Experimental determination of bone cortex holding power of orthopedic screw

Abstract

Cylindrical specimens of bone measuring 15 mm in diameter were obtained from the lateral cortical layer of 10 pairs of femurs and tibias. A central hole 3.2 mm in diameter was drilled in each specimen. The hole was tapped, and a 4.5 mm cortical bone screw was inserted from the outer surface. The montage was submitted to push-out testing up to a complete strip of the bone threads. The cortical thickness and rupture load were measured, and the shear stress was calculated. The results were grouped according to the bone segment from which the specimen was obtained. The results showed that bone cortex screw holding power is dependent on the bone site. Additionally, the diaphyseal cortical bone tissue is both quantitatively and qualitatively more resistant to screw extraction than the metaphyseal tissue.

Validity of synthetic bone as a substitute for osteoporotic cadaveric femoral heads in mechanical testing

“…2 Ranges in the age and degree of osteoporosis of cadaver specimens can also partially account for the variability in mechanical properties. 4,6 Therefore, this variability in the geometric and material properties of cadaveric specimens often requires prohibitively large sample sizes in order to detect statistically significant differences in implant performance.…”

Analysis on the mechanical resistance of fixation of femoral neck fractures in synthetic bone, using the dynamic hip system and an anti-rotation screw

“… 13 , 14 Differences in age and degree of osteoporosis among specimens from cadavers may also partially influence the variability of the mechanical properties. 15 , 16 This variability in geometric and material properties of cadaver specimens frequently requires prohibitively large sample sizes, in order to detect statistically significant differences in implant performance. 17 …”

Evaluation of 2 Cement Techniques for Augmentation of Stripped 1.5 mm Screw Sites in the Distal Metaphysis of Feline Radii

“…Resistance to pullout increases with cortical content and with the diameter of the bone engaged at the implantation site 9,47 . Both of these variables are greater in the radial diaphysis of medium‐to‐large dogs than in the metaphysis of feline radii.…”

“…The torque required to “strip” a screw hole increases linearly with the diameter of the screw 7,8 . Miniscrews are thus predisposed to mechanical stripping, especially when placed in soft metaphyseal bone 9 . This is especially relevant to fractures of the distal aspect of the radius in miniature breeds of dogs and cats: the fracture configuration and bone stock limit the number of screws that can be inserted distal to the fracture site, and minimize the ability to redirect screws if a screw site is stripped 5 .…”