Generation of subject-specific, dynamic, multisegment ankle and foot models to improve orthotic design: a feasibility study.

BACKGROUND: Currently, custom foot and ankle orthosis prescription and design tend to be based on traditional techniques, which can result in devices which vary greatly between clinicians and repeat prescription. The use of computational models of the foot may give further insight in the biomechanical effects of these devices and allow a more standardised approach to be taken to their design, however due to the complexity of the foot the models must be highly detailed and dynamic. METHODS/DESIGN: Functional and anatomical datasets will be collected in a multicentre study from 10 healthy participants and 15 patients requiring orthotic devices. The patient group will include individuals with metarsalgia, flexible flat foot and drop foot.Each participant will undergo a clinical foot function assessment, 3D surface scans of the foot under different loading conditions, and detailed gait analysis including kinematic, kinetic, muscle activity and plantar pressure measurements in both barefoot and shod conditions. Following this each participant will undergo computed tomography (CT) imaging of their foot and ankle under a range of loads and positions while plantar pressures are recorded. A further subgroup of participants will undergo magnetic resonance imaging (MRI) of the foot and ankle.Imaging data will be segmented to derive the geometry of the bones and the orientation of the joint axes. Insertion points of muscles and ligaments will be determined from the MRI and CT-scans and soft tissue material properties computed from the loaded CT data in combination with the plantar pressure measurements. Gait analysis data will be used to drive the models and in combination with the 3D surface scans for scaling purposes. Predicted plantar pressures and muscle activation patterns predicted from the models will be compared to determine the validity of the models. DISCUSSION: This protocol will lead to the generation of unique datasets which will be used to develop linked inverse dynamic and forward dynamic biomechanical foot models. These models may be beneficial in predicting the effect of and thus improving the efficacy of orthotic devices for the foot and ankle.

Diagnosis and targeted percutaneous management of a critical subclavian artery stenosis in a patient with absent peripheral pulses with the use of cardiac computed tomography.

Current clinical practice dictates that invasive management strategies frequently are adopted in patients with both ST-segment elevation and non-ST-segment elevation acute coronary syndromes. Such strategies rely on obtaining vascular access and, as such, are not always technically feasible. We report a case in which cardiac computed tomography was used to great effect in the diagnostic and (targeted) interventional management of a patient who was the recipient of a previous coronary artery bypass grafting and presented with global myocardial ischemia, in whom the lack of peripheral pulses had previously rendered an early invasive strategy hazardous.