Comparison of 3D printed anatomical model qualities in acetabular fracture representation

Abstract

Background: Acetabular fractures account for 10% of pelvis injuries, which are especially difficult to treat in developing countries with less access to resources. 3D printing has previously been shown to be a beneficial method of surgical planning, however the steep initial costs associated with purchasing a 3D printer may prevent some facilities form utilizing this technique. The purpose of this study was to develop 3D printed models for acetabular surgery using methodologies of varying cost to determine differences in model accuracy and overall quality.

Methods: Five acetabular fracture models were developed from de-identified CT data using (I) proprietary and open-source segmentation software and (II) fused deposition modeling (FDM) and stereolithography (SLA) 3D printing methods. The distance between the posterior inferior iliac spine (PIIS) and the ischial spine as well as a unique fracture fragment for each model was compared between the different printing methodologies. The models were then given to 5 physicians and assessed on their overall accuracy compared to traditional 2D images.

Results: Printing methodology did not affect the distance from PIIS to ischial spine (P=0.263). However, fracture fragment representation differed across 3D printed models, with the most accurate model produced by the high-end resin-based printer (P=0.007). The survey analysis showed that the low-cost printing methods produced models that were not as accurate in their representation of the fractured region (P=0.008).

Conclusions: The differences between models developed using traditional methods and low-cost methods have slight differences but may still provide useful information when developing a surgical plan.

Keywords: 3D printing; acetabular fracture; additive manufacturing; anatomic model; surgical planning.

Figure 1

Depiction of the workflow used to produce the anatomical models. High-end models were segmented using the proprietary software Mimics (license cost: $12,975.00) and were printed on the Objet260 (printer cost: $158,900.00 and the uPrint (printer cost: $26,934.00). Low-cost models were segmented using the open-source software 3DSlicer (license cost: $0) and were printed on the Form 2 (printer cost: $3,350.00) and the Ultimaker 2 Extended+ (printer cost: $2,999.00). FDM, fused deposition modeling.

Figure 2

Example of the measurements taken to observe the distance between the posterior inferior iliac spine (PIIS) and the ischial spine on (A) the computer tomography (CT) data and (B) the 3D printed model, as well as the unique fracture fragment on (C) the CT data and (D) the 3D printed model.

Figure 3

Average absolute value measurement error of (A) the distance between the posterior inferior iliac spine (PIIS) and the ischial spine and (B) the acetabular fracture fragment. No significant differences were found between the distance from the PIIS to the ischial spine. There was a significant difference between the measurement of the fracture fragment on the models printed by the Objet compared to the uPrint (P=0.026), Form 2 (P=0.026), and Ultimaker (P=0.010). *P<0.05.

Figure 4

Boxplot of the raw measurement mean error for (A) the distance between the posterior inferior iliac spine (PIIS) and the ischial spine and (B) the acetabular fracture fragment.

Figure 5

Bland-Altman analysis of the measurement error of (A) the distance between the posterior inferior iliac spine (PIIS) and the ischial spine and (B) the acetabular fracture fragment. For both the PIIS to the ischial spine measurement and the fracture measurement, there were no significant linear regression values (r=0.022 and r=0.103, respectively) or indications of proportional bias (P=0.927 and P=0.625, respectively).