Craniomaxillofacial deformities/cosmetic surgery
Splint Sterilization—A Potential Registration Hazard in Computer-Assisted Surgery

https://doi.org/10.1016/j.joms.2011.04.013Get rights and content

Purpose

Registration of preoperative targeting information for the intraoperative situation is a crucial step in computer-assisted surgical interventions. Point-to-point registration using acrylic splints is among the most frequently used procedures. There are, however, no generally accepted recommendations for sterilization of the splint. An appropriate method for the thermolabile splint would be hydrogen peroxide–based plasma sterilization. This study evaluated the potential deformation of the splint undergoing such sterilization. Deformation was quantified using image-processing methods applied to computed tomographic (CT) volumes before and after sterilization.

Materials and Methods

An acrylic navigation splint was used as the study object. Eight metallic markers placed in the splint were used for registration. Six steel spheres in the mouthpiece were used as targets. Two CT volumes of the splint were acquired before and after 5 sterilization cycles using a hydrogen peroxide sterilizer. Point-to-point registration was applied, and fiducial and target registration errors were computed. Surfaces were extracted from CT scans and Hausdorff distances were derived. Effectiveness of sterilization was determined using Geobacillus stearothermophilus.

Results

Fiducial-based registration of CT scans before and after sterilization resulted in a mean fiducial registration error of 0.74 mm; the target registration error in the mouthpiece was 0.15 mm. The Hausdorff distance, describing the maximal deformation of the splint, was 2.51 mm. Ninety percent of point-surface distances were shorter than 0.61 mm, and 95% were shorter than 0.73 mm. No bacterial growth was found after the sterilization process.

Conclusion

Hydrogen peroxide–based low-temperature plasma sterilization does not deform the splint, which is the base for correct computer-navigated surgery.

Section snippets

Materials and Methods

To investigate deformation caused by hydrogen peroxide–based plasma sterilization, a CT scan of the splint was acquired before and after 5 low-temperature sterilization cycles. Quantitative evaluation was based on point-to-point registration and subsequent surface distance measurement of registered scans before and after sterilization.

Results

Calculating the point-based registration of fiducial markers on CT scans before and after sterilization resulted in a mean fiducial distance (fiducial registration error) of 0.74 mm; maximal fiducial distance was 0.81 mm. The mean distance of the 6 target points, the TRE, in the mouthpiece was 0.15 mm; maximal distance was 0.26 mm.

Surfaces generated as described earlier resulted in 422,580 triangles before sterilization and 378,638 triangles after sterilization. The 2 directed Hausdorff

Discussion

Medical devices that have contact with sterile body tissues or fluids are considered critical items. These items, such as a splint used in a sterile operation field, must be sterile when used because any microbial contamination can result in infection. If these items are resistant to heat, the recommended sterilization process is steam sterilization because it has the largest margin of safety. However, reprocessing heat- and moisture-sensitive items such as splints requires a low-temperature

Acknowledgment

This publication was supported by the Austrian Research Promotion Agency FFG (grant 818041B1), proposed and managed by Dr Schicho. Dr Weber and Dr Figl were partly supported by FWF project P19931. A preliminary version of this study was part of a poster presentation by Christoph Weber et al at the SPIE Medical Imaging Conference, San Diego, 2009.

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