The study of screw placement parameters for Ogawa type I acromial fractures by 3D simulation

Abstract

Background: Acromial fractures are rare and there is no consensus on fixation, but an increasing number of studies have reported using two screws to fix Ogawa type I acromial fractures. The objective of this study was to obtain the ideal length, diameter, insertion point, and angle of the screw using a novel 3D simulation.

Methods: The scapular CT data of 100 individuals were obtained to reconstruct 3D models. The transparency of the 3D model was then downgraded along the axial perspective (the view perpendicular to the cross section of the acromion axis) to find the maximum translucent area. Two virtual screws were placed at the anterior edge of the acromion until they penetrated the posterior cortical bon. The largest diameters and lengths of the screw were measured, and the direction and insertion point of the screw were observed.

Results: The mean maximum lengths of the medial and lateral screws were 43.33 ± 6.17 mm and 39.23 ± 6.01 mm, respectively. The mean maximum diameters of the medial and lateral screws were 4.71 ± 1.23 mm and 4.97 ± 1.07 mm, respectively. Differences in screw length, diameter, and insertion point between males and females were found. The differences in screw angle between sexes were not statistically significant.

Conclusions: Based on a 3D model test, we recommend the size, entry points, and angles of screws for Ogawa type I acromial fractures, providing valuable guidance for clinical work. More accurate screw parameters can be obtained preoperatively by establishing an individualized 3D model.

Keywords: 3D technology; Acromion; Axial perspective; Screw fixation.

Fig. 1

The 3D models of the scapula was obtained through image segmentation and region growth operations of the software

Fig. 2

Find the largest screw path. a The largest translucent area resembles an oval shape. b Two computer-aided design screws were placed evenly in the translucent area. Then, the diameters were increased progressively until they reached the borderline of the area

Fig. 3

Observe the largest length and position of the screws. A, B Observed from the above and below of the opaque 3D model, respectively. The screws had the largest lengths and diameters just penetrating the cortical bone. a, b The screws position were observed from the above and below of the translucent 3D model.

Fig. 4

The measurement of distance L1, L2, L3, and L4. a The distances from the medial screw entry point to the acromioclavicular articular surface and the leading edge of the acromial were marked as L1 and L2, respectively. b The distances from the lateral screw entry point to the acromioclavicular articular surface and the leading edge of the acromial were marked as L3 and L4, respectively

Fig 5:

The measurement of angle α and β. a The downdip angle between the screw and plane A was measured and recorded as angle α. b The inclination angle between the screw and plane B was measured and recorded as angle β