Proximal Fusion Level Above First Coronal Reverse Vertebrae: An Essential Factor Decreasing the Risk of Adjacent Segment Degeneration in Degenerative Lumbar Scoliosis

Bone Density Distribution in the Cervical Spine

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Given changes in bone density induced by degenerative disease, general measures of bone health (ie DEXA) are inadequate to evaluate bone density in surgical areas of interest. Regional differences in HU in the cervical spine may influence surgical strategies. The purposes of our study were to determine whether cervical Hounsfield units (HU) vary by level, examine their relationship with age, comorbidities, and alignment, and propose a technique to measure HU in the lateral masses.

METHODS

Two hundred twenty-four patients with degenerative spine pathology with a cervical computed tomography were included (2015-2019). Measurements were performed in each vertebral body (C2-T1; mid-axial, anterior-axial, posterior-axial, mid-coronal, and mid-sagittal) and 2 regions of the lateral masses (C3-C6; mid-cor, mid-sag). To evaluate reliability, 6 observers each measured 355 HU values, inter-relater reliability assessed with intraclass correlation coefficients Correlations of HU with age, BMI, comorbidities, and cervical alignment were evaluated.

RESULTS

Bone density differed by level, with the lowest HU scores in the lower cervical spine (C6-T1) (P < .001). No correlations were found between LM HU and age, BMI, CCI, or alignment (P > .05). Increased kyphosis was weakly correlated with VB HU, while age and CCI showed moderate correlations with VB HU at all levels (P<.001). ICC for HU measurements were good to excellent for the VBs, but poor to moderate for the LMs.

CONCLUSION

Bone is least dense in the lower cervical spine. HU scoring is not reliable in the lateral masses. We recommend that a level-specific approach to bone density is considered in surgical planning.

Upper instrumented vertebrae selection criteria for degenerative lumbar scoliosis based on the hounsfield unit asymmetry of the first coronal reverse vertebrae: an observational study

BACKGROUND

Selection of the upper instrumented vertebra (UIV) is crucial for surgical treatment of degenerative lumbar scoliosis (DLS), given the relevance of UIV in postoperative proximal adjacent segment degeneration (pASD). Our previous research found that selection of UIV not lower than (≤) the first coronal reverse vertebra (FCRV), which marks the turning point of Hounsfield unit (HU) asymmetry, could significantly reduce pASD. However, the degree of HU asymmetry can vary among patients, suggesting a demand for more individualized UIV selection criteria, which we aimed to develop using quantitative HU measurement in the current study.

METHODS

We included 153 consecutive patients with DLS. Quantitative measurement of HU of both sides of the vertebrae of these patients was performed on three planes of CT reconstruction for average values and determination of FCRV. Pre- and postoperative X-ray plain films were examined for radiological measurements and determination of pASD. Further, 35 patients with lumbar disc herniation and without significant scoliosis were also included as the reference group, and their bilateral HU was measured.

RESULTS

In all 153 patients, those with UIV ≤ FCRV had a significantly lower rate of pASD (9.4% vs. 24.6%, P = 0.011). The difference between HU of the left and right sides of the FCRV (dF) could range from close to 0-59.4. The difference between HU of the left and right sides of the vertebrae in the reference group had an average value of 5.21. In 101 dF ≥ 5 DLS patients, those with UIV ≤ FCRV had a significantly lower rate of pASD (7.6% vs. 28.6%, P = 0.005), while this rate was insignificant in the other 52 dF < 5 patients (13.3% vs. 18.2%, P = 0.708). No other general, radiological, or operative parameter was found to have significant influence on the occurrence of pASD.

CONCLUSIONS

Selection of UIV ≤ FCRV can significantly reduce the risk of pASD for patients with DLS with dF ≥ 5. Trial Registration Not applicable, since this is an observational study.

Reliability of end, stable, neutral, first coronal reverse vertebrae identification in degenerative lumbar scoliosis: Intra- and interobserver consistency analysis

Objective

To assess the intra- and interobserver reliability by observer training level used for selecting the end vertebra (EV), neutral vertebra (NV), stable vertebra (SV), and first coronal reverse vertebrae (FCRV) in degenerative lumbar scoliosis (DLS) patients.

Methods

Fifty consecutive upright long-cassette radiographs and CT examination of operative cases of DLS were evaluated by three surgeons at various levels of training. For each iteration, the observers attempted to identify the UEV, NV and SV from x-ray, and FCRV from the CT examination. Intra- and interobserver reliability was assessed by means of Cohen's Kappa correlation coefficient, and raw percentages of agreement were recorded.

Results

Intraobserver reliability was excellent for determining FCRV (K _a = 0.761-0.837), fair to good for determining UEV (K _a = 0.530-0.636), fair to good for determining SV (K _a = 0.519-0.644), and fair to good for determining NV (K _a = 0.504-0.734), respectively. Additionally, we also noted a trend towards better intraobserver reliability with increasing levels of experience. Interobserver reliability was poor between observers beyond chance for UEV, NV, SV (K _a = 0.105-0.358), and good reliability for FCRV (K _a = 0.581-0.624). All three observers agreed on the same level of the FCRV in 24 patients of the time, which presented less Coronal imbalance type C compared to the other 26 patients.

Conclusion

Experience and training level of the observers are important factors affecting the accurate identification of these vertebrae in DLS, intraobserver reliability increases along with increasing levels of observer experience. FCRV is superior to UEV, NV, and SV in the accuracy of identification, Type C coronal malalignment could affect the accurate identification of FCRV.

Hounsfield Unit for Assessing Bone Mineral Density Distribution Within Cervical Vertebrae and Its Correlation With the Intervertebral Disc Degeneration

STUDY DESIGN

Retrospective radiological analysis.

OBJECTIVE

To assess bone mineral mass distribution within cervical vertebrae based on Hounsfield unit (HU) measurement, and explore its correlation with intervertebral disc degeneration.

METHOD

Three hundred and twenty-four patients with degenerative cervical spine disease were retrospectively reviewed and divided into six groups according to age. HU measurement of the whole vertebrae from C3 through C7 was obtained, then HU measurement within upper and lower part of the vertebrae on sagittal plane were obtained from C3 through C7. Disc degeneration on MRI was graded from I to V using the Pfirrmann classification.

RESULTS

There was a significant difference in the HU value from C3 to C7 among Group II to Group VI, the HU value presented consistently decreasing trend from young patients to old patients. In C6 and C7 vertebrae, there were significant differences in HU values between upper and lower parts of the vertebrae. More importantly. In all groups, HU values were highest in the upper part of the C4 vertebrae and then gradually decreased towards C3 and C7. HU value of both upper and lower vertebrae presented decreasing trend along with the aggravation of the disc degeneration.

CONCLUSION

HU values are not typically consistent throughout all levels of the cervical spine and the distribution within the vertebrae is not homogeneous. Decreased vertebral BMD and vertebral osteoporosis may trigger or exacerbate the adjacent intervertebral disc degeneration.