Chronic low back pain is prevalent after lower-limb amputation, so a research team evaluated biomechanical factors among people with unilateral transtibial lower-limb amputations and with or without chronic low back pain. The authors found that people with transtibial lower-limb amputations and chronic low back pain may adopt movement strategies during walking to reduce mediolateral shear forces at the L5-S1 spinal joints, particularly as walking speed increases. However, the researchers recommend further study to understand the time course from pain onset to chronification and the cumulative influence of increased spinal loads over time.
The study used three-dimensional full-body kinematics and kinetics to evaluate 21 participants during level-ground walking at self-selected and three controlled speeds (1.0, 1.3, and 1.6m/s). Nine participants had chronic low back pain and 12 did not.
Peak compressive, mediolateral, and anteroposterior L5-S1 spinal loads were estimated from a full-body, transtibial amputation-specific OpenSim model and compared between groups. Predicted lumbar joint torques from muscle activations were compared to inverse dynamics and predicted and measured electromyographic muscle activations were compared for model evaluation and verification. There were no group differences in compressive or anterior shear forces, according to the study.
During intact stance, peak ipsilateral loads increased with speed to a greater extent in the chronic low back pain group versus the no chronic low back pain group, while during prosthetic stance, peak contralateral loads were larger in the no chronic low back pain group and increased to a greater extent with walking speed compared to the chronic low back pain group.
During intact stance, intact side external obliques had higher activations in the no chronic low back pain group, and internal obliques had higher activations in the chronic low back pain group at faster walking speeds compared to the no chronic low back pain group.
The study, “Comparing spinal loads in individuals with unilateral transtibial amputation with and without chronic low back pain: An EMG-informed approach,” was published in the Journal of Biomechanics.
