Gait Symmetry In And Outside Of A Laboratory After Acl Reconstruction

PURPOSE: To evaluate ground reaction force (GRF) symmetry during gait in individuals with ACL reconstruction within and outside of a laboratory. A secondary purpose was to assess the association between cumulative load during gait with single step loading metrics. METHODS: Fifteen individuals with unilateral ACL reconstruction participated (10 female, 5 male, age: 20.93 ± 2.05 yrs, time since surgery: 29 ± 14.21 months). Laboratory gait biomechanics were recorded at a self-selected speed on a split-belt force-instrumented treadmill. Unmonitored gait biomechanics were collected using force instrumented insoles over a pre-determined route. GRF data were recorded at 2000hz (treadmill) and 200hz (insoles). For each limb, peak GRF, peak loading rate (LR) and impulse were calculated and averaged across all foot strikes. Cumulative impulse was also calculated for Insole data. A limb symmetry index (LSI) was calculated for each metric. Pearson correlation assessed the association between LSI’s and paired T-tests compared analogous LSI’s between laboratory and unmonitored conditions (α = 0.05). RESULTS: Treadmill impulse LSI was correlated with Treadmill GRF LSI (r = 0.81, p = 0.01). Insole cumulative impulse LSI was correlated with Insole GRF LSI (r = 0.92, p = 0.01), insole impulse LSI (r = 0.98, p = 0.01) and insole LR LSI (r = 0.56, p = 0.03). Insole impulse LSI was correlated to Insole GRF LSI (r = 0.91, p = 0.01) and insole LR LSI (r = 0.637, p = 0.01). Insole GRF LSI was correlated to Insole LR LSI (r = 0.60, p = 0.02). There were no correlations between Treadmill LSI’s and Insole LSI’s (r = -0.16 - 0.33, p = 0.22 - 0.99). Insole LR LSI (103.74 ± 9.66) was higher than Treadmill LR LSI (96.14 ± 6.71), (p = 0.01). There were no differences in other LSI’s between conditions. CONCLUSIONS: LSIs were highly correlated within condition, but not between conditions. While LSIs between conditions were not different with the exception of LR. However, LSI’s between conditions were not related and should not be substituted for each other. Vertical LR may be more sensitive to differences in surface or measurement method. Cumulative load LSI was strongly related to other LSIs, and single step metrics may provide a reasonable surrogate of GRF symmetry. Supported by: This project was funded by the Canadian Foundation for Innovation John R. Evans (Project ID:42110, PI: DN Pamukoff)