Postural Control Differences between Patients with Posterior Tibial Tendon Dysfunction and Healthy People during Gait

Abstract

Background: Patients with posterior tibial tendon dysfunction (PTTD) may exhibit postural instability during walking likely due to a loss of medial longitudinal arch, abnormal foot alignment, and pain. While many studies have investigated gait alterations in PTTD, there is no understanding of dynamic postural control mechanisms in this population during gait, which will help guide rehabilitation and gait training programs for patients with PTTD. The purpose of the study was to assess dynamic postural control mechanisms in patients with stage II PTTD as compared to age and gender matched healthy controls.

Methods: Eleven patients with stage II PTTD (4 males and 7 females; age 59 ± 1 years; height 1.66 ± 0.12 m; mass 84.2 ± 16.0 kg) and ten gender and age matched controls were recruited in this study. Participants were asked to walk along a 10 m walkway. Ten Vicon cameras and four AMTI force platforms were used to collect kinematic and center of pressure (COP) data while participants performed gait. To test differences between PTTD vs. control groups, independent t-tests (set at α < 0.05) were performed.

Results: Patients with PTTD had significantly higher double stance ratio (+23%) and anterior-posterior (AP) time to contact (TTC) percentage (+16%) as compared to healthy control. However, PTTD had lower AP COP excursion (-19%), AP COP velocity (-30%), and medial-lateral (ML) COP velocity (-40%) as compared to healthy controls. Mean ML COP trace values for PTTD were significantly decreased (-23%) as compared to controls, indicating COP trace for PTTD tends to be closer to the medial boundary than controls during single-support phase of walking.

Conclusion: PTTD patients showed more conservative and cautious postural strategies which may help maintain balance and reduce the need for postural adjustment during PTTD gait. They also showed more medially shifted COP patterns than healthy controls during single-support phase of walking. Dynamic postural control outcomes could be used to develop effective gait training programs aimed at alleviating a medial shift of COP (everted foot) for individuals with PTTD in order to improve their functionality and gait efficiency.

Keywords: PTTD; center of pressure; gait; postural control; time-to-boundary.

Figure 1

Experimental setup (at UAMS) showing four force platforms which were used to assess center of pressure (COP) movement during single-support phase (only one limb is in contact with the ground) of walking.

Figure 2

Illustration of the rectangular boundary of the foot and the Time-to-Contact (TTC) calculation. $v$ and $a$ (COP velocity and acceleration) were calculated using the first central difference method.

Figure 3

Illustration of normalized COP trace relative to the medial-lateral boundary of the foot: 0% of the COP trace indicates that COP is close to the medial boundary, 100% indicates COP is close to the lateral boundary, and 50% indicates COP is in the middle of the medial-lateral boundary.