Effects of immobilization on plantar-flexion torque, fatigue resistance, and functional ability following an ankle fracture

Background and Purpose. The goal of this investigation was to study the rec over of ankle plantar-flexor peak torque, fatigue resistance, and functiona l ability (stair climbing, walking) following cast immobilization in patien ts with ankle fractures. Subjects. The participants were 10 patients who un derwent open reduction-internal fixation and 8 weeks of cast immobilization following a fracture of the ankle mortise and 10 age- and sex-matched, non injured comparison subjects. Methods. Plantar-flexor torque and fatigue res istance were measured at 1, 5, and 10 weeks of rehabilitation using an isok inetic dynamometer. Ankle plantar-flexor peak torque and fatigue resistance were correlated to timed ambulation, time stair climbing, and unilateral h eel-rises. Results. Following immobilization, plantar-flexor peak torque wa s decreased at all angular speeds and positions. The decrease in peak torqu e was associated with an increase in fatigue resistance. With rehabilitatio n, ankle plantar-flexor torque and fatigue resistance renormaled. Regressio n analysis revealed a strong relationship between plantar-flexor peak torqu e and functional measures. By 10 weeks post-immobilization, peak torque, fa tigue resistance, and all measures of functional performance had returned t o control levels. Conclusion and Discussion. The decrease in muscle perform ance, functional ability, and fatigue resistance induced by 8 weeks of cast immobilization can be reversed with 10 weeks of supervised physical therap y. In addition, this study demonstrated that ankle-plantar flexor torque is a good predictor of stair-climbing and walking performance in patients wit h ankle fractures.