Shank – to – Vertical - Angle in AFOs: Static versus dynamic assessment in a series of cases.

Background
Tuning of ankle-foot orthosis footwear combinations (AFO-FC) has been shown to be effective in aligning the ground reaction force (GRF) closer to the joint rotation center of the lower limbs. The notion of “tuning” the AFO-FC is largely dependent on the shank-to-vertical angle (SVA), which is measured while the subject is static but is meant to represent the SVA in mid-stance.

Objectives
The aim of this study was to compare the SVA measured in standing position with the SVA at temporal mid-stance (TMST) in a series of cases.

Study Design
This study is a case series.

Methods
Four participants had their AFO-FC tuned to optimum SVA using video-based gait analysis with GRF overlay. Initially, the SVA was measured with the subject standing in relaxed stance on the force plate with approximately equal weight on both feet. The SVA was then assessed at TMST.

Results
The measurement of the SVA of the AFO-FC in relaxed stance seems to be the same as the measurement of the SVA in TMST.

Conclusions
Measuring the SVA of the AFO-FC in relaxed stance is an accurate way of determining the SVA at TMST.

Clinical Relevance
Ankle-foot orthosis footwear combination tuning is considered an essential aspect of AFO prescriptions. The SVA is a key principle of AFO-FC tuning. The method for determining the SVA has yet to be tested to ensure that the static measurement correlates to the dynamic measurement during gait.