Estimating soft tissue artifact of the thigh in high knee flexion tasks using optical motion Capture: Implications for marker cluster placement

Can Anthropometry be Used to Dictate Participant-Specific Thigh Marker Placements Which Minimize Error in Hip Joint Center Estimation?

“…The Bland-Altman analysis demonstrated that the mean difference in the magnitude of the 3D position was smallest for the mid-anterolateral (MAL) cluster (2.81-4.41 cm); however, the limits of agreement across all tested marker clusters, which speak to variability across the sample, remained quite wide (lower limits: 0.79-2.54 cm and upper limits: 5.04-17.65 cm). 10 These findings agree with previous findings suggesting that tasks which require increased knee flexion require a more anterior thigh placement and that soft tissue artifact is highly participant specific.…”

“…The data used in this study were collected concurrently with data presented in Buchman-Pearle and Acker. 10 An abbreviated version of the data collection and processing, with details added for the additional data and analyses used in this study, are provided in the following sections.…”

“…However, during motion, soft tissue displaces relative to bones, leading to error in the estimated bone position, known as soft tissue artifact. 1,2 Previous studies have noted that soft tissue artifact displays location, [3][4][5][6][7][8][9][10] task, 3,5,[11][12][13][14][15] and participant specificity. 3,[16][17][18][19] Location specificity refers to the different magnitudes and patterns of artifact that emerge between segments (ie, thigh vs shank) or within segments (ie, anterior vs lateral thigh).…”

“…To address location and task specificity, placement of markers on different areas of a segment have been explored in a range of movements. [3][4][5]10 On the thigh in walking, maximal and minimal soft tissue artifact were observed for markers on the proximalanterior and distal-lateral (DL) thigh, respectively. 4 Alternatively, in a sit-to-stand and step-up task, Stagni et al 3 found that soft tissue artifact was generally highest at the proximal-lateral thigh and lowest at the distal-anterior (DA) thigh.…”

“…However, the small sample sizes in these previous works (of two 3 and four 5 participants) may not address the potential variability across people. One study, 10 conducted in our laboratory on 50 participants, compared the position of the hip joint center reconstructed using the pelvis cluster to that reconstructed using 6 different rigid thigh clusters to estimate the effect soft tissue artifact noninvasively during high knee flexion (ie, tasks where knee flexion exceeds 120°2 0 ). The pelvis-estimated hip joint center was considered the gold standard as pelvis soft tissue artifact is generally smaller than artifact observed on the thigh, 21 and the pelvis cluster is closer to hip joint center, hence these smaller deformations have less of an effect on the reconstructed hip joint center.…”