Effect of screw insertion angle and speed on the incidence of transcortical fracture development in a canine tibial diaphyseal model.

OBJECTIVE

To assess the incidence of transcortical fracture (TCF) development based on screw insertion angle and screw insertion speed.

STUDY DESIGN

Cadaveric experimental study.

SAMPLE POPULATION

Sixty-six canine tibiae.

METHODS

Sixty-six cadaveric tibiae were randomly assigned to one of six groups that varied based on screw insertion angle relative to the pilot hole (0, 5, or 10°) and screw insertion speed (650 or 1350 revolutions per minute [rpm]). Each tibia was mounted in a custom jig. Locking self-tapping screws (3.5 mm) were inserted at varying speeds and insertion angles, based on group assignment. Orthogonal radiographs were evaluated for TCFs. Fisher's exact tests with a Bonferroni correction were performed to evaluate differences in the frequency of TCF between groups.

RESULTS

In Group A (0°/650 rpm: control), a 0% TCF rate was observed (n = 0/80). Group B (5°/650 rpm) had a 3.75% TCF rate (n = 3/80). Group C (10°/650 rpm) had a 12.5% TCF rate (n = 10/80). Group D (10°/hand insertion) had a 3.75% TCF rate (n = 3/80). Group E (10°/1350 rpm) had a 17.5% TCF rate (n = 14/80). Group F (0°/1350 rpm) had a 0% TCF rate (n = 0/80). Groups C and E had the highest TCF rates with a difference in TCF rates observed between the control group and Group C (p = .001) and between the control group and Group E (p < .001).

CONCLUSION

Increased screw insertion angle and insertion speed appear to be predisposing factors for TCF development in cadaveric bone.

CLINICAL SIGNIFICANCE

Ensuring screw insertion is coaxial with the pilot hole and using slower screw insertion speeds may help reduce the risk of TCF development.