Lumbosacral transitional vertebra on whole-spine CT: prevalence and association with rib abnormalities.

Objective: To determine the prevalence of lumbosacral transitional vertebrae (LSTV) and rib abnormalities and investigate the association between LSTV subtypes and rib abnormalities using whole-spine CT.

Materials and methods: The vertebral levels were counted caudally from the cervical vertebra, based on the eighth being the first thoracic vertebra, the twentieth as the first lumbar vertebra, and the twenty-fifth being the first sacral vertebra using sagittal reconstructed CT. Sacralization is when 23 vertebrae are found, whereas lumbarization is the presence of 25 vertebrae.

Results: This retrospective study included 551 patients (407 females and 144 males). There is no evidence of a difference in age and sex that was observed between the LSTV and no LSTV groups (95% CIs; - 0.34, 3.08; p = 0.12 and p = 0.24, respectively). LSTV were reported in 16.3% of participants, consisting of 12.3% of sacralization and 4.0% of lumbarization. The incidence rate of lumbarization was significantly high in male participants (p = 0.031). Rib abnormalities were reported in 14.0% of participants, consisting of 12.6% of twelfth hypoplastic rib and 1.5% of lumbar rib. In patients with LSTV, all twelfth hypoplastic ribs were found in the sacralization group and all lumbar ribs were found in the lumbarization group (p < 0.001). The types based on the Castellvi classification demonstrated a significant difference between the sacralization and lumbarization groups (p = 0.007).

Conclusion: The findings of our study suggest that patients with sacralization and lumbarization are predisposed to having twelfth hypoplastic ribs and lumbar ribs, respectively.