Upper Limb Loss Perturbation Response
Condition: Amputation
Study type: Interventional

Summary: 
      Recent investigations have suggested that persons with upper limb loss experience a high
      prevalence of falls with a quarter of reported falls resulting from a trip. Moreover, studies
      indicate that missing part of an arm may negatively impact balance and that use of a
      prosthesis exacerbates this problem. While the investigators are beginning to understand the
      effects of upper limb loss on balance, the understanding of how Veterans with upper limb loss
      respond to walking disturbances is incomplete. Therefore, the aims of this study are to
      observe the effects of upper limb loss and wearing a prosthesis on the preparation and
      recovery of Veterans who trip during walking. The investigators plan to use unique treadmill
      technology to deliver controlled, yet unexpected, perturbations to Veterans with upper limb
      loss and non-amputee controls, and assess walking stability through body dynamics. Results
      from this study will help us understand why Veterans with upper limb loss fall as a critical
      first step to addressing this problem through balance-targeted interventions that are
      integrated into patient care.
    

Detailed description: 
      The primary aim of this pilot study is to characterize the proactive and reactive locomotor
      response of Veterans with upper limb loss (ULL) to a trip during walking. The investigators'
      recent VA-funded investigations have suggested that persons with ULL experience a high
      prevalence of falls and demonstrate postural control mechanisms that may impair stability.
      Specifically, nearly half of individuals with ULL at or proximal to the wrist level
      experience at least one fall per year and almost a third will experience two or more falls.
      Further, use of a prosthesis increases the likelihood of falling by six times, 25% of
      reported falls resulted from tripping, and nearly a third of individuals who experience a
      fall suffer a fall-related injury. Falls can have considerable economic burden on the VHA and
      lead to long-term diminished quality of life. The investigators' biomechanical studies
      suggest that persons with unilateral ULL display greater postural sway during standing than
      able-bodied individuals which increases when wearing a prosthesis, and right/left asymmetry
      in locomotor stability dynamics that may increase the risk of falling toward the impaired
      limb side and during sound limb side strides. These findings emphasize the need for
      additional research to better understand the mechanisms Veterans with ULL use to control
      balance and how wearing a prosthesis affects these strategies. As the investigators' previous
      research was concerned with steady-state characterization of postural control, the
      investigators now plan to build on this work by studying the effects of ULL and wearing a
      prosthesis on locomotor stability when responding to a trip disturbance during walking. In
      this context, locomotor stability is defined as the ability to recover from a perturbation
      and return to steady-state gait.

      The investigators will address the study aims by analyzing trip-induced proactive and
      reactive locomotor strategy differences in two study comparisons: 1) Veterans with unilateral
      transradial level ULL against matched able-bodied controls (with and without one arm bound),
      and 2) Veterans with unilateral transradial ULL when wearing their customary prosthesis
      against not wearing their prosthesis. Controlled, yet unexpected, simulated trips will be
      delivered through the investigators' custom-built treadmill which permits programmable belt
      velocity disturbances and allows participants to continue walking following recovery. The
      investigators will characterize the proactive and reactive locomotor stability mechanisms
      through a set of biomechanical (angular momentum, arm and trunk kinematics) variables.
      Biomechanical variables will be quantified using an optical motion capture system. The
      investigators expect that Veterans with ULL will demonstrate altered locomotor stability
      mechanisms compared to controls, and these differences will exist between wearing and not
      wearing their customary prosthesis. Results from this study will help us characterize the
      underlying mechanisms of locomotor stability in Veterans with ULL and identify the factors
      associated with their increased prevalence of trip-related falls. Such knowledge is a
      critical first step to addressing this public health problem through stability-targeted
      rehabilitation interventions aimed at reducing falls, fall-related injuries, and associated
      VHA costs in this Veteran patient group. The investigators will use the outcomes from this
      pilot study to guide future VA Merit Award proposals to develop and assess physical training
      intervention methods and wearable and prosthetic technology to improve stability in Veterans
      with ULL. The VHA is an ideal venue to pursue this work as one of its main priorities is to
      elevate the standard-of-care for Veterans with limb loss.
    

Intervention name(s): Perturbation
Intervention type(s): Other
Intervention description(s): Participants from both cohorts will experience a simulated trip while walking on the treadmill. The trip is induced through a rapid acceleration and deceleration of the treadmill belt speed.
Allocation: Randomized
Intervention model: Single Group Assignment
Intervention model description: Participants will receive a small treadmill belt disturbance while walking.
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Stability; Locomotion; Motor Control; Trip; Falls; Upper Limb Loss; Prosthesis; Arm