Rate of presence of 11 thoracic vertebrae and 6 lumbar vertebrae in asymptomatic Chinese adult volunteers

BACKGROUND: An increasing number of studies on spinal morphology in asymptomatic Asian and Western patients have been reported. Variation in spinal anatomy among patients is considered as the cause of wrong-level surgery in up to 40% of cases. The present study examined the rate of presence of 11 thoracic vertebrae and 6 lumbar vertebrae in 293 asymptomatic Chinese adult volunteers. METHODS: From May 27, 2016, to November 11, 2017, a cohort of 325 asymptomatic Chinese adults meeting the study exclusion criteria was recruited. The radiographs were examined by a spine surgeon and a radiologist to assess the number of thoracic and lumbar vertebrae. RESULTS: In total, 293 volunteers were included in this study: 17 (5.8%) had 11 thoracic vertebrae, and 16 (5.5%) had 6 lumbar vertebrae. Among all volunteers, 12 (4.1%) had 7 cervical vertebrae (C), 11 thoracic vertebrae (T), and 5 lumbar vertebrae (L); 5 (1.7%) had 7C, 11T, and 6L; and 11 (3.8%) had 7C, 12T, and 6L. There was no difference between the findings of the spine surgeon and the radiologist. CONCLUSIONS: For the first time, this study describes the rate of presence of 11 thoracic vertebrae and 6 lumbar vertebrae in 293 asymptomatic Chinese adult volunteers. Variations in the number of thoracic and lumbar vertebrae tend to be ignored by spine surgeons. We encourage spinal surgeons and researchers to be aware of such variations when performing thoracic- and lumbar-level surgery and assessing spinal alignment and parameters.