Interobserver and Intraobserver Agreement for Letournel Acetabular Fracture Classification System Using 3-Dimensional Printed Solid Models

Background: The currently accepted classification system of acetabular fractures of Judet-Letournel is a common language among trauma orthopaedists and is an important basis for their therapeutic algorithms. 3-D printing technology has become available in recent years and is used as a diagnostic tool and as a tool in planning and executing surgeries. The aim of this study was to evaluate the reliability of the classification system of Letournet using CT imaging and 3-D models that were manufactured by 3-D printers. In addition, we also examined the contribution of 3-D printed models in diagnosis, classification and subsequently the surgical approach chosen for these fractures.

Methods: We examined 7 cases of acetabular fractures, for each case a file was prepared including CT imaging and an accurate 3-D printed model. 18 orthopaedic trauma surgeons responded to questionnaires, regarding the seven cases about the individual fracture classification based on Letournel as well as their preferred surgical approach for the given fracture. The rates of agreement were analyzed among the participants’ responses regarding classification and surgical approach; these were the rates of the Inter-Observer Agreement and the rates of the Intra-Observer Agreement.

Results: The degree of Inter-Observer Agreement regarding fracture classification based on CT imaging alone was moderate: Kappa W = 0.438, and the degree of the Inter-Observer Agreement regarding fracture classification based on the 3-D printed models alone was higher, but still moderate: Kappa W = 0.553 (p-value < 0.001). It was also found that the degree of Inter-Observer Agreement for the preferred surgical approach according to CT alone was fair: Kappa W = 0.342, and that the degree of Inter-Observer Agreement according to the 3-D printed models alone was lower, but still fair: Kappa W = 0.287 (p-value = 0.005). The rate of Intra-Observer Agreement for the fracture classification, using both of the imaging modalities, was found to be moderate: Kappa = 0.476. The rate of Intra-Observer Agreement regarding the preferred surgical approach when using both of the imaging modalities was moderate: Kappa = 0.407.

Conclusions: The data suggests that within the Letournel classification system for acetabular fractures exists only moderate rates of agreement. Use of the 3-D printed models raised the rates of agreement regarding the fracture classification but lowered the rates of agreement regarding the preferred surgical approach. Three-dimensional models allow for better spatial understanding and enable more accurate classification of the fracture. It is possible that the ability of the surgeon to hold a 3-D model in his hands as part of the preparation and surgical planning will contribute to the understanding of the fracture. This in turn can stimulate renewed thinking about the surgical approach, and thus contribute to achieving a better surgical outcome.