The acetabular fracture is caused by severe intra-articular trauma, frequently from high-velocity injury [2, 3]. The primary purpose of displaced acetabular fractures in the weight-bearing area is the anatomic reconstruction of the articular surface to recover the congruity of the hip joint and rigid internal fixation to allow for rapid postoperative recovery with early rehabilitation [1, 4,5,6]. However, the treatment of posterior wall acetabular fractures remains a relatively challenging task for orthopedic surgeons because of deep osseous geometry, limited direct visualization with close-set neurovascular structure and various fracture patterns like comminution or marginal impaction areas [5, 22]. Previous studies have suggested that despite the use of straightforward reduction and internal fixation techniques, a significant proportion of patients undergoing surgical treatment obtain poor clinical outcomes. In Letournel’s series of 117 isolated posterior wall fracture subgroups, 18% of patients undergoing open reduction and internal fixation had poor results . Matta  also reported in his retrospective study that 32% of patients with posterior wall fractures had poor clinical outcomes after surgery. Similarly, Saterbak et al.  reported that 35% of patients with posterior wall fractures had complete loss of joint space in one year postoperatively. Articular reduction is highly correlated with functional results in treating posterior wall acetabular fractures [2, 4, 5, 20, 21]. In recent years, the internal fixation of posterior wall acetabular fractures has achieved significant progress, but these fixations remain in the initial stage and cannot be widely implemented in clinical practice [24,25,26]. Accurate assessment of fracture characteristics, adequate preoperative surgical planning, and custom-made plates and screws can ensure the success of acetabular surgery, especially for younger and less experienced surgeons [13,14,15,16, 27]. Therefore, meticulous preoperative surgical planning for the treatment of posterior wall acetabular fractures may be beneficial in obtaining precise anatomical reduction to lower the risk of post-traumatic arthritis and achieve good clinical outcomes.
During the past decade, virtual preoperative planning of orthopedic surgery based on a virtual reality model has become increasingly common with the development of computer technology and image processing [7, 17, 19, 27]. Based on the real CT data, Hu et al.  utilized computerized virtual simulation for acetabular fracture reduction and plate fixation, which could help surgeons to better understand fracture patterns and determine correct surgical strategies. Later, some scholars suggested that the combination of computerized virtual planning procedures and the 3D printing-assisted contoured plate fixation method is a valuable tool for surgeons to formulate an appropriate preoperative plan in acetabular fracture surgery [11,12,13, 15]. Although blood loss and surgical time were significantly reduced under the aid of preoperative planning, they had the same common limitations such as technical expertise required for software operation and time consumed in preparing a full size (1:1) 3D-printed hemipelvis model, which would prevent the widespread use of this technique. Therefore, a one-stop computerized virtual planning system was utilized in this study to overcome the above-mentioned demerits. There are several noteworthy characteristics of the one-stop planning system in this study. In previous studies [13, 15, 18], the segmentation of bone fragments required manual operation on all 2D CT slices in all three planes, which was time-consuming and needed software expertise. In this study, a more efficient segmentation method based on a 3D virtual model was used to separate contiguous bone fragments, which necessitated no special knowledge of computer technology and could be operated by orthopedic surgeons themselves. Furthermore, digital plate models must be complicatedly designed and imported from multiple software programs before the virtual simulation of internal fixation [7, 16, 17]. Through such a one-stop computerized virtual surgical planning system, a sequence of preoperative plans, including segmentation, fracture reduction and virtual internal fixation, could be completed quickly within 30 min. The average time for using the software was 18 min in group A, which was much shorter than that reported by Hu et al. (79 min). Additionally, the plate template designed on the virtual post-reduction model was 3D printed using our methodology, instead of a full-sized 3D-printed hemipelvis model. The time needed for a full-sized (1:1) 3D-printed hemipelvis model was 12 h as reported in recent studies, but only 2 h for a plate template in our series, which significantly reduced the time and cost.
This study is unique in case and control groups where patients with similar fracture types were included, who were surgically treated by the same Kocher–Langenbeck approach. Thus, the interference factors could be reduced as much as possible with a higher level of reliability. This study aims to compare the outcomes of the posterior wall acetabular fractures treated by the one-stop preoperative planning system and the traditional method. Compared to the conventional surgical method in group B, both surgical time and blood loss in group A were significantly reduced by the computerized virtual planning system. The decreased surgical time was mainly due to preoperative surgical simulation in a 3D virtual model. Psychological studies have suggested that cognitive preparation and mental readiness are necessary for successful procedures, especially for beginners . Given that the preoperative surgical planning system allows for the preoperative knowledge of fracture morphology, surgeons can avoid extensive soft-tissue dissection and perform fracture reduction more easily, which significantly reduced intraoperative blood loss. Consequently, psychological and physical requirements on surgeons were reduced, as well as risks associated with prolonged general anesthesia. Previous studies have demonstrated that patient-specific plate preparation in acetabular fracture surgery can avoid intraarticular screwing and improve the quality of fracture reduction, especially for comminuted fractures [11,12,13,14,15]. Aided by the 3D-printed plate template designed on the computerized system in group A, the plate can be accurately contoured to achieve optimal compactness with the bone surface, ensuring mechanical strength and reduction accuracy as well as shortening instrumentation time significantly. Moreover, the length of mini-screws in the 3D virtual model was measured to enhance the safety of screw placement, particularly at fixation points in dangerous areas. It is noteworthy that differences between real and virtual conditions should be kept in mind for surgeons. Bone fragments would not be attached to soft tissues in a virtual environment, so plates and screws are easily placed in any direction. However, soft tissues would interfere with reduction and narrow the working space, especially when faced with severely comminuted fractures. In group A, there was one case in group A presented with severely comminuted fractures obtained a poor reduction quality, though an appropriate surgical plan was formulated preoperatively. The planned strategies for reduction had minor changes as soft tissues prevented the fragment manipulation in the desired fashion. Nevertheless, in this study, higher hip-function scores and fracture reduction quality were found in posterior wall acetabular fractures treated by the computer-assisted virtual planning system, although these differences were not significant. In summary, with the aid of the one-stop computerized virtual planning system, the same fracture reduction quality and functional results were obtained with less surgical time and blood loss. Besides, there are educational benefits for young surgeons to enhance the learning curve for understanding fracture patterns and surgical treatment of posterior wall acetabular fractures.
There are also some limitations in the present study. First, the process of repositioning fragments is manual, which is still not precise and fast enough, especially for fractures with severe comminution. Further study may better address this problem by using the mirrored image from the opposite acetabulum, which may be more efficient. Second, the shape of the virtual contoured plate is too ideal to bend the real plate because the destruction of the screw hole should be avoided when bending. Therefore, the virtual contoured plate may not match each brand of the reconstruction plates. Third, the present study is a retrospective design with a relatively small sample size. Further prospective randomized controlled trials with a large sample size may ascertain the role of this one-stop computerized virtual planning system in the surgical treatment of posterior wall acetabular fractures.