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Scientific Articles   |    
Comparison of CT and MRI for Diagnosis of Suspected Scaphoid Fractures
Wouter Mallee, MSc1; Job N. Doornberg, MD, PhD1; David Ring, MD, PhD2; C. Niek van Dijk, MD, PhD1; Mario Maas, MD, PhD1; J. Carel Goslings, MD, PhD1
1 Departments of Orthopaedic Surgery (W.M. and C.N.v.D.), Radiology (M.M.), and Surgery (J.C.G.), Academic Medical Center of Amsterdam (J.N.D), Meibergdreef 9, 1100 DD Amsterdam, The Netherlands. E-mail address for W. Mallee: woutermallee@hotmail.com
2 Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Yawkey Center, Suite 2100, 55 Fruit Street, Boston, MA 02114
View Disclosures and Other Information
Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants of less than $10,000 from the Marti-Keuning-Eckhardt Foundation. One or more of the authors, or a member of his or her immediate family, received, in any one year, payments or other benefits in excess of $10,000 or a commitment or agreement to provide such benefits from commercial entities (Stryker, Wright Medical, Tornier, Acumed, Biomet, Joint Active Systems, Gerson Lehrman Group, MEDACorp, Skeletal Dynamics, IlluminOss Medical, MiMedx Group, AO North America, and AO International).

A commentary by Scott Mitchell, MD, is available at www.jbjs.org/commentary and is linked to the online version of this article.
Investigation performed at Academic Medical Center of Amsterdam, Amsterdam, The Netherlands

Copyright © 2011 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2011 Jan 05;93(1):20-28. doi: 10.2106/JBJS.I.01523
A commentary by Scott Mitchell, MD, is available here
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Abstract

Background: 

There is no consensus on the optimum imaging method to use to confirm the diagnosis of true scaphoid fractures among patients with suspected scaphoid fractures. This study tested the null hypothesis that computed tomography (CT) and magnetic resonance imaging (MRI) have the same diagnostic performance characteristics for the diagnosis of scaphoid fractures.

Methods: 

Thirty-four consecutive patients with a suspected scaphoid fracture (tenderness of the scaphoid and normal radiographic findings after a fall on the outstretched hand) underwent CT and MRI within ten days after a wrist injury. The reference standard for a true fracture of the scaphoid was six-week follow-up radiographs in four views. A panel including surgeons and radiologists came to a consensus diagnosis for each type of imaging. The images were considered in a randomly ordered, blinded fashion, independent of the other types of imaging. We calculated sensitivity, specificity, and accuracy as well as positive and negative predictive values.

Results: 

The reference standard revealed six true fractures of the scaphoid (prevalence, 18%). CT demonstrated a fracture in five patients (15%), with one false-positive, two false-negative, and four true-positive results. MRI demonstrated a fracture in seven patients (21%), with three false-positive, two false-negative, and four true-positive results. The sensitivity, specificity, and accuracy were 67%, 96%, and 91%, respectively, for CT and 67%, 89%, and 85%, respectively, for MRI. According to the McNemar test for paired binary data, these differences were not significant. The positive predictive value with use of the Bayes formula was 0.76 for CT and 0.54 for MRI. The negative predictive value was 0.94 for CT and 0.93 for MRI.

Conclusions: 

CT and MRI had comparable diagnostic characteristics. Both were better at excluding scaphoid fractures than they were at confirming them, and both were subject to false-positive and false-negative interpretations. The best reference standard is debatable, but it is now unclear whether or not bone edema on MRI and small unicortical lines on CT represent a true fracture.

Level of Evidence: 

Diagnostic Level I. See Instructions to Authors for a complete description of levels of evidence.

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    References

    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Usama Zafar
    Posted on March 19, 2011
    Our Experience at Gold Coast Hospital
    Orthopaedic Registrar
    Gold Coast Hospital, Southport, Australia

    To the Editor:

    Our department serves a population of 700,000. In an average fracture clinic of 50 patients (run daily), around 25% present with snuff box tenderness post fall on an outstretched hand. As a general rule patients with no scaphoid fracture on plain x-rays are seen 2 weeks post injury with new x-rays. Of these around 75% have no scaphoid fracture on plain radiographs taken two weeks post injury. Roughly around 50% of these patients have persistent anatomical snuff box tenderness and are treated by cast immobilization for further four weeks. As the hospital serves a large catchment area, it does not have the capacity to carry out CT and MRI on all such patients. Furthermore patients are reluctant to have CT and MRI performed in private sector due to the costs involved. Counselling such patients to get CT and MRI privately to prove they do or do not have a fracture has proved to be very difficult. Even though loss of income is significantly greater than the cost of having private CT or MRI, we have been unable to convince majority of the patients to get private scans. Similarly the loss of revenue that would be generated by these individuals if they were to return to work earlier is significantly higher than the cost of providing more CT and MRI services.

    Another dimension to this discussion is the need to educate the emergency department regarding what constitutes snuff box tenderness. Frequently it is the junior most doctors who assess these patients and at times report minimal discomfort in the snuff box or distal radius as snuff box tenderness. When they discuss such cases with their senior colleagues, the suggestion of snuff box tenderness no matter how mild, gets treated as a scaphoid fracture. Furthermore once the patient has been told by a doctor that they have scaphoid fracture, it is hard to convince them otherwise.

    We like other observers realize the usefulness of CT or MRI in assessing scaphoid fracture but we are acutely aware that it is not possible in public funded health system to be able to carry out CT and MRI in all suspected scaphoid fractures. Though we do believe that if specific criteria were developed, it would be possible to get CT and MRI on patients meeting those criteria.

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