Evaluation of atraumatic hip instability measured by triaxial accelerometry during walking

Hip joint instability has been targeted as an important issue that affects normal hip function. The diagnosis of hip instability could be very challenging and currently, there is no definitive diagnostic test. Hip instability results in an excessive amount of translation of femoroacetabular articulation, leading to changes on the dynamic loading of the hip. These changes in femoroacetabular translation could be evaluated by human movement analysis methods. The purpose of this study was to describe the triaxial and overall magnitude of acceleration in patients diagnosed with hip instability during gait cycle and compare those results with a control group. Our hypothesis was that acceleration values obtained from the instability group would be higher than asymptomatic controls. Ten patients with previously diagnosed hip instability were included and 10 healthy and asymptomatic subjects were enrolled as control group. Triaxial accelerometers attached bilaterally to the skin over the greater trochanter were used to record acceleration during walking on a treadmill. The overall magnitude of acceleration and the axial, anteroposterior and mediolateral accelerations (x/y/z) were obtained during gait. Mean overall magnitude of acceleration was higher in the hip instability group compared with the control group, 1.51 g (SD: 0.23) versus 1.07 g (SD: 0.16) (P = 0.022). The axial, anteroposterior and mediolateral accelerations significantly differed between the two groups. The axial and mediolateral accelerations showed to be higher for the hip instability group while the anteroposterior axis acceleration was lower.