Biomechanics and Motion Analysis

Foot and Ankle Biomechanice with Orthosis Ambulation

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

Figure 19: Orthoses used during testing.

This purpose of this project is to characterize gait of healthy subjects in various conditions as a baseline against which to compare subjects with subtalar and ankle arthritis. Subjects with hind- or mid-foot arthritis patients have stiff, arthritic joints which are painful and impair walking ability especially over non-level surfaces such as ramps or sideslopes. Orthoses may be prescribed to reduce pain and improve gait including a standard rigid ankle foot orthosis (AFO) or hindfoot orthosis (articulated, non-articulated) (Figure 19). Thus, healthy subjects were tested walking over non-level surfaces and walking over level surfaces with and without various types of orthoses.

In another study, data were collected from subjects ascending and descending a 10 o ramp and compared to gait over level surfaces. Sagittal plane motion was increased in both ramp conditions. During ramp ascent, plantarflexion moments increased and greater power was generated with the converse being true during ramp descent. Coronal plane excursion was maximized during ramp ascent and transverse plane motion was maximized during ramp descent. Both ramp conditions resulted in increased rotation moments and transverse power was increased during ramp descent. Although ramps distorted the walking surface in a single dimension, consequent biomechanical gait alterations were found in multiple dimensions. These alterations were interpreted as strategies to manipulate flexibility and stability of the foot while maintaining the body's center of mass within the base of support.

Finally, subjects walking across a 10° sideslope was compared to level surface gait. Walking when the foot was on the high portion of the slope (SSH) resulted in greater eversion motion compared to the other two conditions. Inversion moments were maximized and eversion moments minimized in the SSH condition with the converse occurring when the foot was low on the slope (SSL). Both side-slope conditions were associated with greater coronal power generation and absorption than the level condition. In the sagittal plane, dorsiflexion range was increased in the SSH condition and plantarflexion motion was increased in the SSL condition. Both side-slope conditions resulted in lower sagital plane moments and power generation. This study provided further evidence of conformation of the foot to the supporting surface while maintaining body weight over the feet.