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Vancouver General Hospital University of British Columbia, Vancouver, B.C. V5Z 1M9, Canada
We have read with considerable interest the recent article by Cerezal et al. [1], which appeared in the January 2000 issue, about the usefulness of gadolinium in the evaluation of the vascularity of scaphoid nonunions.
We agree with the authors that gadolinium-enhanced MR imaging has a potentially valuable role in the assessment of scaphoid fractures that may extend beyond the use of this technique in the evaluation of nonunions. In a previous study, we sought to evaluate gadolinium-enhanced MR imaging in the assessment of scaphoid fractures, both in the acute setting as well as in chronic fractures [2].
We noted that in the acute setting the proximal pole almost invariably showed considerable diminishment in enhancement compared with that of the distal pole, as might be expected from the vascular supply [2]. We found that in chronic fractures the degree of enhancement of proximal and distal poles gradually equalized. In one of the patients in our study, nonunion progressed to collapse, but this increase in enhancement of the proximal pole was not noted.
In two of our patients with acute fractures, the proximal poles showed more pronounced diminishment of perfusion than the distal pole [2]. In the first patient, the fracture progressed to chronic nonunion requiring bone grafting. In the second patient, evidence of proximal pole necrosis and collapse was seen.
The results of our study [2] as well as those of Cerezal et al. [1] suggest that at least in selected patients, gadolinium-enhanced MR imaging may be helpful in therapeutic decision making. In particular, in patients with established nonunion, the decision to either continue conservative therapy or perform bone grafting or more extensive procedures, such as proximal row carpectomy or placement of prostheses, may be facilitated. In the acute setting, selected patients, such as those at high risk of avascular necrosis (e.g., those with displaced fractures of>1 mm) may benefit from evaluation with a gadolinium-enhanced study [3]. This study may help determine whether conservative therapy should be abandoned and the patient should go directly to surgery. Clearly, further studies with a larger number of patients are required before this algorithm can be firmly established.
References
Hospital Mompía
Mompía (Cantabria), 39100, Spain
Hospital Santa Cruz Liencres (Cantabria), 39120, Spain
Hospital Mompía
Mompía (Cantabria), 39100, Spain
We thank Drs. Munk and Lee for their interest in our article [1]. Certainly, the preliminary results of the study of Munk et al. [2] regarding the potential application of gadolinium-enhanced MR imaging in the assessment of scaphoid fractures reveal interesting possibilities.
We agree that gadolinium-enhanced MR imaging may be useful in selected acute cases such as in displaced fractures or dislocations with a high risk of developing avascular necrosis. We are working on this application of gadolinium-enhanced MR imaging, but our experience is still limited.
Munk et al. [2] also state:
A potentially more important application would be evaluation of patients with chronic fractures who are being considered for surgery. Healing and incorporation of bone graft are likely to be influenced by the degree of vascularity, hence potentially the type of procedure used could be influenced by the degree of vascularity. This would require evaluation of a larger group and assessment of clinical outcomes.
Munk et al. [2] acknowledge the limitations of their study (i.e., small group of patients, absence of correlation with the surgical and clinical outcomes). Therefore, we believe that the usefulness of gadolinium-enhanced MR imaging cannot be determined on the basis of this study in this group of patients. Moreover, they do not report the patchy pattern of vascularization and ischemia of the proximal fragment found by Urban et al. [3] in histologic studies, a finding that we also frequently encountered in our MR examinations.
Our article focuses on the preoperative assessment of the vascular status of the proximal fragment in scaphoid nonunions, a critical issue in the outcome after surgical treatment that is not correctly evaluated using the different imaging methods.
Gross inspection of the exterior surface of the scaphoid during surgery and visualization of the punctate bleeding points served as the gold standard for our study. Most hand surgeons agree with Green [4] that this test is the most accurate way of determining the vascularity of the proximal pole. Nevertheless, Green acknowledged the limitations of intraoperative scrutiny of the punctate bleeding points as the sole criterion of avascular necrosis and the need for a more objective and consistently reproducible method of vascular analysis.
In our series [1], contrast-enhanced MR imaging findings showed a good correlation with the surgical findings, the histologic findings, and the healing of the nonunion. We believe that gadolinium-enhanced MR imaging is the most reliable imaging method for investigating the vascularity of the proximal pole and the healing potential in scaphoid nonunions.
At our institution, gadolinium-enhanced MR imaging is currently included in the diagnostic algorithm of scaphoid nonunions and aids in the clinical decision regarding the surgical procedure.
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