Präoperative Genauigkeit von kraniofazialen, in selektiver Lasersinterung-Technik gefertigten 3-D-Modellen, im Vergleich zum primären CT-Datensatz

The accuracy of computer-assisted primary mandibular reconstruction with vascularized bone flaps: iliac crest bone flap versus osteomyocutaneous fibula flap

Background

The intention of mandibular reconstruction is to restore the complex anatomy with maximum possible functionality and high accuracy. The aim of this study was to evaluate the accuracy of computer-assisted surgery in primary mandibular reconstruction with an iliac crest bone flap compared with an osteomyocutaneous fibula flap.

Materials and methods

Preoperative computed tomography data of the mandible and the iliac crest or fibula donor site were imported into a specific surgical planning software program. Surgical guides were manufactured using a rapid prototyping technique for translating the virtual plan, including information on the transplant dimensions and shape, into real-time surgery. Using postoperative computed tomography scans and an automatic surface-comparison algorithm, the actual postoperative situation was compared with the preoperative virtual simulation.

Results

The actual flap position showed a mean difference from the virtual plan of 2.43 mm (standard deviation [SD] ±1.26) and a surface deviation of 39% <2 mm and 15% <1 mm for the iliac crest bone flap, and a mean difference of 2.18 mm (SD ±1.93) and a surface deviation of 60% <2 mm and 37% <1 mm for the osteomyocutaneous fibula flap. The position of the neomandible reconstructed with an osteomyocutaneous fibula flap indicated a mean difference from the virtual plan of 1.25 mm (SD ±1.31) and a surface deviation of 82% <2 mm and 57% <1 mm, in contrast to a mean difference of 1.68 mm (SD ±1.25) and a surface deviation of 63% <2 mm and 38% <1 mm for the neomandible after reconstruction with an iliac crest bone flap. For shape analysis, a similarly high accuracy could be calculated for both flaps.

Conclusion

Virtual surgical planning is an effective method for mandibular reconstruction with vascularized bone flaps, and can help to restore the anatomy of the mandible with high accuracy in position and shape. It seems that primary mandibular reconstruction with the osteomyocutaneous fibula flap is more accurate compared with the vascularized iliac crest bone flap.

Evaluation of computer-assisted mandibular reconstruction with vascularized iliac crest bone graft compared to conventional surgery: a randomized prospective clinical trial

BACKGROUND

Computer-assisted surgery plays an increasingly important role in mandibular reconstruction, ensuring the best possible masticatory function and aesthetic outcome.

METHODS

Twenty patients were randomly assigned to computer-assisted or conventional mandibular reconstruction with vascularized iliac crest bone graft in a prospective study design.Virtual surgical planning was based on preoperative CT-data using specific surgical planning software. A rapid prototyping guide transferred the virtual surgery plan to the operation site. During surgery the transplant ischemic time, reconstruction time, time for shaping the transplant and amount of bone removed were measured. Additionally, the difference in the intercondylar distance before and after surgery was calculated.

RESULTS

Computer-assisted surgery shortened the time of transplant ischemia (P < 0.005) and defect reconstruction (P < 0.001) compared to conventional surgery. The time to saw and shape the transplant at the donor site was shorter using conventional surgery (P < 0.005); therefore, the overall time for surgery didn't change (P = 0.527). In the computer-assisted group, the amount of bone harvested equaled the defect size, whereas the transplant size in the conventional group exceeded the defect site by 16.8 ± 5.6 mm (P < 0.001) on average. The intercondylar distance before compared to after surgery was less affected in the computer-assisted than in the conventional group (P < 0.001).

CONCLUSIONS

The presented study shows that computer-assisted surgery can help reduce the time for mandibular defect reconstruction and consequently the transplant ischemic time. In the computer-assisted group, the iliac crest donor site defect was downsized and the postoperative condyle position was less altered, reducing possible risks of postoperative complications and donor site morbidity.

TRIAL REGISTRATION

DRKS00005181.

Craniomaxillofacial surgery planning based on 3D models derived from Cone-Beam CT data

INTRODUCTION

Individual planning of complex maxillofacial corrections may require 3D models which can be manufactured based on DICOM datasets. The gold standard for image acquisition is still high-resolution multi-slice computed tomography (MSCT). However, appropriate datasets for model fabrication can be acquired by modern Cone-Beam CT (CBCT) devices that have been developed specifically for maxillofacial imaging. The clinical utility of individual models fabricated on the basis of CBCT datasets was assessed.

METHODS

In five patients affected by different deficiencies of the maxillofacial skeleton, preoperative imaging was performed with ILUMA CBCT. Segmentation of hard tissues was performed manually by thresholding. Corresponding STL datasets were created and exported to an industrial service provider (Alphaform, Munich, Germany) specializing in rapid prototyping, and 3D models were fabricated by the selective laser sintering (SLS) technique. For variance analysis, landmark measurements were performed on both virtual and 3D models. Subsequently, maxillofacial surgery was performed according to the model-based planning.

RESULTS

All CBCT-based DICOM datasets could be used for individual model fabrication. Detailed reproduction of individual anatomy was achieved and a topographic survey showed no relevant aberrance between the virtual and real models. The CBCT-based 3D models were therefore used for planning and transfer of different maxillofacial procedures.

CONCLUSIONS

CBCT-based datasets can be used for the fabrication of surgical 3D models if the correct threshold is set. Preoperative workflow and patient comfort is improved in terms of the fast-track concept by using this "in-house" imaging technique.

Custom-made, selective laser sintering (SLS) blade implants as a non-conventional solution for the prosthetic rehabilitation of extremely atrophied posterior mandible

The treatment of severely atrophied posterior mandibles with standard-diameter root-form implants may present a challenge. Bone reconstructive surgery represents the treatment of choice; however, it may not be accepted by some patients for economic reasons or due to higher morbidity. Computer-aided design/computer-aided manufacturing (CAD/CAM) technologies have recently opened new frontiers in biomedical applications. Selective laser sintering (SLS) is a CAD/CAM technique that allows the fabrication of complex three-dimensional (3D) structures created by computer-generated image-based design techniques. The aim of this study is to present a protocol for the manufacture and clinical use of custom-made SLS titanium blade implants as a non-conventional therapeutic treatment for the prosthetic rehabilitation of extremely atrophied posterior mandibles. Computed tomography datasets of five patients were transferred to a specific reconstruction software, where a 3D projection of the atrophied mandible was obtained, and custom-made endosseous blade implants were designed. The custom-made implants were fabricated with SLS technique, placed in the extremely atrophied posterior (<4 mm width) mandible, and immediately restored with fixed partial restorations. After 2 years of loading, all implants were in function, showing a good esthetic integration. Blade implants can be fabricated on an individual basis as a custom-designed device. This non-conventional approach may represent an option for restoring the atrophied posterior mandible of elderly patients.

Computer-assisted mandibular reconstruction with vascularized iliac crest bone graft

BACKGROUND

The intention of mandibular reconstructive surgery is to achieve maximum possible functionality, which means the restoration of masticatory function and speech with a good esthetic result.

METHODS

We compared five computer-assisted mandibular reconstructions with 15 conventional mandibular reconstructions performed using vascularized iliac crest bone grafts. Based on preoperative cone beam computed tomography (CBCT) or CT data imported into the specific surgical planning software, a surgical guide was designed by rapid prototyping that helped to exactly translate the virtual surgery plan into the operation site whereby it fit uniquely to the iliac donor site. The ischemic time of the graft was measured intraoperatively and the difference between the amount of bone removed and the amount of bone required was determined. In addition, 3 months after surgery patients had to score the esthetics of their outer appearance using a visual analog scale.

RESULTS

In all patients the graft fit perfectly into the mandibular defect without major adjustments. The time for the shaping process of the transplant and the ischemic time were shorter than in the conventional grafting procedure. The virtual plan reduced the amount of bone removed to the required volume. The patients who underwent computer-assisted reconstruction had a higher degree of satisfaction with their outer appearance.

CONCLUSION

Our clinical experience and the collected data suggest that the described method is very promising for optimizing the surgical result of mandibular reconstructions using iliac crest bone grafts and achieving an excellent esthetic outcome.

LEVEL OF EVIDENCE IV

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Laser direct writing of micro- and nano-scale medical devices

Laser-based direct writing of materials has undergone significant development in recent years. The ability to modify a variety of materials at small length scales and using short production times provides laser direct writing with unique capabilities for fabrication of medical devices. In many laser-based rapid prototyping methods, microscale and submicroscale structuring of materials is controlled by computer-generated models. Various laser-based direct write methods, including selective laser sintering/melting, laser machining, matrix-assisted pulsed-laser evaporation direct write, stereolithography and two-photon polymerization, are described. Their use in fabrication of microstructured and nanostructured medical devices is discussed. Laser direct writing may be used for processing a wide variety of advanced medical devices, including patient-specific prostheses, drug delivery devices, biosensors, stents and tissue-engineering scaffolds.