Clin Orthop Surg.  2010 Mar;2(1):8-12. 10.4055/cios.2010.2.1.8.

Inter- and Intra-observer Variability of a Cervical OPLL Classification Using Reconstructed CT Images

• Chang H
• Kong CG
• Won HY
• Kim JH
• Park JB

• KMID: 1110343
• DOI: http://doi.org/10.4055/cios.2010.2.1.8

Abstract

BACKGROUND: The lateral radiograph-based system described by Tsuyama is used widely to classify ossification of the posterior longitudinal ligament (OPLL) of the cervical spine. However, OPLL is a complex 3-dimensional (3-D) lesion, not a simple and uniplanar one, which is often difficult to identify on a lateral radiograph. Furthermore, its reliability among spine surgeons has not been investigated. Given the popularity of a reconstructed computed tomography (CT), this study examined the inter- and intra-observer reliability of lateral radiograph-based OPLL classification using that modality.
METHODS
Five spine surgeons independently reviewed the lateral radiograph, axial CT, 2-D (sagittal) and 3-D reconstructed CT images of 108 OPLL patients on 2 separate occasions. Based on these images, the reviewers classified each OPLL case according to the Tsuyama's system. The kappa values were used to assess the statistical reliability.
RESULTS
The inter- and intra-observer kappa values were only 0.51 and 0.67 for the lateral radiograph, even in combination with the axial CT images, 0.70 and 0.85 for 2-D CT images, and 0.76 and 0.86 for 3-D CT images, respectively. These kappa values showed a good-to-excellent range for the 2-D and 3-D reconstructed CT images while those of the lateral radiograph indicated a fair range. According to the OPLL types, the inter- and intra-observer reliability was low in the continuous type and high in the circumscribed type on the lateral radiograph. However, the low reliability of the continuous type on lateral radiograph was overcome somewhat using 2-D and 3-D reconstructed CT images.
CONCLUSIONS
The inter- and intra-observer kappa values were only 0.51 and 0.67 for the lateral radiograph, even in combination with the axial CT images, 0.70 and 0.85 for 2-D CT images, and 0.76 and 0.86 for 3-D CT images, respectively. These kappa values showed a good-to-excellent range for the 2-D and 3-D reconstructed CT images while those of the lateral radiograph indicated a fair range. According to the OPLL types, the inter- and intra-observer reliability was low in the continuous type and high in the circumscribed type on the lateral radiograph. However, the low reliability of the continuous type on lateral radiograph was overcome somewhat using 2-D and 3-D reconstructed CT images.

Keyword

Ossification of the posterior longitudinal ligament; Classification; Reliability; Computed tomography

MeSH Terms

Adult
Aged
Cervical Vertebrae/radiography
Female
Humans
Image Processing, Computer-Assisted
Male
Middle Aged
Observer Variation
Ossification of Posterior Longitudinal Ligament/*classification/*radiography
*Tomography, X-Ray Computed

Figure

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  Fig. 1 Sixty-one-yr-old male patient presented with the typical clinical symptoms of cervical myelopathy due to ossification of the posterior longitudinal ligament (OPLL). Most reviewers classified this case into the continuous type OPLL extending C1 to C7 using the lateral radiograph in combination with the axial CT images (A). However, the 2-dimensional (2-D) and 3-D CT reconstructed images showed an interrupted OPLL at the C4-C5 disc level (arrow) (B). Most of the reviewers re-classified this case into the mixed type OPLL extending C1 to C7 using the reconstructed CT images.

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