Introduction: The internal efforts in the human body in motion could provide valuable information for the evaluation and follow-up of subjects with musculo-skeletal pathologies, such as scoliosis, but are still difficult to accurately measure. In this context, the objective of this study is to compare the lombo-sacral (L5-S1) joint efforts during gait (i.e.: mediolateral forces, mediolateral torques, and anteroposterior torques) between typically developed adolescents (TDA) and adolescents with left lumbar or thoracolumbar idiopathic scoliosis (AIS), categorized by their Cobb angle (CA).
Material and methods: 12 TDA, 10 AIS with CA < 20°, 13 AIS with CA between 20° and 40° as well as 16 AIS in preoperative condition performed gait at 4 km/h on instrumented treadmill. Among the latter group, 8 AIS were evaluated after surgical intervention (participants with at least a diminution of 30° of their CA). The acquisition system measured the human body joint motion via optokinetic sensors, and the ground reaction forces via a treadmill fitted with force sensors. The L5-S1 intervertebral efforts were calculated using a tridimensional inverse dynamical model of the human body.
Results: The mediolateral forces were significantly higher for AIS with CA between 20° and 40° and for AIS in pre-operative condition compared to TDA values. But neither mediolateral nor anteroposterior torque was significantly different between groups. After surgical intervention the maximal anteroposterior torque was significantly lower compared to pre-surgical value.
Conclusion: The participants with severe idiopathic scoliosis present higher L5-S1 mediolateral forces than TDA, which could lead to a supplementary asymmetric vertebra growth modulation and the progression of the scoliotic deformities in the framework of the Hueter-Volkman principle. Further research should include the tridimensional reconstruction of the spine in order to observe differences between categories of AIS patients in terms of dynamical behaviors along the spine.