Assessment of a New Gait Asymmetry Index in Patients After Unilateral Total Hip Arthroplasty

<b>Background/Objectives:</b> Comparing a given variable between the lower extremities (LEs) usually involves calculating the value of a selected asymmetry index. The aim of this study was to evaluate the mean-dependent asymmetry index for gait variables. <b>Methods:</b> The three-point crutch gait asymmetry between the non-surgical LE (NS) and surgical LE (S) was assessed in 14 patients after unilateral total hip arthroplasty. An eight-camera motion capture system integrated with two force platforms was used. The values of the new gait asymmetry index (MA) were calculated for such variables as stance phase time (ST), knee flexion and extension range of motion (KFE RoM), hip flexion and extension range of motion (HFE RoM), and vertical ground reaction force (VGRF). <b>Results:</b> An analysis related to gait asymmetry showed significantly higher values for all variables for the NS than for the S (the MA ranged from 9.9 to 42.0%; <i>p</i> < 0.001). In the case of comparisons between the MA and other indices, the intraclass correlation coefficient ranged from 0.566 to 0.998 (<i>p</i> < 0.001) with Bland-Altman bias values that ranged from -18.2 to 0.3 %GC (ST), from 0.0 to 0.5° (KFE RoM), from -12.4 to 1.4° (HFE RoM), and from -11.9 to -0.1 %BW (VGRF). <b>Conclusions:</b> The findings revealed a prominent three-point crutch gait asymmetry for all variables, especially a disturbingly large asymmetry for the HFE RoM and VGRF. The comparisons also showed generally excellent or good agreement with the other indices. Furthermore, the mean MA result from <i>n</i> single values was the same as the MA result calculated using the mean values of a given variable. The MA, as an accurate asymmetry index, can be used to objectively assess pathological gait asymmetry.