Implant load during running on a transtibial bone anchored prosthesis: A multibody modelling case study

Area of Science:

• Biomechanics
• Biomedical Engineering
• Orthopedic Surgery

Background:

• Bone-anchored prostheses (BAPs) offer advantages over traditional sockets for lower leg amputees, including direct load transfer.
• Current BAP implants perform well in daily activities like walking, but safety during high-impact activities like running remains unestablished.

Purpose of the Study:

• To determine the forces and moments on a BAP implant during walking and running.
• To compare loads experienced by a daily use prosthesis (DUP) versus a running-specific prosthesis (RSP) during these activities.

Main Methods:

• A case study involving a single unilateral transtibial BAP user with a press-fit osseointegration implant.
• Data collection using an instrumented split belt treadmill with varying speeds.
• Kinematic reconstruction via multi-body modeling and inverse dynamics for force and moment computation.

Main Results:

• Running on an RSP significantly reduced peak anteroposterior force (40%) and sagittal moment (38%) compared to walking on a DUP.
• Peak axial force increased by 59% during running on the RSP compared to walking.
• Running on the RSP showed higher late-stance sagittal moments but lower peak compression forces than running on the DUP.

Conclusions:

• The forces and moments experienced during running, particularly with an RSP, appear acceptable for the bone-implant system.
• Bending moments may be less detrimental than axial loads, suggesting running poses a lower mechanical failure risk than previously thought.
• Further research is needed to fully understand the mechanical implications on bone stress and long-term implant survival.