Rheumatology 2000; 39: 310-315
© 2000 British Society for Rheumatology
A comparison of three methods for measuring thoracic kyphosis: implications for clinical studies
1 Centre for Musculoskeletal Studies, UDS, The University of Western Australia,
2 Medical Technology & Physics, Sir Charles Gairdner Hospital, Western Australia,
3 University Department of Medicine, The University of Western Australia and Royal Perth Hospital, Western Australia and
4 Department of Imaging Services, Royal Perth Hospital, Western Australia, Australia
Objectives. To compare the Cobb technique for measuring kyphosis with an alternative Cobb method and a computer-assisted curve assessment technique, and to examine the influence of vertebral body and disc shape on kyphosis.
Methods. Kyphosis measurements were derived from 93 lateral spinal radiographs or sagittal computed tomography images of cadaveric spines, using: (i) a computer-assisted method for estimating radius of curvature; (ii) the traditional Cobb method; and (iii) an alternative Cobb method. Regression models were applied for agreement analyses, and to examine the relative contribution of vertebral body and disc shape on the extent of curvature.
Results and conclusions. Strong associations existed between curvature and angle data derived from the three methods, confirming the clinical utility of these techniques for the quantification of thoracic kyphosis. However, the traditional Cobb method tended to overestimate kyphosis in the presence of vertebral body end-plate deformation. The degree of kyphosis was strongly reflective of the extent of deformity of the vertebral bodies, and to a lesser extent the shape of the thoracic discs.
KEY WORDS: Thoracic spine, Kyphosis, Cobb angle, Computer-assisted measurement, Vertebral body, Intervertebral disc, Spinal curvature.
Correspondence to: K. P. Singer, Centre for Musculoskeletal Studies, Department of Surgery, UWA, Level 2, Medical Research Foundation Building, Royal Perth Hospital, Wellington Street, Perth, WA 6000, Australia.