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Balance & Stability

In-Progress Projects

 Fall Risk and Prosthetic Influence on Gait Biomechanics in Upper Limb Amputees

  • Principal Investigators: Matthew J. Major, PhD, Steven A. Gard, PhD 
  • Co-Investigators: John Brinkmann, CPO (NUPOC), Rebecca Stine, MS (Jesse Brown VAMC), Marc Applebaum, MD (Jesse Brown VAMC), Allen Heinemann, PhD (Rehabilitation Institute of Chicago)
  • Student Investigator: Suzanne McConn, MS (Department of Biomedical Engineering, Northwestern University)
  • Funded by: Department of Veterans Affairs, Rehabilitation Research and Development Grant Number 1I21RX001388
  • Status: In Progress

Natural arm dynamics in able-bodied individuals are critical for reducing the metabolic energy required to walk steadily and for recovering from a perturbation to avoid a fall, which may have significant implications for individuals with upper limb loss. Very little attention has been paid to the characteristics of gait, standing balance, and fall risk in this patient group. This study proposes to identify the level and covariates of fall risk in individuals with upper limb loss, and the effects of upper limb prosthesis use on gait and standing balance. These results will quantify a previously undocumented health hazard (i.e. increased fall risk) to persons with upper limb loss.

Through improved understanding of the impact of upper limb loss on falls and ambulation, subsequent studies may identify mechanisms of instability in this patient group, leading to rehabilitation strategies (e.g., fall recovery training) and improved prosthesis designs that facilitate efficient and safe mobility. Improving the gait and functional balance of persons with upper limb loss can increase their participation in daily activities and consequently enhance their self-sufficiency and confidence.



Related Publications

 Lateral Stability and Recovery Strategies among Persons with Below Knee Amputation

  • 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

Approximately half of community dwelling persons with lower-limb amputation fall every year [1]. 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.

Analysis Plan

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). 


  1. Miller, W.C., M. Speechley, and B. Deathe, The prevalence and risk factors of falling and fear of falling among lower extremity amputees. Archives of Physical Medicine and Rehabilitation, 2001. 82(8): p. 1031-7.
  2. Nadollek, H., S. Brauer, and R. Isles, Outcomes after trans-tibial amputation: the relationship between quiet stance ability, strength of hip abductor muscles and gait. Physiotherapy Research International, 2002. 7(4): p. 203-14.
  3. Rougier, P.R. and J. Bergeau, Biomechanical analysis of postural control of persons with transtibial or transfemoral amputation. American Journal of Physical Medicine and Rehabilitation, 2009. 88(11): p. 896-903.
  4. Vrieling, A.H., et al., Balance control on a moving platform in unilateral lower limb amputees. Gait and Posture, 2008. 28(2): p. 222-8.
  5. Quai, T.M., S.G. Brauer, and J.C. Nitz, Somatosensation, circulation and stance balance in elderly dysvascular transtibial amputees. Clinical Rehabilitation, 2005. 19(6): p. 668-76.
  6. Isakov, E., et al., Standing sway and weight-bearing distribution in people with below-knee amputations. Archives of Physical Medicine and Rehabilitation, 1992. 73(2): p. 174-8.
  7. Qiao, M. and D.L. Jindrich, Compensations during unsteady locomotion. Integrative and Comparative Biology, 2014. 54(6): p. 1109-21.
  8. Curtze, C., et al., Balance recovery after an evoked forward fall in unilateral transtibial amputees. Gait and Posture, 2010. 32(3): p. 336-41.
  9. Nederhand, M.J., et al., Dynamic Balance Control (DBC) in lower leg amputee subjects; contribution of the regulatory activity of the prosthesis side. Clinical Biomechanics (Bristol, Avon), 2012. 27(1): p. 40-5.
  10. Vanicek, N., et al., Postural responses to dynamic perturbations in amputee fallers versus nonfallers: a comparative study with able-bodied subjects. Archives of Physical Medicine and Rehabilitation, 2009. 90(6): p. 1018-25.
  11. Buckley, J.G., D. O'Driscoll, and S.J. Bennett, Postural sway and active balance performance in highly active lower-limb amputees. American Journal of Physical Medicine and Rehabilitation, 2002. 81(1): p. 13-20.
  12. Hermodsson, Y., et al., Standing balance in trans-tibial amputees following vascular disease or trauma: a comparative study with healthy subjects. Prosthetics and Orthotics International, 1994. 18(3): p. 150-8.


  • 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. <>


 Sensory-Motor Mechanisms Underlying Fall Risk in Transtibial Amputees

  • Principal Investigator: Matthew J. Major, PhD 
  • Mentors: Steven A. Gard, PhD (Jesse Brown VAMC); Mark Grabiner, PhD (University of Illinois Chicago); Young-Hui Chang (Georgia Institute of Technology); Marc Applebaum, MD (Jesse Brown VAMC); Keith Gordon, PhD (Edward Hines, Jr. VAMC); Mark Huang, MD (Rehabilitation Institute of Chicago)
  • Funded by: Department of Veterans Affairs, Rehabilitation Research and Development, Career Development Award (CDA-2; 1K2RX001322-01A1)
  • Status: In progress

Lower limb prosthesis users are known to be at a substantially increased fall risk compared to able-bodied individuals. The interaction among increased fall risk, reduced balance confidence, and high prevalence of a fear of falling often leads to restricted mobility and loss of independence in this patient group. Furthermore, fall risk increases with progressing age, as aging affects musculoskeletal and somatosensory systems that are vital to controlling upright balance and are already compromised in persons with lower limb amputation.

The cause of falls and the role that sensory-motor function for maintaining upright balance plays in fall risk of lower limb prosthesis users is poorly understood. The effects of reduced sensory-motor function on upright balance in older adults has been extensively studied and led to the development of effective assessment tools and intervention strategies that can minimize fall risk. However, the dearth of similar studies and a relatively poor understanding of the complicating effects of lower limb amputation on upright balance have significantly hampered progress toward addressing this important concern for lower limb prosthesis users. Therefore, the primary objective of this research is to develop an improved understanding of the sensory-motor mechanisms underlying upright balance and fall risk in older persons with lower limb amputation.

A better understanding of the relationships between fall risk and various outcome measures can inform the development of intervention techniques to improve functional balance. An improvement in upright balance will reduce the incidence of falls and fall-related injuries in this patient group; and also will increase their daily community participation, encourage independent living, and improve their overall quality of life.



  • Miller K, Russell M, Surratt K, Jenks T, Poretti K, Eigenbrot S, Akins J, Major MJ (2020) The feasibility and validity of a wearable sensor system to assess the stability of high-functioning lower-limb prosthesis users. Journal of Prosthetics and Orthotics. In press. 


  • Martin C, Hammond II P, Stine R, Major M (2020) Locomotor Response of Older Persons with and without Transtibial Amputation to a Trip Disturbance. Virtual 44th Meeting of the American Society of Biomechanics, August 4-7. 

 Vacuum Assisted Suspension: The Effect of Residuum-Socket Interface Integrity on Perception and Control in Individuals with a Transtibial Amputation

  • Principal Investigators: Jenny Kent, PhD; Matthew J. Major, PhD
  • Co-Investigator: Ryan Caldwell, CP 
  • Research Assistant: Genki Hisano, BSc
  • Funded by: American Orthotic & Prosthetic Association (AOPA) 
  • Status: In progress 

Individuals with a lower limb amputation require a secure interface between the prosthetic socket and the residual limb. Movement at this interface may limit the wearer’s ability to obtain sensory information about the walking surface and also may negatively affect control of the prosthesis.

An inability to control the prosthesis and respond appropriately in a given walking context due to movement between the prosthesis and the residual limb may put an individual at higher risk of a loss of balance or a fall. Vacuum Assisted Suspension (VAS) has been shown to reduce this relative movement; however, research is needed to evaluate the effect of the reduction in movement on the functional ability of the prosthesis user.

Aims and Hypothesis 

The objective of this study is to determine the impact of improving the coupling at the socket- residuum interface via VAS on perceptual ability and limb control in individuals with a transtibial amputation. Two specific aims are:

     1. Determine the impact of increasing vacuum on haptic perception via the affected limb 
     2. Determine the extent to which increasing vacuum level improves user control of the prosthetic

Data from this study will yield clinical evidence about the impact of differences in socket-residuum interface integrity on function.

Selected References 

  • Board WJ, Street GM, Caspers C. A comparison of trans-tibial amputee suction and vacuum socket
    conditions. Prosthet Orthot Int 2001;25(3):202-9. 
  • Ferraro C. Outcomes study of transtibial amputees using elevated vacuum suspension in comparison
    with pin suspension. Jpo 2011;23(2):78-81. 
  • Xu H, Greenland K, Bloswick D, Zhao J, Merryweather A. Vacuum level effects on gait characteristics for unilateral transtibial amputees with elevated vacuum suspension. Clin Biomech 2017;43:95-101.