The effects of rocker sole and SACH heel on kinematics in gait
Introduction
The rocker sole and SACH heels are the most commonly prescribed external shoe modification [1], [2], [3], [4]. Incorporation of the SACH and a metatarsal rocker on a shoe following ankle fusion improves gait kinematics [1], [2]. The SACH heel allows a reasonably natural heel strike [1]. The roller sole, progressively contoured towards the toe, mimics the motion of the talocrural joint during walking. However, limited scientific evidence exists to support these interventions despite these being commonplace in clinical practice in such patients [5].
The lack of normal ankle movement in the affected foot reduces the ability of the patients to walk comfortably. It would have a more pronounced effect in negotiating stairs, because large ranges of dorsiflexion and plantarflexion are required to accomplish this activity. Although gait characteristics have been reported for this population during barefoot level walking [6], [7], [8], [9], little information is available regarding the compensations required for stair ambulation. In addition, only a limited number of scientific studies on the biomechanics of normal stair climbing are available in the literature [9], [10], [11], [12], [13], [14], [15]. We hypothesize that rocker soles and SACH heels change the kinematic patterns throughout the hindfoot and forefoot. Therefore, the purposes of this study were to investigate the effects of rocker soles and SACH heels on kinematics of the foot and ankle during level walking, stair climbing and stair descending in healthy volunteers and to assess the effects of the modified shoes on the motion of the forefoot and hindfoot compared with the traditional shoes.
Section snippets
Subjects
Eleven normal subjects (four males and seven females) participated in this study. The mean age of these subjects was 36.2±8.7 years, mean weight was 62.1±8.1 kg, and mean height was 167.8±4.3 cm. These subjects had no history of lower extremity disorders or pathological conditions. The reason to recruit normal subjects in our study is that only the effect of the shoe modification was examined.
Three-segment rigid body model
This paper used a three-segment rigid body model (Fig. 1) to describe the motion of the forefoot and
Cadence
The mean and SD of the cadence are shown in Table 1. Compared to descending stairs, the subjects demonstrated significantly slower cadence during ascending stairs. No significant difference in cadence was found between the modified shoes and traditional shoes in each activity.
Kinematics
The patterns in the hindfoot and forefoot angles while wearing the modified shoes during level walking, ascending stairs and descending stairs were in some degree consistent with those while wearing the traditional shoes (
Discussion
The patterns of the foot angle during stair climbing and stair descending were consistent with those reported by Powers et al. [18]. In this study, subjects required 21.0° of dorsiflexion/plantarflexion in the hindfoot, and 21.9° of dorsiflexion/plantarflexion in forefoot to complete tasks of stair ascent (Table 2). The sum of these two values was in good agreement with those, previously reported by Livingston et al. [19] (40–43° of dorsiflexion/plantarflexion range of the motion in ankle)
Acknowledgements
This work was supported by National Science Council grant NSC 87-2314-B-006-110- M08, Taiwan.
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