A study on fracture lines of the quadrilateral plate based on fracture mapping

Anatomic reduction and stable internal fixation of displaced acetabular fractures has been considered the accepted treatment for these injuries to decrease the rate of post-traumatic arthrosis [1, 2]. Clinical outcomes were correlated with variables including fracture type, the accuracy of reduction, and patient age [3‐6].

At present, the most clinically used classification is the Judet-Letournel classification [7, 8], which is based on the column theory and describes fracture anatomy in relation to the anterior and posterior columns. Initial radiographic assessment is with plain radiography using the anteroposterior (AP) pelvis and Judet views. However, some fracture types are easily confused. In addition, less experienced orthopedic surgeons have difficulty in understanding the three-dimensional structure of acetabular fracture and Judet-Letournel classification, which is not conducive to select the appropriate treatment plan.

The accuracy of reduction is closely related to the choice of surgical approach. The most commonly used approaches include Stoppa, ilioinguinal (IL), and Kocher-Langenbeck (KL). However, no single approach can meet the needs of all acetabular fracture types. The choice of surgical approach depends on multiple factors, including the fracture pattern, familiarity with complex anatomical structures, fracture morphology, and surgeon’s individual preference.

Since most types of acetabular fracture (excluding simple anterior wall fracture and posterior wall fracture) involve the quadrilateral plate, we envisioned to simplify the method and observe the fracture lines of the quadrilateral plate to guide preoperative planning. Therefore, we applied fracture map technique to the study of fracture lines of the quadrilateral plate and expected to explore the clinical significance.

The Judet-Letournel classification [7, 8] has been widely accepted for classifying acetabular fractures, communicating with peers, selecting surgical approach, and reporting results [12‐14]. This classification is associated with high interobserver and intraobserver reliability when used by orthopedic surgeons with experience in treating acetabular fractures [15]. However, it is more difficult for orthopedic surgeons with less experience to correctly classify acetabular fractures [15, 16].

By understanding the relationship between fracture lines and the Judet-Letournel classification, orthopedic surgeons have features of all fracture types in mind without remembering a complex classification system. For example, the fracture lines of double-column fractures mainly include upper transverse lines and upper oblique lines. The fracture line of the anterior column meets the fracture line (upper oblique line) of the posterior column at the border of the true pelvis and then enters the obturator ring by upper transverse or anterior vertical line together, which is consistent with the fracture characteristics of the double-column fractures (Fig. 4).

In addition, by observing fracture lines of different types of acetabular fractures and understanding of the pelvic anatomy, it can help orthopedic counterparts to choose the appropriate surgical approach. It should be emphasized that fracture lines of the quadrilateral plate are not the only factor in the selection of surgical approach. In general, anterior approach can be used for fractures involving the anterior column and posterior approach can be used for fractures involving the posterior column. However, if the anterior and posterior columns are involved, we also need to take other factors into account in choosing the surgical approach, such as the direction of the fracture displacement, whether accompanied by posterior wall fracture, surgeon’s individual preference, and fixation way. Based on our understanding and previous summary, we had some experience about the choice of surgical approach. Upper transverse and anterior vertical lines mainly involve the anterior column, which were suitable for the anterior approach. While upper oblique, lower oblique, and posterior vertical line mainly involve the posterior column, the posterior approach was appropriate. In addition, because the perpendicular line involved both columns, the combined approach should be chosen in theory. However, a single approach should be chosen for fractures that can be solved by a single approach (Fig. 5).

Quadrilateral plate fractures are often accompanied by medial migration of the femoral head, especially in osteopenic patients [17, 18]. Fixation of such fractures become technically challenging. The internal fixation devices have screws, plates, and steel wires, among which plates are the most commonly used and the biomechanical stability is relatively good. Although various new internal fixation devices have emerged in endlessly, the long-term efficacy needs to be further evaluated [19‐22].

In our study, upper transverse, upper oblique, and perpendicular lines were most common in acetabular fractures involving the quadrilateral plate. Therefore, we have proposed to design an internal fixation system that meets the following requirements: (1) can cover the three most common fracture lines above, (2) can resist the internal movement trend of the quadrilateral plate, (3) can avoid screws entering the hip, and (4) can better serve the bone surface. At present, our study focuses on the measurement of pelvic anatomical parameters and the design of the new plate.

This study had also several limitations. First, the methods and results were descriptive so that others may be suspicious of the interpretation of fracture maps. Second, some hemipelvis images did not match the hemipelvis model perfectly. Third, this requires a CT technician to crop and rotate the 3D reconstruction image of the pelvis to expose the quadrilateral plate. Finally, our analysis did not account for potential variability in function, anatomy, and injury mechanism.

In conclusion, observation of the fracture line by fracture mapping provides us with a new perspective to study acetabular fractures, which helps orthopedists understand the acetabular fracture classification intuitively and comprehensively. Fracture lines of the quadrilateral plate can provide some guidance for the choice of surgical approach and the design of internal fixation for acetabular fractures.