Normative spino-pelvic parameters in patients with the lumbarization of S1 compared to a normal asymptomatic population

A simple method for the selection of valid spinopelvic parameters and lumbar lordosis in patients with transitional lumbosacral vertebrae

PURPOSE

Transitional lumbosacral vertebrae (TLSV) are a congenital anomaly of the lumbosacral region that is characterized by the presence of a vertebra with morphological properties of both the lumbar and sacral vertebrae, with a prevalence of up to 36% in asymptomatic patients and 20% in adolescent idiopathic scoliosis patients. In patients with TLSV, because of these morphological changes and the different numbers of lumbar vertebrae, there are two optional reference sacral endplates that can be selected intently or inadvertently to measure the spinopelvic parameters: upper and lower endplates. The spinopelvic parameters measured using the upper and lower endplates are significantly different from each other as well as from the normative values. Therefore, the selection of a reference endplate changes the spinopelvic parameters, lumbar lordosis (LL), and surgical goals, which can result in surgical over- or under-correction. Because there is no consensus on the selection of sacral endplate among these patients, it is unclear as to which of these parameters should be used in diagnosis or surgical planning. The present study describes a standardization method for measuring the spinopelvic parameters and LL in patients with TLSV.

METHODS

Upper and lower endplate spinopelvic parameters (i.e., pelvic incidence [PI], sacral slope [SS], and pelvic tilt) and LL of 108 patients with TLSV were measured by computed tomography. In addition, these parameters were measured for randomly selected subjects without TLSV. The PI value in the TLSV group, which was closer to the mean PI value of the control group, was accepted as valid and then used to create an optimum PI (OPI) group. Finally, the spinopelvic parameters and LL of the OPI and control groups were compared.

RESULTS

Except for SS, all spinopelvic parameters and LL were comparable between the OPI and control groups. In the OPI group, 60% of the patients showed valid upper endplate parameters, and 40% showed valid lower endplate parameters. No difference was noted in the frequency of valid upper or lower endplates between the sacralization and lumbarization groups. Both the OPI and control groups showed nearly comparable correlations between their individual spinopelvic parameters and LL, except for PI and LL in the former.

CONCLUSIONS

Because PI is unique for every individual, the endplate whose PI value is closer to the normative value should be selected as the reference sacral endplate in patients with TLSV.

Analysis of Spinopelvic Parameters and Lumbar Lordosis in Patients with Transitional Lumbosacral Vertebrae, with Special Reference to Sacralization and Lumbarization

BACKGROUND

Transitional lumbosacral vertebra presents in 2 forms based on its origin: sacralization and lumbarization. These patients have 2 options for sacral endplates (upper and lower) and consequently, 2 sets of values for spinopelvic parameters and lumbar lordosis (LL). This study aimed to evaluate these parameters in asymptomatic patients with sacralization and lumbarization and compare them with each other and normative values.

METHODS

Spinopelvic parameters and LL according to upper and lower endplate were measured using abdominal computed tomography in 1420 asymptomatic patients, of which 108 had Transitional lumbosacral vertebra. These parameters were compared among patients with lumbarization and sacralization and with normal controls. In addition, correlations between the upper and lower endplate parameters were determined.

RESULTS

As compared to the control group, upper endplate measurements yielded lower spinopelvic parameters and LL values while lower endplate values yielded higher values. While these values were significantly different from normative values, these parameters were similar in both lumbarization and sacralization groups. Furthermore, most spinopelvic parameters of both upper and lower endplates were strongly correlated, and the differences between the upper and lower PI and LL values are relatively constant (27° and 14°, respectively.

CONCLUSIONS

Upper and lower endplate parameters are comparable in patients with sacralization and lumbarization; therefore, the average spatial position of a sacralized L5 and a lumbarized S1 within the pelvis is similar and either parameter can be used for radiological measurements. Further studies with symptomatic patients are warranted to confirm these results.

Influences of lumbo-sacral transitional vertebrae for anterior lumbar interbody fusion

Lumbo-sacral transitional vertebrae (LSTV) are frequent congenital variances of the spine and are associated with increased spinal degeneration. Nevertheless, there is a lack of data whether bony alterations associated with LSTV result in reduced segmental restoration of lordosis when performing ALIF. 58 patients with monosegmental stand-alone ALIF in the spinal segment between the 24th and 25th vertebra (L5/S1)/(L5/L6) where included. Of these, 17 patients had LSTV and were matched to a control population by age and sex. Pelvic incidence, pelvic tilt, sagittal vertical axis, lumbar lordosis, segmental lordosis, disc height and depth were compared. LSTV-patients had a significantly reduced segmental lordosis L4/5 (p = 0.028) and L5/S1/(L5/L6) (p = 0.041) preoperatively. ALIF resulted in a significant increase in segmental lordosis L5/S1 (p < 0.001). Postoperatively, the preoperatively reduced segmental lordosis was no longer significantly different in segments L4/5 (p = 0.349) and L5/S1/(L5/6) (p = 0.576). ALIF is associated with a significant increase in segmental lordosis in the treated segment even in patients with LSTV. Therefore, ALIF is a sufficient intervention for restoring the segmental lordosis in these patients as well.

Hip-Spine Relationship between Sagittal Balance of the Lumbo-Pelvi-Femoral Complex and Hip Extension Capacity: An EOS Evaluation in a Healthy Caucasian Population

STUDY DESIGN

A prospective study of healthy volunteers.

OBJECTIVES

The influence of the sagittal alignment of the spine and its influence on the extension reserve have been reported in the literature. However, specific analysis of the intrinsic coxofemoral and extrinsic pelvic component in subjects without any spinal or hip pathologies remains poorly reported. The aim of this study was to categorize the hip extension capacity, or extension reserve (ER), in relation to spinal sagittal alignment whilst standing, in a young healthy population. We hypothesized that the global extension reserve (GER) of the hip joint was influenced by the sagittal spinopelvic alignment.

METHODS

We evaluated the ER of 120 healthy Caucasian volunteers (56 females (46.7%), 74 males (53.3%); mean age 25.6 years), using low dose radiographs from an EOS® X-ray imaging system in 2 functional positions; neutral standing position and in a forward lunge position. The GER is defined as the sum of the intrinsic (hip) extension reserve (IER) and the extrinsic (pelvic) extension reserve (EER). Cases were grouped into 4 sagittal alignment subtypes according to the Roussouly classification, and analyzed.

RESULTS

Global extension reserve values were not significantly different between the 4 Roussouly subtypes (P = .094), nor between patients with a sacral slope (SS) <35° (types 1/2) and ≥ 35° (type 3/4) (P = .837). Statistically significant differences were seen between IER in each subtype (P = .015), and EER (P = .006). No difference in ER was seen between subtypes regarding pelvic incidence (PI).

CONCLUSION

An inverse relationship was found between IER and EER among Roussouly subtypes. The range of motion of the pelvis and the hip joint was higher in patients with a greater sacral slope.

Anterior spinal fusion (ALIF/OLIF/LLIF) with lumbosacral transitional vertebra: A systematic review and proposed treatment algorithm

•Key anterior approaches differences in LSTV include vascular (aortic bifurcation/iliocaval confluence), muscular (psoas) and osseus anatomy (inter-crestal tangent/pubic symphysis), when compared to non-LSTV.•There are increased surgical deviations but not significantly greater complications for anterior approaches in LSTV.•Vascular awareness while accessing L45 will be in the presence of a more cephalad ABF and ICC with sacralized L5, and access to the deeper L56 level will be in the presence of a more caudal ABF and ICC in lumbarized S1.

Measurement of S1 foramen depth for ultrasound-guided S1 transforaminal epidural injection

Background

Ultrasound-guided first sacral transforaminal epidural steroid injection (S1 TFESI) is a useful and easily applicable alternative to fluoroscopy or computed tomography (CT) in lumbosacral radiculopathy. When a needle approach is used, poor visualization of the needle tip reduces the accuracy of the procedure, increasing its difficulty. This study aimed to improve ultrasound-guided S1 TFESI by evaluating radiological S1 posterior foramen data obtained using three-dimensional CT (3D-CT).

Methods

Axial 3D-CT images of the pelvis were retrospectively analyzed. The radiological measurements obtained from the images included 1st posterior sacral foramen depth (S1D, mm), 1st posterior sacral foramen width (S1W, mm), the angle of the 1st posterior sacral foramen (S1A, °), and 1st posterior sacral foramen distance (S1ds, mm). The relationship between the demographic factors and measured values were then analyzed.

Results

A total of 632 patients (287 male and 345 female) were examined. The mean S1D values for males and females were 11.9 ± 1.9 mm and 10.6 ± 1.8 mm, respectively (P < 0.001); the mean S1A 28.2 ± 4.8° and 30.1 ± 4.9°, respectively (P < 0.001); and the mean S1ds, 24.1 ± 2.9 mm and 22.9 ± 2.6 mm, respectively (P < 0.001); however, the mean S1W values were not significantly different. Height was the only significant predictor of S1D (β = 0.318, P = 0.004).

Conclusions

Ultrasound-guided S1 TFESI performance and safety may be improved with adjustment of needle insertion depth congruent with the patient's height.

Lumbosacral Transitional Vertebrae Influence on Acetabular Orientation and Pelvic Tilt

Lumbosacral transitional vertebrae (LSTV) are common congenital variances with a prevalence found in the population up to 35.6%. The literature demonstrates an influence of LSTV on bony pelvic anatomy. The influence on the anatomical acetabular orientation, which is important for cup positioning in total hip arthroplasty, has not yet been described for patients with LSTV. A total of 53 patients with LSTV were identified from a CT Database including 819 subjects. Fifty patients with LSTV could be included and were matched for age and sex against a control group. We examined the influence of LSTV, classified according to Castellvi, on acetabular orientation and pelvic tilt in the supine position. Functional acetabular anteversion and inclination, assessed against the table plane, were compared against anatomical acetabular anteversion and inclination, assessed against the anterior pelvic plane. The anatomical acetabular inclination correlated with the pelvic tilt (r = 0.363, p < 0.001). The anatomical acetabular inclination was significantly larger than the functional acetabular inclination in the supine position (p < 0.001). Castellvi grading of LSTV correlated negatively with pelvic tilt (ρ = −0.387, p = 0.006). Castellvi grading correlated significantly with functional acetabular anteversion (ρ = 0.324, p = 0.022) and anatomical acetabular anteversion (ρ = 0.306, p = 0.022). A higher Castellvi grading was accompanied by a reduced pelvic tilt in the supine position. The functional acetabular anteversion and anatomical acetabular anteversion increased in parallel to the higher Castellvi grading. Therefore, LSTV and Castellvi grading might be assessed on pre-operative X-rays prior to hip arthroplasty and surgeons might consider adjusting cup positioning accordingly.

Influence of lumbosacral transitional vertebrae on spinopelvic parameters using biplanar slot scanning full body stereoradiography-analysis of 291 healthy volunteers

BACKGROUND

Proper identification of lumbosacral transitional vertebrae (LSTV) is important to characterize the relationship between the transitional segment and adjacent levels. Classical classification schemes are inaccurate with respect to the whole spine. We propose a precise vertebral numbering method and investigated the relationship between LSTV and whole-body sagittal alignment.

METHODS

A total of 291 healthy adult volunteers with no history of spinal disease were evaluated with biplanar slot scanning full body stereoradiography to determine the prevalence of LSTV. Vertebrae were counted from the first cervical vertebra using both coronal and sagittal plane images. We then investigated the influence of LSTV on whole-body sagittal alignment in 279 participants. Whole-body key parameters descriptive statistics were compared among groups according to the number of vertebrae (L4, L5, and L6). Statistical analysis was performed between normal and LSTV cases using the Steel-Dwass analysis.

RESULTS

Of the 291 subjects, 14 (4.8%) had 23 vertebrae and 16 (5.5%) had 25 vertebrae. Eleven (3.8%) had Th11, 3 (1.0%) had L4, and 1 (0.3%) had Th11 + L6, 16 (5.5%) had L6. Compared with the normal group, the sacral base in relation to the pelvis was higher in the L4 group and lower in the L6 group. The C2-C7 angle and lumbar lordosis (LL) were increased in both the L4 and L6 groups. All remaining parameters were decreased in the L4 group and increased in the L6 group. The relationship between LL and PI was similar in the normal and LSTV groups, despite the difference in the sacral base location.

CONCLUSIONS

We propose a precise method for numbering the vertebrae using coronal and sagittal full body images. The spinopelvic parameters of the LSTV population significantly differed from those in the normal spine population due to differences in the sacral base location.

Quantitative measurements at the lumbosacral junction are more reliable parameters for identifying and numbering lumbosacral transitional vertebrae

OBJECTIVES

To evaluate quantitative parameters to identify the anatomic variation lumbosacral transitional vertebrae (LSTV) and compare them with the landmarks commonly used at present.

METHODS

A total of 2,845 PET/CT scans were reviewed, and the patients with 23 and 25 presacral vertebrae were included. The quantitative parameters, including the anterior-edge vertebral angle (AVA) of the lowest lumbar-type vertebra, the ratio of the length of the inferior endplate to that of the superior endplate (RISE) of the uppermost sacral-type vertebra and the lumbosacral intervertebral disc angle (LSIVDA), and the anatomical landmarks, including the iliac crest tangent (ICT) level, the iliolumbar ligament (ILL) origin level and psoas proximal insertion, were all evaluated to determine their ability to identify LSTV.

RESULTS

The values of AVA and RISE were significantly different between the LSTV group and the control group, and between subgroups of LSTV. The cutoff value for AVA was 73.0°, with an accuracy, sensitivity, and specificity of 91.1%, 77.5%, and 88.3%, and that for RISE was 0.79, with an accuracy, sensitivity, and specificity of 90.3%, 77.5%, and 94.2%, while that for LSIVDA was 14.15°, with an accuracy, sensitivity, and specificity of 75.9%, 65.7%, and 78.3%, to differentiate L5 sacralization from S1 lumbarization. For differentiating the controls from LSTV, the accuracy, sensitivity, and specificity of the ICT level and proximal psoas insertion were 78.0%, 70.2%, and 95.0%, versus 71.7%, 61.7%, and 94.0%.

CONCLUSIONS

Compared with the anatomical landmarks, the quantitative measurements at the lumbosacral junction, including AVA and RISE, may be more helpful for differentiating subgroups of LSTV especially if only lumbar spine imaging is available.

KEY POINTS

• The quantitative parameters, the anterior-edge vertebral angle (AVA) of the lowest lumbar-type vertebra and the ratio of the length of the inferior endplate to that of the superior endplate (RISE) of the uppermost sacral-type vertebra, are more helpful for distinguishing L5 sacralization from S1 lumbarization than the previously proposed anatomic landmarks. • AVA and RISE represent relevant changes in the curvature at the lumbosacral region and the shape of the transitional vertebral body, respectively. • AVA and RISE are easily assessed, with high intra- and inter-reader reliability.

Vascular anatomy and surgical approach in oblique lateral interbody fusion at lumbosacral transitional vertebrae

BACKGROUND

Oblique lateral interbody fusion (OLIF) at lumbosacral junction is typically performed on the central window between the bifurcations of iliac vessels. However, the central window of lumbosacral transitional vertebrae (LSTVs) is usually obstructed by the iliocaval venous structures. We aimed to describe the vascular anatomy and surgical approach in OLIF at LSTVs compared with those in OLIF at typical L5-S1 junction.

METHODS

Sixty-eight consecutive patients who underwent OLIF at lumbosacral junction were included. Of these, 31 patients had LSTVs and 37 patients had typical L5-S1 junction. The position of the iliocaval junction and the configuration of the left common iliac vein were compared using the preoperative CT and MR images of the lumbar spine. The surgical approach and intraoperative vascular findings were analyzed.

RESULTS

Almost 70% of LSTVs had the iliocaval junction at low or very low position. Mobilization of left common iliac vein for central window was potentially difficult in almost 74% of OLIF at LSTVs while it was not required or was potentially easy in almost 80% of OLIF at typical L5-S1. Vascular injury was identified in 2 (6.5%) patients with OLIF at LSTVs and in 3 (8.1%) patients with OLIF at typical L5-S1 junction (P = 0.904).

CONCLUSIONS

In our series, OLIF at LSTVs was performed through lateral window in 93.5% of the cases. Preoperative evaluation of the iliocaval junction using CT/MR of lumbar spine was reliable and valid in the determination of OLIF approach at lumbosacral junction.

Changes of Fixed Anatomical Spinopelvic Parameter in Patients with Lumbosacral Transitional Vertebrae: A Matched Pair Analysis

Functional spinopelvic parameters are crucial for describing spinal alignment (SA), but this is susceptible to variation. Anatomically fixed pelvic shape is defined by the parameters pelvic radius (PR), pelvic incidence (PI), and sacral table angle (STA). In patients with lumbosacral transitional vertebrae (LSTV), the spinopelvic alignment may be altered by changes of these parameters and influences of SA. There have been no reports studying the relation between LSTV, four (4 LV) and six (6 LV) lumbar vertebrae, and fixed anatomical spinopelvic parameters. A retrospective analysis of 819 abdomen–pelvis CT scans was performed, identifying 53 patients with LSTV. In a matched-pair analysis, we analyzed the influence of LSTV and the subgroups 4 LV (n = 9) and 6 LV (n = 11) on PR, PI, and STA. LSTV were classified according to Castellvi classification. In patients with 6 LV, measurement points at the superior endplates of S1 and S2 were compared. The prevalence of LSTV was 6.5% (53/819), 6 LV was 1.3% (11/819), and 4 LV was 1.1% (9/819) in our study population. PI significantly increased (p < 0.001), STA significantly decreased (p < 0.001), and PR (p = 0.051) did not differ significantly in the LSTV group (n = 53). Similar findings were observed in the 4 LV subgroup, with an increase in PI (p < 0.021), decrease in STA (p < 0.011), and no significant difference in PR (p < 0.678). The same results were obtained in the 6 LV subgroup at measuring point S2 (true S1) PI (p = 0.010), STA (p = 0.004), and PR (p = 0.859), but not at measuring point S1 (true L6). Patients with LSTV, 4 LV, and 6 LV showed significant differences in PI and STA compared to the matched control group. PR showed no significant differences. The altered spinopelvic anatomy in LSTV patients need to be reflected in preoperative planning rebalancing the sagittal SA.

Factors related to postoperative coronal imbalance in adult lumbar scoliosis

OBJECTIVE

The object of this study was to analyze the prevalence of postoperative coronal imbalance (CIB) and related factors in patients with adult lumbar scoliosis.

METHODS

This was a retrospective single-center study of data from patients with adult spinal deformity (ASD) who had undergone corrective surgery performed by a single surgeon between 2009 and 2017. The inclusion criteria were as follows: 1) age at surgery > 40 years, 2) Cobb angles of the thoracolumbar/lumbar (TL/L) curve > 40°, 3) upper instrumented vertebra of T9 or T10, 4) lowest instrumented vertebra of L5 or the pelvis, and 5) minimum 2-year follow-up period. Radiographic parameters were measured before surgery, 2 weeks after surgery, and at the latest follow-up. Curve flexibility was also assessed using side bending radiographs. Clinical outcomes were evaluated using the 22-Item Scoliosis Research Society Outcomes Questionnaire (SRS-22) and the SF-36. CIB was considered to have occurred if the C7 plumbline was more than 2.5 cm lateral to the central sacral vertical line (i.e., coronal vertical axis [CVA] > 2.5 cm) at the final follow-up. Parameters between the patients with (CIB group) and without (coronal balance [CB] group) CIB were compared, and factors related to CIB were evaluated.

RESULTS

From among 66 consecutively treated ASD patients, a total of 37 patients (mean age at surgery 66.3 years, average follow-up 63 months) met the study inclusion criteria. CIB was found in 6 patients at the final follow-up (16.2%), and the CVA of all patients in the CIB group shifted to the convex side of the TL/L curve. A comparative analysis between the CB and CIB groups, respectively, at the final follow-up indicated the following factors were related to CIB: lumbosacral (LS) curve, 11.0°/16.5° (p = 0.02); LS correction rate (CR), 61%/47% (p = 0.02); and CR ratio (LS vs TL/L), 0.93/0.67 (p = 0.0002). Regarding clinical outcomes, the satisfaction domain of the SRS-22 (CB 4.4 vs CIB 3.5) showed a significant difference between the CIB and CB groups (p = 0.02), and patients in the CB group tended to score better on the pain domain (CB 4.3 vs CIB 3.7), but the difference was not significant (p = 0.06).

CONCLUSIONS

Postoperative CIB negatively impacted patients' HRQOL. An imbalanced correction ratio between the TL/L and LS curves may cause postoperative CIB. Therefore, adequate correction of the LS curve may prevent postoperative CIB.

Pelvic Incidence in Spines With 4 and 6 Lumbar Vertebrae

STUDY DESIGN

Anatomical study.

OBJECTIVES

This study was conducted to determine the prevalence of abnormal lumbar vertebrae (4 and 6) and note any differences in pelvic incidence (PI) between spines with 4, 5, and 6 lumbar vertebrae.

METHODS

We screened 2980 dry cadaveric specimens from an osteological collection. Pelvises were reconstructed by articulating the sacra and innominate bones. PI was measured in all specimens via lateral photographs. L6-pelvic incidence (L6PI) was also measured, by articulating L6 to the sacrum and measuring PI from the superior aspect of the L6 vertebral body.

RESULTS

Of the specimens screened, 969 specimens were evaluated. Average age of death for all specimens was 50.4 ± 15.4 years. The prevalence of 6 lumbar vertebrae was 0.8% (n = 23), and the prevalence of 4 lumbar vertebrae was 1.8% (n = 54). PI measured 38.5° in specimens with 4 lumbar vertebrae, and 46.7° and 47.1° in specimens with 5 and 6 lumbar vertebrae, respectively. PI was significantly different between specimens with 4 and 5 lumbar vertebrae (P < .001) but not between specimens with 5 and 6 lumbar vertebrae (P = .38). For specimens with 6 lumbar vertebrae, when L6 was added to the sacrum, mean L6PI was 27.4°.

CONCLUSIONS

In our large cadaveric study of full spines, we reported a lower prevalence of spines with 4 and 6 lumbar vertebrae compared to previous studies. PI was significantly decreased in subjects with 4 lumbar vertebrae compared with those with normal spines, and special caution should be taken when managing sagittal balance in these patients.

Morphology, pathology, and the vertebral posture of the La Chapelle-aux-Saints Neandertal

Although the early postural reconstructions of the Neandertals as incompletely erect were rejected half a century ago, recent studies of Neandertal vertebral remains have inferred a hypolordotic, flat lower back and spinal imbalance for them, including the La Chapelle-aux-Saints 1 skeleton. These studies form part of a persistent trend to view the Neandertals as less "human" than ourselves despite growing evidence for little if any differences in basic functional anatomy and behavioral capabilities. We have therefore reassessed the spinal posture of La Chapelle-aux-Saints 1 using a new pelvic reconstruction to infer lumbar lordosis, interarticulation of lower lumbar (L4-S1) and cervical (C4-T2) vertebrae, and consideration of his widespread age-related osteoarthritis. La Chapelle-aux-Saints 1 exhibits a pelvic incidence (and hence lumbar lordosis) similar to modern humans, articulation of lumbar and cervical vertebrae indicating pronounced lordosis, and Baastrup disease as a product of his advanced age, osteoarthritis, and lordosis. Our findings challenge the view of generally small spinal curvatures in Neandertals. Setting aside the developmentally abnormal Kebara 2 vertebral column, La Chapelle-aux-Saints 1 is joined by other Neandertals with sufficient vertebral remains in providing them with a fully upright (and human) axial posture.

Spinopelvic Parameters and Sagittal Alignment of Symptomatic Degenerative Adult Spinal Disorder Patients With 6 Lumbar Vertebrae

STUDY DESIGN

This was a cross-sectional, observational study.

OBJECTIVE

The main objectives of this study were to observe the prevalence of a true L6 among patients with symptomatic adult spinal degeneration, and to evaluate similarities of their radiographic spinopelvic parameters to L5 patients.

SUMMARY OF BACKGROUND DATA

Spinopelvic parameter values used for diagnosis and surgical planning are different between individuals with 5 or 6 lumbar vertebrae. The difference has not been studied in patients with symptomatic spinal degenerative conditions.

MATERIALS AND METHODS

A total of 775 consecutive symptomatic patients with degenerative spinal disorders were classified as having 5 or 6 lumbar vertebrae in full spine radiographs. Pelvic incidence minus lumbar lordosis (PI-LL), sagittal vertical axis (SVA), pelvic tilt, and T1 pelvic angle were measured in 3 groups: sacral (L5 and L6s) and L6 upper endplate (L6e). Oswestry Disability Index (ODI) was obtained.

RESULTS

In total, 715 (92.3%) patients had L5 and 60 (7.7%) had L6. LL values were comparable between the L5 and L6s (P=0.355) and SVA between all groups (P=0.869). Only SVA had excellent concordance correlation (ρc=0.91) between the L6s and L6e groups. PI-LL had significantly different values (P<0.001 all groups) and distributions between L5 and L6s (P=0.038), and L6s and L6e (P<0.001) groups. In patients with severe disability (ODI>40%) the parameters that deteriorate with increasing degeneration (pelvic tilt, T1 pelvic angle, SVA, LL, PI-LL) were not significantly different between L5 and L6s groups unlike patients with ODI<40% while PI remained similarly different (P<0.001). PI and LL had a multivariate relationship in L6 patients computable as regression model equation: PI (sacrum)=-0.92×LL (L6e)+0.91×LL (sacrum) +1.11×PI (L6e)+10.81 (R=0.88).

CONCULSIONS

L6 variant is fairly common. The radiographic L6 parameters were different from L5 except for SVA and values of patients with severe disability measured from sacrum. PI and LL have a mathematic relationship in L6 patients. The cutoff values for radiographic modifiers need further studies combining radiology and clinical outcome.

LEVEL OF EVIDENCE

Level III.

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.

Variability in Assessing Spinopelvic Parameters With Lumbosacral Transitional Vertebrae: Inter- and Intraobserver Reliability Among Spine Surgeons

STUDY DESIGN

Prospectively collected survey study OBJECTIVE.: The aim of this study was to determine the consistency with which spinopelvic parameters (SPP) are determined in patients with lumbosacral transitional vertebrae (LSTV).

SUMMARY OF BACKGROUND DATA

The incidence of LSTV in the general population is as high as 35.6%. The often fixed nature of LSTV relative to the pelvis, but lumbar-type appearance, may lead to differential use of the S1 endplate when performing SPP assessment. This could have significant impact on SPP derived from these landmarks, resulting in considerable variation in surgical planning and decision-making.

METHODS

Twenty patients demonstrating LSTV on standing lateral 36-inch spinal radiographs were randomly arranged and independently analyzed by 16 experienced spine surgeons using the same computer software. Pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL), and T1 pelvic angle (TPA) were captured. Two weeks after the first assessment, surgeons repeated the measurements after image sequence re-randomization. Intraclass correlation coefficient (ICC) was calculated to evaluate interobserver reliability (IOR) for each SPP. Intraobserver reliability (IAOR) was assessed through an average Pearson correlation coefficient for each parameter for each surgeon.

RESULTS

Sixteen surgeons completed initial measurements. IOR was poor for TPA (0.35, 95% confidence interval [CI] 0.20, 0.58) and PI (0.42, 95% CI 0.26, 0.65) and fair for LL (0.67, 95% CI 0.51, 0.82), and PT (0.63, 95% CI 0.47, 0.81). Fourteen surgeons completed phase-2 measurements to assess IAOR. Average parameter PPC showed excellent IAOR (LL 0.86, TPA 0.77, PI 0.78, PT 0.86). Kappa coefficient showed fair agreement for raters choosing the same endplate for measurement (Phase 1: 0.38, Phase 2: 0.32). By patient, the percentage of raters that chose the S1 endplate for measurement varied from 6.3% to 85.7%.

CONCLUSION

Significant variability exists when surgeons measure SPP in patients with LSTV. These parameters are critical in determining the goals of surgical reconstruction and such variability may have considerable implications for radiographic goals and outcomes of surgical reconstruction.

LEVEL OF EVIDENCE

4.