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

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.

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.

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).

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