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

Abstract BackgroundFractures of the base of the coracoid process are relatively rare, but an increasing number of studies have reported using screws to fix basal coracoid process fractures. This study was performed to simulate the surgical procedure and obtain the ideal diameter, length, insertion point and angle of the screw through the method of 3-D axial perspective in Chinese patients.MethodsWe randomly collected the right scapula computed tomography (CT) scans of 100 adults. DICOM-formatted CT-scan images were imported into Mimics software. The 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 basal 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 researched.ResultsThe screw insertion safe zone can exhibit an irregular fusiform shape from 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. The screw insertion corridor with a diameter of at least 4.5 mm was found in anyone. We found gender-dependent differences for the mean maximum diameters and the maximum lengths of the two screws. The positions of the two insertion points were statistically significant in different genders.ConclusionsThe study provides a valuable guideline for the largest secure corridor of two screws that fixed the fracture at the base of the coracoid process. For the ideal screw placement, we suggest an individual preoperative 3D reconstruction simulation. Further biomechanical studies are needed to verify the function of the screws.