The effects of rocker sole and SACH heel on kinematics in gait

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Abstract

The rocker sole and solid-ankle cushion-heel (SACH) heels are the most commonly prescribed external shoe modification. Only a limited number of scientific evidence exists to support these interventions in clinical practice. The objective of this study was to determine the effects of rocker soles and SACH heels on kinematics during gait. In this study, we investigated the gait parameters during level walking, stair climbing and stair descending in healthy volunteers and assessed the effects of the modified shoes on the motion of the forefoot and hindfoot compared with the traditional shoes. Eleven normal subjects participated in this study. A six-camera motion analysis system was used to capture motion trajectories. The three-dimensional (3D) coordinates of the markers were used to calculate the angles of flexion-extension, valgus–varus, and internal–external rotation at the hindfoot and forefoot joints in a gait cycle by the custom software for foot kinematic analysis. The results showed that the rocker soles offer several advantages from the viewpoint of gait kinematics. The forefoot joint excursion in sagittal plane while wearing rocker shoes was significantly less than that while wearing traditional shoes during level walking, stair climbing and stair descending. It means that they could mimic the action of the forefoot joint, aid in roll off, and simulate forefoot dorsiflexion. Since the bony structures mechanically link the forefoot joint and hindfoot joint to a triplanar axis of motion, they could be used whenever there is minimal or no motion at the forefoot joint or hindfoot joint, because of, for example, fusion, fracture, cast immobilization, orthosis design, pain, or arthritis.

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.

References (19)

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