Biomechanical properties of plate constructs for feline ilial fracture gap stabilization

Vet Surg. 2018 Nov 13. [Epub ahead of print]

OBJECTIVE: To determine the biomechanical properties of plating techniques for comminuted feline ilial fractures.

STUDY DESIGN: Ex vivo study on 40 paired feline hemipelves.

SAMPLE POPULATION: Forty paired fresh-frozen hemipelves that had been collected from 20 cats aged 2-6 years and weighing 4.0-5.5 kg.

METHODS: A transverse 3-mm gap was created in each ilium. Hemipelves were fixed with one of the following methods (n = 10 per group): (1) a dorsal plate and nonlocking screws, (2) a lateral plate and nonlocking screws, (3) a lateral plate and locking screws, or (4) a lateral and dorsal locking compression plate using nonlocking screws. Each specimen was subjected to incremental, sinusoidal cyclic loading until failure, defined as 10-mm displacement. The initial stiffness and number of cycles required to reach 1-, 2-, 5-, and 10-mm axial displacement were statistically analyzed.

RESULTS: The initial stiffness and number of cycles to failure were higher in specimens fixed with double nonlocking plates than in all other fixations (P < .05) except specimens fixed with lateral locking plate at 10-mm displacement (P = .44). Locking implants withstood more cycles to 5- (P < .05) and 10-mm (P < .05) displacement compared with other single-plate nonlocking groups. Screw loosening occurred only in the 3 nonlocking fixations.

CONCLUSION: Double plating improved stiffness and resistance to failure of comminuted feline ilial fracture constructs compared with all other fixations. Single locking plates produced superior constructs compared with single nonlocking constructs.

CLINICAL SIGNIFICANCE: Locking implants are recommended to repair comminuted feline ilial fractures for their extended fatigue life and resistance to screw loosening. Orthogonal plating offers a strong nonlocking alternative.