Avascular necrosis (AVN) of the proximal fragment in scaphoid nonunion: is intravenous contrast agent necessary in MRI?

PURPOSE

The purpose of this prospective study is to assess the diagnostic value of intravenously applied contrast agent for diagnosing osteonecrosis of the proximal fragment in scaphoid nonunion, and to compare the imaging results with intraoperative findings.

MATERIALS AND METHODS

In 88 patients (7 women, 81 men) suffering from symptomatic scaphoid nonunion, preoperative MRI was performed (coronal PD-w FSE fs, sagittal-oblique T1-w SE nonenhanced and T1-w SE fs contrast-enhanced, sagittal T2*-w GRE). MRI interpretation was based on the intensity of contrast enhancement: 0 = none, 1 = focal, 2 = diffuse. Intraoperatively, the osseous viability was scored by means of bleeding points on the osteotomy site of the proximal scaphoid fragment: 0=absent, 1 = moderate, 2 = good.

RESULTS

Intraoperatively, 17 necrotic, 29 compromised, and 42 normal proximal fragments were found. In nonenhanced MRI, bone viability was judged necrotic in 1 patient, compromised in 20 patients, and unaffected in 67 patients. Contrast-enhanced MRI revealed 14 necrotic, 21 compromised, and 53 normal proximal fragments. Judging surgical findings as the standard of reference, statistical analysis for nonenhanced MRI was: sensitivity 6.3%, specificity 100%, positive PV 100%, negative PV 82.6%, and accuracy 82.9%; statistics for contrast-enhanced MRI was: sensitivity 76.5%, specificity 98.6%, positive PV 92.9%, negative PV 94.6%, and accuracy 94.3%. Sensitivity for detecting avascular proximal fragments was significantly better (p<0.001) in contrast-enhanced MRI in comparison to nonenhanced MRI.

CONCLUSION

Viability of the proximal fragment in scaphoid nonunion can be significantly better assessed with the use of contrast-enhanced MRI as compared to nonenhanced MRI. Bone marrow edema is an inferior indicator of osteonecrosis. Application of intravenous gadolinium is recommended for imaging scaphoid nonunion.