Surface Topography, Cobb Angles, and Cosmetic Change in Scoliosis

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Abstract
Preliminary analysis of the clinical value of surface topography in a spinal deformity clinic. The Cobb angle is the gold standard for the monitoring of scoliosis. This study was designed to determine whether surface topography would reflect Cobb angle status with sufficient reliability to permit its safe use as an alternative means of documentation in some circumstances. Surface topography offers the possibility of describing spinal deformity more fully than radiographic measures alone. To be useful, it must ignore changes due to varying posture and reliably detect differences that are clinically significant, while broadening the ability to assess deformity. Surface topography using Quantec (Quantec Image Processing, Warrington, Cheshire, UK) was obtained routinely in all patients attending a spinal deformity unit. Intrasubject variation was reduced by taking the mean for each parameter of four repositioned scans, which gives a smallest detectable change on all measures of approximately 10 U. Fifty-nine patients with two sets of radiographs and topography scans were studied to determine the ability of the different measurements to detect significant change. There was a significant correlation between Cobb angle and Quantec spinal angle. A significant change in Cobb angle could be identified by associated change in at least one topographic measure in a significant proportion of cases. It is unlikely that topography will supplant radiography for the ascertainment of Cobb angles, because the error margins of both are wide, and the two are not measuring the same aspect of the deformity. The Quantec system is useful in patient monitoring as an alternative to radiography, without diminishing the standard of care.