Biomechanical Comparison of Three Different Plate Constructs for Distal Fibula Comminuted Fractures

Research Type: Level 5 - Case report, Expert opinion, Personal observation Introduction/Purpose: Unstable ankle fractures require surgical treatment and the technique of bridge plating can be used for fibular comminuted fractures, where the implant serves as an extramedullary support, fixing the main fragments while leaving the fracture zone undisturbed. The current literature contains numerous biomechanical studies of different types of distal fibular fixation using different types of plate osteosynthesis, such as conventional plate constructs with non-locking or locking screws. Specific studies of comminuted fractures of the distal fibula are rare and usually focus on Weber C fractures. The purpose of this study was to investigate and compare the mechanical stability provided by different plating techniques in comminuted Weber B fibula fractures testing for torsion, axial compression, and lateral bending. Methods: Thirty composite fibulas were divided into three groups (Figure 1A-C): one-third tubular plates (OTP), locking one-third tubular plates (LOTP), and locking distal fibula plates (LDFP). Comminuted fractures were simulated by creating a 3.5 mm gap. Preload was applied prior to each test. Lateral bending stiffness was evaluated by loading until 20 N (Figure 1D). Torsional stiffness was assessed with a loading at 10 degrees/min until 0.4 N·m (Figure 1E). Axial compression stiffness was measured by loading at 0.02 mm/min until 30 N (Figure 1F). Destructive tests for maximum strength were performed using the same setup as the stiffness tests. For maximum torsional strength, a load of 15 degrees/min was applied to failure while maintaining an axial load of 30 N. Maximum lateral bending strength was assessed by applying an increasing load at 10 mm/min until failure. Data were analyzed by one-way analysis of variance with Tukey post hoc test (α=0.05). Results: Torsional stiffness (p < 0.001) and lateral bending stiffness (p < 0.001) were significantly higher for the locking one-third tubular plate (LOTP) group compared to both the locking distal fibula plate (LDFP) and one-third tubular plate (OTP) groups. However, no significant differences were observed in axial compression stiffness (p = 0.08) across the three groups (Figure 2A-C). In terms of maximum force (Figure 2D-E), the LOTP system was significantly higher than the LDFP system for lateral bending (p < 0.01) and showed higher torsional resistance than the OTP system (p < 0.001). However, while the LDFP showed improved maximum load resistance at maximum torque, it did not exhibit significantly better fracture protection during peak loading at lateral bending when compared to the OTP. Conclusion: These results demonstrate that the tested locking one-third tubular plates provide superior stiffness and strength for distal comminuted fibular fractures compared to the non-locking or low-profile locking fibular plates tested. However, it is important to note that mechanical stiffness or peak load to failure alone does not always correlate with clinical outcomes. Most fractures heal without complications, provided the fixation is appropriate for the complexity of the fracture and proper weight bearing and range of motion restrictions are observed. Therefore, while biomechanical factors should guide implant selection, clinical decision-making will require consideration of patient-specific factors, fracture characteristics and plates profiles.