The effects of real and artificial Leg Length Discrepancy on mechanical work and energy cost during the gait

Abstract Background The impacts of Leg Length Discrepancy (LLD) on the kinematic and dynamic parameters of walking have been widely discussed. But little is known on total mechanical work and energy cost. These two variables are more representative of the functional impairment undergone by the LLD patients. Aim To assess the changes of the mechanical work and energy cost of walking in subjects with real LLD and to compare their results with healthy subjects in whom the LLD has been simulated. Method The mechanical work and energy cost data of 60 healthy subjects (speed: 4 km/h) with artificial LLD induced by soles (2 and 4 cm), 20 patients (speed: 3.75 ± 0.5 km/h) with real LLD and 20 matched subjects (speed: 3.75 ± 0.5 km/h) were collected. Statistical comparisons between the groups were performed using a t-paired test and ANOVA. Results Patients with a real LLD showed a significant decrease in mechanical work and energy cost when compared to norms. Patients with real LLD provide a better recovery when compared to subjects with artificial LLD of 2 cm, and a decrease of energy cost and higher muscular efficiency (mechanical work/energy cost) when compared to subjects with artificial LLD of 4 cm. Conclusions Our results showed that patients with a real LLD develop compensatory strategies during gait, probably to minimize the displacement of the body center of mass and consequently reduce the amount of energy expenditure useful for their displacement. Moreover, they adopt a better gait strategy compared to the subjects in whom LLD was simulated.