Vertical ground reaction forces: objective measures of gait following hip arthroplasty

After hip arthroplasty. many patients continue to exhibit abnormal gait pat terns. The purpose of this study was to compare the vertical ground reactio n forces of a group of 27 individuals who have undergone hip arthroplasty w ith a group of 35 normal control subjects, Specific force measures were det ermined from vertical ground reaction forces collected on a treadmill instr umented with two force plates. Symmetry indices were calculated on both gro ups of subjects. First and second peak forces, loading rate, impulse, and s tance time were significantly less, while time to first peak force was sign ificantly greater on the affected leg of the hip arthroplasty subjects when compared to their unaffected leg, or to the control group. The hip arthrop lasty group showed greater asymmetry of ground reaction forces than the con trol group did. Bilateral asymmetric limb loading persists well after unila teral hip replacement surgery. Ground reaction force measures have been sho wn to be an effective means of quantifying the antalgic gait of hip arthrop lasty patients. (C) 2001 Elsevier Science B.V. All rights reserved.