The avulsion strength of threaded anchors with 3.5 and 4.5 mm diameter was assessed by using pigs’ frozen fresh femurs as a model and an assay universal machine. The major trochanter was dried and the anchors, mounted with a flexible steel wire for enabling its fixation on the assay machine, were inserted into the spongy bone near femoral head edge, at 30°, 60° and 90° with femoral diaphysis longitudinal axis. The specimens were fixed on the assay machine and traction was continuously applied at a ratio of 1 mm/ minute until assembly failure occurred. Data concerning maximum load applied, load at proportionality limit, stiffness and resiliency were recorded and compared (p<0.05). The results showed that the maximum load, the load at proportionality limit, and the resiliency were significantly higher (p=0.04, p=0.01 and p=0.02, respectively) for 4.5-diameter anchors inserted at 60°, compared to other angles and to 3.5-diameter anchors at any angle. Load at proportionality limit and stiffness were not significantly different for anchors of both diameters and for different insertion angles.
Shoulder; Tensile Strength; Experimental development; Swine
