Foot and Ankle Biomechanics with Orthosis Ambulation

Principal Investigator: Harold B. Kitaoka, M.D.
Project Coordinator: Diana Hansen — hansen.diana@mayo.edu

Figure 1: Three different type custommade foot orthoses (from left to right): a rigid ankle foot orthosis (AFO), a rigid hindfoot orthosis (HFO-R), and an articulated (HFO-A) hindfoot orthoses

The purpose of this study is to evaluate the triplanar ankle range of motion (ROM) restriction in patients with ankle and subtalar osteoarthritis (OA) treated by three different types of ankle foot orthoses compared to unbraced walking over various ground conditions.

In this study, 13 unilateral ankle OA and 10 unilateral subtalar OA patients were enrolled. Each patient was tested without a brace and shod with a rigid ankle foot orthosis (AFO), rigid hindfoot orthosis (HFO-R), and articulated hindfoot orthosis (HFO-A) (Fig. 1). Level, ascending and descending ramp and side-slope ground conditions were tested. Eleven reflective markers (Fig. 1) were directly mounted on the skin to evaluate the ankle and foot kinematics in our study. The triplanar hindfoot and forefoot motions were collected using computerized motion analysis equipment.

Ankle Osteoarthritis - The AFO and HFO-R provided the best sagittal plane hindfoot motion restriction over all ground conditions. The HFO-R allowed the greatest sagittal plane forefoot motion walking over level and side slope conditions, the greatest frontal plane forefoot motion walking down the ramp, and the greatest transverse plane forefoot motion walking over level and ramp-ascending conditions. In conclusion, the HFO-R not only provides selective restriction to the ankle-hindfoot motion but also allows sufficient forefoot motion compared to the AFO. We consider the HFO-R to be the best option of all tested orthosis for treating patients with ankle OA.

Subtalar Osteoarthritis - The AFO significantly restricted frontal plane hindfoot motion in the descending ramp and side slope when the arthritic subtalar joint was higher than the unaffected side. The HFO-A provided significant frontal plane hindfoot motion restriction in the descending ramp and side slope when the arthritic subtalar joint was lower than the unaffected side. The HFO-R significantly restricted frontal plane hindfoot motion and also allowed greater sagittal plane forefoot motion in most ground conditions. The HFO-R may be considered an optimal orthosis for patients with subtalar OA.