Anatomic tilt x-rays of the distal radius: an ex vivo analysis of surgical fixation.

PURPOSE: To compare anatomic tilt radiographs with standard posteroanterior (PA) and lateral radiographs for their efficacy in detecting screw penetration of the distal radius articular surface.

METHODS

Twenty-four cadaveric human forearm specimens had fixation with a dorsal distal radius plate and screws. Three groups were evaluated: (1) no articular surface screw penetration, (2) radial-sided articular screw penetration, and (3) ulnar-sided articular screw penetration. Standard PA and lateral views and anatomic tilt PA and lateral views were taken of each specimen. Three observers reviewed both individual (PA or lateral) and paired (PA and lateral) radiographs. These radiographs were evaluated based on whether or not articular penetration had occurred. A number between 1 and 5 was assigned to represent the degree of certainty of their assessment. The accuracy of the observers was calculated to determine if screw penetration of the articular surface had occurred and, if so, which screw had penetrated the joint. The sensitivity and specificity of each view, interobserver reliability, and the reviewers' confidence in evaluating presence or absence of screw penetration were calculated.

RESULTS

The use of anatomic tilt lateral views significantly improved the overall accuracy, (0.93 vs 0.64), sensitivity (0.98 vs 0.77), and specificity (0.83 vs 0.38) of the detection of articular screw penetration when compared with standard lateral views. PA and lateral anatomic tilt views, when viewed together, significantly improved (p <.001) the accuracy of each observer's determination of the position of the penetrated screw (0.90 vs 0.67). In addition, anatomic tilt views significantly improved the confidence of the reviewers in their more accurate observations (4.7 vs 3.3, p <.05).

CONCLUSIONS

Anatomic tilt PA and lateral radiographs of the distal radius are an accurate and clinically useful tool for the evaluation of both presence and location of screw penetration of the articular surface after dorsal plating.