Biomechanical evaluation of strength and stiffness of 2.0 mm and 1.5 mm locking plates with various screw configurations on rabbit tibias.

OBJECTIVE

The objective of this study was to compare the strength and stiffness of 1.5 mm and 2.0 mm locking plates with various screw fixation configurations applied to the tibia bones of rabbits.

ANIMAL: Oryctolagus cuniculus (domesticated rabbits).

PROCEDURE: Twenty-five rabbit tibias were randomly assigned to one of five groups. Control bones remained intact, whereas all others were osteotomized to create contact fracture models that were fixated with 2.0 mm locking screws or 1.5 mm locking screws applied to locking plates (LP) in either 4-screw or 6-screw configurations and tested in 4-point bending until failure. Load-deformation curves were generated for each sample and used to calculate stiffness (slope of the curve within the area of elastic deformation) and strength (load to failure).

RESULTS

Intact controls had greater strength and stiffness than any LP fixation. The 1.5mm 4-screw LP construct and the 2.0mm 4-screw LP construct were significantly stronger than the corresponding 6-hole constructs but were not as strong as the intact tibia. The 2.0mm 4-hole LP construct had the stiffest construct and was significantly stiffer than the corresponding 6-hole constructs but was not as stiff as the intact tibia.

CONCLUSION

Fracture fixation with a 2.0 mm 4 screw LP would provide the greatest strength and stiffness in tibial fracture repairs in the rabbit.

CLINICAL RELEVANCE: This project will provide veterinary surgeons with more objective data needed to make the best clinical decisions when surgically repairing fractures in the tibia of rabbits.