Effects of Immobilization on Plantar-Flexion Torque, Fatigue Resistance, and Functional Ability Following an Ankle Fracture

Abstract

The goal of this investigation was to study the recovery of ankle plantar-flexor peak torque, fatigue resistance, and functional ability (stair climbing, walking) following cast immobilization in patients with ankle fractures. The participants were 10 patients who underwent open reduction-internal fixation and 8 weeks of cast immobilization following a fracture of the ankle mortise and 10 age- and sex-matched, noninjured comparison subjects. Plantar-flexor torque and fatigue resistance were measured at 1, 5, and 10 weeks of rehabilitation using an isokinetic dynamometer. Ankle plantar-flexor peak torque and fatigue resistance were correlated to timed ambulation, timed stair climbing, and unilateral heel-rises. Following immobilization, plantar-flexor peak torque was decreased at all angular speeds and positions. The decrease in peak torque was associated with an increase in fatigue resistance. With rehabilitation, ankle plantar-flexor torque and fatigue resistance normalized. Regression analysis revealed a strong relationship between plantar-flexor peak torque and functional measures. By 10 weeks post-immobilization, peak torque, fatigue resistance, and all measures of functional performance had returned to control levels. The decrease in muscle performance, functional ability, and fatigue resistance induced by 8 weeks of cast immobilization can be reversed with 10 weeks of supervised physical therapy. In addition, this study demonstrated that ankle-plantar flexor torque is a good predictor of stair-climbing and walking performance in patients with ankle fractures.