Application of a three-dimensional virtual model to study the effect of fluoroscopic angle on infra-acetabular corridor parameters and screw insertion rates

Nengfeng Ma,Zhoushan Tao,Min Yang,Xufeng Hu

doi:10.1186/s13018-021-02730-w

Abstract

PurposeTo use three-dimensional (3D) virtual models to study how the parameters and insertion rates of the infra-acetabular corridor (IAC) change under different fluoroscopic angles.MethodsThe pelvis computed tomography data of 187 patients are imported into Mimics software in DICOM format to generate a 3D model. The anterior pelvis plane is used as the reference plane to measure the diameter of the optimum IAC when the pelvis model is tilted forward by 5°, 15°, 25°, 35° and 45°. The diameter of at least 3.5 mm is defined as the cutoff for placing a 3.5 mm screw, the rate of infra-acetabular screw (IAS) insertion is calculated, and the mean length of the IAC and the mean tilt of the corridor axis in relation to the sagittal midline plane (SMP) are measured.ResultsThe similar diameters of the IAC can be found under fluoroscopy at 5°–35°, with the largest diameter of 4.08 ± 1.84 mm and the highest screw insertion rate of 60.42% at 15° and 25°, whereas the diameter and insertion rate are lowest at 45°. The corridor length increases with increasing fluoroscopic angle, and the angle of the corridor axis to the SMP decreases gradually.ConclusionThe conventional fluoroscopic angle of the pelvic inlet is not suitable for the IAS insertion. The parameters of the IAC vary according to a certain rule under different fluoroscopic angles, so a surgeon can select the appropriate fluoroscopic angle in accordance with the type of fracture and the fracture line angle.

Highlights

Acetabular fractures are usually intra-articular fractures caused by high-energy injuries
The purpose of this study is to address the following questions: (1) Is it possible to use the anterior pelvic plane (APP), which is formed by the bilateral anterior superior iliac spine and the pubic symphysis, as the reference plane for pelvic parameter measurements in the patient’s supine position? (2) What are the infra-acetabular corridor (IAC) parameters and screw insertion rates of patients in this region? Are there any differences in IAC parameters between males and females? (3) How do the parameters and screw insertion rates of IAC change under different fluoroscopic angles, and is there a certain rule that can be helpful in clinical operation for fluoroscopy of infra-acetabular screw (IAS)?
The results of this study show no statistical difference between the tilt angle of the APP and 0°, which implies that the APP can be used as the pelvic reference plane for patients in the supine position, independent of the tilt angle of the pelvis and the patient’s position, and that a uniform reference plane can be found for different patients according to their anatomical landmarks

Summary

Introduction

Acetabular fractures are usually intra-articular fractures caused by high-energy injuries. The existing studies show significantly smaller measurements of numerical parameters in Asian people than in European people, and there are some differences in spatial measurements due to the inconsistent choice of reference planes. This makes it difficult for clinicians to refer to existing studies in practice. (3) How do the parameters and screw insertion rates of IAC change under different fluoroscopic angles, and is there a certain rule that can be helpful in clinical operation for fluoroscopy of IAS?

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