TRIPOD FIXATION OF RADIAL NECK FRACTURES

Abstract

Introduction: In the past, displaced radial neck fractures have been treated either by excision, prosthetic replacement or internal fixation with a plate and screws. More recent studies have investigated less invasive fixation constructs using two crossed obliquely orientated screws within the radial neck. A new ‘tripod’ technique using three crossed screws has been proposed and was tested to evaluate whether it has at least equivalent stiffness and strength to fixation with a T-plate.

Methods: Twenty composite sawbones with an axially stable simulated radial neck fracture were fixed either with the tripod technique (three crossed 2.3mm screws) or with a 2.3mm T-plate. The specimens were tested for stiffness at 10 N load in three directions (anteroposterior (AP), ulnar-radial (UR) and eccentric axial (EA)) and load to yield and ultimate failure. The modes of failure of fixation were also evaluated.

Results: The tripod had significantly higher stiffness than the T-plate in AP loading (168 N/mm vs 95 N/mm, p=0.006) and trended to superior stiffness in UR loading (121 N/mm vs 77 N/mm, p=0.06). Both constructs were highly stiff in EA compression (513 N/mm vs 638 N/mm). The strength to yield and failure was significantly higher for the tripod in both AP loading (yield: 432 N vs 36 N, failure: 467 N vs 143 N, p< 0.001) and UR loading (yield: 444 N vs 36N, failure: 444N vs 76 N, p< 0.001). The T-plates failed by screw cut-out and subsequent plastic deformation of the plate. The tripod constructs did not fail at the load required to cause brittle fracture in the sawbone specimen, remote to the site of fixation.

Conclusions: The tripod technique is a biomechanically sound construct for the fixation of axially stable radial neck fractures and thus further clinical research to evaluate the clinical application of this technique is justified.