Thickness accuracy of virtually designed patient‐specific implants for large neurocranial defects

Abstract

The combination of computer‐aided design (CAD) techniques based on computed tomography (CT) data to generate patient‐specific implants is in use for decades. However, persisting disadvantages are complicated design procedures and rigid reconstruction protocols, for example, for tailored implants mimicking the patient‐specific thickness distribution of missing cranial bone. In this study we used two different approaches, CAD‐ versus thin‐plate spline (TPS)‐based implants, to reconstruct extensive unilateral and bilateral cranial defects in three clinical cases. We used CT data of three complete human crania that were virtually damaged according to the missing regions in the clinical cases. In total, we carried out 132 virtual reconstructions and quantified accuracy from the original to the generated implant and deviations in the resulting implant thickness as root‐mean‐square error (RMSE). Reconstructions using TPS showed an RMSE of 0.08–0.18 mm in relation to geometric accuracy. CAD‐based implants showed an RMSE of 0.50–1.25 mm. RMSE in relation to implant thickness was between 0.63 and 0.70 mm (TPS) while values for CAD‐based implants were significantly higher (0.63–1.67 mm). While both approaches provide implants showing a high accuracy, the TPS‐based approach additionally provides implants that accurately reproduce the patient‐specific thickness distribution of the affected cranial region.

Customized Cost-Effective Cranioplasty for Large Asymmetrical Defects

“…Furthermore, as demonstrated by the outer-direction deviation, the fabrication accuracy (d1) is predicted to be 0.5613 mm. The suggested implant design (encompassing both d0 and d1) has an overall precision of 0.6345 mm, which is more precise and results in a superior fit compared to the cranial implant obtained through the mirroring technique, which had an overall variation of 0.9294-1.31 mm [40][41][42]. The implant's overall deviation is less than 1 mm of the targeted skull reconstruction area, thus confirming its proper fitting and positioning over the orbital skull region.…”