ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

Fig. 2. Significantly greater tissue displacement was observed in the deep region of the
tendon when transitioning from plantar- to dorsiflexion. This result suggests that tissue
shear deformation was induced with eccentric loading.
(Ophir, et al. 1991). A quartic spline method was used to estimate sub-pixel
displacements (Azar, et al. 2010), and a 3 x 3 node median filter was used for
smoothing the nodal displacement information (Thitaikumar, et al. 2008). Motion
tracking was also performed in the reverse direction by starting at the last frame and
incrementing to the first. A weighted average of the forward and backward
displacement trajectories (Pelc 1995) is reported in this study. Average motion in the
superficial (posterior) region of the tendon and deep (anterior) region were determined
by dividing the ROI into two equal regions (Fig. 2). Paired t-tests were computed to
evaluate the influence of location (deep, superficial) and knee angle (0, 90) on tissue
displacements.
4. RESULTS
Regional differences in Achilles tendon motion were observed as the tendon was
stretched and loaded. Significantly greater motion was observed in the deep region of
the tendon when compared with the superficial region (Fig. 3), with that difference
increasing significantly with a flexed knee (Table 1). However, significantly less motion
was observed in a flexed knee posture compared to an extended knee posture.
5. DISCUSSION
Table 1. Along-fiber tissue displacements (mm) were
significantly greater in the deep region of the Achilles tendon,
with the largest motion observed in a flexed knee posture.
Knee Flexion Superficial Deep p-value:
10 6.7 2.7 7.5 2.9 0.004*
90 5.5 2.1 6.5 2.3 0.010*
p-value: 0.012* 0.012*
Nonuniform motion was observed across the Achilles tendon under eccentric loading
conditions, with the largest motion observed on the deep edge of the tendon. This result
is contrary to what might be expected biomechanically. The superficial aspect of the