Individuals with transtibial limb loss use interlimb force asymmetries to maintain multi-directional reactive balance control

Abstract

Background Deficits in balance control are one of the most common and serious mobility challenges facing individuals with lower limb loss. Yet, dynamic postural balance control among indivdiuals with lower limb loss remains poorly understood. Here we examined the kinematics and kinetics of dynamic balance in individuals with unilateral transtibial limb loss. Methods Five individuals with unilateral transtibial limb loss, and five age- and gender-matched controls completed a series of randomly applied multi-directional support surface translations. Whole-body metrics, e.g. peak center-of-mass displacement and net center-of-pressure displacement were compared across cohorts. Stability margin was computed as the difference between peak center-of-pressure and center-of-mass displacement. Additionally, center-of-pressure and ground reaction force magnitude and direction were compared between the prosthetic, intact, and control legs. Findings Peak center-of-mass displacement and stability margin did not differ between individuals with transtibial limb loss and controls for all perturbation directions except those loading only the prosthetic leg; in such cases the stability margin was actually larger than controls. Despite similar center-of-mass displacement, greater center-of-pressure displacement was observed in the intact leg during anterior-posterior perturbations, and under the prosthetic leg in medial-lateral perturbations. Further, in the prosthetic leg, ground reaction forces were smaller and spanned fewer directions. Interpretation Deficits in balance control among indivdiuals with transtibial limb loss may be due to their inability to use their prosthetic leg to generate forces that are equal in magnitude and direction to those of unimpaired adults. Targeting this force-generating deficit through technological or rehabilitation innovations may improve balance control.

Correlations between measures of dynamic balance in individuals with post-stroke hemiparesis

“…This measure is based on foot placement while accounting for body CoM position and velocity and has been used to assess dynamic balance in young healthy individuals in destabilizing environments (e.g., McAndrew Young et al, 2012), older adults while stepping to targets (Hurt and Grabiner, 2015), amputees (e.g., Bolger et al, 2014; Gates et al, 2013; Hof et al, 2007) and post-stroke individuals (e.g., Hak et al, 2013; Kao et al, 2014). Similarly, whole-body angular-momentum has been used to assess dynamic balance in a number of patient populations including post-stroke hemiparetic individuals (Nott et al, 2014), amputees (e.g., Pickle et al, 2014; Sheehan et al, 2015; Silverman and Neptune, 2011) and older adults (e.g., Pijnappels et al, 2005b).…”

Frequency and Circumstances of Falls Reported by Ambulatory Unilateral Lower Limb Prosthesis Users: A Secondary Analysis

“…More than 50% of lower limb prosthesis (LLP) users report falling at least once a year [1][2][3][4][5], placing them at high risk for adverse health outcomes such as decreased mobility and diminished quality of life [3,6,7]. Attempts to lower the prevalence of falls in LLP users have traditionally focused on developing and validating clinical tests to assess fall risk [8][9][10][11][12], designing and testing prosthetic components to improve patient safety [13][14][15][16], characterizing the biomechanics of key balance strategies to identify deficits in those at risk for falls [17][18][19][20][21][22][23], and identifying risk factors to help recognize potential fallers [2,5,7,24,25]. However, little attention has been directed toward recording, reporting, and characterizing the circumstances of falls in LLP users [1,4,7].…”

Agreement between measurements of stance width using motion capture and center of pressure in individuals with and without Parkinson’s disease

“…This bias that can be explained by the externally-rotated “toe out” posture used by most participants, in which a substantial portion of the foot plantar surface lies lateral to the posterior face of the heel. Overall, these results suggest that foot CoP location, a commonly calculated variable in clinical biomechanics studies (5, 7, 8) can be used to approximate stance width in healthy aging and in individuals with PD in the ON and OFF medication states.…”

“…As typically defined (6), the CoP is the point location of the vertical ground reaction force vector beneath the entire body, and represents a weighted average of all the pressures over the surface area in contact with the ground (6). Whole-body CoP location is often calculated as an important outcome variable in clinical balance studies (5, 7, 8). If bilateral force plates are used, CoP can be calculated separately for each foot (e.g., as it is in instrumented treadmill studies (9)).…”