Subject-specific responses to an adaptive ankle prosthesis during incline walking

• Published in: Journal of biomechanics 2019-10, Vol.95, p.109273-109273, Article 109273
• Main Authors: Lamers, Erik P., Eveld, Maura E., Zelik, Karl E.
• Format: Article
• Language: English
• Subjects: Adult; Amputation; Amputees; Ankle; Ankle - physiology; Ankle Joint; Artificial Limbs; Behavior; Biomechanical Phenomena; Biomechanics; Feet; Female; Foot; Gait; Gait - physiology; Gait analysis; Humans; Incline; Joint Prosthesis; Kinematics; Kinetics; Knee; Knee Joint; Landing; Male; Metabolism; Microcomputers; Microprocessor ankle; Microprocessors; Middle Aged; Prostheses; Prosthesis Design; Prosthetics; Studies; Walking; Walking - physiology
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2019.07.017

Individuals with lower-limb amputation often have difficulty walking on slopes, in part due to limitations of conventional prosthetic feet. Conventional prostheses have fixed ankle set-point angles and cannot fully replicate able-bodied ankle dynamics. Microprocessor-controlled ankles have been developed to help overcome these limitations. The objective of this study was to characterize how the slope adaptation feature of a microprocessor-controlled ankle affected individual prosthesis user gait biomechanics during sloped walking. Previous studies on similar microprocessor-controlled ankles have focused on group-level results (inter-subject mean), but did not report individual subject results. Our study builds upon prior work and provides new insight by presenting subject-specific results and investigating to what extent individual responses agree with the group-level results. We performed gait analysis on seven individuals with unilateral transtibial amputation while they walked on a 7.5° incline with a recently redesigned microprocessor-controlled ankle that adjusts ankle set-point angle to the slope. We computed gait kinematics and kinetics, and compared how users walked with vs. without this set-point adjustment. The microprocessor-controlled ankle increased minimum toe clearance for all subjects. Despite the microprocessor-controlled ankle behaving similarly for each user, we observed marked differences in individual responses. For instance, two users switched from a forefoot landing pattern with the microprocessor-controlled ankle locked at neutral angle to rearfoot landing when the microprocessor-controlled ankle adapted to the slope, while two maintained a forefoot and three maintained a rearfoot landing pattern across conditions. Changes in knee angle and moment were also subject-specific. Individual user responses were often not well represented by inter-subject mean. Although the prevailing experimental paradigm in prosthetic gait analysis studies is to focus on group-level analysis, our findings call attention to the high inter-subject variability which may necessitate alternative experimental approaches to assess prosthetic interventions.