Custom implant design for large cranial defects

• Published in: International journal for computer assisted radiology and surgery Vol. 11; no. 12; pp. 2217 - 2230
• Main Authors: Marreiros, Filipe M. M., Heuzé, Y., Verius, M., Unterhofer, C., Freysinger, W., Recheis, W.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-12-2016; Springer Nature B.V; Springer Verlag
• Subjects: Adult; Aged; Aged, 80 and over; Archaeology and Prehistory; Basis functions; Bone Plates; CAD; Computer aided design; Computer Imaging; Computer Science; Cranial reconstruction; Defects; Design defects; Donor materials; Female; Geometric morphometrics; Health Informatics; Humanities and Social Sciences; Humans; Imaging; Imaging, Three-Dimensional - methods; Implants; Male; Medicine; Medicine & Public Health; Middle Aged; Missing data; Original Article; Pattern Recognition and Graphics; Prostheses and Implants; Prosthesis Design; Radial basis function; Radial basis functions; Radiology; Reconstructive surgery; Reconstructive Surgical Procedures - methods; Skull - diagnostic imaging; Skull - surgery; Splines; Surgery; thin-plate spline; Transplants & implants; Vision; Young Adult; Cranial reconstruction; Radial basis functions and thin-plate spline; Geometric morphometrics; Reconstructive surgery; préhistoire
• ISSN: 1861-6410; 1861-6429; 1861-6429
• DOI: 10.1007/s11548-016-1454-8

Purpose
The aim of this work was to introduce a computer-aided design (CAD) tool that enables the design of large skull defect (>100 
cm
2
) implants. Functional and aesthetically correct custom implants are extremely important for patients with large cranial defects. For these cases, preoperative fabrication of implants is recommended to avoid problems of donor site morbidity, sufficiency of donor material and quality. Finally, crafting the correct shape is a non-trivial task increasingly complicated by defect size.
Methods
We present a CAD tool to design such implants for the neurocranium. A combination of geometric morphometrics and radial basis functions, namely thin-plate splines, allows semiautomatic implant generation. The method uses symmetry and the best fitting shape to estimate missing data directly within the radiologic volume data. In addition, this approach delivers correct implant fitting via a boundary fitting approach.
Results
This method generates a smooth implant surface, free of sharp edges that follows the main contours of the boundary, enabling accurate implant placement in the defect site intraoperatively. The present approach is evaluated and compared to existing methods. A mean error of 89.29 % (72.64–100 %) missing landmarks with an error less or equal to 1 mm was obtained.
Conclusion
In conclusion, the results show that our CAD tool can generate patient-specific implants with high accuracy.