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Computerized Preoperative Planning and 3D Printing in the Repair of Complicated

Periorbital Fractures Paul D. Langer, MD, FACSProfessor of OphthalmologyDirector, Division of Ophthalmic Plastic, Orbital and Reconstructive SurgeryRutgers New Jersey Medical School

The author has no financial interest in the subject of

this presentation

Unlike orbital wall fractures, which are fairly straightforward to correct, complicated periorbital and facial fractures require

significant manipulation and precise alignment of bone fragments in three dimensions to effect repair

Precision of fracture repair may be limited by any of the following:� Comminution of fractures� Missing bone� Edema� Alignment often cannot be checked in 3 dimensions at once (fractures viewed through different incisions at different times)

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1) Virtual, computer-assisted manipulation of bone fragments allows for precise, preoperative alignment of fragments

2) 3-dimensional models and intraoperative guides are produced with stereolithographythat assist in translating the precise virtual repair to the actual repair

Pre-operative Planning Additive Manufacturing� Now synonymous with “3-D printing”� Any manufacturing process that transforms a 3D model into a physical object� Joins successive layers of the same material under automated control� Contrasts with traditional manufacturing techniques, which are “subtractive”

Traditional “subtractive” manufacturing:

Additive Manufacturing� Term encompasses many different technologies including sintering,

laminated object manufacturing, fused deposition modelling, and stereolithography, among others

� All have an essential manufacturing principle in common: a machine reads a design from a 3D printable file (“STL file”) and lays down successive layers of liquid, powder, paper or sheet material to build the model from a series of cross sections

� These layers (corresponding to the virtual cross sections from the CAD model) are joined or automatically fused to create the final shape.

� The primary advantage of this technique is its ability to create almost any shape or geometric feature

Fused deposition modelling: 1 – nozzle ejecting molten plastic, 2 – deposited material (modeled part), 3 – controlled movable table

Additive ManufacturingAdvantages:No need for molds/dyes—prototypes made

on demand, design changes made without adding costDesign changes enacted quickly and easily—

tooling/machining constraints eliminated

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Stereolithography� A laser beam traces a cross section of the part over the surface of a

photoreactive resin (photopolymer) which lies in a vat� Immediately upon contact with the UV light, the resin is “cured”

(hardended)� After the pattern is traced, the part descends into the vat by the

thickness of a “single layer;” the process is then repeated, with the laser drawing out the next cross section, which hardens and is joined to the layer beneath

� At the end of the process, the entire object isformed and completely submerged in the tank

1) Virtual, computer-assisted manipulation of bone fragments allows for precise, preoperative alignment of fragments

2) 3-dimensional models and intraoperative guides are produced with stereolithographythat assist in translating the precise virtual repair to the actual repair

Pre-operative Planning

Pre-operative Planning� Maxillofacial CT scan of the patient (1.25mm cuts maximum) is sent to 3-D printing company (Materialise), which converts it to STL � 3-D virtual model is created on a computer� In conference call, bone fragments can be moved on the computerized 3-D image in any direction, rotated, removed, etc, to effect final desired result

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1) Virtual, computer-assisted manipulation of bone fragments allows for precise, preoperative alignment of fragments

2) 3-dimensional models and intraoperative guides are produced with stereolithographythat assist in translating the precise virtual repair to the actual repair

Pre-operative Planning

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Pre-operative PlanningAdvantages� Allows for presurgical preparedness� Promotes precise surgical alignment and reduces

guesswork� Promotes flexibility in surgical options� Reduces surgical time

Disadvantages� Cost (several thousand dollars)� Time (need 5 working days for all models and planning)

Pre-operative PlanningFuture Directions� Computerized 3-dimensional reconstruction

programs are not proprietary—each hospital will have one� 3D printers are cheaper each year� Once pre-operative computerized planning

becomes commonplace, hospitals will likely purchase own computer programs, have biomedical engineers in-house, and print own models