Poster AA2 - Effect of an Adjustable Prosthetic Socket on Peak Ground Reaction Force Asymmetry in People With Lower Limb Amputation

Introduction: Individuals with lower limb amputations, whether transfemoral (TFA) or transtibial (TTA), often exhibit gait asymmetries between their affected leg (AL) and unaffected leg (UL) during walking [1]. These asymmetries are exhibited in vertical (vGRF) and horizontal (hGRF) ground reaction forces, with the UL bearing greater loading than the AL. Such asymmetries can lead to functional impairments and secondary injuries such as osteoarthritis, osteoporosis, and chronic leg and back pain [2]. The design and fit of a prosthetic socket play a crucial role in enabling effective device utilization, suggesting their potential influence on GRF asymmetry in amputees.

Prosthetic sockets facilitate force and energy transfer between the residual limb and prosthesis, significantly impacting rehabilitation outcomes [3][4]. Despite typically being fitted with rigid carbon fiber sockets, individuals with TFA and TTA commonly experience significant residual limb volume fluctuations throughout the day [5]. An adaptable socket that accommodates these changes could enhance attachment security, improve force transmission, and mitigate asymmetry compared to rigid sockets.

A new modular adjustable socket (Quatro, Quorum Prosthetics, Windsor, CO) has been developed to address volume changes of up to 12%. With adjustable panels, it aims to minimize residual limb movement within the socket, enhancing comfort and potentially reducing asymmetric peak vGRF and hGRF during level-ground walking at various speeds. We hypothesize that the Quatro socket, offering a better fit, will result in less asymmetric peak vGRFs and hGRFs between the AL and UL compared to rigid sockets in individuals with TFA or TTA.

Materials and

Methods: 8 subjects with leg amputations (4 = TFA, 4= TTA) provided informed consent and completed three fitting sessions and one experimental session. During the fitting sessions, each subject was fit with an adjustable socket using Quatro technology that mimics their existing prosthetic socket suspension system. During the experimental session subjects walked on a dual belt force-measuring treadmill (1000 Hz; Bertec, Columbus, OH) on level ground at 0.75, 1.0, 1.25, and 1.5 m/s using a rigid socket and Quatro socket (4 trials per socket) with the same prosthetic components for each socket.
We determined average vGRFs and hGRFs from ten steps for the AL and UL. 1st and 2nd peak vGRF was calculated as the maximum vGRF during the first and second half of stance, respectively. Peak braking hGRF was calculated as the minimum hGRF, and peak propulsive hGRF was calculated as the maximum hGRF during stance. Then, we calculated symmetry index (SI), which is expressed as a percentage, to establish the magnitude of asymmetry between the AL and UL, where 0% is perfect symmetry [6]. SI was calculated using the following equation. SI (%) = |(UL – AL)/(0.5*( UL + AL )) | * 100% (Fig. 1). We then created two linear mixed effects models, one for TFA and one for TTA, to quantify changes in peak vGRF and hGRF between the Quatro and rigid sockets.

Results, Conclusions, and Discussions: For subjects with a TFA, compared to using the rigid socket the use of the Quatro socket decreased peak braking hGRF SI from 35% to 21.5% across all walking speeds (Fig. 1C). We found no statistical differences in peak braking hGRF SI for subjects with TTA. Additionally, we found no statistical differences in 1st or 2nd peak vGRF or peak propulsive hGRF for subjects with a TFA or TTA. Our results suggest that use of an adjustable prosthetic socket may reduce peak hGRF asymmetry in individuals with TFA, which could improve function and reduce secondary injury.

Acknowledgements (Optional): Funding from the VA RR&D Service RX003643

References: [1] Adamczyk, P. G., & Kuo, A. D., IEEE Trans. Neural Syst. Rehabil. Eng., 2015,[2] Gailey, R., et al., JRRD, 2008, [3] Aydin, A. and S.C. Okur, Med. Sci. Mont., 2018, [4] Pirouzi, G., et al., Sci. World J., 2014, [5] Sanders, J.E. and S. Fatone, JRRD, 2011, [6] Robinson, R.O., et al., J. Manip. Physiol. Ther., 1987.