Use of three‐dimensional printed ‘haptic’ models for preoperative planning in an Australian plastic surgery unit

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A 68‐year‐old woman presented with a local recurrence of squamous cell carcinoma (SCC) invading into the angle of the right mandible. The patient reported a fixed, soft tissue mass growing over 6 months and her past history was significant for a previous SCC of the right upper lip, surgically excised 4 years prior (Fig. 1). There was no clinically detectable cervical or supraclavicular lymphadenopathy. Computed tomography (CT) and positron emission tomography scan revealed a 54 × 42 × 55 mm mass eroding into the angle of the right mandible and a second focus of fluorodeoxyglucose (FDG) uptake in the right mandibular ramus, but no neck or distant metastases. Fine‐needle aspirate of the mass showed atypical squamous cells consistent with metastatic SCC.
In addition to the standard imaging modalities, preoperative planning was aided by the use of a three‐dimensional (3D) printed model of the right hemi‐mandible, with and without the associated soft tissue tumour, constructed using an in‐house, low‐cost 3D printer (Fig. 2) (MakerBot Replicator Z18, New York, NY, USA). The patient underwent a right‐sided modified radical neck dissection (levels 1–5), right mandibular resection (from distal‐to‐coronoid process to mid‐symphysis) and reconstruction with a composite fibula free flap (Fig. 3).
Three‐dimensional printing describes a process in which a solid model is fabricated from 3D computer data. Fused deposition modelling (FDM), a 3D printing technique, is currently the most cost‐effective, accessible and commonly used method and involves an additive process whereby melted thermoplastic filament is deposited onto a build plate in layers.1 Using a 3D modelling program (Cubify, 3D Systems, Rock Hill, SC, USA), the process begins with the conversion of two‐dimensional CT data into a 3D virtual image, known as a computer‐assisted design (CAD) file. The CAD file is then interpreted by the 3D printer to produce a 3D model. Although 3D printing has been utilized in industrial design for decades, it has only become adapted for medical applications within the last decade. Its increasing relevance in plastic surgery has become apparent, including in surgical planning and education, production of customized prostheses and volumetric analyses for breast reconstruction.3
We describe a case in which a 3D‐printed model was used to aid in the preoperative planning of both tumour resection and subsequent free flap reconstruction. We have recently utilized an in‐house 3D printer to produce accurate models of bony and soft tissue pathologies derived from routine CT scans. Our current models of the mandible cost approximately AUD$25 each in thermoplastic filaments. The accuracy of FDM 3D printers is continually improving, with our current printer having an accuracy of 0.0025 mm and a resolution of 0.1 mm. Hence, they are suitable for creating small complex anatomical models.1 Furthermore, the production time is fast, with the current model of a hemi‐mandible taking approximately 3 h to construct. Of note, this technology is potentially available to any hospital with access to a CT scanner.
Three‐dimensional printing a bony model is relatively simple and well established. In contrast, 3D printing of soft tissue poses a greater challenge, which we have overcome using the latest improved software and image processing techniques. To the best of our knowledge, we are one of the first centres globally to successfully use an in‐house, consumer‐level 3D printer to produce models of soft tissue tumours, with a level of accuracy that is clinically useful. Having two models to compare (i.e. one with bone only and another with bone and tumour attached) facilitated in planning the extent of surgical resection as well as the method of reconstruction required.
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