Appendix D - Oxford Foot Model

The Oxford Foot Model will be appended to the main model if the session setting "Multisegment Foot" is set to Oxford (see “Step 5 – Subject and Session details”). The material presented here is for for the right foot, the left foot is defined accordingly.

Shank

To simplify the marker set, the original Oxford Foot Model definition of the shank is not used. Instead, the shank definition that is used for the lower body model is used, i.e. if a CAST marker set is used for the lower body, the CAST shank definition will be applied.

Hindfoot

Defnition:	Figure:
The long axis of the foot (y-axis) is defined by the line connecting FCC and Mid_Forefoot_Base_proj (see Forefoot for definition of this landmark); the sagittal plane is defined by FCC2:
Tracking markers:

Reference

Stebbins et al. (2006), Variation 5 (p. 405). Note that the definition used by Qualisys has been adapted to use a projection of the Mid_Forefoot_Base landmark to define the long axis of the hindfoot, instead of assuming the axis to be horizontal. This was done so that the definition can be used for persons that cannot place their foot flat on the floor.

Forefoot

Defnition:	Figure:
Mid_Forefoot_Base is midpoint of FMT and P1MT:
Mid_forefoot_base_proj is Mid_forefoot_base projected on plane defined by FMT, FM5 and FM1:
FM2_proj is FM2 projected on a plane defined by FMT, FM1 and FM5:
The long axis of the forefoot (y-axis) runs from Mid_Forefoot_Base_Proj to FM2_proj; the orientation is defined so that the z-axis is perpendicular to the plane formed by FMT, FM1 and FM5:
Tracking markers:

Reference

Stebbins et al. (2006), section 2.3.4 (p. 403).

Hallux

Defnition:	Figure:
The landmark HLX_proj is at the x and y coordinates of FM1 and the z coordinate of PM6. This means that HLX_proj is at the same height relative to the floor as PM6 but below FM1:
The Hallux_x landmark is a projection of HLX_proj in the X direction of the Forefoot coordinate system.
The Y axis of the Hallux connects HLX_proj and PM6; the orientation is defined so that the transverse (X/Y) plane includes the Hallux_x landmark:
Tracking markers: Note: D1M_HLX is a virtual marker. It is defined based on the static trial and at the position of FM1. It is tracked using the coordinate system of the forefoot segment.

Reference

Stebbins et al. (2006), section 2.4.3 (p. 404)

Arch height

Arch height is calculated as the distance between P1MT and the landmark P1M_FF. The result is divided by the distance FM2 and FCC.

P1M_FF is a projection of P1MT onto the plane formed by FMT, FM5and D1M_HLX.

Note: D1M_HLX is a virtual marker. It is defined based on the static trial and at the position of FM1. It is tracked using the coordinate system of the forefoot segment.

Reference

Stebbins et al. (2006), section 2.4.3 (p. 404)

Foot maker placement compared to single segment foot

Single segment foot

FM1/5 placed at dorsal aspect of metatarsal head (Capozzo 1995).
FCC is placed at the same height as midpoint of FM1 and FM5. This is closer to “upper ridge of calcaneus”.

Equinus foot

Oxford Foot Model

FM1/5 are placed medially and laterally on the foot such that their centers lie along the line through the distal heads of the first and fifth metatarsal heads (Stebbins 2006).
FCC is placed at the same height has midpoint of FM1 and FM5. FCC ends up lower and FCC2 can be placed at “upper ridge of calcaneus”.

Equinus foot