Study Overview
A 2026 study published in *Diagnostics (Basel, Switzerland)* investigated the reliability of the L3 transverse process as a consistent anatomical landmark for lumbar spine enumeration across varying vertebral segmentation patterns. The research team, led by Jankowski et al., analyzed 66 cases from a retrospective cohort of trauma CT scans with confirmed vertebral numbering. The study aimed to determine whether the L3 level, often cited as the site of the longest transverse process, could serve as a segmentation-independent marker for lumbar spine identification. The authors emphasized that accurate vertebral numbering is critical in clinical settings, particularly for interventional procedures and spinal surgery, where errors could lead to incorrect treatment decisions.
Methods and Sample Characteristics
The study included 66 participants with confirmed vertebral counts, comprising 46 men (69.7%) and 20 women (30.3%), with a mean age of 42.6 years. Thoracic segmentation patterns were categorized as C7T11 (10 cases), C7T12 (43 cases), and C7T13 (13 cases). Lumbar segmentation within the C7T12 group included C7T12L4 (8 cases), C7T12L5 (17 cases), and C7T12L6 (18 cases). Bilateral lumbar transverse-process lengths were measured using multiplanar reconstructions. The longest transverse process was identified through morphological and presacral numbering. Statistical analyses included the Fisher–Freeman–Halton exact test, Monte Carlo simulation, and Holm correction for multiple comparisons. Inter-observer reliability was assessed with intraclass correlation coefficients (ICC).
Key Findings
In the study cohort, the L3 transverse process was identified as the longest in 45 out of 66 cases (68.2%) based on single-process measurements and 49 out of 66 (74.2%) using bilateral mean lengths. Within the C7T12 group, these proportions were 76.7% and 83.7%, respectively. However, the reliability of L3 as a landmark varied significantly across thoracic segmentation patterns. For example, L3 was the longest transverse process in 30.0% of C7T11 cases versus 76.7% of C7T12 cases and 69.2% of C7T13 cases. Using bilateral mean lengths, the corresponding figures were 30.0%, 83.7%, and 76.9%. Presacral numbering also showed variability, with the 22nd presacral vertebra frequently bearing the longest transverse process in C7T11 and C7T12 cases, but this shifted to vertebra 23 in C7T13 configurations. The study concluded that neither L3 nor the 22nd presacral vertebra reliably indicated lumbar identity across different segmentation patterns.
Limitations
The study acknowledged several limitations. Subgroups with non-standard thoracic segmentation (C7T11 and C7T13) were relatively small, which may have reduced the precision of some estimates. Additionally, the C7T12L5 reference group was highly selected, comprising 17 cases after excluding those meeting transitional anatomy criteria. This selection process could limit the generalizability of findings. The authors also noted that statistical analyses required exact methods due to sparse contingency tables, and some estimates had wide confidence intervals, such as the 30% L3 prevalence in C7T11 cases (Wilson interval: 10.8–60.3%). These factors highlight the need for further research with larger, more diverse cohorts to validate the findings.
Clinical Implications
The study's findings suggest that the L3 transverse process cannot be reliably used as a standalone landmark for lumbar spine enumeration, particularly in patients with atypical vertebral segmentation. Clinicians should exercise caution when relying on this marker for precise vertebral numbering, as errors could impact diagnostic accuracy and treatment outcomes. The authors emphasized that full-spine counting remains necessary for reliable vertebral identification, especially in interventional or surgical contexts. While the L3 transverse process may serve as a general reference in some cases, its utility is limited by variability in thoracic and lumbar segmentation patterns. Future studies should explore alternative anatomical markers or imaging techniques to improve accuracy in diverse patient populations.