Higher Computed Tomography (CT) Scan Resolution Improves Accuracy of Patient-specific Mandibular Models When Compared to Cadaveric Gold Standard.

BACKGROUND: 3D-printed patient-specific anatomical models are becoming an increasingly popular tool for planning reconstructive surgeries to treat oral cancer. Currently there is a lack of information regarding model accuracy, and how the resolution of the computed tomography (CT) scan affects the accuracy of the final model. PURPOSE: The primary objective of this study was to determine the CT z-axis resolution necessary in creating a patient specific mandibular model with clinically acceptable accuracy for global bony reconstruction. This study also sought to evaluate the effect of the digital sculpting and 3D printing process on model accuracy. STUDY DESIGN: This was a cross-sectional study using cadaveric heads obtained from the Ohio State University Body Donation Program. INDEPENDENT VARIABLES: The first independent variable is CT scan slice thickness of either 0.675 , 1.25, 3.00, or 5.00 mm. The second independent variable is the three produced models for analysis (unsculpted, digitally sculpted, 3D printed). MAIN OUTCOME VARIABLE: The degree of accuracy of a model as defined by the root mean square (RMS) value, a measure of a model's discrepancy from its respective cadaveric anatomy. ANALYSES: All models were digitally compared to their cadaveric bony anatomy using a metrology surface scan of the dissected mandible. The RMS value of each comparison evaluates the level of discrepancy. One-way ANOVA tests (P < .05) were used to determine statistically significant differences between CT scan resolutions. Two-way ANOVA tests (P < .05) were used to determine statistically significant differences between groups. RESULTS: CT scans acquired for 8 formalin-fixed cadaver heads were processed and analyzed. The RMS for digitally sculpted models decreased as slice thickness decreased, confirming that higher resolution CT scans resulted in statistically more accurate model production when compared to the cadaveric gold standard. Furthermore, digitally sculpted models were significantly more accurate than unsculpted models (P < .05) at each slice thickness. CONCLUSIONS: Our study demonstrated that CT scans with slice thicknesses of 3.00 mm or smaller created statistically significantly more accurate models than models created from slice thicknesses of 5.00 mm. The digital sculpting process statistically significantly increased the accuracy of models and no loss of accuracy through the 3D printing process was observed.

An In-House Computer-Aided Design and Computer-Aided Manufacturing Workflow for Maxillofacial Free Flap Reconstruction is Associated With a Low Cost and High Accuracy.

PURPOSE: In-house computer-aided surgical design and computer-aided manufacturing (CAD/CAM) can be used in oral and maxillofacial surgery for virtual surgical planning and 3-dimensional printing of patient-specific models. The purpose of this study was to measure the cost and accuracy of an in-house CAD/CAM workflow for maxillofacial free flap reconstruction. MATERIALS AND METHODS: A retrospective cohort study of patients undergoing mandibular resection and free flap reconstruction was performed between July 2017 and March 2018 in which in-house CAD/CAM was used. The predictor variable was the in-house CAD/CAM workflow. The outcome variables were in-house workflow cost, as measured by the material expenses, and accuracy, as measured by comparative distance, osteotomy angle, and surfaced overlay measurements and the root mean square (RMS) between the preoperative virtual reconstructive plan and the postoperative computed tomography scan. Additional variables evaluated were time required for in-house CAD/CAM workflow, and clinical and radiographic outcomes. RESULTS: In-house CAD/CAM was used for 26 patients undergoing mandibular resection for benign or malignant disease and free flap reconstruction with fibula (n = 24) or scapula free flap (n = 2). Overall flap success rate was 95%. The mean in-house workflow cost per case was $3.87 USD. There were no significant differences between the mean comparative distance and osteotomy angle measurements between the planned and actual mandibular reconstructions with an RMS ranging from 5.11 to 9.00 mm for distance measurements and 17.41° for the osteotomy angle measurements. The mean surface overlay difference was 1.90 mm with an RMS of 3.72 mm. CONCLUSIONS: The in-house CAD/CAM workflow is a low cost and accurate option for maxillofacial free flap reconstruction. The in-house workflow should be considered as an alternative to current practices using proprietary systems in select cases.

Dynamic flow for efficient partial decellularization of tracheal grafts: A preliminary rabbit study.

Objective: Bioengineered tracheal grafts are a potential solution for the repair of long-segment tracheal defects. A recent advancement is partially decellularized tracheal grafts (PDTGs) which enable regeneration of host epithelium and retain viable donor chondrocytes for hypothesized benefits to mechanical properties. We propose a novel and tunable 3D-printed bioreactor for creating large animal PDTG that brings this technology closer to the bedside. Methods: Conventional agitated immersion with surfactant and enzymatic activity was used to partially decellularize New Zealand white rabbit (Oryctolagus cuniculus) tracheal segments (n = 3). In parallel, tracheal segments (n = 3) were decellularized in the bioreactor with continuous extraluminal flow of medium and alternating intraluminal flow of surfactant and medium. Unprocessed tracheal segments (n = 3) were also collected as a control. The grafts were assessed using the H&E stain, tissue DNA content, live/dead assay, Masson's trichrome stain, and mechanical testing. Results: Conventional processing required 10 h to achieve decellularization of the epithelium and submucosa with poor chondrocyte viability and mechanical strength. Using the bioreactor reduced processing time by 6 h and resulted in chondrocyte viability and mechanical strength similar to that of native trachea. Conclusion: Large animal PDTG created using our novel 3D printed bioreactor is a promising approach to efficiently produce tracheal grafts. The bioreactor offers flexibility and adjustability favorable to creating PDTG for clinical research and use. Future research includes optimizing flow conditions and transplantation to assess post-implant regeneration and mechanical properties. Level of Evidence: NA.