The current study examined the radiological results of simultaneous surgical treatment of ipsilateral pelvic ring and acetabular fractures to evaluate the factors that may contribute to inadequately reduced acetabular fractures. The results revealed that the most common fracture type was B2.2 for pelvic ring fractures and anterior column for acetabular fractures. Additionally, the univariate analysis demonstrated that associated acetabular fractures and quality of the pelvic reduction, according to Matta’s criteria, were the two factors that affected the reduction quality of subsequent acetabular fractures. However, no significant factors were identified in the multivariate analysis.
Anatomical reduction to minimize the risk for post-traumatic osteoarthritis is the main goal of osteosynthesis for acetabular fractures. Tannast et al. reviewed a series of 816 patients with acetabular fractures and followed them for 2–20 years [8]. They showed that non-anatomical fracture reduction was the most significant factor associated with the requirement for total hip arthroplasty. Additionally, most studies that reported the outcomes after acetabular fractures have indicated the importance of anatomical fracture reduction [8,9,10, 19, 20]. There are several factors that might affect reduction of acetabular fractures, including complexity of the fracture pattern. Thirteen acetabular fractures (48.1 %) were classified as associated fractures using Letournel’s classification. Among the 13 associated acetabular fracture patterns, 10 were graded as being of fair to poor reduction quality on AP iliac, oblique, or obturator oblique view X-ray. Additionally, there were greater step-offs on CT scans for the associated fracture patterns. Therefore, our results show that the classification might lead to inadequate reductions of acetabular fractures.
However, the acetabulum is part of the pelvis; therefore, in cases of pelvic ring fracture without sufficient reduction, the reduction of the acetabulum may not be adequate. Suzuki et al. confirmed that the initial adequate reduction of the posterior pelvic lesion is necessary to obtain optimal reduction of the acetabulum [4]. Since accurate reduction of the posterior pelvic ring is key to anatomical reduction of the acetabular fracture, the sequences of fracture reduction and fixation may be critical. Although this study consisted of 19 patients undergoing treatment by anterior approaches (ilioinguinal, anterior intrapelvic, and pararectus), the principles of the reduction sequence did not differ. These approaches mostly aimed to reduce and fix anterior lesions; however, posterior pelvic ring injures, such as crescent fracture, sacral fractures, and sacroiliac joint diastasis, can also be managed using these approaches. On the other hand, posterior approaches were still necessary when a displaced posterior pelvic ring existed, and should be performed prior to anterior approaches. There were three cases of spinopelvic osteosynthesis and three cases of open reduction and fixation to address posterior sacroiliac joint injuries. These six patients also underwent subsequent anterior approaches for treatment of the acetabular fractures.
The reduction of the posterior pelvic ring is crucial in obtaining satisfactory radiological results; however, there has been no discussion on how to optimally evaluate the pelvic reduction quality before beginning osteosynthesis of the acetabulum. Our study shows that Matta’s criteria may be useful in evaluating the reduction of the acetabulum. Since fluoroscopy is the most commonly used tool for intraoperative evaluation of fracture reduction, Matta’s criteria can be used before osteosynthesis for acetabular fractures to determine whether the reduction should be more accurate before proceeding with the osteosynthesis. This method may be applied intraoperatively to ensure the quality of the subsequent reduction of the acetabulum.
There have been similar reports of combined pelvic ring and acetabular fractures [4, 7, 11, 12, 21]. According to previous findings, the most common fracture type of the pelvis in similar cohorts was the lateral compression type [4, 7, 21]. However, Osgood et al. found that the AP compression type was the most common in their cohort [11]. In our study, the most common fracture type was the lateral compression type. Because the most common type of pelvic fracture in our study was B2.2 (lateral compression type), the injury force was probably applied directly and laterally towards the greater trochanter of the femur, which would be similar to the injury force resulting in anterior column fractures of the acetabulum [22], the most common type of acetabular fractures in our study. Therefore, we observed similar fracture types from injuries to the pelvis and acetabulum, consistent with previous studies.
Although we made efforts to avoid bias, this study had some limitations. First, this study included a relatively small number of patients, which might result in statistical bias. However, similar to previous studies, the incidence of simultaneous pelvic and acetabular fractures was low, and the number of enrolled patients was naturally limited. Second, although one of the major findings of this study was the proposal to apply Matta’s criteria for intraoperative assessment of the pelvic ring, this was evaluated using postoperative images. The actual intraoperative usefulness of Matta’s criteria in predicting the quality of acetabular fracture reduction in this cohort should be determined in a future study. However, the strength of our study includes the fact that the patients were all treated by a single surgeon at a single institute with a similar treatment protocol. All patients were followed up with complete postoperative X-ray and CT evaluations, and 3 independent examiners interpreted the imaging findings with excellent inter-observer reliability. Therefore, the data obtained were reliable and convincing. Owing to the aforementioned limitations, a meta-analysis should be conducted in the future to thoroughly investigate this specific group of patients.
