IS FULL WEIGHTBEARING SAFE FOLLOWING ACHILLES TENDON REPAIR?

Akizuki KH, Gartman EJ, Nisonson B, Ben-Avi SS, McHugh MP

Nicholas Institute of Sports Medicine and Athletic Trauma and The Cooper Union School of Engineering, New York, NY

Following Achilles tendon repair, immediate weightbearing and immobilization closer to neutral plantarflexion are thought to limit atrophy and stiffness, but may place deleterious stress on the repair. The purpose of this study was to estimate the relative stress on the Achilles tendon during weightbearing with immobilization in varying degrees of plantarflexion. EMG activity from the plantarflexors was recorded during walking in 10 subjects (6 men, 4 women) without ankle pathology. Four walking conditions were examined: (1) normal walking, (2) immobilized (cam walker) in neutral plantarflexion, (3) immobilized with a ½" heel lift, (4) immobilized with a 1" heel lift. EMG activity relative to plantarflexor torque was determined for each subject during isometric contractions at 25%, 50%, 75% and 100% of maximal voluntary contraction (MVC). EMG activity during walking was calculated as a percentage of MVC based on the EMG-torque relationship during graded isometric contractions. During normal walking the plantarflexor torque was estimated to be 30+/-12% (SD) of MVC, compared with 21+/-15% MVC for immobilization in neutral (p<0.01), 17+/-15% MVC with the addition of a ½" heel lift (p<0.01) and 12+/-12% MVC with the addition of a 1" heel lift (p<0.01). The 1" heel lift resulted in less than 10º plantarflexion in all subjects. When the ankle is immobilized, stress on the Achilles tendon is determined by the degree of plantarflexion and the contractile activity of the plantarflexors. In the immobilized ankle, the addition of a 1" heel lift was sufficient to minimize plantarflexor activity during walking.

American Academy of Orthopaedic Surgeons 68th Annual Meeting, San Francisco, CA, Feb 28-Mar 4, 2001.