A guideline for screw fixation of coracoid process base fracture by 3D simulation

Abstract

Background Fractures of the base of the coracoid process are relatively rare, but an increasing number of studies have reported using screws to fix coracoid process base fractures. This study was performed to simulate the surgical procedure and obtain the ideal diameter, length, insertion point and angle of the screw from a 3-D axial perspective in Chinese patients. Methods We randomly collected right scapula computed tomography (CT) scans from 100 adults. DICOM-formatted CT scan images were imported into Mimics software. A 3D digital model of the right scapula was established. Two virtual cylinders representing two screws were placed from the top of the coracoid process to the neck of the scapula and across the base of the coracoid process to fix the base of the coracoid process. The largest secure diameters and lengths of the virtual screws were measured. The positions of the insertion points and the directions of the screws were also examined. Results The screw insertion safe zone can exhibit an irregular fusiform shape according to the reconstructed scapula model. The mean maximum diameters of the medial and lateral screws were 7.08 ± 1.19 mm and 7.34 ± 1.11 mm, respectively. The mean maximum lengths of the medial and lateral screws were 43.11 ± 6.31 mm and 48.16 ± 6.94 mm, respectively. A screw insertion corridor with a diameter of at least 4.5 mm was found in all patients. We found sex-dependent differences in the mean maximum diameters and maximum lengths of the two screws. The positions of the two insertion points were statistically different across sexes. Conclusions The study provides a valuable guideline for determining the largest secure corridor for two screws in fixing a fracture at the base of the coracoid process. For ideal screw placement, we suggest individualised preoperative 3D reconstruction simulations. Further biomechanical studies are needed to verify the function of the screws.

The safe zone of long screw fixation for Ogawa type I coracoid process fracture—Using quadrant method for 3D simulation operation and 2D fluoroscopy verification

“…In this study, 4.5 mm-diameter virtual screws were used. Ogawa et al recommended using 4.5 mm AO malleolar screws or cannulated screws; 3.5-5.0 mm screws were also used in previous research, with few reports of screw failure [1,7,8,10,20,24,26,[31][32][33]. In our surgeries, mainly 3.5-4.5 mm screws were used, and no broken screws were found during postoperative follow-up.…”

“…The axial superimposition of the coracoid process cortical bone essentially formed the boundary line of this fusiform region. When the screws did not penetrate the boundary in the axial perspective view, the screws were located entirely in the bone [17,20]; however, intraoperative reproduction of the fusiform region imaging is relatively tricky. This is related to factors such as lack of reduction for the coracoid process fracture, obstruction of the clavicle, selection of the patient position, light transmission performance of operating bed, or di culty placing the C-arm Mobile X-Ray systems.…”

“…There is no uniform standard for the screw entry point [17,20,[23][24][25]. In this study, an area of about 1-2 mm anterior to the coracoclavicular ligament on the posterior edge of the superior surface of the coracoid process was chosen as the screw entry point (Fig.…”

“…It also is far from the coracoid process insertion at the coracoclavicular ligament's trapezoid [4], avoiding damaging the coracoclavicular ligament [16,18]. There is no uniform standard for the screw entry point [17,20,[23][24][25]. In this study, an area of about 1-2 mm anterior to the coracoclavicular ligament on the posterior edge of the superior surface of the coracoid process was chosen as the screw entry point (Fig.…”

“…Hill et al reported the xation of coracoid fractures with two screws [19]. Sun et al proposed inserting two screw channels in the coracoid process, since two screws can have better rotation and increase stability than a single screw [20]. However, considering the possible problem of clavicular obstruction and the further increased risk of iatrogenic injuries, double screws should be used with extreme caution to x coracoid process fractures.…”