Evaluation of Canine Fracture Fixation Bone Plates

Tacvorian, Edward

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Evaluation of Canine Fracture Fixation Bone Plates

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The understanding of bone healing and principles of fracture fixation have improved greatly over the past fifty years. Plating systems are ideal for use in fracture fixation as they facilitate direct and indirect bone healing due to the stability they provide at the fracture site. Their main failure mode, however, is through fatigue from the consistent loading and unloading of the plated bone when healing. The goal of this study was to evaluate the mechanical properties of the most prominent veterinary plating systems representing a comminuted fracture when mated to a bone model. These assemblies were loaded to acute failure in four-point bending and cycled in torsion to mimic fatigue loading. Based on the analyzed test data we are able to make a number of conclusions. After performing four-point bending tests, the String Of Pearls (SOP) system sustained the highest bending mechanical properties with a bending stiffness of 80.4±12.5 N/mm, bending structural stiffness of 8.7±1.4 N-m2, and bending strength of 11.6±1.7 N-mm. The Advanced Locking Plate System #10 (ALPS10) sustained the lowest bending mechanical properties with a bending stiffness of 40.0±1.9 N/mm, bending structural stiffness of 4.3±0.2 N-m2, and bending strength of 5.1±1.2 N-mm. Analysis of the cyclic fatigue data allow us to conclude that the Dynamic Compression Plate (DCP) system is able to maintain the highest absolute torque value across 15,000 torsion cycles and Fixin the lowest. This translates to 5.4±0.7 N-m and 3.5±0.4 N-m, respectively, when analyzed with Dixon-Mood equations and 5.4±2.5±N-m and 3.5±1.3 N-m, respectively, when analyzed with probability plots. In addition, the ALPS10 system is able to maintain the highest percentage of its failure torque and SOP the lowest. This translates to 76.4±16.3% and 43.6±5.3%, respectively, when analyzed with Dixon-Mood equations, and 72.9±28.6% and 44.2±22.1% when analyzed with probability plots. To aid in proper fracture healing, plating systems offering reduced or no contact with bone when applied in addition to screw holes across the entire plate length are preferred. The results of this evaluation are a start to better understanding plating system mechanics, which to develop further, will require further fatigue life testing in both loading conditions.

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