The effect of ankle osteoarthritis and total ankle arthroplasty on center of pressure position.

Total ankle arthroplasty (TAA) is a common surgical approach for patients with end-stage ankle osteoarthritis (OA). However, very little is known about the path of the center of pressure (COP) of the foot, and thus important aspects of load transfer, muscle mechanical advantage, and balance, in patients before or after surgery. The objective of this study was to trace the pathway of the COP under the foot in patients with symptomatic ankle OA, comparing asymmetry between affected and unaffected limbs. From force plate data, proximodistal and mediolateral positions of the COP beneath the foot were calculated and compared for the affected and unaffected foot in patients with unilateral ankle OA (N = 93) before and after TAA. Gender and age at surgery had little or no effect in this study. Patients with ankle OA had minimal COP position asymmetry before surgery, and this asymmetry was reduced following surgery. Before surgery, patients had a slower walking speed and a shorter path of the COP which began relatively distal to the heel and ended relatively proximal to the hallux. TAA increased the proximodistal distance the COP traveled under both the unaffected and affected foot, a pattern that was maintained for over 2-year postsurgery. TAA allows patients with ankle OA to maintain a longer COP path than they had before surgery on both sides that is closer to that reported for unaffected individuals, extending effectively from the heel to the hallux, potentially improving pedal mechanics.