Taylor Spatial Frame : kinematics, mechanical properties and automation

The Taylor Spatial Frame (TSF) is a recently introduced form of a circular external orthopaedic fixator for long bone fracture reduction and deformity correction. The TSF is constructed from two circular rings interconnected with six variable-length struts. Its kinematics are based on the Stewart-Gough platform. The TSF is attached to the patient's anatomy using fine wires and half-pins. In this thesis, three aspects of the TSF are analysed. First, the solution to non-trivial forward and inverse kinematics has been addressed. Second, the mechanical properties of the TSF fixator are investigated. Individual component stiffness is assessed separately and then the complete fixator is modelled. Simple stiffuess models of fine wires and half-pins are derived. Considerations for the use of the TSF for the peri-articular fractures are investigated and potential modifications are proposed. The effect of backlash in the frame components on the accuracy of the fixator has been analysed. Finally, in rder to validate the kinematics solution, to provide a training aid for surgeons and to demonstrate the concept of accurately controlled interfragmentary motion, a prototype of an active TSF was designed and built. Computationally efficient algorithms for solving the forward and inverse kinematics have been developed that require little numerical processing overhead and can be implemented on a mobile computing device. It was found that the TSF fixator has similar axial stiffuess to the circular Ilizarov ring fixator, since wires and half-pins are significantly less stiff than the frames. Furthermore, the TSF exhibits more uniform stiffuess for a range of off-axis loads and is significantly stiffer for torsional loads than the Ilizarov fixator. Slack, in the form of a backlash, can lead to severe strains in the unloaded frames and therefore fractures, and hence precautions are recommended. Finally, considerations and prototype for the automated TSF are presented that can be utilised for demonstration purposes and surgeon training.