Indicators of dynamic stability in transtibial prosthesis users C. Kendell a,b, *, E.D. Lemaire a,c , N.L. Dudek a,c , J. Kofman d a The Ottawa Hospital Rehabilitation Centre, Canada b Faculty of Health Sciences, University of Ottawa, Canada c Faculty of Medicine, University of Ottawa, Canada d Department of Systems Design Engineering, University of Waterloo, Canada 1. Introduction Dynamic stability is an important factor for safe mobility. This is especially important for people with lower-limb amputations since they have a higher incidence of falls than the general population. A survey found that 82% of polled individuals with lower-limb amputations had fallen within the previous year; with 49% of those falls occurring while the person wore their prosthesis [1]. For individuals with unilateral amputations, 54% had fallen within the previous year, with 75% of those people reporting more than one fall [2]. Intrinsic factors (i.e., psychological issues, medication, vision loss, age, disease), environmental factors, and prosthetic factors (i.e., fit and alignment) contribute to instability that can result in falling [1,2]. Stability is ‘‘the property of a body that causes it when disturbed from a condition of equilibrium or steady motion to develop forces or moments that restore the original condition’’ [3]. Dynamic stability for lower-limb prosthetic gait has not been thoroughly addressed in the literature, partly due to the lack of an appropriate, portable instrument to quantify dynamic stability. Common stability assessment methods used in the clinic and gait laboratory are limited. Clinical tests are designed to be conducted in a short amount of time, with little equipment, and often assess the minimum number of tasks to characterize stability. Motion capture systems restrict assessment to a laboratory setting and require expertise for accurate data collection, analysis, and interpretation. Ideally, a quantitative multi-factorial approach for dynamic stability assessment that provides clinically meaning- ful output, measures stability over a variety of walking conditions, and is easily applied in the clinic and in the community, is needed. Recently, a method was developed for assessing dynamic stability based on plantar pressure. Using plantar pressure data collected from a multi-celled shoe–insole pressure sensor (F-Scan Mobile, Tekscan Inc., Boston, USA), six dynamic stability para- meters relating to plantar center-of-pressure anterior/posterior and medial/lateral motion and gait timing, were identified [4]. The parameters were used to develop a dynamic stability index [5] based on a fuzzy-logic model. The purpose of the current study was to investigate the dynamic stability of individuals with unilateral transtibial amputations using the six parameters. Subjects navigated six conditions: level-ground walking, uneven ground walking, stair ascent/descent, and ramp ascent/descent. Differ- ences between the intact and prosthetic limbs were examined, as Gait & Posture 31 (2010) 375–379 ARTICLE INFO Article history: Received 9 October 2009 Received in revised form 16 December 2009 Accepted 7 January 2010 Keywords: Gait Dynamic stability Plantar pressure Biomechanics Prosthetics Center of pressure ABSTRACT An improved understanding of factors related to dynamic stability in lower-limb prosthesis users is important, given the high occurrence of falls in this population. Current methods of assessing stability are unable to adequately characterize dynamic stability over a variety of walking conditions. F-Scan Mobile has been used to collect plantar pressure data and six extracted parameters were useful measures of dynamic stability. The aim of this study was to investigate dynamic stability in individuals with unilateral transtibial amputation based on these six parameters. Twenty community ambulators with a unilateral transtibial amputation walked over level ground, uneven ground, stairs, and a ramp while plantar pressure data were collected. For each limb (intact and prosthetic) and condition, six stability parameters related to plantar center-of-pressure perturbations and gait temporal parameters, were computed from the plantar pressure data. Parameter values were compared between limbs, walking condition, and groups (unilateral transtibial prosthesis users and able-bodied subjects). Differences in parameters were found between limbs and conditions, and between prosthesis users and able-bodied individuals. Further research could investigate optimizing parameter calculations for unilateral transtibial prosthesis users and define relationships between potential for falls and the dynamic stability measures. ß 2010 Elsevier B.V. All rights reserved. * Corresponding author at: The Ottawa Hospital Rehabilitation Centre, 505 Smyth Road, Ottawa, Ontario, Canada K1H 8M2. Tel.: +1 613 737 8899x75321. E-mail address: kendellcynthia@gmail.com (C. Kendell). Contents lists available at ScienceDirect Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost 0966-6362/$ – see front matter ß 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2010.01.003