An Orbital Floor Implant Angulation Guide with 3D-Printed Customization

Introduction: Achieving optimal implant angulation can be challenging in orbital fracture repair, and the posterior edge may wind up low without support from a well-defined bony ledge, resulting in under-correction of enophthalmos. There may be intrinsic difficulties in judging angulation, particularly as perception is influenced by operative head tilt, as well as technical challenges in further elevating the posterior aspect of a cantilevered implant once the anterior aspect has been anchored to the rim. We present a simple patient-customizable intraoperative guide that addresses both potential concerns.

Method: One arm of a Castroviejo caliper was machined to produce a contoured implant elevator, while the other was replaced with a stabilizing orbital rim footplate, custom 3D printed with P430XL ABSplus material (Stratasys, Eden Prairie, MN) via a uPrint SE 3D printer (Stratasys) to match the external rim contour in a parasagittal section (Fig. 1A). Once screwed to the anterior rim, the anterior–posterior contour of the implant can then be adjusted to the optimal angle determined by preoperative scan analysis by placing the elevator under the implant (Fig. 1B), the footplate on the exposed anterior rim, and turning the thumbscrew until the desired position is achieved.

Results: In a cadaveric model, an orbital fracture without a stable posterior bony ledge was created via a swinging eyelid approach. Periosteum overlying the anterior rim was then raised with a Freer elevator, exposing the desired resting position for the custom footplate. A contoured titanium floor implant (3D Titan, Stryker, Kalamazoo, MI) was then secured to the rim using 4-mm self-drilling titanium screws, with the posterior aspect depressed within the maxillary sinus. The implant angulation guide was then positioned as described (Fig. 2) and the thumbscrew manipulated to elevate the posterior implant, which remained appropriately positioned after the guide was removed.

Conclusion: While intraoperative navigation can assist with implant placement for complex fractures, such setups entail obtaining specially formatted CT scans and may be inconvenient for routine use. Likewise 3D-printed custom implants are produced from expensive materials with demonstrated long term biocompatibility and, when not well positioned, lose their volumetric advantage over conventional implants. We foresee that this simple intraoperative guide with inexpensive customization based on routine scans (Fig. 3) can help ensure appropriate implant position, thereby improving volumetric correction without the use of navigation or custom implants.

Fig. 1 Orbital implant angulation guide (A), showing the contoured implant elevator (red arrow) and 3D printed footplate (blue arrow). Elevator with implant (B).

Fig. 2 Implant angulation guide in situ with printed footplate resting on external bony rim.

Fig. 3 CT scan demonstrating fractured (A) and unaffected contralateral orbit (B). 3D printed footplate is customized to the contour of the patient's anterior orbital rim (red). The angle formed by the intact orbital floor and anterior rim (dashed yellow) determines optimal retractor angle setting.

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