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Updated: Jun 29, 2026

Three-dimensional Navigation-guided, Prone, Single-position, Lateral Lumbar Interbody Fusion Technique
Published on: July 15, 2021
Comparative analysis of posterior column screw trajectories: pararectus vs. lateral window of the pelvis
Hoon-Sang Sohn1, Won-Tae Cho2, Jae-Woo Cho3
1Department of Orthopaedic Surgery, Wonju Severance Christian Hospital, Wonju, Korea, Republic of.
Objective:
The pararectus approach (PRA) offers good visualization of the entry point for posterior column screw insertion with an adequate screw length. However, conventional practice typically employs the lateral window (LW) of the pelvic approach. This study aimed to compare the radiographic trajectory of posterior column screws inserted via the PRA with that of screws inserted via the LW approach.
Methods:
We retrospectively analyzed 68 cases of posterior column screw placement during acetabular fracture surgery, beginning in March 2020, when metal-reformatted images could be generated from postoperative pelvic computed tomography (CT) scans. Group 1, consisting of 32 cases where screws were inserted through the second window of the PRA, was compared with Group 2, which included 36 cases using the LW in combination with various pelvic approaches. Demographic data (including body mass index [BMI] and presence of sacral dysplasia), the coronal angle of the posterior column screw in three-dimensional (3D) images, Sagittal Angle to Linea Terminalis (SALT), Sagittal Angle to Ischial Line (SAIL), and screw length (measured from 3D-CT metal-reformatted images) were analyzed.
Results:
Demographic data, including BMI and the presence of sacral dysplasia, were not significantly different between the two groups. The average coronal angle of the posterior column screw was 4.6° in Group 1 and 12.2° in Group 2, indicating a significant difference between both groups. For sagittal angles, SALT was 75.8° in Group 1 and 34.6° in Group 2, while SAIL was - 24.5° and - 4.1° in Groups 1 and 2, respectively, with both differences being statistically significant. The average screw length, measured by 3D-CT, was 73.2 mm and 93.7 mm in Groups 1 and 2, respectively, also demonstrating a significant difference between both groups.
Conclusion:
Although the PRA allows good visualization of the posterior column screw entry point, it presents limitations in achieving optimal sagittal and coronal insertion angles due to the anatomical constraints of the abdomen and surrounding structures. In contrast, the LW approach demonstrated a screw trajectory that more closely aligns with the ideal anatomical corridor.
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