Is the iliolumbar ligament a reliable identifier of the L5 vertebra in lumbosacral transitional anomalies?

Frequency of Coexistent Spinal Segment Variants: Retrospective Analysis in Asymptomatic Young Adults

BACKGROUND AND PURPOSE

Spinal segment variants are highly prevalent and can potentially lead to incorrect spinal enumeration and, consequently, interventions or surgeries at the wrong vertebral levels. Our aim was to assess the prevalence of spinal segment variants and to study the potential association among these variants in a population without histories of spine symptoms.

MATERIALS AND METHODS

Consecutive computed tomography exams of 450 young adults originally evaluated for non-spinal conditions and without a history of spinal diseases from a single institution. In addition to using descriptive statistics for reporting frequencies of spinal segment variants, the association between these variants was studied by calculating odds ratios and their 95% confidence interval. Consecutive CT exams were evaluated to determine the total number of presacral segments, presence of cervical rib, thoracolumbar transitional vertebra, iliolumbar ligament, and lumbosacral transitional vertebra.

RESULTS

The spinal segment distribution variants (an atypical number of presacral segments or an atypical distribution of thoracolumbar vertebrae), cervical rib, thoracolumbar transitional vertebra, and lumbosacral transitional vertebra were reported in 23.8%, 4.2%, 15.3%, and 26.4% of cases in our study population. The presence of a cervical rib or a thoracolumbar transitional vertebra was associated with concurrent lumbosacral transitional vertebra (OR = 3.28; 95% CI, 1.29-8.47 and 1.87; 95% CI, 1.08-3.20, respectively). The inability to visualize the iliolumbar ligament was also associated with the presence of cervical ribs (OR = 3.06; 95% CI, 1.18-7.80).

CONCLUSIONS

In a population of asymptomatic young adults, spinal segment variants are both highly prevalent with a high rate of coexistence. When a spinal segment variant (eg, transitional vertebra) is diagnosed, additional imaging might be considered for accurate spine enumeration before interventions or operations.

Redefining the Classification for Bertolotti Syndrome: Anatomical Findings in Lumbosacral Transitional Vertebrae Guide Treatment Selection

OBJECTIVE

We present the Jenkins classification for Bertolotti syndrome or symptomatic lumbosacral transitional vertebra (LSTV) and compare this with the existing Castellvi classification for patients presenting for treatment.

METHODS

We performed a retrospective cohort study of 150 new patients presenting for treatment of back, hip, groin, and/or leg pain from July 2012 through February 2022. Using magnetic resonance imaging, computed tomography, and radiography, the patients with a radiographic finding of LSTV, an appropriate clinical presentation, and identification of LSTV as the primary pain generator via diagnostic injections were diagnosed with Bertolotti syndrome. Patients for whom conservative treatment had failed and who underwent surgery to address their LSTV were included in the present study.

RESULTS

The Castellvi classification excludes 2 types of anatomic variants: the prominent anatomic side and the potential transverse process and iliac crest contact. Of 150 patients with transitional anatomy, 103 (69%) were identified with Bertolotti syndrome using the Jenkins classification and received surgery (46 men [45%] and 57 women [55%]). Of the 103 patients, 90 (87%) underwent minimally invasive surgery. The patients presented with pain localized to the back (n = 101; 98%), leg (n = 79; 77%), hip (n = 51; 49%), and buttock (n = 52; 50%). Only 84 of the Jenkins classification patients (82%) met any of the Castellvi criteria. All 19 patients for whom the Castellvi classification failed had had type 1 anatomy using the Jenkins system and underwent surgery (decompression, n = 16 [84%]; fusion, n = 1 [5%]; fusion plus decompression, n = 2 [11%]). Of these 19 patients, 17 (89%) had improved pain scores. The 19 patients exclusively diagnosed via the Jenkins classification had no significant differences in improved pain compared with those diagnosed using the Castellvi classification.

CONCLUSIONS

The Jenkins classification improves on the prior Castellvi classification to more comprehensively describe the functional anatomy, identify uncaptured anatomy, and better predict optimal surgical procedures to treat those with Bertolotti syndrome.

Anatomy and morphology of iliolumbar ligament

PURPOSE

To address limited amount of available data and contradictory statements in published works 60 Iliolumbar ligaments extracted from 30 cadavers were examined to describe their insertions and morphology.

METHODS

The ligaments were removed during the standard autopsy procedures with a use of an oscillating saw, a chisel and a scalpel. The specimens were photographed before the extraction and measured alongside their anterior margin. Next, they were preserved in formaldehyde, stripped of other soft tissues and then examined, photographed and described.

RESULTS

The mean length of the ligaments was 31.7 mm. 44 specimens were described as single-banded, 13 as double-banded and 3 as other. In 24 cases costal process of L_V has been fixed to the iliac plate by short ligamentous bands. In 38 cases there was a thick fibrous membrane connected to the ligament. No legitimate insertions on L_IV vertebra were observed.

CONCLUSIONS

Typical iliolumbar ligament consists of a single ligamentous band. Most common variability of the ligament consist of two bands. In approximately 40% of cases the costal process of L_V can be additionally stabilized to the iliac plate by short, strong ligamentous bands. In 63% of cases a connection between the iliolumbar ligament and a fibrous membrane placed in the frontal plane, superiorly to the ligament, has been observed. There seems to be no convincing proof of existence of the insertion of the iliolumbar ligament on the L_IV vertebra.

The Great Mimickers of Spinal Pathology

Back pain is one of the leading causes of health costs worldwide, particularly because of the further increased aging population. After clinical examination, spinal imaging is of utmost importance in many patients to reach the correct diagnosis. There are many imaging pitfalls and mimickers of spinal pathology on radiographs, magnetic resonance imaging, and computed tomography. These mimickers may lead to a misdiagnosis or a further imaging work-up if they are not recognized and thus lead to unnecessary examinations and increased health care costs. In this review we present the common mimickers of spinal pathology and describe normal variations when reading imaging studies of the spine.

Association between lumbar sacralization and increased degree of vertebral slippage and disc degeneration in patients with L4 spondylolysis

OBJECTIVE

The aim of this study was to evaluate the effect of lumbar sacralization on the level of vertebral slip and disc degeneration in patients with L4 spondylolysis.

METHODS

The authors analyzed data from 102 cases in which patients underwent surgical treatment for L4 spondylolysis and spondylolisthesis at their institution between March 2007 and September 2016. Lumbar sacralization was characterized by the presence of pseudarthrosis and/or bony fusion between the L5 transverse process and sacrum, and the type of lumbosacral transitional vertebra (LSTV) was evaluated with the Castellvi classification. The amount of vertebral slippage was measured using the Taillard technique and Meyerding grade. Degeneration of the L4-5 segment was quantified using the Pfirrmann and Modic classifications. Patients were divided into 2 groups based on the presence or absence of sacralization, and the amount of vertebral slip and degeneration of the L4-5 segment was compared between groups.

RESULTS

Lumbar sacralization was present in 37 (36%) of 102 patients with L4 spondylolysis. The LSTV was type IIa in 10 cases, type IIb in 7, type IIIa in 2, and type IIIb in 18. The levels of vertebral slip and disc degeneration in the group of patients with sacralization were significantly greater than in the group without sacralization. No significant difference was found between the 2 groups with respect to Modic changes.

CONCLUSIONS

The increased stability between a sacralized L5 and the sacrum may predispose the L4-5 segment to greater instability and disc degeneration in patients with L4 spondylolysis.

Role of iliac crest tangent in correct numbering of lumbosacral transitional vertebrae

Background/aim

The iliac crest tangent (ICT) has recently emerged as a reliable landmark to correctly number the lumbosacral transitional vertebrae (LSTV). We retrospectively evaluated the reproducibility and accuracy of the ICT as a landmark in subjects without disc degeneration.

Materials and methods

Fifty-eight patients with LSTV [19 female, 41 (26–52) years] and 55 controls without LSTV [23 female, 40 (26–55) years] who had undergone spinal computed tomography were included. The ICT was drawn on the coronal images, with the cursor in the sagittal view set to the posterior ⅓ of the vertebral body located one level above the LSTV. When more than 1.25 vertebral body was counted below the ICT, the LSTV was considered as S1, otherwise it was considered as L5. The gold standard was counting the vertebrae craniocaudally.

Results

The interobserver agreement was good for determining ICT level (Cohen’s kappa = 0.78, P < 0.001). The rate of correct numbering by ICT in the LSTV group was significantly less than in the controls (43.1% vs. 96.4%, respectively, P < 0.001). Patients with sacralization had a significantly lower correct numbering rate than patients with lumbarization (33.3% vs. 63.2%, respectively, P = 0.03).

Conclusion

ICT does not seem to be a reliable landmark for correct numbering of LSTV in patients with no intervertebral disc degeneration.

Interpretation of Spinal Radiographic Parameters in Patients With Transitional Lumbosacral Vertebrae

STUDY DESIGN

Retrospective radiographic review.

OBJECTIVES

To understand the effect of variability in sacral endplate selection in transitional lumbosacral vertebrae (TLSV) and its impact on pelvic, regional, and global spinal alignment parameters.

BACKGROUND

TLSV can have the characteristics of both lumbar and sacral vertebrae. Difficulties in identification of the S1 endplate may come from nomenclature, number of lumbar vertebrae, sacra, and morphology and may influence the interpretation and consistency of spinal alignment parameters.

METHODS

Patients with TLSV were identified and radiographic measurements including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), sagittal vertical axis (SVA), T1-pelvic angle (TPA), pelvic incidence-lumbar lordosis (PI-LL) mismatch, thoracic kyphosis (TK), and spinal inclination (T1SPi) were obtained. Radiographic measurements were performed twice with the sacral endplate at the cephalad and caudal options. Paired t tests assessed the difference between different selection groups.

RESULTS

Of 1,869 patients, 70 (3.7%) were found to have TLSV on radiographic imaging. Fifty-eight (82.9%) had lumbarized sacral segments whereas 12 (17.1%) had sacralized lumbar segments. T1-SPi (mean: -1.77°) and TK (mean: 34.86°) did not vary from altering sacral endplate selection. Selection of the caudal TLSV as the sacral endplate resulted in an increase in all pelvic parameters (PI: 66.8° vs. 44.3°, PT: 25.1° vs. 12.7°, and SS: 41.6° vs. 31.6°), regional lumbar parameters (LL: -54.1° vs. 44.0°, PI-LL: 12.7° vs. 0.3°), and global parameters (SVA: 46.1 mm vs. 28.3 mm, TPA: 23.3° vs. 10.8°) as compared to selecting the cephalad TLSV. All mean differences between radiographic parameters were found to be statistically significant (p < .001).

CONCLUSIONS

Variation in sacral endplate selection in TLSV significantly affects spinal alignment parameter measurements. A standardized method for measuring TLSV is needed to reduce measurement error and ultimately allow more accurate understanding of alignment targets in patients with TLSV.

LEVEL OF EVIDENCE

Level III.

Psoas proximal insertion as a simple and reliable landmark for numbering lumbar vertebrae on MRI of the lumbar spine

OBJECTIVE

To evaluate the value of psoas muscle proximal insertion for correct numbering of the lumbar vertebrae in MRI, in particular in case of lumbosacral transitional vertebra (LSTV).

METHODS

Two radiologists assessed 477 MRI scans of the lumbar spine with a sagittal localizer sequence on the whole spine for numbering vertebrae caudally from C2. Proximal insertion of the psoas was determined as the most proximal vertebra with psoas over half of its body on coronal T2 STIR sequence. The last lumbar vertebra was named considering both its number and the presence or absence of LSTV according to Castellvi classification. These same parameters were also assessed on 207 PET-CT scans of another cohort including the whole spine.

RESULTS

Proximal insertion of the psoas was L1 in 94.1% of cases: 98.5% in case of modal anatomy, 81.4% in case of LSTV, and 51.7% in case of missing or supernumerary lumbar vertebra without LSTV. There was no statistically significant difference between MRI and CT data. The inter-reader agreement for determination of psoas proximal insertion was excellent (kappa = 0.96).

CONCLUSION

Proximal insertion of the psoas muscle is a helpful marker for correct numbering of the lumbar vertebrae in MRI and to detect a complete lumbosacral segmentation anomaly.

KEY POINTS

• Proximal insertion of the psoas muscle can be easily identified on a coronal T2 STIR sequence. • Psoas proximal insertion on the spine almost always designates the first lumbar vertebra and is helpful to accurately number all lumbar vertebrae, especially in case of lumbosacral transitional vertebra. • Conversely, when psoas muscle does not insert five lumbar bodies above the apparent lumbosacral joint, the probability of variation in the number of lumbar vertebrae is high.

Spinal Enumeration by Morphologic Analysis of Spinal Variants: Comparison to Counting in a Cranial-To-Caudal Manner

Objective

To compare the spinal enumeration methods that establish the first lumbar vertebra in patients with spinal variants.

Materials and Methods

Of the 1446 consecutive patients who had undergone computed tomography of the spine from March 2012 to July 2016, 100 patients (62 men, 38 women; mean age, 47.9 years; age range, 19-88 years) with spinal variants were included. Two radiologists (readers 1 and 2) established the first lumbar vertebra through morphologic analysis of the thoracolumbar junction, and labeled the vertebra by counting in a cranial-to-caudal manner. Inter-observer agreement was established. Additionally, reader 1 detected the 20th vertebra under the assumption that there are 12 thoracic vertebra, and then classified it as a thoracic vertebra, lumbar vertebra, or thoracolumbar transitional vertebra (TLTV), on the basis of morphologic analysis.

Results

The first lumbar vertebra, as established by morphologic analysis, was labeled by each reader as the 21st segment in 65.0% of the patients, as the 20th segment in 31.0%, and as the 19th segment in 4.0%. Inter-observer agreement between the two readers in determining the first lumbar vertebra, based on morphologic analysis, was nearly perfect (κ value: 1.00). The 20th vertebra was morphologically classified as a TLTV in 60.0% of the patients, as the first lumbar segment in 31.0%, as the second lumbar segment in 4.0%, and as a thoracic segment in 5.0%.

Conclusion

The establishment of the first lumbar vertebra using morphologic characteristics of the thoracolumbar junction in patients with spinal variants was consistent with the morphologic traits of vertebral segmentation.

Lumbosacral transitional vertebrae: significance of local bone marrow edema at the transverse processes

OBJECTIVE

To evaluate the association between low back pain and bone marrow edema in lumbosacral transitional vertebra (LSTV) transverse processes, and to assess the prevalence of LSTV in a physically active population.

MATERIALS AND METHODS

Individuals with LSTV on coronal MRI studies were identified in a retrospective review by keyword search from PACS. In total, 140 cases were reviewed by two fellowship-trained musculoskeletal radiologists. Data on associated low back pain were collected from patient records at the time of the imaging.

RESULTS

Bone marrow edema was observed in 44% of the cases, but no correlation with low back pain was found. On coronal MRI, the prevalence of LSTV was 2.6%, with type II LSTV being the most common subtype.

CONCLUSIONS

No correlation with bone marrow edema at the transverse processes of the LSTV and low back pain was observed. In our selected study population, the prevalence of LSTV was low.

A review of lumbosacral transitional vertebrae and associated vertebral numeration

PURPOSE

To review the current literature on methods of accurate numeration of vertebral segments in patients with Lumbosacral transitional vertebrae (LSTVs). LSTVs are a common congenital anomaly of the L5-S1 junction. While their clinical significance has been debated, unquestionable is the need for their identification prior to spinal surgery. We hypothesize that there are no reliable landmarks by which we can accurately number transitional vertebrae, and thus a full spinal radiograph is required.

METHODS

A Pubmed and EMBASE search using various combinations of specific key words including "LSTV", "lumbosacral transitional vertebrae", "count", "vertebral numbering", and "number" was performed.

RESULTS

The gold standard for spinal segment numeration in patients with LSTV remains whole spine imaging and counting caudally, starting from C2. If whole spine imaging is not available, the use of the iliac crest tangent sign on coronal magnetic resonance imaging (MRI) has fairly reliable sensitivity and specificity (81 and 64-88%, respectively) for accurate numeration of LSTV. The role of paraspinal anatomic markers such as the right renal artery, superior mesenteric artery, aortic bifurcation, and conus medullaris, for identification of vertebral levels is unreliable and should not be used.

CONCLUSIONS

A sagittal whole spine view should be added as a scout view when patients obtain lumbar MRI to standardize the vertebral numbering technique. To date, there has been no other method for accurate numeration of a transitional vertebral segment, other than counting caudally from C2. These slides can be retrieved under Electronic Supplementary Material.

Prevalence of Lumbosacral Transitional Vertebra in Individuals with Low Back Pain: Evaluation Using Plain Radiography and Magnetic Resonance Imaging

Study Design

Descriptive cross-sectional study.

Purpose

To determine the frequency of lumbosacral transitional vertebrae (LSTV) in patients with low back pain (LBP) and the role of iliolumbar ligament (ILL) origin from L5 in LSTV cases.

Overview of Literature

Transitional vertebrae are developmental variants of the spine. LSTV is a common congenital abnormality, and failure to recognize this anomaly may result in serious consequences during surgery.

Methods

All patients aged 11–90 years of either gender with LBP for any duration, who presented for X-ray and magnetic resonance imaging (MRI) of the lumbosacral spine, were included. X-rays of the lumbosacral spine in anteroposterior and lateral views were acquired. In addition, T1- and T2-weighted sagittal and axial MRI was performed. Images were evaluated on a workstation.

Results

Of 504 patients, transitional vertebrae were observed in 75 patients (15%). Among them, 39 (52%) patients had Castellvi type III and 36 (48%) patients had Castellvi type II. However, on MRI, 42 (56%) patients had O'Driscoll type II, 18 (24%) patients had O'Driscoll type IV, and 15 patients (20%) had O'Driscoll type III. ILL origin from L5 was significantly higher (n=429, 100%) among patients with a normal lumbosacral junction than among patients with a transitional lumbosacral junction (n=22, 29.3%) (p<0.001).

Conclusions

LSTV occurs at a high frequency in patients with LBP. Furthermore, in the presence of LSTV, the ILL is not a reliable marker for the identification of L5.

Localizing the L5 Vertebra Using Nerve Morphology on MRI: An Accurate and Reliable Technique

BACKGROUND AND PURPOSE

Multiple methods have been used to determine the lumbar vertebral level on MR imaging, particularly when full spine imaging is unavailable. Because postmortem studies show 95% accuracy of numbering the lumbar vertebral bodies by counting the lumbar nerve roots, attention to lumbar nerve morphology on axial MR imaging can provide numbering clues. We sought to determine whether the L5 vertebra could be accurately localized by using nerve morphology on MR imaging.

MATERIALS AND METHODS

One hundred eight cases with full spine MR imaging were numbered from the C2 vertebral body to the sacrum with note of thoracolumbar and lumbosacral transitional states. The origin level of the L5 nerve and iliolumbar ligament were documented in all cases. The reference standard of numbering by full spine imaging was compared with the nerve morphology numbering method. Five blinded raters evaluated all lumbar MRIs with nerve morphology technique twice. Prevalence and bias-adjusted κ were used to measure interrater and intrarater reliability.

RESULTS

The L5 nerve arose from the 24th presacral vertebra (L5) in 106/108 cases. The percentage of perfect agreement with the reference standard was 98.1% (95% CI, 93.5%-99.8%), which was preserved in transitional and numeric variation states. The iliolumbar ligament localization method showed 83.3% (95% CI, 74.9%-89.8%) perfect agreement with the reference standard. Inter- and intrarater reliability when using the nerve morphology method was strong.

CONCLUSIONS

The exiting L5 nerve can allow accurate localization of the corresponding vertebrae, which is essential for preprocedure planning in cases where full spine imaging is not available. This neuroanatomic method displays higher agreement with the reference standard compared with previously described methods, with strong inter- and intrarater reliability.

Role of Anatomical Landmarks in Identifying Normal and Transitional Vertebra in Lumbar Spine Magnetic Resonance Imaging

Study Design

Retrospective study.

Purpose

Identification of transitional vertebra is important in spine imaging, especially in presurgical planning. Pasted images of the whole spine obtained using high-field magnetic resonance imaging (MRI) are helpful in counting vertebrae and identifying transitional vertebrae. Counting vertebrae and identifying transitional vertebrae is challenging in isolated studies of lumbar spine and in studies conducted in low-field MRI. An incorrect evaluation may lead to wrong-level treatment. Here, we identify the location of different anatomical structures that can help in counting and identifying vertebrae.

Overview of Literature

Many studies have assessed the vertebral segments using various anatomical structures such as costal facets (CF), aortic bifurcation (AB), inferior vena cava confluence (IC), right renal artery (RRA), celiac trunk (CT), superior mesenteric artery root (SR), iliolumbar ligament (ILL) psoas muscle (PM) origin, and conus medullaris. However, none have yielded any consistent results.

Methods

We studied the locations of the anatomical structures CF, AB, IC, RRA, CT, SR, ILL, and PM in patients who underwent whole spine MRI at our department.

Results

In our study, 81.4% patients had normal spinal segmentation, 14.7% had sacralization, and 3.8% had lumbarization. Vascular landmarks had variable origin. There were caudal and cranial shifts with respect to lumbarization and sacralization. In 93.8% of cases in the normal group, ILL emerged from either L5 alone or the adjacent disc. In the sacralization group, ILL was commonly seen in L5. In the lumbarization group, ILL emerged from L5 and the adjacent disc (66.6%). CFs were identified at D12 in 96.9% and 91.7% of patients in the normal and lumbarization groups, respectively. The PM origin was observed from D12 or D12–L1 in most patients in the normal and sacralization groups.

Conclusions

CF, PM, and ILL were good identification markers for D12 and L5, but none were 100% accurate.

Anatomical differences in patients with lumbosacral transitional vertebrae and implications for minimally invasive spine surgery

OBJECTIVE

The objective of this study was to investigate the neurovascular and anatomical differences in patients with lumbosacral transitional vertebrae (LSTV) and the associated risk of neurovascular injury in minimally invasive spine surgery.

METHODS

The authors performed a retrospective study of CT and MR images of the lumbar spine obtained at their institution between 2010 and 2014. The following characteristics were evaluated: level of the iliac crest in relation to the L4–5 disc space, union level of the iliac veins and arteries in relation to the L4–5 disc space, distribution of the iliac veins and inferior vena cava according to the different Moro zones (A, I, II, III, IV, P) at the L4–5 disc space, and the location of the psoas muscle at the L4–5 disc space. The findings were compared with findings on images obtained in 28 age- and sex-matched patients without LSTV who underwent imaging studies during the same time period.

RESULTS

Twenty-eight patients (12 male, 16 female) with LSTV and the required imaging studies were identified; 28 age- and sex-matched patients who had undergone CT and MRI studies of the thoracic and lumbar spine imaging but did not have LSTV were selected for comparison (control group). The mean ages of the patients in the LSTV group and the control group were 52 and 49 years, respectively. The iliac crest was located at a mean distance of 12 mm above the L4–5 disc space in the LSTV group and 4 mm below the L4–5 disc space in the controls. The iliac vein union was located at a mean distance of 8 mm above the L4–5 disc space in the LSTV group and 2.7 mm below the L4–5 disc space in the controls. The iliac artery bifurcation was located at a mean distance of 23 mm above the L4–5 disc space in the LSTV group and 11 mm below the L4–5 disc space in controls. In patients with LSTV, the distribution of iliac vein locations was as follows: Zone A, 7.1%; Zone I only, 78.6%; Zone I encroaching into Zone II, 7.1%; and Zone II only, 7.1%. In the control group, the distribution was as follows: Zone A only, 17.9%; Zone A encroaching into Zone I, 75%; and Zone I only, 7.1%. There were no iliac vessels in Zone II in the control group. The psoas muscle was found to be rising away laterally and anteriorly from the vertebral body more often in patients with LSTV, resulting in the iliac veins being found in the “safe zone” only 14% of the time, greatly increasing the risk of vascular injury.

CONCLUSIONS

In patients with LSTV, the iliac crest is more likely to be above the L4–5 disc space, which increases the technical challenges of a lateral approach. The location of the psoas muscle rising away laterally and ventrally in patients with LSTV compared with controls and with the union of the iliac veins occurring more often above the L4–5 disc space increases the risk for iatrogenic vascular injury at the L4–5 level in this patient population.

Thoracolumbar junction: morphologic characteristics, various variants and significance

OBJECTIVE:

This study aimed to assess the types of vertebral segments at the thoracolumbar junction, as they relate to the most caudal ribs, to evaluate the reliability of this assessment using axial CT with curved planar reformatting (CPR) images, to describe the morphologic characteristics of a thoracolumbar transitional vertebra (TLTV), to introduce a new classification system for the TLTV and to evaluate the reliability of the classification system using axial CT with CPR images.

METHODS:

This was a retrospective review of 744 consecutive patients who underwent spine CT imaging that included the thoracolumbar junction. Two radiologists (Readers 1 and 2) independently evaluated the axial CT with CPR images for all cases (n = 744). Each radiologist differentiated the vertebral segments at the thoracolumbar junction as TLTV or non-TLTV (thoracic segment or lumbar segment). In addition, each radiologist classified the 94 patients with the TLTV using a novel classification system. Interobserver agreement between the two radiologists regarding the differentiation of vertebral segments at the thoracolumbar junction was analysed with kappa statistics. Similarly, intra- and interobserver agreement regarding TLTV classification was analysed with kappa statistics.

RESULTS:

Interobserver agreement between the two readers with respect to the differentiation of vertebral segments at the thoracolumbar junction via axial CT with CPR images was nearly perfect (κ-value: 0.959). Interobserver agreement between the two readers with respect to TLTV classification using axial CT with CPR images was nearly perfect (κ-value: 0.846). In addition, intraobserver agreement for Reader 1 was also nearly perfect (κ-value: 0.877).

CONCLUSION:

Morphologic analysis of the thoracolumbar junction may help accurate spinal enumeration.

ADVANCES IN KNOWLEDGE:

Consideration of various variants at the thoracolumbar junction should help radiologists and clinicians to interpret the morphology of the thoracolumbar junction. This may facilitate communication with the referring clinician, thereby reducing the error in spinal enumeration.

Merits of different anatomical landmarks for correct numbering of the lumbar vertebrae in lumbosacral transitional anomalies

PURPOSE

Anatomical landmarks and their relation to the lumbar vertebrae are well described in subjects with normal spine anatomy, but not for subjects with lumbosacral transitional vertebra (LSTV), in whom correct numbering of the vertebrae is challenging and can lead to wrong-level treatment. The aim of this study was to quantify the value of different anatomical landmarks for correct identification of the lumbar vertebra level in subjects with LSTV.

METHODS

After IRB approval, 71 subjects (57 ± 17 years) with and 62 without LSTV (57 ± 17 years), all with imaging studies that allowed correct numbering of the lumbar vertebrae by counting down from C2 (n = 118) or T1 (n = 15) were included. Commonly used anatomical landmarks (ribs, aortic bifurcation (AB), right renal artery (RRA) and iliac crest height) were documented to determine the ability to correctly number the lumbar vertebrae. Further, a tangent to the top of the iliac crests was drawn on coronal MRI images by two blinded, independent readers and named the 'iliac crest tangent sign'. The sensitivity, specificity and the interreader agreement were calculated.

RESULTS

While the level of the AB and the RRA were found to be unreliable in correct numbering of the lumbar vertebrae in LSTV subjects, the iliac crest tangent sign had a sensitivity and specificity of 81 % and 64-88 %, respectively, with an interreader agreement of k = 0.75.

CONCLUSION

While anatomical landmarks are not always reliable, the 'iliac crest tangent sign' can be used without advanced knowledge in MRI to most accurately number the vertebrae in subjects with LSTV, if only a lumbar spine MRI is available.