Optimal Screw Orientation for Fixation of Type B Intracapsular Condylar Head Fractures: A Comparative Finite Element...

Although screw fixation of condylar head fractures is increasingly favored, optimal orientation strategies remain poorly defined, with limited evidence guiding intraoperative decision-making. This study compared the biomechanical behavior of four screw orientations in the fixation of type B condylar fractures.

A 3D maxillofacial model was reconstructed from CT and MRI data, incorporating a virtual type B fracture. Twelve simulations tested four distinct screw orientations across three functional occlusal biting scenarios. The stress distributions were analyzed in the screws, bone fragments, articular disc, articular surface, articular tubercle, and mandibular bone. The displacement was also recorded.

While the first orientation (two screws parallel to each other and at 90° to the fracture line) showed the lowest screw stress (anterior: 91.8 MPa; fractured side: 113.7 MPa), the fourth performed best under non-fractured side biting (175.3 MPa). In contrast, the third orientation led to the highest stress on the screws (357.0 MPa). The first and fourth orientations minimized peak stress on the fractured-side condylar surface, whereas the second and third exhibited higher stress concentrations. Interfragmentary displacement remained < 0.06 mm across all orientations, with the first demonstrating superior micromotion control and the lowest bone stress (38.2 MPa).

The first orientation is biomechanically optimal, minimizing hardware stress while maintaining construct stability. The fourth orientation is a viable alternative when surgical access or anatomical constraints exist. Conversely, the third orientation should be avoided due to excessive stress concentrations that predispose the construct to fatigue failure or bone resorption.