New Tip for Reducing Wrong Site Spine Surgery Risk

Surgeons need total clarity when it comes to identifying the correct vertebral segment. But for patients with a thoracolumbar transitional vertebra and/or a lumbosacral transitional vertebra, wrong site spine surgery is a definite possibility.

A new study from the Spine Center, Yokohama Minami Kyosai Hospital in Kanagawa, Japan, addresses this issue. The study, “Changes in Lumbosacral Anatomy and Vertebral Numbering in Patients with Thoracolumbar and/or Lumbosacral Transitional Vertebrae,” appears in the July-September 2021 edition of JBJS Open Access.

The authors noted that the traditional Castellvi lumbosacral transitional vertebra classification addresses coronal, but not sagittal or axial images. Co-author Yasunori Tatara, M.D., Ph.D. is with the Spine Center at Yokohama Minami Kyosai Hospital in Kanagawa, Japan, and explained to OTW, “When I was writing my paper on the S2-alar-iliac screw, I realized the importance of the presence of the transitional vertebra in the lumbosacral region.”

“Therefore, I decided to write a new paper focusing on transitional vertebrae. In this study, we investigated the incidence of the thoracolumbar transitional vertebra and lumbosacral transitional vertebra and examined their anatomical features on CT images.”

The research team examined medical records for 880 patients who had received spinopelvic fixation between July 2014 and March 2020. The authors then searched for patients with thoracolumbar transitional vertebrae and lumbosacral transitional vertebrae.

They found lumbosacral transitional vertebrae in 111 patients, with the most common type being Castellvi type-III. Thoracolumbar transitional vertebrae were associated with lumbosacral transitional vertebrae (87 out of 111). The team found that on sagittal images, the lumbosacral transitional anatomy of Castellvi lumbosacral transitional vertebrae resembled that of normal L5-S1, and the lumbosacral transitional anatomy of S6 lumbosacral transitional vertebrae resembled that of normal S1-S2.

“The most frequent lumbosacral transitional vertebra type was Castellvi type-III lumbosacral transitional vertebrae,” said Dr. Tatara to OTW. “Thoracolumbar transitional vertebrae coexisted with lumbosacral transitional vertebrae at a high incidence, and the converse was also true.”

“Although a lumbosacral transitional vertebra has both L5 and S1 elements,” he further explained, “Castellvi lumbosacral transitional vertebrae have a higher proportion of L5 elements than S1 elements. The S1 upper segment of Castellvi lumbosacral transitional vertebrae appeared as S2 on axial CT images; therefore, particularly for Castellvi type-IIIb lumbosacral transitional vertebrae, considering S1 as S2 is clinically less problematic.”

“Although a thoracolumbar transitional vertebra has both T12 and L1 elements, a thoracolumbar transitional vertebra is likely to be considered L1 on radiographs because of its association with the rudimentary rib. However, given the high incidence of thoracolumbar transitional vertebrae coexisting with lumbosacral transitional vertebrae, monitoring thoracolumbar transitional vertebrae would aid in reducing vertebral numbering errors.”

“The 3-dimensional CT images are suitable for detecting transitional vertebrae, and our findings may contribute to reducing the incidences of wrong-site surgery and diagnostic errors in patients with these conditions.”