Fig. 2. 38-year-old man with TLTV.

A, B. Posteroanterior chest radiograph (A) and supine abdominal radiograph (B) demonstrate 24 presacral mobile vertebra. C. Axial CT image showing 19th vertebra, with paired ribs that are 3.8 cm or greater in length and originate from facet at pedicle. Therefore, 19th vertebra is morphologically thoracic vertebra. D. On axial CT image, 20th vertebra, which has short rib on left side and accessory ossification center on right side, is TLTV. E. On curved planar reformatted image of left rib of 20th vertebra, rib length is measured by drawing line at midpoint of rib width from proximal head of rib to distal body. Rib measures 30.4 mm and is classified as short rib. F. On axial CT image, 21st vertebra, exhibiting both fused transverse processes without articulating ribs, is identified as first lumbar vertebra. Thus, this patient has 24 presacral mobile vertebra with seven cervical, 12 thoracic, one TLTV, and four lumbar vertebra. TLTV = thoracolumbar transitional vertebra