Principal Investigators: Matthew J. Major, PhD; Keith Gordon, PhD
Research Engineers: Geoffery Brown, MS; Lilly Tran, MS; Mary Wu, MS (Northwestern University)
Student Investigators: Xinlin Chen, Franklyn Ndubuisi-Obi, Chelsi Serba (Northwestern University); SeanDwijendra (Rush University)
Funded by: NUCATS Voucher (Tier 1) Program
Status: In Progress
Background and Significance
Approximately half of community dwelling persons with lower-limb amputation fall every year . Frontal-plane asymmetries observed during quiet standing [2-6] suggest that persons with below-knee amputation (BKA) have limited ability to respond to lateral perturbations during gait. Although sagittal plane stability has been investigated [4, 8-10], the mechanisms underlying successful recovery following a destabilizing lateral perturbation are poorly understood. Characterizing the mechanisms utilized by this pathological group to achieve locomotor stability will serve as a platform to inform therapeutic and prosthetic interventions to minimize the risk of falls and fall-related injury.
Aims and Hypothesis
The purpose of this pilot study is to quantify the response mechanisms persons with unilateral BKA employ to resist and recover from lateral perturbations during walking. Due to the loss of an active ankle joint and critical forms of proprioceptive feedback [4, 5, 10-12], we hypothesize that, compared to intact controls, persons with BKA will depend heavily on passive mechanisms of stabilization (e.g., wider steps, greater margins of stability, increased double support time) that deemphasize accurate sensation and response to perturbations.
To quantify the mechanisms used to control lateral stability, we will measure how 10 individuals with BKA who are classified as community ambulators compare with 10 age- and gender-matched control participants in their response to lateral force perturbations applied during treadmill walking using a motorized perturbation system (See Figure).
Impact and Plans for Future Research
Given the novelty of the proposed research and limited knowledge on this topic, findings from this study will be of immediate clinical relevance by providing greater understanding of the mechanisms that persons with BKA adopt to maintain frontal-plane stability and to identify deficiencies in these strategies. By demonstrating their reliance on passive mechanisms of stability, we will emphasize the importance of designing effective balance training and ankle-foot prostheses with mechanical properties tuned to match individual stabilization strategies. These efforts will elevate amputee clinical care by helping to enhance the quality of evidence-based practice. Importantly, these results will provide strong rationale for future grant proposals that will investigate: 1) interactions between prosthesis mechanical properties and recovery strategies following perturbation to inform prosthesis optimization, and 2) effects of targeted therapeutic interventions on recovery strategies to address balance deficiencies in this pathological group.
Plan for Future Funding
This novel and relatively unexplored topic requires adequate pilot data to generate future funding through competitive grant proposals. NUCATS sponsorship is supporting our efforts to generate preliminary results directed toward securing future funding. We intend to use these preliminary data for grant proposals (NIH R01, VA Merit).
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Major MJ, Serba CK, Chen X, Reimold N, Ndubuisi-Obi F, Gordon KE. Proactive Locomotor Adjustments Are Specific to Perturbation Uncertainty in Below-Knee Prosthesis Users. Scientific Reports, January 30 2018. <www.nature.com/articles/s41598-018-20207-5>
Major, Matthew (2016) Locomotor Stability of Upper and Lower Limb Prosthesis Users. VA Research Day, Jesse Brown VAMC, May 20, Chicago, IL.