Tibiocalcaneal motion during running, measured with external and bone markers

Abstract

Objective. The purpose of this study was to compare tibiocalcaneal motion during running based on skeletal markers with tibiocalcaneal motion based on external markers.

Design. In vivo measurements of external and skeletal tibiocalcaneal kinematics.

Background. External (shoe, skin) markers are typically used to determine rearfoot kinematics. However, it is not known if such markers are able to provide a good representation of the skeletal (tibiocalcaneal) kinematics.

Methods. Bone pins were inserted into the tibia and calcaneus of five subjects. The 3-D motion of markers attached to bone pins as well as of external markers attached to the shank and shoe were determined during the stance phase of five running trials. Intersegmental motion was expressed in terms of Cardan angles (plantarflexion/dorsiflexion, abduction/adduction, inversion/eversion).

Results. It was found that the skeletal inversion/eversion, abduction/adduction, and plantarflexion/dorsiflexion motions were similar across the subjects. The shape of the tibiocalcaneal rotation curves based on external markers were similar to those based on bone markers. However, the rotations were generally overestimated when using external markers, e.g. the average maximal eversion motion calculated from external markers was 16.0 ° whereas the skeletal maximal eversion motion was only 8.6 °. These discrepancies were mainly due to the relative movement between shoe markers and underlying calcaneus.

Conclusions. External markers are only gross indicators of the skeletal tibiocalcaneal motion. The rotations derived from external shoe and shank markers typically overestimate the skeletal tibiocalcaneal kinematics.