The Role of Visual Attention and Environmental Complexity in Real-world Mobility for People With Lower Limb Amputation

Virginia Commonwealth University30 enrolled

Overview

Despite high medical expenses (\>$500K/patient), mobility improvements achieved during rehabilitation for people with lower limb amputation (LLA) fail to translate into improved real-world outcomes. Even with advances in prosthesis technology enabling faster gait speed, greater walking endurance, and improved mobility confidence, people with LLA report persistent dissatisfaction with real-world mobility, limited ability to walk in the community, and difficulty achieving recommended physical activity levels. Real-world walking requires thinking and moving simultaneously (e.g., cognitive-motor dual-tasking), visually attending to the environment, and navigating varying terrain. In contrast, clinical mobility assessments are usually performed without additional visual or cognitive demands, in controlled environments, and on level surfaces. Current clinical tools used to assess ambulation progression during rehabilitation do not adequately assess these changes in people who have experienced LLA.

A step toward rectifying a critical gap in care for those with LLA by quantifying the effect of vision-based and non-vision-based cognitive-motor dual-tasking and high and low complexity terrain on gait speed and gaze behavior. Cognitive-motor dual-task assessment paradigms are well-established in other populations and often used to better approximate real-world walking demands. However, the type of cognitive task used is an important factor. The most common methods for dual-task assessment in people with LLA are limited to cognitive tasks lacking overt visual attention (e.g., serial subtraction - performing repeated subtractions from a given starting number).Although walking while performing non-vision-based cognitive tasks results in slower gait speed than single-task walking, this type of task has limited ecological validity and the observed dual-task performances have not been associated with real-world walking outcomes. Performing vision-based cognitive-motor dual-tasks is particularly important for people with LLA. Due to lost somatosensory input from the amputated limb, the central nervous system increases dependence on visual input for sensorimotor integration. As a result, people with LLA report needing to "concentrate on every step", and affix their gaze on each subsequent step compared to 3 steps ahead like adults without LLA. Current clinical assessments fail to detect impairments during mobility tasks requiring visual attention in complex environments. The lack of understanding of the interaction between visual attention and complex environment precludes a comprehensive mobility assessment, allows undetected impairments to persist, and limits translation of rehabilitation gains into improved real-world mobility outcomes.

Interventions

Comprehensive assessment of walking patterns and functional mobilityOTHER

Assessment of accelerometry: Daily duration (minutes) of sitting, standing, stepping, Daily step count, Daily walking bouts stepping cadence, Timed Up and Go and Two-minute Walk Test

Comprehensive assessment of eye movements during walkingOTHER

Comprehensive assessment of eye movements during walking including Target Fixation Time (seconds; %) and Number of fixations

Questionnaire Assessments completedOTHER

The following assessments will be completed: World health organization disability assessment schedule 2.0 (WHODAS), and Activities Specific Balance Confidence Scale.

Eligibility

Sex: ALLMin age: 18 Years

Medical Language ↔ Plain English

Inclusion Criteria: * unilateral transtibial LLA of either dysvascular (diabetes, peripheral vascular disease, and/or infection) or traumatic etiology * 18 years old minimum * able to ambulate 2 minutes without rest * 9 months since LLA * fitted with terminal prosthesis * 20/60 vision or better (with or without glasses/contacts) Exclusion Criteria: * congenital or cancer-related LLA * ankle-level or above LLA on the contralateral limb * residual limb wound or contralateral foot ulcer * unstable heart condition (including unstable angina, uncontrolled cardiac dysrhythmia, acute myocarditis, hypertension, and acute pericarditis) * acute systemic infection * prisoner * inability to follow a 3-step command * concussion/brain injury in the past 12 months * active cancer treatment * preexisting neurological condition (i.e., multiple sclerosis, Parkinson's disease) * participating in prosthetic rehabilitation * color-blindness * history of seizure(s) * inability to read and communicate in English. Participants in the control group must meet the non-amputation-related criteria noted above, be within ±2 years and the same biological sex as their paired participants with LLA.

Outcomes

Primary Outcomes

Gait Analysis-Walking Speed

Measure walking speed meters/second. Captured during dual-task and single-task walking, it is used to measure motor performance. Normal Speed: Healthy adults usually walk at 1.2 to 1.4 meters per second.Fall Risk: A speed below 1.0 meter per second shows a higher risk for falls.Frailty Warning: A speed below 0.6 to 0.8 meters per second suggests a high risk of functional decline or disability.