rrmann , MD
Purpose:To compare the accuracy of dynamic gadolinium-enhanced magnetic resonance (MR) imaging with that of standard MR imaging for assessing the viability of the proximal pole of the scaphoid in patients with nonunion.
Materials and Methods:The study protocol was submitted to the institutional review board, and the need to obtain additional approval was waived for this retrospective study. Twenty-eight patients (mean age 6 standard deviation, 24.3 years 6 6.4) with nonunion of a scaphoid fracture underwent dynamic gadolinium-enhanced MR imaging of the wrist 28 days 6 19 before surgery. Dynamic gadolinium-enhanced MR imaging consisted of acquisition of 40 consecutive coronal T1-weighted images over 1 minute. Two readers retrospectively evaluated MR images obtained with a standard protocol and rated the viability of the proximal scaphoid pole. The steepest upslope of gadolinium uptake was calculated in a region of interest placed in the proximal scaphoid pole by a third reader. Receiver operating characteristic curves were calculated, and the areas under the receiver operating characteristic curve ( A z values) were compared. Diagnostic performance in determining scaphoid viability was calculated for readers 1 and 2. Histologic fi ndings in 11 patients and surgical fi ndings in all patients served as the standard of reference.
Results:The sensitivity, specifi city, and accuracy of standard MR imaging in the detection of scaphoid necrosis were 54%, 93%, and 75%, respectively, for reader 1 and 62%, 93%, and 78% for reader 2. Interreader reliability was excellent ( k = 0.92). The A z was 0.82 for reader 1 and 0.87 for reader 2. The diagnostic performance of dynamic gadolinium-enhanced MR imaging, determined with the steepest upslope value, was inferior to that of standard MR imaging, with an A z of 0.57. Findings at histologic examination (viable bone, necrotic bone, callus formation) did not correlate with those at dynamic gadolinium-enhanced MR imaging.
Conclusion:Because the diagnostic performance of dynamic gadoliniumenhanced MR imaging in the evaluation of scaphoid viability was inferior to that of a standard MR imaging protocol, dynamic acquisition may not be needed in patients with nonunion of scaphoid fractures.q RSNA, 2011