Axial Biomechanical Performance Evaluation of Locally-developed Modular External Fixator

In the Philippines and other developing countries, access to high-stability external fixators for trauma-induced bone fracture management is limited, as modular external fixators, especially those with snap-on features, are manufactured overseas and are prohibitively expensive for most Filipino patients.

This study aimed to assess the biomechanical performance of a locally-developed modular external fixator prototype for tibial diaphyseal fractures in comparison to available external fixators, such as Roger Anderson and Hoffmann. This provides an initial evaluation for the use of the external fixator as an alternative in terms of its stability.

Using axial compression testing compliant with the ASTM F1541-24 standards, the ultimate strength, yield strength, safe strength, and stiffness were measured across various fixator types and tightening mechanisms, with or without the aid of a wrench. Statistical tools such as the t-test assuming equal variances, one-way analysis of variance, and Tukey-Kramer test with a 0.05 level of significance were used to determine any significant differences.

The mechanical performance of the external fixator prototype increased by a factor of 1.5 to 2.5 after the clamps were tightened with the wrench. However, when hand-tightened, it still performed sufficiently, showing a comparable mechanical performance with the Roger Anderson Fixator. In terms of the ultimate, safe, and yield strengths, it performed competitively in comparison with the Hoffmann system. However, there is a significant difference in stiffness between the prototype and the Hoffmann system.

The locally-developed external fixator was comparable biomechanically to the commercially available external fixators and the prototypes in different studies.