The Glasgow-Maastricht foot model, evaluation of a 26 segment kinematic model of the foot

Abstract

Background: Accurately measuring of intrinsic foot kinematics using skin mounted markers is difficult, limited in part by the physical dimensions of the foot. Existing kinematic foot models solve this problem by combining multiple bones into idealized rigid segments. This study presents a novel foot model that allows the motion of the 26 bones to be individually estimated via a combination of partial joint constraints and coupling the motion of separate joints using kinematic rhythms.

Methods: Segmented CT data from one healthy subject was used to create a template Glasgow-Maastricht foot model (GM-model). Following this, the template was scaled to produce subject-specific models for five additional healthy participants using a surface scan of the foot and ankle. Forty-three skin mounted markers, mainly positioned around the foot and ankle, were used to capture the stance phase of the right foot of the six healthy participants during walking. The GM-model was then applied to calculate the intrinsic foot kinematics.

Results: Distinct motion patterns where found for all joints. The variability in outcome depended on the location of the joint, with reasonable results for sagittal plane motions and poor results for transverse plane motions.

Conclusions: The results of the GM-model were comparable with existing literature, including bone pin studies, with respect to the range of motion, motion pattern and timing of the motion in the studied joints. This novel model is the most complete kinematic model to date. Further evaluation of the model is warranted.

Keywords: Gait analysis; Kinematic foot model; Multi-segment foot model.

Fig. 1

Points on which the scaling algorithm is based. 1) Posterior Calcaneus, distal of achillis tendon 2) Central plantar heel 3) Heel medial 4) Heel lateral 5) Achilles tendon between malleoli 6) Malleolus medial 7) Malleolus lateral 8) Navicular tuberosity 9) Navicular dorsal 10) Fifth metatarsal basis 11) First metatarsal head, medial 12) TMT2 dorsal 13) MTP3 plantar 14) Hallux tip 15) Second toe tip 16) Fifth toe tip

Fig. 2

RoM for all joints. The bold black line is population average, grey band was the population standard deviation (which were only calculated when data for all participants was present on that particular time step). Coloured lines are averaged joint patterns per individual, where joints are grouped by: a) rearfoot to midfoot b) navicular to cuneiforms c) TMT d) MTP e) inter-phalangeal joints