Introduction of a three-dimensional computed tomography measurement method for acetabular fractures

Abstract

Introduction Acetabular fractures consist of complex fracture patterns whereby bone fragments are displaced in different directions. Two-dimensional computed tomography (2DCT) gap and step-off measurements tend to underestimate the multidirectional features of these fractures. The aim was to develop a three-dimensional computed tomography (3DCT) measurement method for acetabular fractures and validate whether this method will provide an observer independent fracture characterization. Materials and methods Sixty patients, operated for an acetabular fracture between 2007 and 2018, were included. The displacement was measured on the pre- and postoperative CT scans. Pre- and postoperative CT-based 3D models were made for each patient. Multiple 3D measurements, namely the 3D step-off, gap and the total gap area were introduced to quantify the preoperative and postoperative displacement. The Wilcoxon signed rank analysis was used to compare the 2DCT and 3DCT measurements. Results The preoperative displacement was significantly underestimated by 2DCT measurements in comparison with 3DCT measurements (2D vs. 3D; step-off 8 vs. 16 mm with P < 0.001; gap 19 vs. 21 mm with P = 0.001). The same applies to the postoperative residual displacement (2D vs. 3D; step-off 0 vs. 6 mm; gap 3 vs. 8 mm; P < 0.001). The total gap area, defined as the surface area between all fracture lines in the 3D model, was measured for each patient, resulting in a median value of 722 mm 2 preoperatively and 168 mm 2 postoperatively, with excellent inter- and intra-rater reliability. Conclusion 2DCT measurements tend to underestimate the initial and residual displacement in complex acetabular fractures. A 3DCT analysis of these injuries was developed to overcome this and should be used in addition to the Judet/Letournel and AO/OTA classification systems, in order to provide an observer independent quantifiable fracture description and accurate assessment of the fracture reduction.

Feasibility of Imaging-Based 3-Dimensional Models to Design Patient-Specific Osteosynthesis Plates and Drilling Guides

“…According to CT-based criteria, the reduction was graded as perfect in 3 of 10 patients and good in 7 of 10 patients. 14 The preoperative and postoperative axial CT slices at the acetabular dome are presented in eFigure 2 in the Supplement .…”

“… 13 The quality of the reduction was graded according to Matta criteria and the newly proposed CT-based criteria. 8 , 14 , 15 …”

The accuracy of gap and step-off measurements in acetabular fracture treatment

“…For example, a both column (AO 62 C) fracture does not have a reference point because the acetabulum is disconnected from the rest of the pelvis. Additionally, it is questionable whether a single gap or step-off measurement is sufficient to assess the severity of the fracture and the quality of the reduction in complex fractures with multiple fracture lines 20 . Apart from the differences between measurements on various imaging modalities, the inter- and intra-observer reliability for gap and step-off measurements in acetabular fracture surgery was low as determined in our previous study 21 .…”

Traditional versus mirror three-dimensional printing technology for isolated acetabular fractures: a retrospective study with a median follow-up of 25 months

“…7 Combined with the strong internal fixation of the fractures, such an understanding can ultimately achieve good postoperative results. 9,20 Traditional surgical strategies are frequently based on the use of X-ray or CT images to determine the morphological features of the fractures while ignoring the normal contralateral acetabular structure. 11 Fracture information captured by conventional CT reconstruction techniques is limited; this is mainly due to the fact that the fracture information is not personalised because the rim of each individual’s acetabulum varies in shape.…”