IF IT LOOKS IN IS IT REALLY IN? INTRA-ARTICULAR SCREW PENETRATION OF THE DISTAL RADIUS – A RADIOLOGICAL STUDY.

Abstract

Aim: Subtle intra-articular screw penetration of the distal radius during fracture fixation is difficult to determine using standard PA and lateral radiographs. The purpose of our study was to determine which radiographs most reliably identify penetration into the joint.

Methods: A distal volar locking plate was applied to an isolated radius bone and a series of plain radiographs taken. The radius, fixed along its long axis, was allowed to rotate through 180 degrees and inclined, in increments, to 40 degrees. In the control group the distal screws did not breach the articular surface. In the study group the screws penetrated the articular surface by 2mm. In each group 65 plain radiographs were taken and the presence or absence of screw penetration scored by two blinded observers.

Results: Using Weighted Kappa analysis the overall inter-observer agreement for all views was 0.5 (CI 0.39–0.63). However in 7 radiographs there was complete inter-observer agreement correctly identifying screw penetration of the articular surface. The articular surface was correctly identified as intact in 13 views. Only a 75 degrees pronated view, without inclination, was 100 % sensitive and specific for identifying the absence or presence of screw penetration through the articular surface.

Conclusion: The intra-operative use of a 75 degrees pronated view may reduce the need for repeated use of the image intensifier and excessive irradiation during plate fixation of distal radius fractures.