The Journal of Bone and Joint Surgery (American). 2006;88:106-112.
doi:10.2106/JBJS.D.02834
© 2006 The Journal of Bone and Joint Surgery, Inc.
Reliability and Reproducibility of Dens Fracture Classification with Use of Plain Radiography and Reformatted Computer-Aided Tomography
Lance Barker, BS1,
James Anderson, MD1,
Randall Chesnut, MD1,
Gary Nesbit, MD1,
Tjhi Tjauw, MD1 and
Robert Hart, MD, MA1
1 Departments of Orthopaedics and Rehabilitation (L.B. and R.H.), Radiology
(J.A., G.N., and T.T.), and Neurosurgery (R.C.), Oregon Health and Science
University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97239. E-mail
address for R. Hart:
hartro{at}ohsu.edu
Investigation performed at the Departments of Orthopaedics and
Rehabilitation, Radiology, and Neurosurgery, Oregon Health and Science
University, Portland, Oregon
The authors did not receive grants or outside funding in support of their
research for or preparation of this manuscript. They did not receive payments
or other benefits or a commitment or agreement to provide such benefits from a
commercial entity. No commercial entity paid or directed, or agreed to pay or
direct, any benefits to any research fund, foundation, educational
institution, or other charitable or nonprofit organization with which the
authors are affiliated or associated.
Background: The classification system of dens fractures by Anderson
and D'Alonzo has been widely used in clinical studies. Of the three types of
fractures, Type II and Type III are of particular importance because the
distinction between them may affect treatment decisions. The purposes of this
study were to assess whether this classification is reliable and reproducible
and to determine whether computed tomography can improve its reliability and
reproducibility.
Methods: Plain radiographs and spiral computed tomography images of
dens fractures in eleven patients were assessed, and the fractures were
assigned a classification of Type II or Type III at two readings, separated by
six months, by two spine surgeons and three neuroradiologists. Kappa
coefficients of agreement between the raters as well as the reproducibility of
the classifications made by the individual raters were calculated
independently for the fracture classifications based on the plain radiographs
and those based on the reformatted computed tomography scans.
Results: The kappa coefficient for classifications based on plain
radiographs was 0.30 and 0.25 (fair agreement) at the first and second
readings, respectively. For classifications based on computed tomography
scans, the corresponding kappa coefficients were 0.46 (moderate agreement) and
0.67 (substantial agreement). The kappa coefficients for intrarater
reliability among the five raters averaged 0.56 (moderate agreement) when
computed tomography scans were used and 0.28 (fair agreement) when plain
radiographs were used.
Conclusions: Substantial variation with regard to the classification
of dens fractures was found within our group of raters. Greater agreement
occurred when reformatted computed tomography scans rather than plain
radiographs were used as the basis for classification. When classifying dens
fractures according to the system of Anderson and D'Alonzo, one should
consider using reformatted computed tomography scans and reaching a consensus
with multiple raters.

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