Pullout strength variance among self-tapping screws inserted to different depths.
The cortical self-tapping screw (STS) has replaced the non-STS as an aid in fracture fixation. In a recent biomechanical investigation, Berkowitz and colleagues found that STS pullout strength increased with insertion depth up to 1 mm past the far cortex only. In the present study, we wanted to apply a standardized protocol of assessing pullout strength to STSs of different compositions and manufacturers while eliminating the sample-size and block-variance issues that affected the previous investigation. Ninety STSs were randomly divided into 5 groups, each representing a different insertion depth. Peak force was determined with trials ending in screw pullout or failure. A statistically significant difference in pullout strength was identified with insertion depths up to 1 mm past the far cortex. No block variance was detected. These results support the recommendation that STSs be inserted only 1 mm past the far cortex in healthy cortical bone.
Schoenfeld
Andrew
A
Harvard Medical School/Brigham and Women's Hospital, Boston, MA 02215, USA. ajschoen@neucom.edu
Vrabec
Gregory
G
Battula
Suneel
S
Salvator
Ann
A
Njus
Glen
G
D001696:Biomechanical Phenomena; D001863:Bone Screws; D018786:Bone Substitutes; D004867:Equipment Design; D019544:Equipment Failure Analysis; D004869:Equipment Safety; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D008422:Materials Testing; D008954:Models, Biological; D015999:Multivariate Analysis; D011336:Probability; D011897:Random Allocation; D012680:Sensitivity and Specificity; D033081:Shear Strength; D013314:Stress, Mechanical
D018786:Bone Substitutes