Hemidystrophic Thorax Mimicking Scoliosis

BACKGROUND: We regularly use Angle of Trunk Rotation (ATR) measurements for scoliosis screening and also for clinical follow-up of our scoliosis patients under treatment. In some patients, when ATR measurements exceed the screening threshold but without a significant degree of curvature on the X-ray (Cobb angle), a Hemidystrophic Thorax (HDT) is diagnosed. The purpose of this paper was to present a case series of patients with this kind of thoracic deformity because this may be mimicking scoliosis to a significant degree. MATERIALS AND METHODS: This case series is a consecutive series of patients where the first author detected a hemidystrophic thorax instead of or in combination with scoliosis. A 3D scan of the trunk was made and adjusted to the coordinates in order to achieve an upright orientation of the upper trunk. The scan was scaled in order to determine certain anatomic landmarks, as performed in preparation for bracing. The scan was cut horizontally at the xiphoid level and the plane at this level was analysed visually in order to detect deformations that were different to the typical scoliotic deformations in the horizontal plane. RESULTS: Seven cases were analysed and described in more detail. CONCLUSION: The condition of HDT may lead to significant rib humps that mimic scoliosis. According to our case series, mild scoliosis can also be associated with HDT. HDT, according to the cases presented in this study, seems to be a relatively benign deformity. Long-term observations are necessary before a final conclusion can be drawn with respect to prognosis.