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Fractures of the orbital floor are common in traffic accidents and assaults, and inadequate treatment can result in serious complications. Accurate anatomical reconstruction of the orbit using implants is the preferred treatment. Implants require degradability, adequate mechanical properties to support the orbital contents, and osteoinductivity or osteoconductivity so that the implant is replaced by de novo bone over time. Here, we report on a semi-automatic process for the generation of virtual models of patient-specific implants for orbital floor reconstruction. These models were generated using clinical computed tomography images of five clinical cases of orbital fracture. To fabricate accurately shaped implants based on the models, we utilized stereolithography, a high-resolution additive manufacturing technique. We prepared resins from bioresorbable, photo-curable functionalized poly(trimethylene carbonate) oligomers and osteoinductive nano-hydroxyapatite to manufacture composite implants. Incorporation of 40 wt.% nano-hydroxyapatite into photo-crosslinked poly(trimethylene carbonate) leads to an increase of the E modulus, ultimate strength and toughness from 2.8 to 60 MPa, 2.4 to 7.1 N/mm2 and 330 to 1671 N/mm2, respectively. Additionally, water uptake increased from 0.8% to 7.3%, and water contact angle decreased from 80°to 68°. Patient-specific, homogeneous, and mechanically stable implants can readily be prepared using these composite resins.

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Distal radius fractures are common and fracture patterns and fixation can be complex. Computerized anatomy evaluation (CAE) might offer non-invasive and enhanced anatomy assessment that might help with implant selection and placement and screw length determination. Our goal was to test the accuracy of two CAE methods for anatomical volar plate positioning and screw lengths measurement of the distal radius. We included 56 high-resolution peripheral quantitative computed tomography scans of intact, human distal radii. Plates were placed manually onto 3D printed models (method 1), which was compared with automated computerized plate placement onto the 3D computer models (method 2). Subsequently, screw lengths were determined digitally for both methods. Screw lengths evaluations were compared via Bland-Altman plots. Both CAE methods resulted in identical volar plate selection and in anatomical plate positioning. For screw length the concordance correlation coefficient was ≥0.91, the location shift ≤0.22 mm, and the scale shift ≤0.16. The differences were smaller than AE1 mm in all samples. Both CAE methods allow for comparable plate positioning and subsequent screw length measurement in distal radius volar plating. Both can be used as a non-invasive teaching environment for volar plate fixation. Method 2 even offers fully computerized assessments. Future studies could compare our models to other anatomical areas, post-operative volar plate positioning, and model performance in actual distal radius fracture instead of intact radii. Clin. Anat. 32:361-368, 2019.