Acetabular Lateral View: Effective Fluoroscopic Imaging to Evaluate Screw Penetration Intraoperatively

Abstract

BACKGROUND Screw penetration into the hip joint is a severe complication during acetabular fracture surgery. The standard fluoroscopic views of the pelvis cannot provide adequate safety during screw insertion. The aim of this research was to determine and evaluate the accuracy of the acetabular lateral view for screw placement. MATERIAL AND METHODS Twenty screws were randomly chosen and intentionally penetrated into the articular surface (1-2 mm), and the remaining 20 screws were extra-articular ones positioned in close proximity to the articular surface. Three surgeons, each evaluating 40 screws, provided a total of 120 rated observations for each screw position. We compared the traditional view or combined with lateral acetabular view with the criterion standard based on unaided visual assessment. A blinded and independent review of each pelvic intraoperative fluoroscopy was made by 3 independent observers. Specificity, sensitivity, positive predictive value, negative predictive value, correct interpretation, intra-class correlation coefficients (ICC), and Youden index were calculated. RESULTS There were significant differences in sensitivity, NPV, correct interpretation, and Youden index between the 2 groups (P<0.05). The ICC was 0.531 when the antero-posterior, iliac, and obturator oblique views were used. The ICC was remarkably increased when using a combination of the ''lateral'' view and the standard views for screw perforation of the joint. CONCLUSIONS Use of the lateral view of the acetabulum can be a complementary method to identify malpositioned screws, and it helps increase the accuracy rate of inserting screws in the treatment of posterior wall fracture.

Figure 1

The pelvic model used in the research. (A) Three screw tips penetrate into the articular surface by 2 mm in this specimen. (B) All screw contained within the bony corridor in this model. (C) One intra-articular screw is exhibited in this model.

Figure 2

The fluoroscopic projection method of traditional and proposed radiographs used in pelvic model from a mobile fluoroscopy unit. (A) Anterior-posterior (AP) view. (B) Iliac obturator oblique view. (C) Obturator oblique view. (D) Lateral view of acetabular which is similar to lateral view of pelvic.

Figure 3

Fluoroscopic images of pelvic models with screws inserted. (A, B) The images demonstrate that AP and iliac views are not sufficient to identify the relationship between screws and acetabulum. (C) Obturator view shows a false-positive evaluation. (D) Lateral view of acetabular exhibits clearly that 3 screws have surpassed the articular surface. These images were presented randomly to 3 surgeons.

Figure 4

The evaluation results when combined with or without lateral view in 3 observers. The results exhibited that evaluations combined with lateral view were improved in Group B.

Figure 5

The clinical application of lateral view in acetabular surgery. (A) The patient’s position was fixed laterally and cannot be changed easily. (B) Intraoperative fluoroscopic image with lateral view of acetabulum showed the position of screws, and no one penetrates into articular surface. (C, D) fluoroscopic image showed traditional views might be affected by operation table or other assistant equipment such as waist block.