This study focused on the morphological channel used for LC2 screw insertion. LC2 screws constitute an important surgical strategy to treat LC2 iliac crescents or acetabular anterior column fractures, but a high perforation rate has been reported using the traditional canal . In this study, a different plane from the traditional canal was chosen to reduce the rate of LC2 perforation. The results of this study led to the conclusion that LC2 screws should be inserted below the connecting plane of the midpoint of the AIIS and PSIS upper flat regions. Perforation occurred easily for LC2 screw insertion above the identified midplane. The morphological characteristics of the revised LC2 screw channel were determined in this study, and it was concluded that the tip of the LC2 screw should be inserted at the midpoint between the PSIS upper flat region and AIIS. The results of this research study can help ensure the successful use of LC2 screws in treating pelvic fractures.
Percutaneous screw fixation of iliac wing fractures is an established technique but remains technically demanding. It has been reported that misplaced screws produce many complications, such as injuries to the surrounding soft tissue and proliferation of vessels or nerves. In traditional treatment for lateral compression fractures, radiographic imaging must be performed and several positions of the C-arm must be considered before operation to plan the exact positioning of LC2 screws. Currently, a “Teepee” view along the supraacetabular bony canal can provide an optimal view for guide-wire insertion. However, obtaining a Teepee view several times and adjusting the guide pin may increase radiographic exposure and surgical time. Therefore, an auxiliary method, such as anatomical measurement of the bony canal parameters, is needed to support LC2 screw insertion. Therefore, considering the high rate of LC2 screw perforation using the traditional method, a revised midplane was proposed in this study to evaluate the anatomic characteristics of the LC2 bony canal. The plane between the AIIS and middle PSIS upper flat region was chosen because the PSIS is not obvious in all patients, and the bottom surface of the chosen plane is wide and flat. Furthermore, the PSIS upper flat region can more easily observed intraoperatively by radiography than the PSIS.
When the LC2 screw was first introduced, Starr reported that the illum became thicker near the greater sciatic notch, but the precise parameters of the bony canal were not obtained . Berry measured the length extending from the widest point of the posterior superior iliac spine (PSIS) to the tip of the anterior inferior iliac spine (AIIS) using specific points in specimens and reported that the corresponding bony canal provided a longer and potentially safer anchoring site than that identified by Starr . Due to technical limitations, the internal bony canal was only measured using normal CT, which can only be used to perform measurements along one cutting direction . Mimics enables precise measurement of the bony canal identified by Berry or a revised version. Mimics can visualize internal structure for cutting the pelvis along any designed direction. After defining the direction of the optimal osseous channel for the LC2 screw, the revised bony canal for the screw was comprehensively measured. Two aspects should be considered for LC2 screw insertion: the minimum width of the osseous channel cross section, which determines the screw diameter, and the screw length for ideal insertion.
In this study, the narrowest widths of three surfaces of the bony canal were measured to determine the optimal position for LC2 screw insertion. The width for screw insertion was found to increase for cutting planes approaching the lower surface and decrease for cutting planes approaching the upper surface. McCord studied 10 different fixation techniques and found that the longer the iliac nail in the iliac crest was, the more stable the nail was . However, the irregularity of the LC2 bony channel results a different length for the inserted screw than the maximum length of the bony channel. Furthermore, the narrowest canal inner diameter should not be simply taken as the maximum diameter of the inserted LC 2 screw, because the central axis of the screw channel does not overlap with that of the narrowest channel. To determine the optimal insertion position, a simulation was performed for screw placement in the midplane and among the three planes of the revised LC2 screw tunnel. The length of the screw inserted through the midpoint of the narrowest region was selected as the optimal screw length, and this midpoint intersected with the central axis of the screw channel. The insertion point of the screw was also effectively determined through simulation, and the intersection of the midpoint of the AIIS and the iliac body was determined to be the ideal insertion point of the LC2 screw. Therefore, it was concluded that it was safe to insert screws along or below the middle cutting plane, where the screw lengths were comparable to those employed using the traditional method.
Limitations were placed on the number of enrolled subjects, and more patients will be included in future studies. The traditional canal lying just under the revised canal was not measured but reported in previous studies, and the minimal width of the traditional canal was 12.3 ± 2.6 mm and 9.2 ± 3.0 mm in male and female, which was comparable with our revised canal . Therefore, it further confirmed the research value of the revised bony canal proposed in this study. In our next study, more anatomic parameters will be calculated to assist with LC2 screw insertion, and boundaries for LC2 screws will be accurately identified.