Accuracy and precision of measurements performed on three-dimensional printed pelvises when compared to computed tomography measurements

Accuracy of anatomic 3-dimensionally printed canine humeral models

OBJECTIVE

To evaluate the accuracy of various three-dimensional print (3DP) technologies using morphometric measurements.

STUDY DESIGN

Experimental.

SAMPLE POPULATION

Cadaveric canine humeri and size-matched 3DP models.

METHODS

Fiduciary radiopaque markers were affixed to canine humeri of three different sizes (4, 13, 29 kg) at predetermined anatomical landmarks. 3DP models were created using one of three printers; desktop printers Form 3L and Ultimaker 5S, and industrial printer Objet Connex (n = 5/group/printer). Marker based morphometric dimensions between cadavers and 3DP models were statistically compared using 2-factor repeated measures ANOVA followed by Tukey's post-hoc test (p < .05).

RESULTS

Bone size and printer type both significantly affected 3DP accuracy, with size having the larger effect (p < .0001 and p < .02, respectively). Regardless of printing technology, model size was smaller than native bone in most cases. At the humeral condylar level, the best accuracy was seen in the medium-sized humerus with the Ultimaker printer ([0.09 mm], p < .03). Accuracy was reduced in the proximal humerus in all groups.

CONCLUSION

Desktop printers were overall more accurate than the industrial printer. Although significant differences were identified between models of different sizes, the submillimetric magnitude of these differences is unlikely to be clinically relevant.

CLINICAL SIGNIFICANCE

While preoperative planning using 3DP models is becoming mainstream, accurate representation of the actual bone is critical. This study demonstrates that common desktop printers are suitable for this purpose.

Geometric accuracy of an acrylonitrile butadiene styrene canine tibia model fabricated using fused deposition modelling and the effects of hydrogen peroxide gas plasma sterilisation

Background

Three-dimensional (3D) printing techniques have been used to produce anatomical models and surgical guiding instruments in orthopaedic surgery. The geometric accuracy of the 3D printed replica may affect surgical planning. This study assessed the geometric accuracy of an acrylonitrile butadiene styrene (ABS) canine tibia model printed using fused deposition modelling (FDM) and evaluated its morphological change after hydrogen peroxide (H₂O₂) gas plasma sterilisation. The tibias of six canine cadavers underwent computed tomography for 3D reconstruction. Tibia models were fabricated from ABS on a 3D printer through FDM. Reverse-engineering technology was used to compare morphological errors (root mean square; RMS) between the 3D-FDM models and virtual models segmented from original tibia images (3D-CT) and between the models sterilised with H₂O₂ gas plasma (3D-GAS) and 3D-FDM models on tibia surface and in cross-sections at: 5, 15, 25, 50, 75, 85, and 95% of the tibia length.

Results

The RMS mean ± standard deviation and average positive and negative deviation values for all specimens in E_FDM-CT (3D-FDM vs. 3D-CT) were significantly higher than those in E_GAS-FDM (3D-GAS vs. 3D-FDM; P < 0.0001). Mean RMS values for E_FDM-CT at 5% bone length (proximal tibia) were significantly higher than those at the other six cross-sections (P < 0.0001). Mean RMS differences for E_GAS-FDM at all seven cross-sections were nonsignificant.

Conclusions

The tibia models fabricated on an FDM printer had high geometric accuracy with a low RMS value. The surface deviation in E_FDM-CT indicated that larger errors occurred during manufacturing than during sterilisation. Therefore, the model may be used for surgical rehearsal and further clinically relevant applications in bone surgery.

Graphical abstract

An investigation into the effect of changing the computed tomography slice reconstruction interval on the spatial replication accuracy of three-dimensional printed anatomical models constructed by fused deposition modelling

Introduction

Three‐dimensional (3D) printed models can be constructed utilising computed tomography (CT) data. This project aimed to determine the effect of changing the slice reconstruction interval (SRI) on the spatial replication accuracy of 3D‐printed anatomical models constructed by fused deposition modelling (FDM).

Methods

Three bovine vertebrae and an imaging phantom were imaged using a CT scanner. The Queensland State Government’s Animal Care and Protection Act 2001 did not apply as no animals were harmed to carry out scientific activity. The data were reconstructed into SRIs of 0.1, 0.3, 0.5 and 1 mm and processed by software before 3D printing. Specimens and printed models were measured with calipers to calculate mean absolute error prior to statistical analysis.

Results

Mean absolute error from the original models for the 0.1, 0.3, 0.5 and 1 mm 3D‐printed models was 0.592 ± 0.396 mm, 0.598 ± 0.479 mm, 0.712 ± 0.498 mm and 0.933 ± 0.457 mm, respectively. Paired t‐tests (P < 0.05) indicated a statistically significant difference between all original specimens and corresponding 3D‐printed models except the 0.1 mm vertebrae 2 (P = 0.061), 0.3 mm phantom 1 (P = 0.209) and 0.3 mm vertebrae 2 (P = 0.097).

Conclusion

This study demonstrated that changing the SRI influences the spatial replication accuracy of 3D‐printed models constructed by FDM. Matching the SRI to the primary spatial resolution limiting factor of acquisition slice width or printer capabilities optimises replication accuracy.