the interdependence among biological, psychological, and social factors, which should be collectively considered during the development of rehabilitative strategies to treat secondary musculoskeletal conditions within this population.

Resolving the Burden of Low Back Pain in Military Service Members and Veterans (RESOLVE): Protocol for a Multisite Pragmatic Clinical Trial.

BACKGROUND: Physical therapy (PT) is frequently used for the management of low back pain (LBP) within the US Departments of Defense (DOD) and Veterans Affairs (VA). However, variations in PT practice patterns and use of ineffective interventions lower the quality and increase the cost of care. Although adherence to the clinical practice guidelines (CPGs) can improve the outcomes and cost-effectiveness of LBP care, PT CPG adherence remains below 50%. The Resolving the Burden of Low Back Pain in Military Service Members and Veterans (RESOLVE) trial will evaluate the effectiveness of an active PT CPG implementation strategy using an education, audit, and feedback model for reducing pain, disability, medication use, and cost of LBP care within the DOD and VA health care systems. DESIGN: The RESOLVE trial will include 3,300 to 7,260 patients with LBP across three DOD and two VA medical facilities using a stepped-wedge study design. An education, audit, and feedback model will be used to encourage physical therapists to better adhere to the PT CPG recommendations. The Oswestry Disability Index and the Defense and Veterans Pain Rating Scale will be used as primary outcomes. Secondary outcomes will include the LBP-related medication use, medical resource utilization, and biopsychosocial predictors of outcomes. Statistical analyses will be based on the intention-to-treat principle and will use linear mixed models to compare treatment conditions and examine the interactions between treatment and subgrouping status (e.g., limb loss). SUMMARY: The RESOLVE trial will provide a pragmatic approach to evaluate whether better adherence to PT CPGs can reduce pain, disability, medication use, and LBP care cost within the DOD and VA health care systems.

Changes in Trunk and Pelvis Motion Among Persons With Unilateral Lower Limb Loss During the First Year of Ambulation.

OBJECTIVE: To retrospectively investigate trunk-pelvis kinematic outcomes among persons with unilateral transtibial and transfemoral limb loss with time from initial independent ambulation with a prosthesis, while secondarily describing self-reported presence and intensity of low back pain. Over time, increasing trunk-pelvis range of motion and decreasing trunk-pelvis coordination with increasing presence and/or intensity of low back pain were hypothesized. Additionally, less trunk-pelvis range of motion and more trunk-pelvis coordination for persons with more distal limb loss was hypothesized. DESIGN: Inception cohort with up to 5 repeated evaluations, including both biomechanical and subjective outcomes, during a 1-year period (0, 2, 4, 6, 12 months) after initial ambulation with a prosthesis. SETTING: Biomechanics laboratory within military treatment facility. PARTICIPANTS: Twenty-two men with unilateral transtibial limb loss and 10 men with unilateral transfemoral limb loss (N=32). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Triplanar trunk-pelvis range of motion and intersegmental coordination (continuous relative phase) obtained at self-selected (∼1.30m/s) and controlled (∼1.20m/s) walking velocities. Self-reported presence and intensity of low back pain. RESULTS: An interaction effect between time and group existed for sagittal (P=.039) and transverse (P=.009) continuous relative phase at self-selected walking velocity and transverse trunk range of motion (P=.013) and sagittal continuous relative phase (P=.005) at controlled walking velocity. Trunk range of motion generally decreased, and trunk-pelvis coordination generally increased with increasing time after initial ambulation. Sagittal trunk and pelvis range of motion were always less and frontal trunk-pelvis coordination was always greater for persons with more distal limb loss. Low back pain increased for persons with transtibial limb loss and decreased for persons with transfemoral limb loss following the 4-month time point. CONCLUSIONS: Temporal changes (or lack thereof) in features of trunk-pelvis motions within the first year of ambulation help elucidate relationships between (biomechanical) risk factors for low back pain after limb loss.

A Comparison of Mental Workload in Individuals with Transtibial and Transfemoral Lower Limb Loss during Dual-Task Walking under Varying Demand.

OBJECTIVES: This study aimed to evaluate the influence of lower limb loss (LL) on mental workload by assessing neurocognitive measures in individuals with unilateral transtibial (TT) versus those with transfemoral (TF) LL while dual-task walking under varying cognitive demand. METHODS: Electroencephalography (EEG) was recorded as participants performed a task of varying cognitive demand while being seated or walking (i.e., varying physical demand). RESULTS: The findings revealed both groups of participants (TT LL vs. TF LL) exhibited a similar EEG theta synchrony response as either the cognitive or the physical demand increased. Also, while individuals with TT LL maintained similar performance on the cognitive task during seated and walking conditions, those with TF LL exhibited performance decrements (slower response times) on the cognitive task during the walking in comparison to the seated conditions. Furthermore, those with TF LL neither exhibited regional differences in EEG low-alpha power while walking, nor EEG high-alpha desynchrony as a function of cognitive task difficulty while walking. This lack of alpha modulation coincided with no elevation of theta/alpha ratio power as a function of cognitive task difficulty in the TF LL group. CONCLUSIONS: This work suggests that both groups share some common but also different neurocognitive features during dual-task walking. Although all participants were able to recruit neural mechanisms critical for the maintenance of cognitive-motor performance under elevated cognitive or physical demands, the observed differences indicate that walking with a prosthesis, while concurrently performing a cognitive task, imposes additional cognitive demand in individuals with more proximal levels of amputation.

Biomechanical and neurocognitive performance outcomes of walking with transtibial limb loss while challenged by a concurrent task.

Individuals who have sustained loss of a lower limb may require adaptations in sensorimotor and control systems to effectively utilize a prosthesis, and the interaction of these systems during walking is not clearly understood for this patient population. The aim of this study was to concurrently evaluate temporospatial gait mechanics and cortical dynamics in a population with and without unilateral transtibial limb loss (TT). Utilizing motion capture and electroencephalography, these outcomes were simultaneously collected while participants with and without TT completed a concurrent task of varying difficulty (low- and high-demand) while seated and walking. All participants demonstrated a wider base of support and more stable gait pattern when walking and completing the high-demand concurrent task. The cortical dynamics were similarly modulated by the task demand for both groups, to include a decrease in the novelty-P3 component and increase in the frontal theta/parietal alpha ratio power when completing the high-demand task, although specific differences were also observed. These findings confirm and extend prior efforts indicating that dual-task walking can negatively affect walking mechanics and/or neurocognitive performance. However, there may be limited additional cognitive and/or biomechanical impact of utilizing a prosthesis in a stable, protected environment in TT who have acclimated to ambulating with a prosthesis. These results highlight the need for future work to evaluate interactions between these cognitive-motor control systems for individuals with more proximal levels of lower limb loss, and in more challenging (ecologically valid) environments.

Modulation of Vertical Ground Reaction Impulse With Real-Time Biofeedback: A Feasibility Study.

Given its apparent representation of cumulative (vs peak) loads, this feasibility study investigates vertical ground reaction impulse (vGRI) as a real-time biofeedback variable for gait training aimed at reducing lower limb loading. Fifteen uninjured participants (mean age = 27 y) completed 12 2-min trials, 1 at each combination of 4 walking speeds (1.0, 1.2, 1.4, and 1.6 m/s) and 3 targeted reductions in vGRI (5, 10, and 15%) of the assigned ("target") limb, with the latter specified relative to an initial baseline (no feedback) condition at each speed. The ability to achieve targeted reductions was assessed using step-by-step errors between measured and targeted vGRI. Mean (SD) errors were 5.2% (3.7%); these were larger with faster walking speeds but consistent across reduction targets. Secondarily, we evaluated the strategy used to modulate reductions (ie, stance time or peak vertical ground reaction force [vGRF]) and the resultant influences on knee joint loading (external knee adduction moment [EKAM]). On the targeted limb, stance times decreased (P < .001) with increasing reduction target; first and second peaks in vGRF were similar (P > .104) across all target conditions. While these alterations did not significantly reduce EKAM on the target limb, future work in patients with knee pathologies is warranted.

Mediolateral joint powers at the low back among persons with unilateral transfemoral amputation.

OBJECTIVE: To analyze mediolateral joint powers at the low back during gait among persons with and without unilateral transfemoral amputation to better understand the functional contributions of tissues in and around the low back to altered lateral trunk movements in this population. DESIGN: Retrospective analysis of biomechanical gait data. SETTING: Gait laboratory. PARTICIPANTS: Twenty persons with unilateral transfemoral amputation and 20 uninjured controls (N=40). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Net joint powers, and total generation (+) and absorption (-) energies, at the low back (L5/S1 spinal level) were analyzed in the frontal plane using inverse dynamics analyses on over-ground gait data collected at self-selected walking speeds (∼1.3m/s). RESULTS: Compared with uninjured controls, 4 distinctly larger positive phases of mediolateral joint power at L5/S1 were evident in persons with transfemoral amputation, occurring before and after each heel strike. Total generation energies throughout the gait cycle were also larger (P<.001) among persons with transfemoral amputation (4.8±1.4J) than among uninjured controls (1.3±0.7J). CONCLUSIONS: Larger positive phases of joint power at L5/S1 in the frontal plane support previous suggestions that persons with transfemoral amputation use a more active mediolateral trunk movement strategy, although such an active trunk movement strategy with transfemoral amputation may contribute to higher metabolic energy expenditures and low back pain risk.

Does intact limb loading differ in servicemembers with traumatic lower limb loss?

BACKGROUND: The initiation and progression of knee and hip arthritis have been related to limb loading during ambulation. Although altered gait mechanics with unilateral lower limb loss often result in larger and more prolonged forces through the intact limb, how these forces differ with traumatic limb loss and duration of ambulation have not been well described. QUESTIONS/PURPOSES: The purpose of this study was to determine whether biomechanical variables of joint and limb loading (external adduction moments, vertical ground reaction force loading rates, and impulses) are larger in the intact limb of servicemembers with versus without unilateral lower limb loss and whether intact limb loading differs between shorter (≤ 6 months) versus longer (≥ 2 years) durations of ambulation with a prosthesis. METHODS: A retrospective review was conducted of all clinical and research gait evaluations performed in the biomechanics laboratory at Walter Reed Army Medical Center and Walter Reed National Military Medical Center between January 2008 and December 2012. Biomechanical data meeting all inclusion and exclusion criteria were obtained for 32 individuals with unilateral transtibial limb loss, 49 with unilateral transfemoral limb loss, and 28 without limb loss. Individuals with unilateral lower limb loss were separated by their experience ambulating with a prosthesis at the time of the gait collection, ≤ 6 months or ≥ 2 years, to determine the effect of duration of ambulation with a prosthesis. RESULTS: Intact limb mean and peak vertical ground reaction force loading rates (median [range; 95% confidence interval]) were larger for transtibial subjects with ≤ 6 months of experience ambulating with a prosthesis versus control subjects (mean: 12.13 body weight [BW]/s [4.45-16.79; 10.18-12.81] versus 9.03 BW/s [4.64-14.47; 8.26-9.74]; effect size [ES] = 0.40; p = 0.003; and peak: 17.23 BW/s [6.58-25.25; 15.46-19.01] versus 13.60 BW/s [9.82-19.51; 12.98-15.05]; ES = 0.43; p = 0.001), respectively. Intact limb mean and peak vertical ground reaction force loading rates were also larger in subjects with transfemoral limb loss with ≤ 6 months and ≥ 2 years of experience ambulating with a prosthesis versus control subjects (mean: 12.67 BW/s [5.88-18.15; 11.06-14.47] and 12.59 BW/s [8.08-17.39; 11.83-13.68] versus 9.03 BW/s [4.64-14.47; 8.26-9.74]; ES ≥ 0.53; p < 0.001; peak: 19.82 BW/s [11.93-29.43; 18.35-23.05] and 21.33 BW/s [16.68-36.69; 20.66-24.26] versus 13.60 BW/s [9.82-19.51; 12.98-15.05]; ES ≥ 0.68; p < 0.001, respectively). Similarly, intact limb vertical ground reaction force impulses (0.63 BW·s [0.53-0.81; 0.67-0.69] and 0.62 BW·s [0.55-0.74; 0.60-0.63] versus 0.57 BW·s [0.50-0.66; 0.55-0.58]; ES ≥ 0.53, p < 0.001) were also larger among both groups of transfemoral subjects versus control subjects, respectively. Limb loading variables were not statistically different between times ambulating with a prosthesis within groups with transtibial or transfemoral limb loss. CONCLUSIONS: Larger intact limb loading in individuals with traumatic transtibial loss were only noted early in the rehabilitation process, but these variables were present early and late in the rehabilitation process for those with transfemoral limb loss. Such evidence suggests an increased risk for early onset and progression of arthritis in the intact limb, especially in those with transfemoral limb loss. CLINICAL RELEVANCE: Interventions should focus on correcting modifiable gait mechanics associated with arthritis, particularly among individuals with transfemoral limb loss, to potentially mitigate the development and progression in this population.

A patient-centered 'test-drive' strategy for ankle-foot orthosis prescription: Protocol for a randomized participant-blinded trial.

BACKGROUND: Ankle-foot orthoses (AFOs) are commonly used to overcome mobility limitations related to lower limb musculoskeletal injury. Despite a multitude of AFOs to choose from, there is scant evidence to guide AFO prescription and limited opportunities for AFO users to provide experiential input during the process. To address these limitations in the current prescription process, this study evaluates a novel, user-centered and personalized 'test-drive' strategy using a robotic exoskeleton ('AFO emulator') to emulate commercial AFO mechanical properties (i.e., stiffness). The study will determine if brief, in-lab trials (with emulated or actual AFOs) can predict longer term preference, satisfaction, and mobility outcomes after community trials (with the actual AFOs). Secondarily, it will compare the in-lab experience of walking between actual vs. emulated AFOs. METHODS AND ANALYSIS: In this participant-blinded, randomized crossover study we will recruit up to fifty-eight individuals with lower limb musculoskeletal injuries who currently use an AFO. Participants will walk on a treadmill with three actual AFOs and corresponding emulated AFOs for the "in-lab" assessments. For the community trial assessment, participants will wear each of the actual AFOs for a two-week period during activities of daily living. Performance-based and user-reported measures of preference and mobility will be compared between short- and long-term trials (i.e., in-lab vs. two-week community trials), and between in-lab trials (emulated vs. actual AFOs). TRIAL REGISTRATION: The study was prospectively registered at www.clininicaltrials.gov (Clinical Trials Study ID: NCT06113159). Date: November 1st 2023. https://classic.clinicaltrials.gov/ct2/show/NCT06113159.

Peak tibial axial acceleration during walking is related to intact-side lower limb pain in persons with unilateral transtibial amputation.

BACKGROUND: Persons who undergo unilateral transtibial amputation are at an increased risk of secondary musculoskeletal joint pain and degeneration, which has been linked to excessive loading rates of the intact-side limb. Tibial axial acceleration, a feasible measure of loading rates with wearable sensors, would be clinically useful to relate to joint pain in persons with unilateral transtibial amputation. RESEARCH QUESTION: What is the relationship between peak tibial axial accelerations and intact-side joint pain in persons with unilateral transtibial amputation during walking? METHODS: Persons with unilateral transtibial amputation (n = 51) were separated into two groups based on the presence of intact-side limb pain (with pain: n = 16; without pain: n = 35). Tibial axial accelerations were measured with bilateral shank-mounted IMUs while participants completed three 10-meter walk tests. Peak tibial axial accelerations for each limb and between-limb symmetry were compared between groups using analysis of co-variance; significance was set at 0.05. RESULTS: Between persons with vs. without intact-side limb pain, peak tibial axial accelerations were smaller on the prosthetic side (0.64 vs. 0.81 g; p = 0.04), similar on the intact side (0.82 vs. 0.79 g; p = 0.53), and more asymmetrical between sides (intact > prosthetic) (0.81 vs. 1.03 g; p = 0.01). SIGNIFICANCE: Symmetry in peak tibial axial acceleration can assist with identifying preferential limb loading during walking and, with future research, could serve as a useful clinical target for intact-side limb unloading strategies to help mitigate secondary musculoskeletal pain in persons with unilateral transtibial amputation.

Comparing spinal loads in individuals with unilateral transtibial amputation with and without chronic low back pain: An EMG-informed approach.

Chronic low back pain (cLBP) is highly prevalent after lower limb amputation (LLA), likely due in part to biomechanical factors. Here, three-dimensional full-body kinematics and kinetics during level-ground walking, at a self-selected and three controlled speeds (1.0, 1.3, and 1.6 m/s), were collected from twenty-one persons with unilateral transtibial LLA, with (n = 9) and without cLBP (n = 12). Peak compressive, mediolateral, and anteroposterior L5-S1 spinal loads were estimated from a full-body, transtibial amputation-specific OpenSim model and compared between groups. Predicted lumbar joint torques from muscle activations were compared to inverse dynamics and predicted and measured electromyographic muscle activations were compared for model evaluation and verification. There were no group differences in compressive or anterior shear forces (p > 0.466). During intact stance, peak ipsilateral loads increased with speed to a greater extent in the cLBP group vs. no cLBP group (p=0.023), while during prosthetic stance, peak contralateral loads were larger in the no cLBP group (p=0.047) and increased to a greater extent with walking speed compared to the cLBP group (p=0.008). During intact stance, intact side external obliques had higher activations in the no cLBP group (p=0.039), and internal obliques had higher activations in the cLBP group at faster walking speeds compared to the no cLBP group. Predicted muscle activations demonstrated similar activation patterns to electromyographic-measured activations (r = 0.56-0.96), and error between inverse dynamics and simulated spinal moments was low (0.08 Nm RMS error). Persons with transtibial LLA and cLBP may adopt movement strategies during walking to reduce mediolateral shear forces at the L5-S1 joint, particularly as walking speed increases. However, future work is needed to understand the time course from pain onset to chronification and the cumulative influence of increased spinal loads over time.

The effect of carbon fiber custom dynamic orthosis use and design on center of pressure progression and perceived smoothness in individuals with lower limb trauma.

BACKGROUND: Carbon-fiber custom dynamic orthoses are used to improve gait and limb function following lower limb trauma in specialty centers. However, the effects of commercially available orthoses on center of pressure progression and patient perception of orthosis smoothness during walking are poorly understood. METHODS: In total, 16 participants with a unilateral lower extremity traumatic injury underwent gait analysis when walking without an orthosis, and while wearing monolithic and modular devices, in a randomized order. Device alignment, stiffness, participant rating of perceived device smoothness, center of pressure velocity, and ankle zero moment crossing were assessed. FINDINGS: The modular device was approximately twice as stiff as the monolithic device. Alignment, smoothness ratings, peak magnitude of center of pressure velocity, and zero moment crossing were not different between study devices. The time to peak center of pressure velocity occurred significantly later for the modular device compared to the monolithic and no orthosis conditions, with large effect sizes observed. INTERPRETATION: Commercially available orthoses commonly used to treat limb trauma affect the timing of center of pressure progression relative to walking without an orthosis. Despite multiple design differences, monolithic and modular orthoses included in this study did not differ with respect to other measures of center of pressure progression. Perceived smoothness ratings were approximately 40% greater with the study orthoses as compared to previous studies in specialty centers, which may be due to a more gradual center of pressure progression, as indicted by lower peak magnitude of center of pressure velocity with both study orthoses.

Spinal Pathology and Muscle Morphologies with Chronic Low Back Pain and Lower Limb Amputation.

INTRODUCTION: Low back pain (LBP) is highly prevalent after lower limb amputation (LLA) and contributes to substantial reductions in quality of life and function. Towards understanding pathophysiological mechanisms underlying LBP after LLA, this article compares lumbar spine pathologies and muscle morphologies between individuals with LBP, with and without LLA. MATERIALS AND METHODS: We queried electronic medical records of Service members with and without LLA who sought care for LBP at military treatment facilities between January 2002 and May 2020. Two groups with cLBP, one with (n = 15) and one without unilateral transtibial LLA (n = 15), were identified and randomly chosen from a larger sample. Groups were matched by age, mass, and sex. Lumbar muscle morphology, Pfirrmann grades, Modic changes, facet arthrosis, Meyerding grades, and lordosis angle were determined from radiographs and magnetic resonance images available in the medical record. Independent t-tests compared variables between cohorts while multiple regression models determined if intramuscular fat influenced Pfirrmann grades. Chi-square determined differences in presence of spondylolysis and facet arthrosis. RESULTS: Lordosis angle was larger with LLA (P = 0.01). Spondylolysis was more prevalent with LLA (P = 0.008; 40%) whereas facet arthrosis was similar between cohorts (P = 0.3). Muscle area was not different between cohorts, yet intramuscular fat was greater with LLA (P ≤ 0.05). Intramuscular fat did not influence Pfirrmann grades (P > 0.15). CONCLUSIONS: Despite similar lumbar muscle size, those with unilateral LLA may be predisposed to progress to symptomatic spondylolisthesis and intramuscular fat. Surgical and/or rehabilitation interventions may mitigate long-term effects of diminished spinal health, decrease LBP-related disability, and improve function for individuals with LLA.

Mechanical loading of bone-anchored implants during functional performance tests in service members with transfemoral limb loss.

Introduction: For individuals with limb loss, bone-anchored implants create a direct structural and functional connection to a terminal prosthesis. Here, we characterized the mechanical loads distal to the abutment during several functional performance tests in Service members with transfemoral (TF) limb loss, to expand on prior work evaluating more steady-state ambulation on level ground or slopes/stairs. Methods: Two males with unilateral TF limb loss and two males with bilateral TF limb loss participated after two-stage osseointegration (24 and 12 months, respectively). Tri-directional forces and moments were wirelessly recorded through a sensor, fit distal to the abutment, during six functional tests: Timed Up and Go (TUG), Four Square Step Test (FSST), Six Minute Walk Test (6MWT), Edgren Side-Step Test (SST), T-Test (TTEST), and Illinois Agility Test (IAT). Additionally, participants performed a straight-line gait evaluation on a 15 m level walkway at a self-selected speed (0.93-1.24 m/s). Peak values for each component of force and moment were extracted from all six functional tests; percent differences compared each peak with respect to the corresponding mean peak in straight-line walking. Results: Peak mechanical loads were largest during non-steady state components of the functional tests (e.g., side-stepping during SST or TTEST, standing up from the ground during IAT). Relative to walking, peak forces during functional tests were larger by up to 143% (anterior-posterior), 181% (medial-lateral), and 110% (axial); peak moments were larger by up to 108% (flexion-extension), 50% (ab/adduction), and 211% (internal/external rotation). Conclusions: A more comprehensive understanding of the mechanical loads applied to bone-anchored implants during a variety of activities is critical to maximize implant survivability and long-term outcomes, particularly for Service members who are generally young at time of injury and return to active lifestyles.