Preventing Proximal Radio-Ulnar Joint Screw Penetration during Coronoid Fracture Fixation: A 3D-Digital Modeling and Cadaver Study.

Abstract

Objective: Intra-articular screw penetration is a probable complication of coronoid fracture fixation. The present study aimed to determine the best radiography technique for visualizing the proximal radioulnar joint (PRUJ) space. Moreover, it aimed to determine the safe angle and length of the screw to avoid PRUJ penetration during coronoid fracture fixation.

Methods: The Mimics software was used to construct a three-dimensional model of a healthy man's forearm from a computer tomography scan. It was analyzed using the Solidworks software to determine the X-ray angle that clearly showed the PRUJ space to detect penetration of screws from the coronoid process into the PRUJ and determine the maximum screw angle and length that could be used without intra-articular penetration. To verify these findings, a cadaveric study combined with radiographs was conducted.

Results: To visualize PRUJ space, the optimal X-ray angle was 13º lateral to the perpendicular line when the forearm was positioned at full supination. If the coronoid process was segmented into zones 1 (closest to the radioulnar joint) to 4 (farthest from the joint), the screw could only be inserted at a right angle in zone 1. In zones 2, 3, and 4, inclination angles less than 15, 35, and 60 would prevent intra-articular penetration, respectively.

Conclusions: The X-rays could visualize the PRUJ space with an anteroposterior radiograph at an angle of 13º ulnar deviation from the perpendicular plane. During coronoid process fracture fixation, shorter screws with less lateral inclination were safer when inserting screws in the zones of the coronoid process adjacent to the PRUJ.