Influence of Prosthetic Foot Stiffness on Transtibial Osseointegrated Bone-Anchored Limb Outcomes - PROJECT SUMMARY The overarching goal of this proposal is to determine the influence of prosthetic foot stiffness on multi- domain loading-related outcomes in individuals with transtibial (TT) bone-anchored limbs (BALs) (i.e., osseointegrated prostheses). BALs are a promising alternative to socket prostheses that have shown to improve overall mobility, physical function, and health-related quality of life. To facilitate positive outcomes, proper load sharing between the implant and bone is pivotal for the mechanobiology of osseointegration at the bone-implant interface, which is directly dependent on loads transferred from the ground to the residual limb. While originated for transfemoral (TF) amputation levels, such implants have recently emerged at the TT level, and one of the primary clinical concerns surrounding TT versus TF BALs is the change in force transmission. While prosthetic foot stiffness plays a direct role in transferring forces from the ground to the implant, there is a paucity of evidence pertaining to how stiffness parameters influence loading at the bone-implant interface and overall clinical outcomes in TT BAL users. As such, current prosthetic prescriptions are largely based on clinical practice guidelines based on evidence originating from socket prosthesis users, which are likely suboptimal. Specifically, due to the difference in force transmission between the two prosthesis types, we identify three significant knowledge gaps that currently influence potential success versus failure/rejection of TT osseointegrated BALs: 1) Standard of care in BAL users is primarily based on evidence from TF amputation levels or socket prosthesis users, 2) Loading is critical to pain and failure rate outcomes in BALs yet cannot be directly measured, 3) Unknown how prosthetic componentry influences force attenuation applied to the implant, sensory feedback, or clinical outcomes. We will address these gaps by implementing a Phase I Clinical Trial that will investigate four Specific Aims: Aim 1) Assess how prosthetic foot stiffness influences bone-implant interface loading in individuals with TT BALs; Aim 2) Determine how prosthetic foot stiffness influences function, pain, and multi-joint biomechanics during activities of daily living in both individuals with TT BALs and standard socket prosthesis users; Aim 3) Establish how prosthetic foot stiffness influences osseoperception and fall risk (balance and reactive control during trip recovery) in both individuals with TT BALs and standard socket prosthesis users; Exploratory Aim 4) Determine the optimal foot stiffness properties that maximize knee joint loading symmetry, minimize stress shielding, and minimize metabolic cost using design optimization coupled with dynamic optimal control methods. By quantifying these relationships, we will provide evidence to support best practices that are specific to TT BALs. In the long-term, these results will impact clinical care by helping develop and guide componentry selection guidelines that are specific to TT BAL users in an effort to facilitate positive outcomes by optimizing bone-implant interface loading in TT BAL users.
