Workflow
Hospital supplied CT scan data (DICOM format) was converted to STL mesh using the open source software Invesalius v3.0b1 - www.cti.gov.br/invesalius/

In terms of manifoldness, the STL mesh generated by Invesalius was of quite poor quality - as you can see in the reference mesh object. I suspect this is due to the algorithm by which DICOM data is converted to mesh data, as it relies on converting relative image intensity, i.e. relative bone density, to 'manifoldness of mesh'. So, instead of repairing the generated mesh, I used it as reference mesh in (free) MeshMixer. In particular, the pull (to reference geometry) tool was the most efficient way to deform a spherical primitive STL to the reference STL.

Note: Three other DICOM -> STL conversion tools, (ImageJ, Slicer and InVesalius v3.0b3) all crashed while trying to generate the mesh. Usable output was only achieved with InVesalius 3.0b1.

Printing
First Printed 2012-11-17. Sliced with Slic3r 0.9.5, using 0.2mm layer height, single wall and 15% infill. At 40 mm/s (slow speed) print time is 3 hours.

Total project time
- A week of finding, experimenting and learning new tools,
- 4 to 6 hours 'actual' productivity, after discovering the pull tool in MeshMixer.

Acknowledgments
- Many thanks to Prof. Seth Horowitz for his article 3D Printing For CT Scan Analysis, Space Education - www.makezine.com/2012/05/01/3d-printing-improves-ct-scan-analysis-space-education/
- A big Thank You to my surgeon and nursing staff at LKH Innsbruck, Austria for the very fine repair job; I am eternally grateful that I can still walk and cycle.