Accuracy of the Surface Contour of Three-Dimensional-Printed Canine Pelvic Replicas.

OBJECTIVE: The aim of this study was to determine the differences in surface contour between models of native pelvic bones and their corresponding three-dimensional (3D)-printed replicas. STUDY DESIGN: Digital 3D models of five cadaveric hemipelves and five live dogs with contralateral pelvic fractures were generated based on computed tomographic images and 3D printed. The 3D-printed replicas underwent 3D scanning and digital 3D models of the replicas were created. The digital 3D model of each replica was superimposed onto the model of the native hemipelvis. Errors in the replicas were determined by comparing the distances of 120,000 corresponding surface points between models. The medial surface, lateral surface and dorsal surface of the acetabulum (DSA) of each hemipelvis were selected for further analysis. The root mean square error (RMSE) was compared between various selected areas using a one-way repeated measures analysis of variance, followed by a Bonferroni post-hoc test. RESULTS: The RMSE of the hemipelvis was 0.25 ± 0.05 mm. The RMSE significantly decreased from the medial surface (0.28 ± 0.06mm), to the lateral surface (0.23 ± 0.06mm), to the DSA (0.04 ± 0.02mm) (p < 0.001). CONCLUSION: The 3D-printed replicas were adequate in serving as a template for the pre-contouring of bone plates in fracture repair of pelvic fractures, particularly those that demand accurate reduction such as acetabular fractures.

Evaluation of Threaded External Skeletal Fixation Pin Insertion with and without Predrilling in Avian Bone.

OBJECTIVE: The aim of this study was to document the effects of positive-profile threaded external skeletal fixation (ESF) pin insertion without predrilling on heat generation, structural damage and pullout strength in avian bone than that with predrilling. STUDY DESIGN: This study was an ex vivo study. MATERIALS AND METHODS: Twenty paired tibiotarsi and 40 paired humeri from 20 Mallard duck cadavers were used. Specimens were randomized to have positive-profile threaded ESF pins placed with or without predrilling insertion sites. Heat generation (maximum-baseline temperature) was measured during drilling and pin insertion with infrared thermography. Structural damage (gross trans-cortical damage and thread quality) was evaluated and scored using a visual analog scale (VAS). Mechanical testing was performed to evaluate pullout strength of inserted pins. RESULTS: VAS scores for trans-cortical surfaces were significantly higher than for cis-cortical surfaces; however, no difference was noted between predrilled and non-predrilled specimens. No significant difference in heat generation or pullout strength was noted between pins placed with and without predrilling. CONCLUSION: Pin insertion without predrilling in avian humeri and tibiotarsi does not cause significantly more structural damage or heat generation, or reduced pullout strength, compared with predrilling. Overall, our results indicate that predrilling prior to ESF pin placement provides no obvious advantage in avian bone.