Perpendicular pull-out force of locking versus non-locking plates in thin cortical bone using a canine mandibular ramus model.

Objective: To compare the holding strength of a conventional plate-screw construct with a locking plate-screw construct in the thin cortical bone of the canine mandibular ramus.

Study Design: Mechanical study.

Animals: Paired cadaveric canine mandibles (n = 10 pairs).

Methods: Perpendicular pull-out testing was performed on 2.0-mm limited-contact dynamic compression plate (LC-DCP)-screw constructs and 2.0-mm string-of-pearls (SOP) plate-screw constructs applied to the ramus of the canine mandible. Pull-out force was applied perpendicular to the long axis of the plates. Construct stiffness and load at failure were determined from load-displacement curves and method of failure was determined from high speed digital video recordings. A paired t-test was used to compare mean construct stiffness and load at failure between groups.

Results: SOP plate-screw constructs had a significantly higher mean construct stiffness and load at failure than did LC-DCP-screw constructs. LC-DCP constructs failed by screw pull-out while bone slicing and fracture were prominent mechanisms of failure for SOP constructs.

Conclusions: SOP plate-screw constructs sustained a significantly higher perpendicular load at failure than did LC-DCP-screw constructs.