Abstract
The objective of this study is to determine the intraobserver and interobserver reliability of end vertebra definition and Cobb angle measurement using printed and digital radiographs of 48 patients with scoliosis. The Cobb angle and the end vertebra were assessed by six observers in 48 patients with scoliosis using printed and digital radiographs. Definition of end vertebra and measurement of the Cobb angle was repeated three times with a 3 week interval. Intraclass correlation coefficients (ICC) were used to determine the interobserver and intraobserver reliabilities. 95% prediction limits for the errors in measurements are provided. For the Cobb angle a mean ICC of 0.97 was determined for intra- and interobserver reliability measurement of the printed radiographs. For the electronic radiographs a mean ICC value of 0.93 was determined for interobserver reliability and a mean ICC value of 0.96 for intraobserver reliability. Intraobserver ICC for definition of end vertebrae was 0.8 for both methods. Interobserver ICC was 0.83 for the manual and 0.74 in the digital method. One pitfall in angle measurement implies the Cobb method itself which measures in two dimensions. Until we develop a proper tri-dimensional measuring system an error is introduced. For the Cobb angle measurement the definition of end vertebrae introduces the main source of error. Digital radiography does not improve the measurement accuracy.
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References
Beekmann CE, Hall V (1979) Variability of scoliosis measurement from spinal roentgenograms. Phys Ther 59:764–765
Carman DL, Browne RH, Birch JG (1990) Measurement of scoliosis and kyphosis radiographs. Intraobserver and interobser variation J Bone Joint Surg Am 72(3):328–33
Fleiss JL (1986) Reliability of measurement. In: Fleiss JL (ed) The design and analysis of clinical experiments. Wiley, Toronto, pp 1–32
Geijer H, Beckman K, Jonsson B, Andersson T, Persliden J (2001) Digital radiography of scoliosis with a scanning method: initial evaluation. Radiology 218(2):402–410
Geijer H, Verdonck B, Beckman KW, Andersson T, Persliden J (2003) Digital radiography of scoliosis with a scanning method: radiation dose optimization. Eur Radiol 13(3):543–551 (Epub14 June 2002)
Gross C, Gross M, Kuschner S (1983) Error analysis of scoliosis curvature measurement. Bull Hosp Jt Dis Orthop Inst 43(2):171–177
Lonstein JE, Carlson JM (1984) The prediction of curve progression in untreated idiopathic scoliosis during growth. J Bone Joint Surg Am 66(7):1061–1071
Morrissy RT, Goldsmith GS, Hall EC, Kehl D, Cowie GH (1990) Measurement of the Cobb angle on radiographs of patients who have scoliosis. Evaluation of intrinsic error J Bone Joint Surg Am 72(3):320–327
Oda M, Rauh S, Gregory PB, Silverman FN, Bleck EE (1982) The significance of roentgenographic measurement in scoliosis. J Pediat Orthop 2:378–382
Sevastikoglou JA, Bergquist E (1969) Evaluation of the reliability of radiological methods for registration of scoliosis. Acta Orthop Scand 40:608–613
Shea KG, Stevens PM, Nelson M, Smith JT,Masters KS, Yandow SA (1998) Comparison of manual versus computer-assisted radiographic measurement. Intraobserver measurement variability for Cobb angles. Spine 23(5):551–555
Shrout PE, Fleiss JL (1979) Intraclass correlations: uses in assessing rater reliability. Psychol Bull 86:420–428
Weinstein SL, Ponseti IV (1983) Curve progression in idiopathic scoliosis. J Bone Joint Surg Am 65(4):447–455
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Gstoettner, M., Sekyra, K., Walochnik, N. et al. Inter- and intraobserver reliability assessment of the Cobb angle: manual versus digital measurement tools. Eur Spine J 16, 1587–1592 (2007). https://doi.org/10.1007/s00586-007-0401-3
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DOI: https://doi.org/10.1007/s00586-007-0401-3