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

Comparison of Hounsfield Unit, Vertebral Bone Quality, and Dual-Energy X-Ray Absorptiometry T-Score for Predicting Cage Subsidence After Posterior Lumbar Interbody Fusion

Study designRetrospective cohort study.ObjectivesTo compare Hounsfield unit (HU), vertebral bone quality (VBQ), and dual-energy X-ray absorptiometry (DEXA) T-score in predicting cage subsidence (CS) after posterior lumbar interbody fusion.MethodsWe retrospectively reviewed patients undergoing PLIF and measured L4 HU and VBQ. Baseline characteristics between CS and non-CS groups were compared. Multiple logistic regression analysis was used to identify risk factors for CS. Receiver operating characteristic (ROC) curves were used to explore the predictive value of variables for CS. Subgroup analysis was conducted for patients with available DEXA results.ResultsEighty-four patients were analyzed. The subsidence group was older, with lower L4 HU (92.6 (35.4) vs 130.8 (47.8), P < 0.001) and higher VBQ (3.30 (0.64) vs 2.99 (0.63), P = 0.041) compared to the non-CS group. Low L4 HU (OR 0.979, P = 0.022) was an independent risk factor for subsidence, while VBQ was not. ROC analysis indicated that L4 HU (AUC = 0.733, P < 0.001) exhibited superior predictive performance compared to VBQ (AUC = 0.643, P = 0.032). Subgroup analysis in patients with DEXA showed that the femoral neck T-score (AUC = 0.67, P = 0.037) could differentiate CS, with L4 HU exhibiting the highest predictive ability (AUC = 0.778, P < 0.001), both outperforming VBQ (AUC = 0.645, P = 0.075).ConclusionsAmong the three BMD parameters, only low L4 HU could be an independent risk factor for CS. Preoperative HU is mandatory in patients at risk for osteoporosis when undergoing spine surgery.

Upper Instrumented Vertebra Hounsfield Unit Assessment and Association With Mechanical Complications Following Posterior Spinal Fusion

BACKGROUND

Bone mineral density is often considered in preoperative surgical planning for spinal fusions. CT imaging-based measurement of Hounsfield units (HU) has been suggested as a surrogate marker for dual-energy x-ray absorptiometry scans. However, research establishing a threshold for HU at the uppermost instrumented vertebrae (UIV) that can mitigate the risk of mechanical and junctional complications following posterior spinal fusion is limited.

METHODS

Adults who underwent posterior spinal fusion and had 1-year follow-up data available were included in this retrospective cohort study. HU measurements were collected at various vertebral levels, including at the UIV. Inter- and intrarater reliability were calculated using the using intraclass correlation coefficients (ICCs). HU thresholds for mechanical and junctional complications were established using receiver operating characteristic (ROC) curve analyses, while accounting for age, sex, UIV level, and osteoporosis.

RESULTS

Across 70 patients, mean age was 64.4 years, 65.3% were female, and 10.0% had osteoporosis. The intrarater reliability ICCs were classified as excellent (ie, greater than 0.9) for all vertebral levels, whereas the interrater reliability ICCs were classified as good (ie, greater than 0.8) for all vertebral levels. ROC curve analyses identified a HU cutoff of 105. Patients below the HU threshold had markedly higher rates of mechanical and junctional complications (52.0% vs. 8.9%, P < 0.001), specifically adjacent segment disease (32.0% vs. 2.2%, P < 0.001).

CONCLUSION

CT-based measurement of HU at the upper instrumented vertebra has excellent intrarater and good interrater reliability. In this cohort of lumbar and thoracolumbar spinal fusion patients, patients with HU under 105 at the UIV had an increased risk of mechanical and junctional complications following spinal fusions. Future studies may work to refine HU assessment and the association with postoperative complications, as using HU to guide surgical candidacy and UIV selection may be beneficial.

Hounsfield unit correlates with intervertebral disc degeneration in premenopausal and menopausal women: a radiological study

OBJECTIVES

This study aims to investigate whether Hounsfield unit (HU) value is correlated with intervertebral disc (IVD) degeneration (IVDD) by comparing premenopausal with menopausal women patients.

METHODS

A total of 101 female patients who underwent treatment in our hospital between February 2022 and February 2023 were retrospectively reviewed and included in this study. All patients were divided into either the premenopausal group or the menopausal group, according to age and menopause status. The changes in disc height index (DHI) on X-ray, the Hounsfield unit (HU) value on computed tomography (CT), and the area of the nucleus pulposus (NP) on magnetic resonance imaging (MRI) were assessed and compared between the two groups.

RESULTS

There is a significant difference in the Pfirrmann grading of T12-S1 discs between the premenopausal and menopausal groups; the menopausal group has more degenerated discs compared with the premenopausal group (P < 0.001). There is no significant difference in DHI measurements between the premenopausal and menopausal groups. HU values in the premenopausal group are greater compared with the menopausal group from T12 to S1 vertebrae (all P < 0.001). Regarding the NP area on MRI, the L2-L3 IV disc space have a bigger area in the premenopausal group compared with the menopausal group (P = 0.029), with no significant difference in other IVD segments.

CONCLUSIONS

The HU value on CT is significantly decreased with IVDD progression after menopause. The change in HU value could indirectly reflect vertebral bone mineral density. Therefore, the decline of estrogen after menopause leads to vertebral osteoporosis, which might contribute to IVDD progression.

Influence of Cervical Level Fused on Subsidence of Cage and Allograft in Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

This study aims to evaluate the relationship between the cervical levels fused and the degree of subsidence following anterior cervical discectomy and fusion (ACDF) procedures.

BACKGROUND

Subsidence following ACDF may worsen clinical outcomes. Previous studies have linked lower cervical levels with higher rates of subsidence, but none have quantified the relative degree of subsidence between levels.

MATERIALS AND METHODS

Patients who underwent ACDF from 2016 to 2021 at a tertiary medical center were included in this study. Lateral cervical radiographs from the immediate postoperative period and the final follow-ups were used to calculate subsidence. Analysis of variance was used to examine the association between cervical levels fused and subsidence. Multivariable linear regression analysis controlled for age, sex, smoking status, osteopenia/osteoporosis, number of fused levels, cage-to-body ratio, and cage type while examining the relationship between the cervical level fused and subsidence.

RESULTS

This study includes 122 patients who underwent 227 levels fused. There were 16 (7.0%) C3-C4 fusions, 55 (24.2%) C4-C5 fusions, 97 (42.7%) C5-C6 fusions, and 59 (26.0%) C6-C7 fusions. There was a significant difference in the degree of anterior subsidence between cervical levels fused ( P = 0.013) with a mean subsidence of 1.0 mm (SD: 1.6) for C3-C4, 1.1 mm (SD: 1.4) for C4-C5, 1.8 mm (SD: 1.5) for C5-C6, and 1.8 mm (SD: 1.6) for C6-C7 fusions. Relative to C6-C7 fusions, C4-C5 ( P = 0.016), and C3-C4 ( P = 0.014) fusions were associated with decreased anterior subsidence, whereas C5-C6 ( P = 0.756) fusions were found to have similar degrees of anterior subsidence in the multivariable analysis.

CONCLUSION

We found upper cervical levels experienced a smaller degree of anterior subsidence than lower levels, after controlling for demographic and implant characteristics. Surgeons can consider using larger cages at lower cervical levels to minimize these risks.

Bony Bridge Evaluation Following Alveolar Bone Grafting by Hounsfield Unit Visualization

Although alveolar bone grafting (ABG) is the standard treatment for cleft lip and palate with alveolar clefts, no studies have visually demonstrated the qualitative changes in grafted bones over time. In this study, the authors attempted to depict the changes in ossification of the grafted bone over time using color mapping based on differences in Hounsfield units (HUs). Alveolar bone grafting was performed in 7 cases. Computed tomography data procured ∼1 month before ABG, 1 day after surgery, and 6 months after surgery were extracted using Mimics (version 26.0)-a medical image analysis software. The difference in the HU values was visualized through color mapping in the axial, coronal, and sagittal planes, and changes in the HU values of the grafted bone over time and structure were observed. The HU values were high in all areas immediately after surgery; however, 6 months after surgery, cortical bone-like structures with high HU values were observed around the grafted bone, regardless of the presence of dynamic teeth changes. Moreover, the HU values were evidently high in areas where tooth movement was observed. Changes in the HU values over time can contribute to quantitative suggestions regarding the filling volume and filling pressure in ABG techniques and aid in determining the optimal orthodontic force most conducive to tooth movement during orthodontic treatment. Hence, this technique is expected to be valuable for both research and clinical practice.

SDC4 drives fibrotic remodeling of the intervertebral disc under altered spinal loading

Alterations in physiological loading of the spine are deleterious to intervertebral disc health. The caudal spine region Ca3-6 that experiences increased flexion, showed disc degeneration in young adult mice. Given the role of Syndecan 4 (SDC4), a cell surface heparan sulfate proteoglycan in disc matrix catabolism and mechanosensing, we investigated if deletion could mitigate this loading-dependent phenotype. Notably, at spinal levels Ca3-6, Sdc4- KO mice did not exhibit increased collagen fibril and fibronectin deposition in the NP compartment or showed the alterations in collagen crosslinks observed in wild-type mice. Similarly, unlike wild-type mice, NP cells in Sdc4 -KO mice retained transgelin (TGLN) expression and showed absence of COL X deposition, pointing to the preservation of their notochordal characteristics. Proteomic analysis revealed that NP tissues responded to the abnormal loading by increasing the abundance of proteins associated with extracellular matrix remodeling, chondrocyte development, and contractility. Similarly, downregulated proteins suggested decreased vesicle transport, autophagy-related pathway, and RNA quality control regulation. Notably, NP proteome from Sdc4 KO suggested that increased dynamin-mediated endocytosis, autophagy-related pathway, and RNA and DNA quality control may underscore the protection from increased flexion-induced degeneration. Our study highlights the important role of SDC4 in fine-tuning cellular homeostasis and extracellular matrix production in disc environment subjected to altered loading.

Is There a Positive or Negative Correlation Between Cervical Vertebral Bone Quality and Intervertebral Disc Degeneration by Pfirrmann Grading

Objective

Cervical degeneration involves many pathophysiological changes. Vertebral bone loss, sclerotic hyperplasia of the vertebral body and intervertebral disc degeneration (IDD) are most common degenerative factors. However, whether there is a correlation between changes in vertebral bone mass and IDD remains unclear. In this study, based on magnetic resonance imaging (MRI), Pfirrmann method was used to grade cervical disc degeneration, and vertebral bone quality (VBQ) was measured. The correlation between VBQ and IDD was analyzed, and its potential mechanism was discussed as well.

Methods

From June 2019 to June 2023, clinical data of patients undergoing surgical treatment for cervical degenerative disc diseases (CDDD) in our department were retrospectively analyzed. Preoperative MRI was collected, the degree of IDD was assessed by Pfirrmann grading, and VBQ was measured by T1-weighted image of MRI. With VBQ score = 3.08 as the threshold, Spearman correlation analysis was used to quantified the correlation between IDD grade and VBQ, and multiple ordered Logistic regression analysis was used to evaluate the effect of VBQ on IDD grade.

Results

The preoperative MRI data of 94 patients (male, 42; female, 52) with CDDD were collected. Spearman correlation analysis: When VBQ score ≤ 3.08, the IDD grade was negatively correlated with VBQ (p < 0.05, r = -0.153). When VBQ score > 3.08, the IDD grade was positively correlated with VBQ (p < 0.05, r = 0.306). Multiple ordered Logistic regression analysis: When VBQ score ≤ 3.08, the effect of VBQ on IDD was negatively correlated (p < 0.05, β = -0.597). When VBQ score > 3.08, the effect of VBQ on IDD was positively correlated (p < 0.05, β = 0.986).

Conclusions

Either excessive increased or decreased VBQ in the cervical spine may accelerate the progression of IDD. The reason may be that both abnormal interference from the VBQ may imbalance the cervical spinal biomechanics and compromise the absorption of nutrients in the disc, thus accelerating the IDD. Therefore, cervical VBQ may have a bidirectional effect on IDD.

The Degree of Cervical Intervertebral Disc Degeneration Is Associated With Denser Bone Quality of the Cervical Sub-endplate and Vertebral Body

OBJECTIVE

The relationship between cervical disc degeneration and bone quality of adjacent vertebral body remains controversial. This study aims to investigate the relationship between cervical disc degeneration and bone quality of the adjacent vertebral body and sub-endplate bone with a new MRI-based bone quality score in patients over 50 years with cervical spondylosis.

METHODS

We retrospectively reviewed 479 cervical disc segments from 131 patients. Disc degeneration at levels C3/C4-C6/C7 was graded using T2-weighted MRI. Vertebral body quality (VBQ) score and sub-endplate bone quality (EBQ) score from C3 to C7 were computed from T1-weighted MRI images. Additionally, bone mineral density (BMD) of the cervical vertebrae was measured in 52 patients using a novel phantom-less quantitative computed tomography (PL-QCT) system. The correlation between bone quality score and Pfirrmann grade was analyzed and risk factors for VBQ and EBQ were further evaluated.

RESULTS

Significant differences were found in cranial VBQ among different Pfirrmann grades, with a score of 2.55 ± 0.54 for Grade 5 discs, which was lower compared to Grades 4 (2.70 ± 0.56) (p < 0.05) and 3 (2.81 ± 0.58) (p < 0.01). Caudal VBQ for Grade 5 discs (2.43 ± 0.52) was also significantly lower than for Grade 3 discs (2.66 ± 0.54) (p < 0.01). EBQ scores decreased with increasing Pfirrmann grades. Negative correlations were observed between both cranial and caudal VBQ and EBQ scores and Pfirrmann grades. Grades 4 and 5 discs were identified as independent risk factors for decreased caudal VBQ and EBQ, whereas only Grade 5 was a significant risk factor for decreased cranial EBQ. Additionally, a moderate correlation (0.4 < R < 0.6, p < 0.05) was noted between vertebral body BMD and VBQ at each cervical level.

CONCLUSION

In individuals over 50 years with cervical spondylosis, the severity of disc degeneration was closely correlated with denser bone quality in both the caudal vertebral body and sub-endplate, as measured by VBQ and EBQ scores. These findings suggest that worsening disc degeneration is associated with increased bone density in specific areas of the cervical spine.

Hounsfield Unit Utilization in Cervical Spine for Bone Quality Assessment: A Scoping Review

Bone mineral density (BMD) is an essential indicator of bone strength and plays a crucial role in the clinical management of various spinal pathologies. Hounsfield units (HUs) calculated from computed tomography (CT) scans are a well-established, effective, and non-invasive method to determine bone density in the lumbar spine when juxtaposed to dual-energy X-ray absorptiometry (DEXA) scans, the gold standard for assessing trabecular bone density. Only recently have studies begun to investigate and establish HUs as a reliable and valid alternative for bone quality assessment in the cervical spine as well. In addition, multiple recent studies have identified cervical HUs as an accurate predictor of cage subsidence, an undesired complication of anterior cervical discectomy and fusion (ACDF) of anterior cervical corpectomy and fusion (ACCF) procedures. Subsidence involves migration of the spinal fusion cage into vertebral bodies, causing a loss of disk space, negatively altering spine alignment, and possibly necessitating further unwanted surgical intervention. Using the PRISMA-ScR checklist and the registered scoping review protocol (INPLASY2024100126), this review explores the current research on the use of cervical spine HU measurements as both a determinant of BMD and as a prognosticator of postoperative subsidence following cervical spine procedures (i.e., ACDFs and ACCFs) with the aim of improving clinical and surgical outcomes.

Long-term effects of COVID-19 infection on bone mineral density

Background

In this study, we aimed to identify bone mineral density (BMD) trajectories of hospitalised patients with coronavirus disease 2019 (COVID-19) and to determine the prognostic role of the trajectory groups.

Methods

This is a retrospective study of hospitalised patients with COVID-19 treated in our hospital from November 2022 to February 2023. BMD was manually measured from the thoracic 12 (T12) and lumbar one (L1) vertebra using chest computed tomography images. We constructed group trajectory models using group-based trajectory modelling. We performed the logistic regression analysis to associate the BMD trajectory pattern with clinical outcomes.

Results

This study included 1767 patients. The mean follow-up time after discharge was 181.5 days (standard deviation (SD) = 9.7). There were 1137 (64.3%) male patients, and more than 80% of patients were aged >60 years. We successfully identified three latent BMD trajectories to reveal the dynamic effects of COVID-19 infection on bone health in patients, namely, the early low-normal decline group, the average, and the early high-rapid decline group. All groups demonstrated consistent overall declining trends. A significant association was observed between BMD trajectory pattern (T12 or L1) and baseline characteristics of sex, age, and penetrating keratoplasty (P < 0.05). Our study showed that the BMD trajectories were significantly associated with mortality. Furthermore, we found that these trajectories were also associated with the length of hospital stay.

Conclusions

This study provided evidence for the COVID-19 process to bone health, as well as evidence on strengthening bone health management before and after COVID-19 infection. BMD trajectories may help manage bone health and guide treatment in patients with COVID-19.

Sdc4 deletion perturbs intervertebral disc matrix homeostasis and promotes early osteopenia in the aging mouse spine

Syndecan 4 (SDC4), a cell surface heparan sulfate proteoglycan, is known to regulate matrix catabolism by nucleus pulposus cells in an inflammatory milieu. However, the role of SDC4 in the aging spine has never been explored. Here we analyzed the spinal phenotype of Sdc4 global knockout (KO) mice as a function of age. Micro-computed tomography showed that Sdc4 deletion severely reduced vertebral trabecular and cortical bone mass, and biomechanical properties of vertebrae were significantly altered in Sdc4 KO mice. These changes in vertebral bone were likely due to elevated osteoclastic activity. The histological assessment showed subtle phenotypic changes in the intervertebral disc. Imaging-Fourier transform-infrared analyses showed a reduced relative ratio of mature collagen crosslinks in young adult nucleus pulposus (NP) and annulus fibrosus (AF) of KO compared to wildtype discs. Additionally, relative chondroitin sulfate levels increased in the NP compartment of the KO mice. Transcriptomic analysis of NP tissue using CompBio, an AI-based tool showed biological themes associated with prominent dysregulation of heparan sulfate GAG degradation, mitochondria metabolism, autophagy, endoplasmic reticulum (ER)-associated misfolded protein processes and ER to Golgi protein processing. Overall, this study highlights the important role of SDC4 in fine-tuning vertebral bone homeostasis and extracellular matrix homeostasis in the mouse intervertebral disc.

Causal relationship between bone mineral density and intervertebral disc degeneration: a univariate and multivariable mendelian randomization study

BACKGROUND

Although previous studies have suggested a possible association between bone mineral density (BMD) and intervertebral disc degeneration (IDD), the causal relationship between them remains unclear. Evidence from accumulating studies indicates that they might mutually influence one another. However, observational studies may be affected by potential confounders. Meanwhile, Mendelian randomization (MR) study can overcome these confounders to assess causality.

OBJECTIVES

This Mendelian randomization (MR) study aimed to explore the causal effect of bone mineral density (BMD) on intervertebral disc degeneration (IDD).

METHODS

Summary data from genome-wide association studies of bone mineral density (BMD) and IDD (the FinnGen biobank) have been acquired. The inverse variance weighted (IVW) method was utilized as the primary MR analysis approach. Weighted median, MR-Egger regression, weighted mode, and simple mode were used as supplements. The Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) and MR-Egger regression were performed to assess horizontal pleiotropy. Cochran's Q test evaluated heterogeneity. Leave-one-out sensitivity analysis was further conducted to determine the reliability of the causal relationship. Multivariate MR (MVMR) analyses used multivariable inverse variance-weighted methods to individually and jointly adjust for four potential confounders, body mass index (BMI), Type2 diabetes, hyperthyroidism and smoking. A reverse MR analysis was conducted to assess potential reverse causation.

RESULTS

In the univariate MR analysis, femoral neck bone mineral density (FNBMD), heel bone mineral density (eBMD), lumbar spine bone mineral density (LSBMD), and total body bone mineral density (TB BMD) had a direct causal effect on intervertebral disc degeneration (IDD) [FNBMD-related analysis: OR(95%CI) = 1.17 (1.04 to 1.31), p = 0.008, eBMD-related analysis: OR(95%CI) = 1.06 (1.01 to 1.12), p = 0.028, LSBMD-related analysis: OR(95%CI) = 1.20 (1.10 to 1.31), p = 3.38E-7,TB BMD-related analysis: OR(95%CI) = 1.20 (1.12 to 1.29), p = 1.0E-8]. In the MVMR analysis, it was revealed that, even after controlling for confounding factors, heel bone mineral density (eBMD), lumbar spine bone mineral density (LSBMD), and total body bone mineral density (TB BMD) still maintained an independent and significant causal association with IDD(Adjusting for heel bone mineral density: beta = 0.073, OR95% CI = 1.08(1.02 to 1.14), P = 0.013; Adjusting for lumbar spine bone mineral density: beta = 0.11, OR(95%CI) = 1.12(1.02 to 1.23), P = 0.03; Adjusting for total body bone mineral density: beta = 0.139, OR95% CI = 1.15(1.06 to 1.24), P = 5.53E - 5). In the reverse analysis, no evidence was found to suggest that IDD has an impact on BMD.

CONCLUSIONS

The findings from our univariate and multivariable Mendelian randomization analysis establish a substantial positive causal association between BMD and IDD, indicating that higher bone mineral density may be a significant risk factor for intervertebral disc degeneration. Notably, no causal effect of IDD on these four measures of bone mineral density was observed. Further research is required to elucidate the underlying mechanisms governing this causal relationship.

Hounsfield unit for assessing bone mineral density distribution within lumbar vertebrae and its clinical values

Study Design

Retrospective radiological analysis.

Objective

The aim of this study is to evaluate the distribution of bone mineral density (BMD) in lumbar vertebrae using the Hounsfield unit (HU) measurement method and investigate the clinical implications of HU values for assessing lumbar vertebrae BMD.

Method

Two hundred and ninety-six patients were retrospectively reviewed and divided into six groups according to age: Group 1(20-29 years old), Group 2 (30-39 years old), Group 3 (40-49 years old), Group 4 (50-59 years old), Group 5 (60-69 years old), Group 6 (70-79 years old). Six different locations from each vertebra of L1-L5 were selected as regions of interest: the anterior, middle and posterior parts of the upper and lower slices of the vertebrae. HU values were measured for the six regions of interest, followed by statistical analysis.

Results

The HU values of vertebrae showed a decreasing trend from young patients to elderly patients in Group 1 to Group 5. There was no significant difference in HU values among different vertebrae in the same age group. In all age groups, the HU values of the anterior and posterior part of the vertebral body were significantly different from L1 to L3, with the anterior part of the vertebral body having lower HU values than the posterior part. The HU values of the anterior and posterior part of the vertebral body of L4 and L5 were statistically significant only in Group 5 and Group 6, and the HU values of the anterior part of the vertebral body were lower than those of the posterior part. The HU values of posterior part of L4 and L5 in Group6 were higher than those in Group5.

Conclusion

Bone mineral density in the lumbar vertebrae is not uniformly distributed, potentially attributed to varying stress stimuli. The assessment of local HU values in the lumbar spine is of significant importance for surgical treatment.

Value of Hounsfield units measured by chest computed tomography for assessing bone density in the thoracolumbar segment of the thoracic spine

STUDY DESIGN

A retrospective study.

PURPOSE

To investigate the correlation between Hounsfield unit (HU) values measured by chest computed tomography (CT) and dual-energy Xray absorptiometry (DXA) T-scores. HU-based thoracolumbar (T11 and T12) cutoff thresholds were calculated for a cohort of Chinese patients.

OVERVIEW OF LITERATURE

For patients with osteoporosis, the incidence of fractures in the thoracolumbar segment is significantly higher than that in other sites. However, most current clinical studies have focused on L1.

METHODS

This retrospective study analyzed patients who underwent chest CT and DXA at our hospital between August 2021 and August 2022. Thoracic thoracolumbar segment HU values, lumbar T-scores, and hip T-scores were computed for comparison, and thoracic thoracolumbar segment HU thresholds suggestive of potential bone density abnormalities were established using receiver operating characteristic curves.

RESULTS

In total, 470 patients (72.4% women; mean age, 65.5±12.3 years) were included in this study. DXA revealed that of the 470 patients, 90 (19%) had osteoporosis, 180 (38%) had reduced osteopenia, and 200 (43%) had normal bone mineral density (BMD). To differentiate osteoporosis from osteopenia, the HU threshold was established as 105.1 (sensitivity, 54.4%; specificity, 72.2%) for T11 and 85.7 (sensitivity, 69.4%; specificity, 61.1%) for T12. To differentiate between osteopenia and normal BMD, the HU threshold was 146.7 for T11 (sensitivity, 57.5%; specificity, 84.4%) and 135.7 for T12 (sensitivity, 59.5%; specificity, 80%).

CONCLUSIONS

This study supports the significance of HU values from chest CT for BMD assessment. Chest CT provides a new method for clinical opportunistic screening of osteoporosis. When the T11 HU is >146.7 or the T12 HU is >135.7, additional osteoporosis testing is not needed unless a vertebral fracture is detected. If the T11 HU is <105.1 or the T12 HU is <85.7, further DXA testing is strongly advised. In addition, vertebral HU values that fall faster than those of the T11 and L1 vertebrae may explain the high incidence of T12 vertebral fractures.

Novel Risk Factors for Cervical Facet Joint Degeneration in the Subaxial Cervical Spine: Correlation with Cervical Sagittal Alignment and Bone Mineral Density

OBJECTIVE

The impact of cervical sagittal alignment on cervical facet joint degeneration (CFD) and the risk factors for CFD in patients with degenerative cervical myelopathy (DCM) were investigated in the current study.

METHODS

A total of 250 surgical patients with DCM were recruited. The clinical data and radiographical characteristics, including CFD, cervical sagittal balance parameters, Hounsfield unit (HU) values, disc degeneration (DD), and modic change, were collected. The detailed correlation between these characteristics and CFD was analyzed. Characteristics, including CFD, were compared among the various cervical alignment types and different CFD groups. Finally, the risk factors for CFD were revealed via logistic regression.

RESULTS

CFD was prevalent in DCM patients. Age, cervical sagittal vertical axis (cSVA), range of motion, T1 slope, thoracic inlet angle, DD, HU value, and modic change correlated with CFD segmentally and globally (P < 0.05). The lordosis and sigmoid types had a significantly higher CFD prevalence (P < 0.05). Furthermore, the average CFD threshold for the severe CFD group was 1.625 (area under the curve, 0.958). Additionally, 167 patients with average CFD <1.625 and 83 patients with CFD of ≥1.625 were classified into the mild CFD group and severe CFD group, respectively. Finally, multivariate analysis was performed, and age, cSVA, HU value, modic change, and DD were determined to be independent risk factors for CFD.

CONCLUSIONS

The load distribution tends to shift to a more shear-like pattern in the sigmoid and kyphosis types and in those with a higher cSVA, thereby promoting CFD. Aging, cervical malalignment, low bone mineral density, DD, and modic change were revealed to result in high risks of CFD.

Causal relationship between intervertebral disc degeneration and osteoporosis: a bidirectional two-sample Mendelian randomization study

Introduction

The relationship between intervertebral disc degeneration (IVDD) and osteoporosis (OP), diagnosed primarily using bone mineral density (BMD), remains unclear so far. The present study, therefore, aimed to investigate the potential relationship between osteoporosis and intervertebral disc degeneration using Mendelian randomization and genome-wide association analyses. Specifically, the impact of bone mineral density on the development of intervertebral disc degeneration was evaluated.

Materials and methods

The genome-wide association studies (GWAS) summary data of OP/BMDs and IVDD were collected from the FinnGen consortium, the GEFOS consortium, and MRC-IEU. The relationship between IVDD and OP was then explored using TSMR. The inverse-variance weighted (IVW) method was adopted as the primary effect estimate, and the reliability and stability of the results were validated using various methods, including MR-Egger, weighted median, simple mode, weighted mode, and MR-PRESSO.

Results

No significant causal relationship was observed between OP and IVDD (IVW, P > 0.05) or between femoral neck BMD (FA-BMD) and IVDD when OP and FA-BMD were used as exposures. However, increased levels of total body BMD (TB-BMD) and lumbar spine BMD (LS-BMD) were revealed as significant risk factors for IVDD (TB-BMD: IVW, OR = 1.201, 95% CI: 1.123-1.284, P = 8.72 × 10-8; LS-BMD: IVW, OR = 1.179, 95% CI: 1.083-1.284, P = 1.43 × 10-4). Interestingly, both heel BMD (eBMD) and femur neck BMD (FN-BMD) exhibited potential causal relationships (eBMD: IVW, OR = 1.068, 95% CI: 1.008-1.131, P = 0.0248; FN-BMD, IVW, OR = 1.161, 95% CI: 1.041-1.295, P = 0.0074) with the risk of IVDD. The reverse MR analysis revealed no statistically causal impact of IVDD on OP and the level of BMD (P > 0.05).

Conclusion

OP and the level of FA-BMD were revealed to have no causal relationship with IVDD. The increased levels of TB-BMD and LS-BMD could promote the occurrence of IVDD. Both eBMD and FN-BMD have potential causal relationships with the risk of IVDD. No significant relationship exists between IVDD and the risk of OP. Further research is warranted to comprehensively comprehend the molecular mechanisms underlying the impact of OP and BMD on IVDD and vice versa.

Intervertebral Disk Degeneration and Bone Mineral Density: A Bidirectional Mendelian Randomization Study

This study aimed to investigate the causal relationship between bone mineral density (BMD) and intervertebral disk degeneration (IVDD) using a two-sample bidirectional Mendelian randomization analysis. Summary-level data from the Genome-Wide Association Study (GWAS) were used. Instrumental variables (IVs) for IVDD were selected from the large-scale Genome-Wide Association Study (GWAS) (20,001 cases and 164,682 controls). Bone mineral density (BMD) at five different sites (heel (n = 426,824), total body (TB) (n = 56,284), forearm (FA) (n = 8143), femoral neck (FN) (n = 32,735), and lumbar spine (LS) (n = 28,498)) was used as a phenotype for OP. Bidirectional causality between IVDD and BMD was assessed using inverse variance weighting (IVW) and other methods. Related sensitivity analyses were performed. Myopia was also analyzed as a negative control result to ensure the validity of IVs. Heel bone mineral density (heel BMD), total body bone mineral density (TB-BMD), femoral neck bone mineral density (FN-BMD), and lumbar spine bone mineral density (LS-BMD) have a direct causal relationship on intervertebral disk degeneration (IVDD) [heel BMD-related analysis: beta = 0.06, p = 0.03; TB-BMD-related analysis: beta = 0.18, p = 8.72E-08; FN-BMD-related analysis: beta = 0.15, p = 4.89E-03; LS-BMD-related analysis: beta = 0.16, p = 1.43E-04]. There was no evidence of a significant causal effect of IVDD on BMD. In conclusion, our study found a significant positive causal effect of lower BMD on IVDD, and we identified significant causal effects of heel, TB-, FN-, and LS-BMD on IVDD, but there was no evidence of a significant causal effect of IVDD on BMD.

Does vertebral osteoporosis delay or accelerate lumbar disc degeneration? A systematic review

The effect of vertebral osteoporosis on disc degeneration is still debated. The purpose of this study was to provide a systematic review of studies in this area to further reveal the relationship between the two. Relevant studies were searched in electronic databases, and studies were screened according to inclusion and exclusion criteria, and finally, basic information of the included studies was extracted and summarized. This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A total of 34 publications spanning 24 years were included in our study. There were 19 clinical studies, including 12 prospective studies and 7 retrospective studies. Of these, 7 considered vertebral osteoporosis to be positively correlated with disc degeneration, 8 considered them to be negatively correlated, and 4 considered them to be uncorrelated. Two cadaveric studies were included, one considered the two to be negatively correlated and one considered them not to be correlated. Seven animal studies were included, of which five considered a positive correlation between vertebral osteoporosis and disc degeneration and two considered a negative correlation between the two. There were also 6 studies that used anti-osteoporosis drugs for intervention, all of them were animal studies. Five of them concluded that vertebral osteoporosis was positively associated with disc degeneration, and the remaining one concluded that there was no correlation between the two. Our systematic review shows that the majority of studies currently consider an association between vertebral osteoporosis and disc degeneration, but there is still a huge disagreement whether this association is positive or negative. Differences in observation time and follow-up time may be one of the reasons for the disagreement. A large number of clinical and basic studies are still needed in the future to further explore the relationship between the two.

Hounsfield Unit for Evaluating Bone Mineral Density and Strength: Variations in Measurement Methods

OBJECTIVE

To assess the consistency and accuracy of various measurements of the Hounsfield unit (HU) in lumbar vertebrae.

METHODS

The study reviewed lumbar spine computed tomography images of 60 postmenopausal women aged >50 years. A total of 240 vertebrae were measured and analyzed for the variations of HU values in different sections and regions. Investigated the relationship between HU values of the lumbar spine under different measurements and dual-energy X-ray absorptiometry results and the ability to identify patients with osteoporosis.

RESULTS

HU values measured in midsagittal (r = 0.763), midcoronal (r = 0.768), and midaxial (r = 0.786) sections exhibited a strong positive correlation with dual-energy X-ray absorptiometry T-scores. HU values measured in midsagittal and midaxial sections of the vertebral body were in good agreement (P > 0.1), but decreased in the midcoronal (P < 0.001). HU values in the middle of the vertebral body were significantly higher than in the near end plate (P < 0.001). HU values varied between L1 and L4 vertebrae, but all had a good ability to identify osteoporosis and did not differ significantly in screening ability (P > 0.05).

CONCLUSIONS

An averaged HU value in axial multilevel is a comprehensive assessment of vertebral bone density. Using the HU value of the lumbar spine can help identify patients with osteoporosis, and the screening ability does not differ significantly across vertebral segments.

The impact of disease time, cervical alignment and range of motion on cervical vertebral Hounsfield unit value in surgery patients with cervical spondylosis

STUDY DESIGN

This study was a retrospective review.

OBJECTIVE

Bone mineral density (BMD) at the surgical site is associated with complications of surgical internal fixation, and it is very important to study the cervical BMD of patients with cervical spondylosis who need surgery and the related factors that affect cervical BMD. It is still unclear about the age-related influence of disease time, cervical alignment and range of motion (ROM) on cervical vertebral Hounsfield unit (HU) value.

METHODS

This retrospective study was conducted on patients who underwent cervical surgery at one institution between January 2014 and December 2021. Age, sex, body mass index (BMI), disease type, comorbidities, neck pain, disease time, C2-7 Cobb angle (CA), cervical ROM and the C2-C7 vertebral HU value were recorded. The association between cervical HU value and each parameter of interest was assessed using the Pearson correlation coefficient. Multivariable linear regression analysis was performed to examine the relative influence of the multiple factors on cervical vertebral HU value.

RESULTS

Among patients younger than 50 years old, the HU value of the cervical vertebral in females was higher than that of males, but after the age of 50 years, the value of females was lower than that of males and decreased significantly after 60 years old. In addition, cervical HU value was significantly correlated with the disease time, flexion CA and ROM. Our age-related subgroup of multivariate linear regression analyses shows that disease time and flexion CA negatively affected the C6-7 HU value in more than 60-year-old males and in more than 50-year-old females.

CONCLUSIONS

Disease time and flexion CA were negatively affecting the C6-7 HU values in more than 60-year-old males and in more than 50-year-old females. More attention should be paid to bone quality in cervical spondylosis patients with longer disease time and larger convex of flexion CA.

Hounsfield unit for assessing asymmetrical loss of vertebral bone mineral density and its correlation with curve severity in adolescent idiopathic scoliosis

Background

Low bone mass concomitantly occurs in patients with adolescent idiopathic scoliosis (AIS) and can persist until skeletal maturity. The purpose of this study was to assess the asymmetrical loss of vertebral bone mineral density (vBMD) and its correlation with curve severity in patients with AIS using Hounsfield unit (HU) values measured from computed tomography scans.

Methods

A total of 93 AIS patients were retrospectively recruited. The HU values of the vertebral body (VB-HU) and pedicle screw trajectory (PST-HU) were measured from four vertebrae above (Apex − 4) to four below (Apex + 4) the apical vertebra (Apex) of the major curve. The VB-HU and PST-HU at the upper end vertebra, Apex, and lower end vertebra within the concave and convex sides of the major and minor curves and stable vertebrae were obtained.

Results

A significant correlation was found between the Cobb angle and VB-HU at the periapical levels of the major curve. VB-HU and PST-HU at periapical levels were significantly greater within the concavity than the convexity of both major and minor curves. The asymmetric ratios of VB-HU and PST-HU were significantly correlated with the major curve Cobb angle, peaked at the apex, and gradually diminished from the apex to the end vertebrae. The asymmetrical loss of vBMD aggravated with the progression of curve severity, presenting as VB-HU, significantly decreased within the convexity and insignificantly decreased within the concavity of the major curve.

Conclusion

The asymmetrical loss of vBMD was associated with the progression of curve severity in AIS. For patients with severe AIS, the distraction of the pedicle screws at the concave side should be a priority in correcting the major curve, and supplemental anchors and larger-sized screws should be placed within the convex side around the apex of the major curve to reduce the risk of screw loosening after surgery.

Treatment of three-level cervical spondylotic myelopathy using ACDF or a combination of ACDF and ACCF

Objectives

This study aims to compare the outcomes between two anterior decompression and fusion techniques to treat multilevel cervical spondylotic myelopathy (MCSM).

Methods

After the screening for eligibility, a total of 66 patients were admitted to this study. These participants underwent anterior surgeries due to MCSM in our hospital between June 2016 and July 2018. All participants underwent either the anterior cervical discectomy and fusion (ACDF) surgery (ACDF group) or the combination of ACDF and anterior cervical corpectomy and fusion (ACCF), which was the anterior cervical hybrid decompression and fusion (ACHDF) surgery group. All the patients were followed up ≥18 months, the average latest followed up time was 23.64 (±2.69) months. The length of hospitalization, operation time, blood loss, visual analog scale (VAS), Japanese Orthopaedic Association (JOA) score, improvement rate, Hounsfield units (HU) of C3–C7, cobb angle, and anterior column height of fusion levels pre and post operation were analyzed.

Results

There were no statistical differences between the ACDF and ACHDF groups regarding the length of hospitalization, operation time, blood loss, HU of C3–C7, VAS, JOA score, improvement rate, cobb angle, and anterior column height in fusion levels in pre-operation and 3 months after operation (all P > 0.05). However, compared with the ACHDF group, the ACDF group achieved significantly better improvement in the anterior column height of fusion levels in the final 18–29 months post-operatively (P < 0.05).

Conclusions

Both approaches of ACDF alone and a combination of ACDF and ACCF can achieve satisfactory outcomes in the treatment of MCSM, but ACDF has better outcomes in maintaining anterior column height of fusion levels.