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Updated: May 11, 2026
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Adjustable Stiffness, External Fixator for the Rat Femur Osteotomy and Segmental Bone Defect Models
Published on: October 9, 2014
In vitro biomechanical testing of a micro external skeletal fixator
1Dr. med. vet. Ramona Deiss, Bahnhofstrasse 56, 3127 Mühlethurnen, Switzerland, Phone: +41 79 786 86 32,
Summary
The Universal Micro External Fixator (UMEX) system offers a valid alternative for treating fractures in small animals, demonstrating competitive stiffness and requiring less space than the IMEX External Skeletal Fixation (SK) system.
Area of Science:
- Biomechanical testing
- Veterinary orthopedics
- Small animal surgery
Background:
- External fixation is crucial for stabilizing fractures in small animals.
- Existing systems may have limitations in terms of size and pin placement.
- The Universal Micro External Fixator (UMEX) system is a newer alternative.
Purpose of the Study:
- To biomechanically evaluate three Universal Micro External Fixator (UMEX) configurations.
- To compare UMEX to the IMEX External Skeletal Fixation (SK) system.
- To assess stiffness, pin placement space, and weight for small animal fracture treatment.
Main Methods:
- Tested three UMEX configurations (Ia, Ib, II modified) and one SK configuration (Ia).
- Stabilized Delrin rods in a 1 cm fracture gap model.
- Evaluated constructs under axial compression, craniocaudal bending, mediolateral bending, and torsion.
Main Results:
- UMEX type II modified was significantly stiffer than other UMEX and SK, except in craniocaudal bending where SK was superior.
- UMEX constructs were lighter and required less space for pin placement than SK.
- UMEX type Ia was the weakest configuration tested.
Conclusions:
- More complex constructs generally offer superior stiffness.
- The UMEX system is a viable option for treating long-bone fractures in very small animals.
- UMEX provides advantages in space and weight compared to the SK system.
