Effect of sensor location for modifying center of pressure during gait using haptic feedback in people with chronic ankle instability.

BACKGROUND: Gait retraining using haptic biofeedback medially shifts the center of pressure (COP) while walking in orthopedic populations. However, the ideal sensor location needed to effectively shift COP medially has not been identified in people with chronic ankle instability (CAI). RESEARCH QUESTIONS: Can a heel sensor location feasibly be employed in people with CAI without negatively altering kinematics? Does a heel sensor placement relative to the 5th metatarsal head (5MH) impact COP location while walking in people with CAI? METHODS: In this exploratory crossover study, 10 participants with CAI walked on a treadmill with vibration feedback for 10 minutes with a plantar pressure sensor under the heel and 5MH. Separate 2×2 repeated measures analyses of covariances (rmANCOVAs) were used to compare the averaged COP location and 3-D lower extremity kinematics from the first 10% of stance before and after training and between sensor locations. Baseline measures served as covariates to adjust for baseline differences. RESULTS: Feedback triggered by a heel sensor resulted in 40% of participants avoiding a heel strike. There were no significant main effects or interactions between time and sensor location on COP location when controlling for baseline COP (p>0.05). However, with the 5MH placement, participants displayed less ankle internal rotation(IR) (5MH/Heel: -4.12±0.00º/ -6.43±0.62º), less forefoot abduction (-4.29±0.00º/ -5.14±1.01º), more knee flexion (3.40±0.32º/ 0.14±0.57º), less knee external rotation (-10.95±0.00º/-11.24±1.48º), less hip extension (-0.20±0.00º/-1.42±1.05º), and less hip external rotation (3.12±0.00º/3.75±1.98º). SIGNIFICANCE: A 5MH location may be more feasible based on difficulties maintaining heel strike when the sensor was under the heel. While no sensor location was statistically better at changing the COP, the 5MH location decreased proximal transverse plane motions making participants' gait more like controls. Individual response variations support comprehensive lower extremity assessments and the need to identify responder profiles using sensory feedback in people with CAI.

Immediate effects of vibration biofeedback on ankle kinematics in people with chronic ankle instability.

BACKGROUND: People with chronic ankle instability are more inverted during initial contact and loading response which may increase the risk of subsequent ankle injuries. Vibration feedback gait retraining causes medial center of pressure shifts but its impact on ankle kinematics remains unknown. The purpose of this study was to understand kinematic ankle changes in people with chronic ankle instability following vibration feedback gait retraining. METHODS: Nineteen participants with chronic ankle instability walked with vibration feedback for 10 min on a treadmill and for one mile in the real-world. A vibration stimulus occurred at the lower leg when pressure under the 5th metatarsal exceeded a threshold. Three-dimensional kinematics of the ankle were recorded in the lab before and after training. Paired t-tests compared baseline and posttest ankle, hindfoot, and forefoot positions during initial contact and loading response for the lab and real-world conditions. FINDINGS: After lab training the ankle (mean difference:-1.68 ± 1.62°, effect size:0.95) and forefoot (mean difference:-1.68 ± 1.67°, effect size:0.92) were more abducted. After real-world training, the ankle (mean difference:-1.19 ± 2.12°, effect size:0.54) and forefoot (mean difference:-1.87 ± 3.00°, effect size:0.63) were more everted. Similarly the ankle (mean difference:-2.37 ± 4.79°, effect size:0.46) and forefoot (mean difference:-2.78 ± 4.91°, effect size:0.51) were more abducted after real-world training. INTERPRETATION: Vibration feedback decreases inversion and adduction during loading response. However, RW compared to lab training may have more beneficial frontal plane changes for people with chronic ankle instability.

Acute Vibration Feedback During Gait Reduces Mechanical Ankle Joint Loading in Chronic Ankle Instability Patients.

BACKGROUND: Individuals with chronic ankle instability (CAI) exhibit altered vertical ground reaction forces (vGRF), a laterally shifted center of pressure, and an inverted foot position during walking. These neuromechanical alterations are linked with altered ankle joint loading in this population. Vibration-based gait retraining improves center of pressure positioning but effects on neuromechanical variables influencing joint loading remains unknown. RESEARCH QUESTION: Do patients with CAI exhibit altered vGRF and ankle joint contact forces (JCF) after receiving a single session of vibration-based gait retraining? METHODS: Ten individuals with CAI underwent a single session of vibration-based gait retraining. Kinematic and kinetic data were collected during walking on an instrumental treadmill with force plates embedded in it. Following a baseline gait assessment without feedback, participants walked at a self-selected speed for 10 minutes while receiving feedback. Data was collected during an early (1 st and 2 nd minute) and late adaptation phase (9 th and 10 th minute) and, compared to baseline values. Impact and propulsive vGRF variables (i.e. peak, time to peak, and loading rate) were obtained. Musculoskeletal modeling was used to calculate ankle JCF variables (peak, impulse, and loading rate) during stance phase. RESULTS: Propulsive vGRF and ankle JCF outcomes were significantly reduced during the early and late adaptation phases (p ≤ 0.039). SIGNIFICANCE: These results indicate that vibration-based gait retraining can immediately reduce propulsive vGRF and ankle JCF and may represent a modality that could help restore appropriate ankle joint loading patterns in those with CAI.

The effect of laboratory and real world gait training with vibration feedback on center of pressure during gait in people with chronic ankle instability.

BACKGROUND: External feedback has can medially shift the center of pressure (COP) location in people with chronic ankle instability(CAI) during walking. However, previous modalities are restricted to controlled environments which limits motor learning. Vibration feedback during gait may maximize motor learning by allowing for training in the laboratory and real world (RW) but has not been investigated in those with CAI. RESEARCH QUESTION: Does vibration feedback change COP location in people with CAI following laboratory and RW training? METHODS: Nineteen CAI participants walked for 10 min on a treadmill (lab training) and a one mile loop on a sidewalk (RW training) with vibration feedback. When pressure under the 5th metatarsal exceeded a threshold, a vibration stimulus was applied to the lateral malleolus encouraging the participant to medially shift the COP. One minute baseline, posttest, and short term retention gait assessments were taken for each environment. The stance phase of gait was divided into 10 subphases and data were averaged within each subphase. Repeated measures ANOVAs were completed for each subphase to compare COP location over time. RESULTS: After lab based training the COP was more medial at posttest for the first 90 % of stance versus baseline (Mean differences (MD): -0.57 to -5.12 mm, p < 0.023). Relative to baseline, the COP remained more medial at retention from 20 to 90% of stance (MD: -1.69 to -4.40 mm, p < 0.049). For RW training, the COP was more medial at posttest for the first 70 % of stance versus baseline (MD: -4.24 to -8.27 mm, p < 0.017) and the first 60 % of stance at retention versus baseline (MD: -4.14 to -6.42 mm, p < 0.049). SIGNIFICANCE: Vibration feedback during laboratory and RW gait training has the ability to immediately shift the COP location medially and retain this shift for a short period in individuals with CAI.