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Evaluation of External Skeletal Fixator Constructs in a Bone Model of the Tibiotarsus of Red-Tailed Hawks (Buteo jamaicensis)
07 August 2019 (online)
Introduction: Acrylic and Fixteur Externe du Service de Sante des Armees (FESSA) have been used as connecting bars in birds for fracture repair. The null hypothesis was there are no differences in torsional properties of the ESF construct between the FESSA and acrylic connecting bars and with a large IM pin/small transfixation pins versus a small IM pin/larger transfixation pins.
Materials and Methods: Delrin bone models were fabricated. Four different combinations of pin size and rod type were studied. The gap model was rotated in torsion at 5 degree/s to failure or to 80 degrees. The effects of external fixator (FESSA, acrylic) and IM/transfixation pin combination (large IM/small transfixation, small IM/large transfixation) on biomechanical properties were assessed using a mixed model analysis of variance. Construct yield was considered clinical failure.
Results: Both FESSA constructs had significantly greater stiffness at yield and mean yield torque than acrylic constructs. None of the FESSA constructs failed but some acrylic constructs did fail.
Discussion/Conclusion: The FESSA with the small IM pin was stiffest at the yield point yet both FESSA constructs had similar biomechanical properties. Acrylic constructs failed by fracture of the acrylic rod at the location of the insertion of the proximal transfixation pin. The FESSA demonstrates additional advantages over acrylic connecting bars. This study demonstrates that the FESSA may be a superior method of fixation for tibiotarsal fracture repair in the avian species.
Acknowledgment: No disclosures. Funded by the Center for Companion Animal Health (CCAH) and the Associate of Avian Veterinarians