Three-Dimensional Reconstruction of Orbital Fractures

Our research focuses on developing a standard protocol for reconstructing different orbital defects, using 3D technology, addressing possible pitfalls and identifying ways to avoid them. The orbit is a complex, anatomical region containing many nerves, muscle and blood vessels, making it difficult to access and repair, surgically. Proper treatment requires accurate radial construction of the orbital volume and its unique anatomical structures.

We have classified orbital defects into three categories, each requiring a different virtual reconstruction method as initial step in designing a patient specific implant. In addition, we emphasize the unique anatomical structures to be reconstructed, thus avoiding major pitfalls. This protocol tailors an individual approach for every kind of orbital defect and provides a step-by-step explanation of the reconstruction and the PSI design process.

We believe this protocol will significantly reduce complication by avoiding common pitfalls usually associated with precision errors. Our three dimensional laboratory will focus on automated digital reconstruction of orbital defects, and an automated PSI design, using AI technology. To begin, load the facial bone CT image, DICOM files of the patient into the software.

Select the corneal view and click add. On the next screen, click 3D to open the bone segmentation interface. In the bone segmentation interface, observe the 3D volume on the left screen and the coronal CT view on the right.

Click on the bone segmentation icon in the lower toolbar and choose thin bones. Click on separate areas of the orbit and periorbital area until the full orbit is completely defined by the chosen color. Confirm the accuracy of the new mask after scrolling through different DICOM planes.

After approving the segmentation, create a mesh and fully observe the 3D model for smoothness and absence of voids. Click file and save the 3D model as an STL file. To reconstruct the orbital wall, click file followed by import model, and select the STL file exported in the segmentation sequence.

On the lower toolbar, click add details, followed by add find detail, and then click apply. For automatic reconstruction, ensure full clay continuity around the perimeter of the defect. If gaps exist in the fractured floor area, use the add clay feature to manually connect these areas and achieve full continuity.

Use the smooth feature to refine the added clay. Right click on the activated new mask and select clay utilities, followed by copy to mesh. On the mesh object, select the margins of the floor defects, using the lasso select tool under select mesh area.

Use mesh tools for automatic gap filling. Press the delete key to remove the selected area, and click fill holes in mesh repeatedly until the button becomes inactive, completing the automatic reconstruction of the floor defect. For anatomic repositioning, under select or move clay, choose the reposition tool and deselect the move only option.

Click to center to move the triad to the center of rotation, located at the anatomical edge. Select reposition piece and choose rotate only. Holding the shift key, rotate the piece through the triad center to achieve the correct anatomical position.

For mirroring, use the mirror clay tool to position the plane oriented to the medial side. Check mirror, entire piece, and preview. Then click apply.

Superimpose the mirrored and fractured orbits. Use the register pieces tool to select the mirrored orbit as the source, and the fractured orbit as the target. Place markers on unique anatomic locations in the mirrored orbit and similar locations in the fractured orbit.

Click apply to superpose the segments, then click auto for optimal super imposition. Under select or move clay, select reposition origin, followed by to center. Move the triad to the center of the mirrored orbit floor.

Choose rotate only and align the Z axis vertically, X axis horizontally, and Y axis anteroposteriorly. Under select or move clay, select reposition piece. Open show or hide advanced settings and change the translate step to 0.8 millimeters.

Use the translate Z arrowheads relative to local axes to sink the mirrored orbit into the fractured orbit until the intact borders start to appear. Under select or move clay, select select clay and use the lasso select tool to outline the anatomical perimeter of the floor. Choose invert selection and delete the remaining areas.

To create the mesh outline, smooth the borders for a refined appearance. Select both the orbit and floor objects. Right click and choose Boolean or combine as new to merge them into a single object.

After duplicating the final object, right click and select see through, then click turn on. Under curves, select draw curve and outline a form just around the original fractured area. After fully outlining, click fit to clay under the create icon.

Similarly, create the anchoring arms of the implant. To finalize the implant under detail clay, select emboss with curve and set a distance of 0.8 millimeters. Select the inside of the outlined area and click raise.

Use add clay and smooth to connect the anchoring arms to the main body of the implant. Next, use Boolean and remove from functions on the duplicated object. Right click on clay coarseness in the object list and set it to 0.1 millimeters.

Under sculpt clay, select the carve tool and set the tool size to 2.1 millimeters. Create fixation holes on the most distant parts of the anchoring arms. Adjust the tool size to 1.5 and one millimeter to create drainage holes on the rest of the implant.

Finally, choose Boolean and remove from to subtract the original fractured orbit from the final patient specific implant. A large displacement of the orbital floor fracture was observed in both anteroposterior and lateral lateral aspects. Postoperative CT images confirmed the correct, implant placement, using lateral and medial ledges for support, while avoiding the posterior ledge to prevent movement restrictions.