Abstract. The article presents a number of posturographic methods enabling objective postural symmetry assessment in patients undergoing rehabilitation after total hip replacement surgery. The key goal of such rehabilitation is fast restoration of a proper body weight distribution. The postural symmetry measures proposed in the article enable generalized quantification of the CoP (Center of Pressure) trajectories measured during standard static posturography diagnostics and the so-called follow-up posturography examination. The follow-up posturography is a relatively new but promising method of physical rehabilitation. All of the herein discussed posturographic measures have been designed specifically to quantify postural symmetry either in a standing and relaxed upright position, in the absence of any deterministic external stimulation (static posturography) or in the presence of a visual biofeedback stimulation enforcing the coordinated slow swaying movements of the body (the follow-up posturography). The experimental results presented in this paper constitute the outcome of the long-term cooperation between the Institute of Electronics of the Silesian University of Technology and the Silesian Rheumatology and Rehabilitation Hospital. The usefulness of the proposed postural symmetry measures has been verified in a series of clinical trials carried out in a selected group of patients undergoing rehabilitation after total hip replacement surgery.

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BackgroundDevelopment of a reliable and objective test of spasticity is important for assessment and treatment of children with cerebral palsy. The pendulum test has been reported to yield reliable measurements of spasticity and to be sensitive to variations in spasticity in these children. However, the relationship between the pendulum test scores and other objective measures of spasticity has not been studied. The present study aimed to assess the effectiveness of an accelerometer-based pendulum test as a measurement of spasticity in CP, and to explore the correlation between the measurements of this test and the global index of deviation from normal gait in in children with cerebral palsy.MethodsWe studied thirty-six children with cerebral palsy, including 18 with spastic hemiplegia and 18 with spastic diplegia, and a group of 18 typically-developing children. Knee extensor spasticity was assessed bilaterally using the accelerometer-based pendulum test and three-dimensional gait analysis. The Gillette Gait Index was calculated from the results of the gait analysis.ResultsThe data from the accelerometer-based pendulum test could be used to distinguish between able-bodied children and children with cerebral palsy. Additionally, two of the measurements, first swing excursion and relaxation index, could be used to differentiate the degree of knee extensor spasticity in the children with cerebral palsy. Only a few moderate correlations were found between the Gillette Gait Index and the pendulum test data.ConclusionsThis study demonstrates that the pendulum test can be used to discriminate between typically developing children and children with CP, as well as between various degrees of spasticity, such as spastic hemiplegia and spastic diplegia, in the knee extensor muscle of children with CP. Deviations from normal gait in children with CP were not correlated with the results of the pendulum test.Electronic supplementary materialThe online version of this article (doi:10.1186/1743-0003-11-166) contains supplementary material, which is available to authorized users.

The paper presents an original method enabling postural symmetry evaluation using weighted averages of the wavelet correlation coefficients obtained individually for the corresponding x and y components of the cantered follow-up posturographic trajectories registered during the clockwise and counterclockwise visual stimulations. In the process the x and y components of both trajectories undergo 7-stage db2 discrete wavelet decomposition. The correlations of the detail coefficients are evaluated at all levels of the decomposition structure whereas the correlations of the approximation coefficients are calculated only at its last level. Applied weighting factors constitute the sums of energies of the reconstructed details or approximations corresponding to a particular level of decomposition. The ultimate measure of postural symmetry in the herein presented method is the quantity based on the vector distance of the point whose coordinates constitute the values of the obtained weighted correlation coefficients (individually for the x and y components), from the point representing the state of ideal symmetry. This quantity assumes the values within the range of [0,1], where 1 is identified with the maximum postural symmetry dynamics whereas the value of 0 represents the state of maximum anti-symmetry dynamics (analysed trajectories are out of phase by π [rad]). The applicability of the herein presented method was verified in the process of postural symmetry evaluation carried out in the group of 30 patients rehabilitated after total hip arthroplasty.

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