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Novel Sigmoid Notch Radiographic View: Evaluating the DRUJ Articular Surface and Preventing Intra-articular Screw Breach
Jason Scott Klein, MD1; David Chen, MD1; Jorge Luis Orbay, MD1; David C. Landy, MD, PhD2; Michael R. Mijares, MD1; Patrick W. Owens, MD1
1Jackson Memorial Hospital/University of Miami, Miami, FL; 2Orthopaedic Surgery, University of Chicago, Chicago, IL

Background: Understanding distal radius fracture patterns and their articular involvement is essential to guiding treatment. The objective of this study is to describe a novel radiographic “sigmoid notch view” to assess for DRUJ screw penetrance and to direct safer screw placement.
Materials/Methods: Distal radius volar locking plates were applied to ten fresh-frozen cadaveric arms. Five cadavers were plated with a distal ulnar locking screw breaching the sigmoid notch and five without a screw violating the DRUJ. A mini-C arm captured PA, sunrise, and "sigmoid notch view" radiographs, which is an axial view obtained with 15-20 degrees of wrist extension. For each cadaver-situation, blinded hand fellowship trained surgeons answered the following questions: does the screw directed towards the sigmoid notch breach the cortex and would you reposition the screw based on your interpretation. P-values for the comparison of sensitivities and specificities across views were calculated with generalized linear mixed models assuming a binary distribution and using a logit-link function. Intraclass correlation coefficients were calculated to assess the interobserver reliability of each view using this same model.
Results: The sensitivity for diagnosing intra-articular breach was 39%, 69%, and 80% for the PA, sigmoid notch, and sunrise views, respectively. The specificity was 76%, 95%, and 95%, respectively. For clinical decision making on when to move the screw, the views had a sensitivity of 65%, 80%, and 83% and specificity of 62%, 80%, and 87%, respectively. The sensitivity for articular grading of the sunrise view was statistically significantly greater than the sigmoid notch view (P=.04) although there was no difference in specificities (P>.99). The sensitivity for screw repositioning of the sunrise view was not statistically significantly different than the sigmoid notch view (P=.21) nor was the difference in specificities (P=.17). Both the sunrise and the sigmoid notch view were superior to the PA view to identify DRUJ breach and to guide clinical decision-making (P<0.01). The intraclass correlation coefficients were 0.31, 0.95, 0.99 for the views, respectively.
Conclusions: Both the sigmoid notch and sunrise views performed well in identifying DRUJ breach and for directing screw repositioning. Based on these results, we recommend that either the sunrise view or the sigmoid notch view (if not both) should be obtained intra-operatively to guide clinical decision-making. Therefore, the novel sigmoid notch view should be added to the surgeon's armamentarium as a valuable tool to help improve sigmoid notch visualization, avoid DRUJ screw penetrance, and prevent unnecessary screw repositioning.

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