Dynamic balance changes within three weeks of fitting a new prosthetic foot component

Abstract

Balance during walking is of high importance to prosthesis users and may affect walking during baseline observation and evaluation. The aim of this study was to determine whether changes in walking balance occurred during an adaptation period following the fitting of a new prosthetic component. Margin of stability in the medial-lateral direction (MOS_ML) and an anterior instability margin (AIM) were used to quantify the dynamic balance of 21 unilateral transtibial amputees during overground walking. Participants trialled two prosthetic feet presenting contrasting movement/balance constraints; a Higher Activity foot similar to that of their own prosthesis, and a Lower Activity foot. Participants were assessed before (Visit 1) and after (Visit 2) a 3-week adaptation period on each foot. With the Higher Activity component, MOS_ML decreased on the prosthetic side, and increased on the sound side from Visit 1 to Visit 2, eliminating a significant inter-limb difference apparent at Visit 1 (Visit 1-sound=0.062m, prosthetic=0.075m, p=0.018; Visit 2-sound=0.066m, prosthetic=0.074m, p=0.084). No such change was seen with the Lower Activity foot (Visit 1-sound=0.064m, prosthetic=0.077m, p=0.007; Visit 2-sound=0.063m, prosthetic=0.080m, p<0.001). Significant changes in AIM were observed at Visit 2 (Visit 1: -0.16 (0.08) m, Visit 2: -0.17 (0.08) m; F=23.396, p<0.01). These findings suggest that changes in balance during walking can occur following the initial receipt of a device regardless of whether the component is of the same functional category as the one an individual is accustomed to using.

Keywords: Amputee; Biomechanics; Gait; Rehabilitation; Walking.

Figure 1. Ensemble results

(a) Medial-lateral margin of stability (MOS_ML) at visits 1 and 2 before and after a three week adaptation period on Higher Activity and Lower Activity feet. (b) Anterior Instability Margin (AIM) at visits 1 and 2 before and after a three week adaptation period on Higher Activity and Lower Activity feet. * differences significant at p=0.05. X – prosthetic side, O – sound side.

Figure 2. Medial-lateral margin of stability (MOS_ML) for 21 participants with unilateral transtibial amputation on Higher Activity and Lower Activity feet. Solid bars indicate significant differences/changes (p<0.05). Negative values indicate a decrease in margin of stability. Tabulated values indicate the number of individuals who showed significant decreases (−) significant increases (+) and no significant changes (ns)

(a) Individual changes over a three week adaptation period. Positive values indicate an individual increased their margin of stability (XcoM remained further within the lateral boundary of the base of support). (b) Individual differences from prosthetic to sound side. Positive values indicate a greater margin of stability on the sound side (XcoM remained further within the lateral boundary of the base of support). (c) Individual differences from Higher Activity to Lower Activity foot at Visit 1 and Visit 2. Positive values indicate a greater margin of stability on the Lower Activity foot (XcoM remained further within the lateral boundary of the base of support).

Figure 2. Medial-lateral margin of stability (MOS_ML) for 21 participants with unilateral transtibial amputation on Higher Activity and Lower Activity feet. Solid bars indicate significant differences/changes (p<0.05). Negative values indicate a decrease in margin of stability. Tabulated values indicate the number of individuals who showed significant decreases (−) significant increases (+) and no significant changes (ns)

(a) Individual changes over a three week adaptation period. Positive values indicate an individual increased their margin of stability (XcoM remained further within the lateral boundary of the base of support). (b) Individual differences from prosthetic to sound side. Positive values indicate a greater margin of stability on the sound side (XcoM remained further within the lateral boundary of the base of support). (c) Individual differences from Higher Activity to Lower Activity foot at Visit 1 and Visit 2. Positive values indicate a greater margin of stability on the Lower Activity foot (XcoM remained further within the lateral boundary of the base of support).

Figure 3. Anterior Instability Margin (AIM) for 21 participants with unilateral transtibial amputation. Solid bars indicate significant differences/changes (p<0.05). Negative values indicate a decrease in margin of stability. Tabulated values indicate the number of individuals who showed significant decreases (−) significant increases (+) and no significant changes (ns)

(a) Individual changes over a three week adaptation period. Positive values indicate an increase in margin of stability from the initial visit to the end of the adaptation period (XcoM was further within or towards the base of support at contralateral foot contact at Visit 2). (b) Individual differences from prosthetic to sound limb on Higher Activity and Lower Activity feet. Positive values indicate a greater margin of stability on the sound side (XcoM was further within or towards the base of support at contralateral foot contact). (c) Individual differences from Higher Activity to Lower Activity foot limb at Visit 1 and Visit 2. Positive values indicate a greater margin of stability on the Lower Activity foot (XcoM was further within or towards the base of support at contralateral foot contact when using the Lower Activity foot in comparison to the Higher Activity foot).

Figure 3. Anterior Instability Margin (AIM) for 21 participants with unilateral transtibial amputation. Solid bars indicate significant differences/changes (p<0.05). Negative values indicate a decrease in margin of stability. Tabulated values indicate the number of individuals who showed significant decreases (−) significant increases (+) and no significant changes (ns)

(a) Individual changes over a three week adaptation period. Positive values indicate an increase in margin of stability from the initial visit to the end of the adaptation period (XcoM was further within or towards the base of support at contralateral foot contact at Visit 2). (b) Individual differences from prosthetic to sound limb on Higher Activity and Lower Activity feet. Positive values indicate a greater margin of stability on the sound side (XcoM was further within or towards the base of support at contralateral foot contact). (c) Individual differences from Higher Activity to Lower Activity foot limb at Visit 1 and Visit 2. Positive values indicate a greater margin of stability on the Lower Activity foot (XcoM was further within or towards the base of support at contralateral foot contact when using the Lower Activity foot in comparison to the Higher Activity foot).