====== Thoracic kyphosis ======
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Angle between the top of T4 and the bottom of T12

Normal 41 º +/- 12 º

Sice T1 is often difficult to visualize, convention is to measure top of T4 to bottom of T12. Sometimes denoted as TK4.

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Thoracic [[kyphosis]] was measured on chest radiographs of 316 "normal" subjects by means of a modification of the Cobb technique for measuring scoliosis. Patients were accepted as "normal" if they had no thoracic or spinal complaints or radiographic abnormalities in the chest including the thoracic spine. A total of 159 males and 157 female subjects 2-77 years old was studied. The relation among age, gender, and kyphosis were determined using least squares fits of first-order linear mathematical models. These results were also used to determine the expected ranges of kyphosis for a "normal" patient of a given age and gender. The degree of kyphosis increased with age and the rate of increase was higher in females than in males
((Fon GT, Pitt MJ, Thies AC Jr. Thoracic kyphosis: range in normal subjects. AJR
Am J Roentgenol. 1980 May;134(5):979-83. PubMed PMID: 6768276.)).
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In postmenopausal [[osteoporosis]] patients, thoracolumbar kyphosis will occur even if there is no [[thoracolumbar compression fracture]], and when the BMD(L) [[T-score]] <-1.65, postmenopausal women are more likely to develop thoracolumbar kyphosis in the future
((Guo R, Li B, Zeng Z, Jiang X, Zhang D, Xie T, Hu X, Gao L. Thoracolumbar kyphosis in postmenopausal osteoporosis patients without vertebral compression fractures. Ann Transl Med. 2022 Jan;10(2):52. doi: 10.21037/atm-21-6285. PMID: 35282066; PMCID: PMC8848406.)).