Greater than recommended stiffness and power setting of a stance-phase powered leg prosthesis can improve step-to-step transition work and effective foot length ratio during walking in people with transtibial amputation

People with unilateral transtibial amputation (TTA) using a passive-elastic prosthesis exhibit lower positive affected leg trailing work (AL W ) and a greater magnitude of negative unaffected leg leading work (UL W ) during walking than non-amputees, which may increase joint pain and osteoarthritis risk in the unaffected leg. People with TTA using a stance-phase powered prosthesis (e.g., BiOM, Ottobock, Duderstadt, Germany) walk with increased AL W and potentially decreased magnitude of UL W compared to a passive-elastic prosthesis. The BiOM includes a passive-elastic prosthesis with a manufacturer-recommended stiffness category and can be tuned to different power settings, which may change AL W UL W and the prosthesis effective foot length ratio (EFLR). Thirteen people with TTA walked using 16 different prosthetic stiffness category and power settings on a level treadmill at 0.75-1.75 m/s. We constructed linear mixed effects models to determine the effects of stiffness category and power settings on AL W UL W and EFLR and hypothesized that decreased stiffness and increased power would increase AL W , not change and decrease UL W magnitude, and decrease and not change prosthesis EFLR, respectively. We found there was no significant effect of stiffness category on AL W but increased stiffness reduced UL W magnitude, perhaps due to a 0.02 increase in prosthesis EFLR compared to the least stiff category. Furthermore, we found that use of the BiOM with 10% and 20% greater than recommended power increased AL W and decreased UL W magnitude at 0.75-1.00 m/s. However, prosthetic power setting depended on walking speed so that use of the BiOM increased UL W magnitude at 1.50-1.75 m/s compared to a passive-elastic prosthesis. Ultimately, our results suggest that at 0.75-1.00 m/s, prosthetists should utilize the BiOM attached to a passive-elastic prosthesis with an increased stiffness category and power settings up to 20% greater than recommended based on biological ankle values. This prosthetic configuration can allow people with unilateral transtibial amputation to increase AL W and minimize UL W magnitude, which could reduce joint pain and osteoarthritis risk in the unaffected leg and potentially lower the metabolic cost of walking.