Validity and interobserver agreement of a new radiographic grading system for intervertebral disc degeneration: Part I. Lumbar spine

Many different radiographic grading systems for disc degeneration are described in literature. However, only a few of them are tested for interobserver agreement and none for validity. Furthermore, most of them are based on a subjective terminology. The aim of this study, therefore, is to combine these systems to a new one in which all subjective terms are replaced by more objective ones and to test this new system for validity and interobserver agreement. Since lumbar and cervical discs need to be graded differently, this study was divided into the present Part I for the lumbar and a Part II for the cervical spine. The new radiographic grading system covers the three variables "Height Loss", "Osteophyte Formation" and "Diffuse Sclerosis". On lateral and postero-anterior radiographs, each of these three variables first has to be graded individually. Then, the "Overall Degree of Degeneration" is assigned on a four-point scale from 0 (no degeneration) to 3 (severe degeneration). For validation, the radiographic degrees of degeneration of 44 lumbar discs were compared to the respective macroscopic ones, which were defined as "real" degrees of degeneration. The agreement between observers with different levels of experience was determined using the radiographs of 84 lumbar discs. Agreement was quantified using quadratic weighted Kappa coefficients (Kappa) with 95% confidence limits (95% CL). The validation of the new radiographic grading system revealed a substantial agreement between the radiographic and the "real" macroscopic overall degree of degeneration (Kappa=0.714, 95% CL: 0.587-0.841). The radiographic grades, however, tended to be slightly lower than the "real" ones. The interobserver agreement was substantial for all the three variables and for the overall degree of degeneration (Kappa=0.787, 95% CL: 0.702-0.872). However, the inexperienced observer tended to assign slightly lower degrees of degeneration than the experienced one. In conclusion, we believe that the new radiographic grading system is an almost objective, valid and reliable tool to quantify the degree of degeneration of individual lumbar intervertebral discs. However, the user should always remember that the "real" degree of degeneration tends to be underestimated and that slight differences between the ratings of observers with different levels of experience have to be expected.

[1]  G B Andersson,et al.  The Effect of Disc Degeneration and Facet Joint Osteoarthritis on the Segmental Flexibility of the Lumbar Spine , 2000, Spine.

[2]  B. Flannigan,et al.  Magnetic Resonance Imaging in the Diagnosis of Disc Degeneration: Correlation with Discography , 1987, Spine.

[3]  B. Vernon‐roberts,et al.  Degenerative changes in the intervertebral discs of the lumbar spine and their sequelae. , 1977, Rheumatology and rehabilitation.

[4]  J. Cauley,et al.  Degenerative lumbar listhesis and bone mineral density in elderly women. The study of osteoporotic fractures. , 1999, Spine.

[5]  Keita Ito,et al.  Correlation of radiographic and MRI parameters to morphological and biochemical assessment of intervertebral disc degeneration , 2005, European Spine Journal.

[6]  K. Schellhas,et al.  Cervical Discogenic Pain: Prospective Correlation of Magnetic Resonance Imaging and Discography in Asymptomatic Subjects and Pain Sufferers , 1996, Spine.

[7]  S. Madan,et al.  Interobserver error in interpretation of the radiographs for degeneration of the lumbar spine. , 2003, The Iowa orthopaedic journal.

[8]  J. Kellgren,et al.  Rheumatism in Miners. Part II: X-ray Study , 1952 .

[9]  M Kormano,et al.  Disc degeneration in magnetic resonance imaging. A comparative biochemical, histologic, and radiologic study in cadaver spines. , 1991, Spine.

[10]  Jacob Cohen,et al.  The Equivalence of Weighted Kappa and the Intraclass Correlation Coefficient as Measures of Reliability , 1973 .

[11]  Z. Friedenberg,et al.  DEGENERATIVE DISC DISEASE OF THE CERVICAL SPINE. , 1963, The Journal of bone and joint surgery. American volume.

[12]  J. Kellgren,et al.  Radiological Assessment of Osteo-Arthrosis , 1957, Annals of the rheumatic diseases.

[13]  Lindsay J. Rowe,et al.  Degenerative Diseases of the Vertebral Column , 1985, Radiology.

[14]  W. Frobin,et al.  Precision measurement of disc height, vertebral height and sagittal plane displacement from lateral radiographic views of the lumbar spine. , 1997, Clinical biomechanics.

[15]  W. Frobin,et al.  Height of lumbar discs measured from radiographs compared with degeneration and height classified from MR images , 2001, European Radiology.

[16]  P. Dangerfield,et al.  Quantitative analysis of diurnal variation in volume and water content of lumbar intervertebral discs , 1998, Clinical anatomy.

[17]  T J Masaryk,et al.  Degenerative disk disease: assessment of changes in vertebral body marrow with MR imaging. , 1988, Radiology.

[18]  P Brinckmann,et al.  An Improved Method of Stature Measurement for Quantitative Determination of Spinal Loading: Application to Sitting Postures and Whole Body Vibration , 1992, Spine.

[19]  M. Nevitt,et al.  Reliability of new indices of radiographic osteoarthritis of the hand and hip and lumbar disc degeneration. , 1993, The Journal of rheumatology.

[20]  C. Pfirrmann,et al.  Magnetic Resonance Classification of Lumbar Intervertebral Disc Degeneration , 2001, Spine.

[21]  J. S. Lawrence,et al.  The Epidemiology of Chronic Rheumatism , 1964 .

[22]  P. Brinckmann,et al.  Vertebral height, disc height, posteroanterior displacement and dens-atlas gap in the cervical spine: precision measurement protocol and normal data. , 2002, Clinical biomechanics.

[23]  A. Baert,et al.  Radiological prevalence of lumbar intervertebral disc calcification in the elderly: an autopsy study , 1996, Skeletal Radiology.

[24]  M M Panjabi,et al.  Disc Degeneration Affects the Multidirectional Flexibility of the Lumbar Spine , 1994, Spine.

[25]  E. Baader.  [Rheumatism in miners]. , 1951, Zeitschrift fur Rheumaforschung.

[26]  H. Paajanen,et al.  Age-related MRI changes at 0.1 T in cervical discs in asymptomatic subjects , 2004, Neuroradiology.

[27]  C. Hirsch,et al.  Anatomical and Clinical Studies on Lumbar Disc Degeneration , 1949 .

[28]  Paul Clopton,et al.  Intervertebral disk calcification of the spine in an elderly population: radiographic prevalence, location, and distribution and correlation with spinal degeneration. , 2004, Radiology.

[29]  Ken Yong-Hing,et al.  Apophysial Joint Degeneration, Disc Degeneration, and Sagittal Curve of the Cervical Spine: Can They Be Measured Reliably on Radiographs? , 1997, Spine.

[30]  D. Ogilvie-Harris,et al.  In Vivo Diurnal Variation in Intervertebral Disc Volume and Morphology , 1994, Spine.

[31]  J. R. Landis,et al.  The measurement of observer agreement for categorical data. , 1977, Biometrics.

[32]  Christoph Weiler,et al.  Classification of Age-Related Changes in Lumbar Intervertebral Discs: 2002 Volvo Award in Basic Science , 2002, Spine.

[33]  King H. Yang,et al.  Mechanism of Disc Rupture: A Preliminary Report , 1991, Spine.

[34]  W. Hutton,et al.  The stages of disc degeneration as revealed by discograms. , 1986, The Journal of bone and joint surgery. British volume.

[35]  C. Silberstein.  The Evolution of Degenerative Changes in the Cervical Spine and an Investigation into the “Joints of Luschka”* , 1965, Clinical orthopaedics and related research.

[36]  Jh. Kellgren.  Radiological assessment of osteoarthrosis , 1957 .

[37]  The pathology of articular and spinal diseases , 1949 .

[38]  H. Farfan,et al.  Mechanical disorders of the low back , 1973 .

[39]  Hans-Joachim Wilke,et al.  Review of existing grading systems for cervical or lumbar disc and facet joint degeneration , 2006, European Spine Journal.

[40]  M. B. Coventry,et al.  THE INTERVERTEBRAL DISC: ITS MICROSCOPIC ANATOMY AND PATHOLOGY , 1945 .

[41]  J. P. Thompson,et al.  Preliminary Evaluation of a Scheme for Grading the Gross Morphology of the Human Intervertebral Disc , 1990, Spine.