People with chronic ankle instability (CAI) demonstrate altered gait or walking mechanics which cause people to walk on the outside of their foot and increases the risk of additional ankle sprains, abnormal cartilage strain, and early joint degeneration. Evidence indicates that common treatments for CAI do not impact gait, leaving unresolved impairments that can lead to lifelong disability. Recent lab-based gait retraining with visual and auditory feedback has immediately improved walking mechanics. However, real-world training is hypothesized to generate long-term changes by incorporating short, frequent training sessions over a variety of surfaces. These are key training parameters to produce lasting change. Pilot data using real-world vibration feedback (RW-VF) suggest that a single session immediately improves walking mechanics with changes lasting for up to 5 minutes. Despite promising initial results, there remains a critical need to determine the impact of multiple RW-VF sessions as an initial step to developing a protocol capable of long-term improvements. The purpose of this proposal is to determine the extent to which 2-weeks of RW-VF restores gait biomechanics in those with CAI. Twenty people with CAI will be enrolled and complete a two-week gait retraining protocol with vibration feedback. Walking mechanics before, immediately after, and 1 week and 4 weeks following the training will be compared. These contributions can be significant as positive results will support a paradigm shift in treatments for people with CAI and lay the foundation for large scale clinical trials aimed at optimizing long term gains. The outcomes of future research have the potential to advance evidenced based rehabilitation interventions not only for people with CAI but also for people who have sustained a variety of musculoskeletal injuries as there is strong evidence that other lower extremity pathologies cause lifelong limitations, including changes in walking mechanics which lead to degenerative changes to other joints.

Background: There are 3.1 million lateral ankle sprains in the United States per year, of which about 40% will develop persistent limitations leading to chronic ankle instability (CAI). People with CAI demonstrate altered walking gait mechanics including increased inversion (ie: the foot rolling outward) and a lateral shift in the location of the center of pressure (COP) under the foot. These changes cause people to walk on the outside of their foot and increases the risk for additional ankle sprains, abnormal cartilage strain, and early post traumatic ankle arthritis (PTOA). Evidence indicates that common treatments for CAI do not impact gait, leaving unresolved impairments that can lead to lifelong disability. Recently walking with novel sensory feedback techniques (visual, auditory, and visual stimuli) has immediately improved walking mechanics during laboratory training. However, real-world (RW) training is hypothesized to generate long-term changes by incorporating short, frequent training sessions over a variety of surfaces which are key training parameters to produce lasting change. Vibration feedback (VF) is currently the only tool capable of being deployed in the real world. Recent pilot data suggest that a single VF training session in the RW immediately improves ankle and COP position with changes lasting for up to 5 minutes. Despite these promising initial results, there remains a critical need to determine the impact of multiple real-word vibration feedback (RW-VF) sessions as an initial step to developing a protocol capable of long-term improvements.

Purpose: The purpose of this proposal is to examine the effectiveness of a new treatment approach by determining the extent to which 2-weeks of RW-VF restores gait biomechanics in those with CAI.

Design: Cohort Study Methods: Kinematic and kinetic data will be captured from 20 participants with CAI at two baseline training sessions within 48 hours of each other (B1 and B2) while the participant walks on an instrumented treadmill. These data will be used to calculate the minimal detectable change (MDC), which is the stability of the walking measures. Following B2, participants will be fitted with the VF tool and complete the first of six training sessions. During training sessions, participants will walk six standardized but unique 1-mile RW routes with VF within a two-week time period. The order of the routes will be determined by a random number generator. Three additional biomechanical walking assessments will be completed within 72 hours of (P-2), one week following the final training (F-1), and 4 weeks following the final training (F-4).

Data Analysis: The primary analysis will determine the impact of RW-VF on COP location during the stance phase of walking in people with CAI. COP location will be compared before and after treatment (B1:P-2) using paired t-tests to determine the immediate impact of RW-VF training. The change between B1 and P-2 will be compared to the MDC to rule out measurement error. Next, COP location between B1 and F-1, and B1 and F-4 will be calculated to determine the extent to which the COP change is retained and compared to the MDC to rule out measurement error. Finally, COP data from posttest and retention timepoints will be compared to a database of walking biomechanics data from healthy controls using independent t-tests to determine similarities between people with and without CAI following training. The secondary analysis will repeat the primary using ankle position in the frontal plane (inversion/ eversion) during stance.

Significance: These contributions have the potential to be significant because positive results will support a paradigm shift in treatments for people with CAI. Positive results will also lay the foundation for large scale clinical trials comparing the current standard of care to the standard of care with the addition of RW-VF training to optimize long term gains. The outcomes of future research have the potential to advance evidenced based rehabilitation interventions not only for people with CAI but also for people who have sustained a variety of musculoskeletal injuries as there is strong evidence that other lower extremity pathologies cause lifelong limitations, including changes in walking mechanics which lead to degenerative changes to other joints.

CAI group:

Inclusion Criteria:

• between the ages of 18 - 35 years
• will have a history of at least 1 significant lateral ankle sprain which occurred at least 12 months prior to enrollment defines as a sprain which caused at least 1 day of interrupted physical activity
• have a history of recurrent sprains and/or episodes of "giving way"
• have a sense of ankle instability measured by a score of ≥ 11 on the Identification of Functional Ankle Instability (IdFAI)
• have self-reported functional limitations measured by a score of < 90% of the Foot and Ankle Ability Measure (FAAM)-Activities of Daily Living subscale and < 80% on the FAAM-Sport subscale.

Exclusion Criteria:

• evidence of bilateral CAI using the criteria above
• history of previous surgery in either lower extremity
• history of a fracture requiring realignment in either lower extremity
• an acute (< 12 weeks from enrollment) injury to either lower extremity
• any condition known to affect gait such as peripheral neuropathy, diabetes, neurological disorders, or neurodegenerative diseases
• knowingly pregnant.

Criteria for precollected healthy control data Inclusion/ Exclusion Criteria

• between the ages of 18-35 years
• no previous history of lower extremity surgery
• no lower extremity injury history in the past 6 months
• no history of neurological disorders (i.e.: stroke, cerebral palsy, multiple sclerosis, etc.)
• not knowingly pregnant. Patient reported outcomes (ie: FAAM, IdFAI) were not collected as part of the previous study, therefore cannot be used as inclusion or exclusion criteria.

Deidentified individual data that supports the results will be shared beginning 9 to 36 months following publication provided the investigator who proposes to use the data has approval from an Institutional Review Board (IRB), Independent Ethics Committee (IEC), or Research Ethics Board (REB), as applicable, and executes a data use/sharing agreement with UNC.

starting 9 months and continuing for 36 months following publication

Investigator has approved IRB, IEC, or REB and an executed data use/sharing agreement with UNC.