OBJECTIVE: To determine the mechanical resistance to traction and flexion of three models of Schanz pins, two of them available in Brazil, and the one proposed in this study: a conic pin with 5.0 mm diameter, 40 mm thread length, 3.2 mm bore, and the one proposed in this paper, with 5.0 mm in diameter, 3.2 mm bore, and 15 mm thread length, in order to show which one is the most effective. METHODS: The authors built 48 test samples divided in six groups, with eight sample per group. Traction strength was tested in groups 1, 2, and 3 using a traction machine manufactured by ITM®. To check flexion strength in groups 4, 5, and 6, they used a bench perforator manufactured by Cardoso® FFC-20 in the pin installation, and then the Universal Assay Machine ZD100PU. RESULTS: In traction tests, the conic pins stood a mean traction of 98.462 kgf, those with uniform long thread (40 mm) 283.70 kgf, and the proposed pins with uniform thread of 15 mm, stood the mean strength of 116.947 kgf. The statistic difference among the groups was not significant. In the flexion test, the conic pins stood a strength of 6.563 kgf, the pins with uniform thread of 40 mm stood the mean strength of 6.177 kgf, and the proposed pins stood the mean strength of 30.275 kgf, there being a significant difference when compared to the previous groups. CONCLUSIONS: The three models of Schanz pins presented equivalent traction strength, and the proposed model - thread length of 15 mm - is significant more resistant to flexion strengths.
External fixators; Bone nails; Material resistance
