Analysis of the hindfoot and tibia segment-based axes in the Oxford Foot Model - anatomy and accuracy

Thesis

The Oxford Foot Model (OFM) is a multi-segment foot model, which consists of three rigid segments (tibia, hindfoot and forefoot). The segments are defined by surface markers placed on bony landmarks on the foot and leg. The accuracy of the OFM angle calculations depends on how the markers and segment axes relate to the underlying anatomy. Several previous studies have reported particularly large variability in the hindfoot-tibia rotation and this finding has made gait data interpretation and, consequently, treatment recommendation more uncertain. The aim of this research project was to investigate the agreement between marker-based and anatomy-based hindfoot and tibia segment axes in the Oxford Foot Model. Twentyone adult females participated in the study (42 feet). The calcaneus and talus first principal axes, as well as 3D coordinates of markers and of the points corresponding to the ideal marker locations, were extracted from CT images. Gait analysis was used to measure lower-limb joint kinematics during level walking trials. The results showed that there is a significant discrepancy between the OFM hindfoot (A P) axis and the calcaneus first principal axis in the transverse plane. This relationship suggested a clinical implication that the A-P axis definition in relation to the underlying anatomy is likely to be less accurate in a deformed foot like clubfoot. Moreover, the insignificant root mean squared difference between the hindfoot-tibia kinematics, estimated by a rigid-body transformation method and that computed from the standard stereophotogrammetric procedure implied that the hindfoot and tibia rigidity assumption was valid in estimating the motion of the underling anatomy from the marker-based segment axes definition. Furthermore, a discrepancy between the OFM hindfoot and tibia axes and the corrected OFM hindfoot and tibia axes in the transverse plane was evident, and this led to differences in the transverse plane joint angles during walking. Therefore it can be inferred that these two reasons instigate the large variability in transverse plane hindfoot-tibia kinematics, as reported by past literatures. This information has potential to optimise the hindfoot and tibia segment definitions in accurately describing the motion of the underlying anatomy and thus improve interpretation of gait data and subsequently treatment recommendations for patients with foot deformity.

Authors: Paik, AMH

• DOI: 10.5287/ora-qqrqeq5bz
• Type of award: MSc by Research
• Level of award: Masters
• Awarding institution: University of Oxford
• Language: English