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Updated: Jul 9, 2026
Adjustable Stiffness, External Fixator for the Rat Femur Osteotomy and Segmental Bone Defect Models
Published on: October 9, 2014
Comparison of two systems for tibial external fixation in rabbits
R H Meffert1, J E Tis, S Lounici
1Department of Orthopaedic Surgery, Johns Hopkins University, Baltimore, Maryland 21205-2196, USA.
Background And Purpose:
Use of rabbits in orthopedic investigations is common. In this study, focus is on factors that influence bone healing and on distraction osteogenesis. Biomechanical characteristics of two external fixator systems (Orthofix device and Hoffmann device) for long bones were tested.
Methods:
Twelve freshly dissected tibiae were obtained from six skeletally mature New Zealand White rabbits, and four-point bending stiffness in two planes (90 and 180 degrees to the fixator pins) and torsional stiffness and strength of the bone-fixator complex were evaluated by use of a material testing machine.
Results:
In four-point bending, Orthofix device had higher stiffness and strength, compared with Hoffmann device. When the load was applied 180 degrees to the pins, both devices had higher stiffness, compared with that at 90 degrees. In torsional testing, Orthofix device had significantly higher stiffness and strength.
Conclusions:
Significant differences in structural properties between the two systems were evident. Loading direction and gap conditions were important factors in determining properties of the systems. Therefore, type of external fixation system and fixation technique should be considered when designing experiments, using the rabbit long bone model.
