Quiet postural control of patients with total hip arthroplasty following joint arthritis.

To assess the postural strategies developed by patients after total hip arthroplasty (THA), 14 patients were measured 12 days after surgery. The respective role played by both sound and prosthetic legs and the compensatory mechanisms were assessed through a separate measure of the center-of-pressure (CP) trajectories under each foot. The movements of the center-of-gravity (CG) were estimated from those of the resultant CP to determine postural performance. The postural behavior was compared with those of a group of age-matched healthy subjects required to adopt a slightly asymmetrical weight distribution. Patient results indicate greater movements for both plantar and resultant CP displacements, principally along the antero-posterior (AP) axis, a decreased contribution of the hip mechanisms in the production of CP displacements along the medio-lateral (ML) axis, greater resultant CP and CG movements along the AP axis and increased differences between CP and CG along both ML and AP axes. The postural specificity of the THA patients appears to be due to a global sensorimotor impairment that alters the control of the loading-unloading mechanism at the hip level.