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.
The algorithm presented in this paper provides the means for the real-time recognition of the key signature associated with a given piece of music, based on the analysis of a very small number of initial notes. The algorithm can easily be implemented in electronic musical instruments, enabling real-time generation of musical notation. The essence of the solution proposed herein boils down to the analysis of a music signature, defined as a set of twelve vectors representing the particular pitch classes. These vectors are anchored in the center of the circle of fifths, pointing radially towards each of the twelve tones of the chromatic scale. Besides a thorough description of the algorithm, the authors also present a theoretical introduction to the subject matter. The results of the experiments performed on preludes and fugues by J.S. Bach, as well as the preludes, nocturnes, and etudes of F. Chopin, validating the usability of the method, are also presented and thoroughly discussed. Additionally, the paper includes a comparison of the efficacies obtained using the developed solution with the efficacies observed in the case of music notation generated by a musical instrument of a reputable brand, which clearly indicates the superiority of the proposed algorithm.
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.
This paper presents a method enabling a postural symmetry assessment based on the evaluation of similarity of temporary and average CoP (Center of Pressure) displacements registered in response to the clockwise and counterclockwise visual stimuli applied while performing the so-called follow-up posturography. This kind of visual feedback diagnostics is an intermediary between the static posturography and the dynamic posturography. One of its advantages is the ability to evaluate the dynamic performance of the human balance and posture control mechanisms using relatively inexpensive and popular static posturography platforms. The method presented in this paper was developed as a means for measuring the effectiveness of the rehabilitation program following total hip arthroplasty. The postural symmetry is, in this case, evaluated as the degree of mutual symmetry of the visually stimulated loading exerted on the left and right lower limbs. Usability of the method was verified in the group of 30 patients rehabilitated after total hip arthroplasty. The statistical analysis confirmed a significant growth of the values of the proposed symmetry measure over the period of the 21-day rehabilitation program (p < 0.001). There were, however, no significant correlations between that measure and the symmetry measures applied in the case of static posturography. The obtained results support the statement that the herein presented diagnostic approach enables the quantification of some other aspects of postural symmetry, namely the dynamic ones. This also corroborates the diagnostic value of the method discussed in this paper. INDEX TERMS postural symmetry evaluation, posturography, the follow-up posturography, biomedical signal processing, total hip arthroplasty.
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