PLATE FIXATION OF MID-SHAFT CLAVICLE FRACTURES: A BIOMECHANICAL COMPARISON OF UNICORTICAL, BICORTICAL, LOCKING AND NONLOCKING OPTIONS

Abstract

Background and Aims: Plate fixation of acute mid-shaft clavicle fractures is becoming increasingly popular. However limb and life threatening complications such as injury to the subclavian vessels have been reported. One possible solution to reduce the risk of this complication is the use of unicortical screw fixation.

The aim of this study was to compare biomechanical properties of pre-contoured plate fixation using different screw fixation modes in a mid-shaft clavicle fracture model.

Methods: Fourth generation biomechanical clavicle sawbones with a mid-shaft osteotomy were plated in one of three modes: nonlocking bicortical, locking bicortical and locking unicortical mode. The specimens were then tested to failure in four-point bending and pull-off tests.

Results: Failure due to fracture through the sawbone was more common in nonlocking bicortical mode while plate bending was more common in the locking bicortical group. The ultimate load at failure was significantly lower in the locking bicortical group compared to the nonlocking bicortical group, however there was no significant difference between the locking unicortical group and nonlocking bicortical group.

In the pull-off tests 100% of nonlocking bicortical and locking bicortical plates failed by fracture of the sawbone. 100% of the locking unicortical plates failed by plate and screw pull-off from the sawbone. The load at failure was highest for the locking unicortical plate but this was not significantly different to the other groups.

Conclusion: This study shows that specimens fixed with locking unicortical screw fixation withstood comparable or superior loads in four-point bending and pull-off test when compared to nonlocking bicortical and locking bicortical screw fixation. In addition both locking screws and unicortical screws appear to provide a protective effect against periprosthetic sawbone fracture. Locking unicortical screw fixation of pre-contoured plates may be a viable alternative in the fixation of mid-shaft clavicle fractures.