[Clinical and posturographic comparison of patients with recent total hip arthroplasty]

To highlight the congruence of clinical and posturographic tests in patients undergoing hip arthroplasty.

Ten patients (six males and four females) were included in this study and tested when at admission and discharge from the rehabilitation department (12 and 27 days after surgery respectively). The patients were asked to stand undisturbed in the upright position, eyes closed on a system composed of two force platforms. Five successive 32s trials (sampled at 64 Hz) were conducted with rest intervals of similar duration between trials. The plantar center of pressure (CP), displacements, and resultant CP (CPRes) were then computed and analyzed in various ways. In parallel, various clinical tests, including muscular force, hip range of motion, walking speed, functional independence, pain, sensitivity, lateral reach, and get up and go aimed at evaluating global coordination. Correlations, using the non-parametric Spearman coefficient, were computed from the differences between clinical and posturographic parameters obtained at admission and discharge from the rehabilitation department.

Certain statistically significant differences in postural behavior was observed both for clinical and posturographic tests between admission and discharge. Body weigh distribution over the two legs was largely asymmetric at onset and, though it declined, persisted at discharge. There was not difference for the mean positions of both the plantar CP and the resultant of the CP movements. On the contrary, it was noteworthy that the variances of CP displacements (data dispersion) were initially larger on the sound leg along the anteroposterior axis and that this compensatory feature disappeared at the end of the stay. At discharge, the variances computed from the sound and the prosthetic limb became equivalent. All the clinical tests demonstrated statistically significant improvements in results at discharge compared with admission. Several significant correlations involving clinical tests and mean positions along the anteroposterior axis, the degree of body weight asymmetry and variances along both the mediolateral and anteroposterior axes were found.

These results enable a better understanding of strategies used by hip arthroplasty patients to keep balance. Even though their sensitivity was quite different, both clinical and posturographic measurements demonstrated their ability to assess recovery from surgery. These two evaluation techniques are complementary.