Association between lumbar vertebral body bone quality and cranial/caudal endplate bone quality with intervertebral disc degeneration: a retrospective study of 2018 patients

Abstract

Background

Lumbar disc degeneration and osteoporosis are common degenerative diseases in middle-aged and elderly populations. Although these conditions may be closely related pathophysiologically, their exact comorbidity relationship and underlying mechanisms remain unclear. This study aimed to use imaging indicators to systematically investigate the association between vertebral body bone quality and cranial/caudal endplate bone quality, as well as the severity of lumbar disc degeneration, and to explore the potential clinical value of combined CT–MRI assessment for risk stratification.

Methods

This was a retrospective study including 2018 patients (8072 intervertebral discs and 10,090 vertebral bodies) who underwent both lumbar CT and MRI at our hospital between September 2023 and June 2025. Data collected included age, sex, body mass index (BMI), smoking status, computed tomography (CT)-based vertebral body and endplate attenuation values (Hounsfield Units, HU), magnetic resonance imaging (MRI)-based cranial and caudal Endplate Bone Quality (EBQ) scores, and the degree of disc degeneration assessed according to the Pfirrmann grading system. Patients were divided into mild-to-moderate and severe degeneration groups based on the mean Pfirrmann grade. To comprehensively evaluate the association of various variables with disc degeneration grades, independent-samples t tests, chi-square tests, scatter plots with fitted linear regression lines, and Spearman correlation analyses were performed. Finally, a binary logistic regression model was used to identify independent risk factors.

Results

Univariate analysis showed that the severity of disc degeneration was significantly associated with sex, age, average vertebral body CT attenuation, and endplate bone quality (P < 0.05). Binary logistic regression further confirmed that female sex (OR = 1.68), advanced age (OR = 1.093), low average vertebral body CT attenuation value (OR = 0.988), and high cranial EBQ score (OR = 1.235) were independently associated with severe disc degeneration. Further subgroup analysis revealed that the correlation between decreased bone quality and degeneration was more pronounced in female patients. Additionally, segmental analysis indicated that the risk factors for degeneration differed across lumbar spine segments.

Conclusion

This study found that decreased bone quality of the lumbar vertebral bodies and endplates was significantly associated with the severity of disc degeneration, suggesting a comorbid association between bone quality impairment and disc degeneration, which appeared more pronounced in female patients. Therefore, in clinical practice, the combined assessment of CT-based bone attenuation (HU) and MRI-based endplate bone quality (EBQ) may help identify individuals at high risk for lumbar degenerative diseases and support earlier targeted prevention and management.

Background

Lumbar disc degeneration (LDD) is the primary cause of low back pain. Although the precise pathological mechanisms remain poorly understood, it is widely accepted that factors such as insufficient nutrient supply, imbalance in local microenvironment homeostasis, and changes in mechanical stress play key roles in driving LDD progression [1]. The vertebral body, endplate, and intervertebral disc function as an integrated unit, and alterations in the vertebral body and endplate are likely to influence disc degeneration by affecting nutrient transport and mechanical load distribution [2, 3].

Osteoporosis (OP) is a progressive systemic skeletal disorder characterised by reduced bone mass, decreased bone density, and the deterioration of bone microarchitecture. These changes not only alter vertebral morphology and spinal biomechanics but also significantly affect the overall mechanical properties of the spine [4]. Although both OP and LDD are common age-related conditions and often coexist, the exact relationship between them—whether osteoporosis mitigates or accelerates disc degeneration—remains controversial in existing research [5].

Accurate assessment of bone quality is essential for investigating its association with disc degeneration. The diagnosis of osteoporosis primarily relies on systemic and regional bone density measurements [6]. Currently, dual-energy X-ray absorptiometry (DEXA) is considered the gold standard for assessing bone density. However, due to radiation exposure and the potential overestimation of bone density in the presence of degenerative changes, DEXA is not routinely used in all clinical settings. In recent years, advances in imaging technology have made computed tomography (CT) widely used for evaluating bone density. The CT attenuation value, measured in Hounsfield Units (HU), is an objective measure of bone tissue quality [7]. Moreover, magnetic resonance imaging (MRI) has also been introduced for bone quality assessment. For instance, the Vertebral Bone Quality (VBQ) scoring system is used to evaluate vertebral bone quality, whereas the Endplate Bone Quality (EBQ) score focuses specifically on the bone quality of the spinal endplates, a critical region in spinal integrity [8, 9].

Lumbar disc degeneration (LDD) and osteoporosis (OP) are common degenerative diseases in middle‑aged and elderly populations. Although these two conditions may be closely related in terms of pathophysiology, their comorbidity relationship and underlying mechanisms are not yet fully understood. Therefore, this study aimed to systematically investigate the associations of vertebral body bone quality and cranial and caudal endplate bone quality with the severity of lumbar disc degeneration using CT- and MRI-based imaging indicators.

Methods

Study population

This was a retrospective cross-sectional study. A total of 2664 patients who underwent both lumbar CT and MRI examinations at our hospital between September 2023 and June 2025 were initially considered. The specific inclusion and exclusion criteria are as follows: Inclusion Criteria: (1) Underwent both lumbar spine CT and lumbar spine MRI examinations at our hospital within an interval not exceeding one month; (2) Complete imaging data were available. Exclusion Criteria: (1) Interval between lumbar spine CT and MRI examinations exceeding one month; (2) Presence of scoliosis (Cobb angle > 20°) [10] or lumbar spondylolisthesis; (3) History of spinal surgery involving procedures such as vertebral bone cement augmentation or lumbar internal fixation; (4) Use of medications affecting bone metabolism (e.g., oestrogen, bisphosphonates) within the past six months. Based on the exclusion criteria, 646 patients were excluded. A total of 2,018 patients were ultimately included for imaging data analysis (958 men and 1,060 women; mean age 54.66 ± 16.08 years; mean body mass index 26.13 ± 3.83 kg/m²; smoking status: non-smoker/smoker = 1733/285). Smoking status was defined as follows: a non-smoker was defined as a participant who had never smoked regularly; a smoker was defined as a current smoker or a former regular smoker (≥ 1 cigarette/day for ≥ 6 months). This study encompassed a total of 10,090 vertebral bodies and 8072 intervertebral discs across the L1–L5 segments. A flowchart of the study is shown in Fig. 1. This study was approved by the Institutional Review Board of our hospital, which waived the requirement for informed consent.

Fig. 1.

Study flowchart. A total of 2664 patients were screened, 646 were excluded according to the predefined criteria, and 2018 patients were ultimately included for analysis

Imaging measurements

The measurement process was completed on the hospital’s Picture Archiving and Communication System (PACS) using a standardized protocol to ensure reproducibility and accuracy. All imaging parameters were independently assessed by two physicians who received unified training, under blinded conditions. For continuous indicators, the average of the measurements from the two physicians was used as the final result. To evaluate inter-observer agreement, the intraclass correlation coefficient (ICC) was calculated for continuous imaging indicators. An ICC > 0.75 was considered to indicate good agreement, and an ICC > 0.90 was considered to indicate excellent agreement. For semi‑quantitative indicators (such as Pfirrmann grading), if the initial assessments by the two physicians were inconsistent, a third senior physician performed an independent evaluation to make the final determination.The specific measurement methods are as follows (Fig. 2):

Fig. 2.

Schematic illustration of imaging parameter measurements. A–E Representative T2-weighted mid-sagittal MRI images illustrating Pfirrmann grading (Grades I-V) of lumbar intervertebral discs; F–H Schematic demonstration of CT attenuation measurements, including sagittal localization and axial ROI placement for vertebral body trabecular bone and endplate attenuation; I, J Schematic demonstration of EBQ measurements on mid-sagittal T1-weighted images, showing ROI placement within a 3-mm-deep subchondral band adjacent to the cranial and caudal endplates, and CSF ROI placement at the L3 level for signal normalization

(1) Disc degeneration grade: The severity of disc degeneration from L1/2 to L4/5 was assessed on T2-weighted MRI sagittal images using the Pfirrmann grading system (Grades I-V) [11]. Specific criteria are detailed in Table 1.

Table 1.

Pfirrmann grading system for lumbar disc degeneration

Grade	Nucleus pulposus structure	Demarcation between nucleus and annulus	Nucleus signal intensity*	Disc height
I	Homogeneous, bright white	Clear	High	Normal
II	Inhomogeneous, with or without horizontal bands	Clear	High	Normal
III	Inhomogeneous, gray	Unclear	Intermediate	Normal to slightly reduced
IV	Inhomogeneous, gray to black	Lost	Intermediate to low	Normal to moderately reduced
V	Inhomogeneous, black	Lost	Low	Collapsed

*Comparable to CSF (cerebrospinal fluid)

(2) Vertebral body CT attenuation value (HU): On three-dimensional reconstructed lumbar spine CT images, three axial slices per vertebral body were selected: one slice just below the superior endplate, one at the mid-vertebral body level, and one just above the inferior endplate. A region of interest (ROI) as large as possible was placed within the trabecular bone area on each slice to avoid the cortical bone, osteophytes, and posterior venous plexus. The HU value for each ROI was obtained using PACS measurement tools, and the average HU value for each lumbar vertebral body was calculated.

(3) Endplate CT attenuation value (HU) [12]: An axial CT slice traversing the vertebral endplate was selected. An ROI was manually drawn in the central region of the endplate, excluding areas with osteophytes or calcifications to minimize measurement bias. The CT attenuation values for this region were automatically calculated. In this study, endplates were defined relative to each disc level: the cranial endplate corresponds to the inferior endplate of the cranial vertebra, and the caudal endplate corresponds to the superior endplate of the caudal vertebra.

(4) Endplate Bone Quality (EBQ) score [13]: The EBQ score was assessed by measuring the average signal intensity within a 3-mm-deep subchondral band adjacent to the cranial and caudal endplates of each intervertebral disc on mid-sagittal T1-weighted images. All measurements were performed on the hospital PACS workstation using Centricity Universal Viewer Zero Footprint Client. The 3-mm region was defined as a band extending 3 mm perpendicular to the endplate surface into the adjacent vertebral body marrow. This region was manually outlined to primarily capture the subchondral bone area while avoiding structures that might affect measurement accuracy, such as calcifications or osteophytes. The signal intensity of each region was normalized to the cerebrospinal fluid (CSF) signal intensity measured on the same mid-sagittal slice at the L3 vertebral body level, with care taken to avoid partial-volume effects, and this normalized value was recorded as the EBQ score.

(5) Mean Pfirrmann grade (MPG): The average Pfirrmann grade for the L1-L5 intervertebral discs in each patient.

(6) Mean vertebral body CT attenuation value (MVB-CT HU): The average CT attenuation value of the L1-L5 vertebral bodies for each patient.

(7) Mean cranial endplate CT attenuation (MCranEpi-CT HU): the average CT attenuation of the cranial endplates from L1/2 to L4/5 for each patient.

(8) Mean caudal endplate CT attenuation value (MCaudEpi-CT HU): The average CT attenuation value of the caudal endplates from L1/2 to L4/5 for each patient.

(9) Mean cranial EBQ (MCranEBQ): The average EBQ score of the cranial endplates from L1/2 to L4/5 for each patient.

(10) Mean caudal EBQ (MCaudEBQ): The average EBQ score of the caudal endplates from L1/2 to L4/5 for each patient.

Statistical methods

Statistical analysis was performed using SPSS software (version 26.0). To evaluate inter‑observer agreement, the intraclass correlation coefficient (ICC) was used to assess the measurement consistency between two observers for continuous imaging indicators. Measurement data conforming to a normal distribution are presented as mean ± standard deviation (x̄ ± s), and comparisons between groups were conducted using the independent samples t-test. Count data are presented as numbers (percentages) and compared between groups using the chi-square test; Fisher’s exact test was applied when expected cell counts were < 5. Scatter plots were generated to visually demonstrate the association between continuous variables (e.g. age, CT attenuation values, and EBQ) and the ordinal categorical variable (Pfirrmann grade). These plots display both the trend line derived from linear regression (including the regression equation) and the Spearman rank correlation coefficient (ρ) with its significance level, illustrating the overall trend and the strength of the rank correlation, respectively. Variables with P < 0.05 in the univariate analysis were included in a binary logistic stepwise regression (forward, likelihood ratio method) to identify factors independently associated with severe disc degeneration. A P-value < 0.05 was considered statistically significant.

Results

Overall sample characteristics and univariate analysis

This study ultimately enrolled 2018 patients, with a mean age of 54.66 ± 16.08 years and a mean BMI of 26.13 ± 3.83 kg/m². The patients’ general characteristics are presented in Table 2. The assessment of inter‑observer agreement demonstrated good consistency between the two observers for continuous imaging indicators (ICC > 0.75), with ICC values ranging from 0.80 to 0.97.

Table 2.

Baseline characteristics of the included patients

Item	Value (Mean ± SD)
Male/Female(n)	958/1060
Age (years)	54.66 ± 16.08
BMI (kg/m2)	26.13 ± 3.83
Smoking status (No/Yes)	1733/285
MVB-CT HU (HU)	150.19 ± 55.19
MCranEpi-CT HU (HU)	406.45 ± 69.84
MCaudEpi-CT HU (HU)	372.22 ± 54.72
MCranEBQ	3.06 ± 0.80
MCaudEBQ	3.03 ± 0.81
Disc Degeneration Grade (Pfirrmann) Distribution
L1/2
Grade I (n, %)	10(0.5%)
Grade II (n, %)	691(34.2%)
Grade III (n, %)	655(32.5%)
Grade IV (n, %)	427(21.2%)
Grade V (n, %)	235(11.6%)
L2/3
Grade I (n, %)	11(0.5%)
Grade II (n, %)	448(22.2%)
Grade III (n, %)	527(26.1%)
Grade IV (n, %)	690(34.2%)
Grade V (n, %)	342(16.9%)
L3/4
Grade I (n, %)	15(0.7%)
Grade II (n, %)	218(10.8%)
Grade III (n, %)	469(23.2%)
Grade IV (n, %)	941(46.6%)
Grade V (n, %)	375(18.6%)
L4/5
Grade I (n, %)	4(0.2%)
Grade II (n, %)	30(1.5%)
Grade III (n, %)	250(12.4%)
Grade IV (n, %)	947(46.9%)
Grade V (n, %)	787(39.0%)

First, the average Pfirrmann grade for the L1-L5 intervertebral discs (i.e. the mean Pfirrmann grade) was calculated for each patient. Based on the mean Pfirrmann grade, patients were divided into a mild-to-moderate degeneration group (≤ 3 points, N = 509) and a severe degeneration group (> 3 points, N = 1509). Univariate analysis (Table 3) showed that compared to the mild-to-moderate group, patients in the severe degeneration group had a significantly higher proportion of females, were older, had a lower mean vertebral body CT attenuation value, and had higher cranial and caudal EBQ scores (all P < 0.05). However, no statistically significant differences were found between the two groups in terms of BMI, smoking status, or mean CT attenuation values of the cranial and caudal endplates.

Table 3.

Univariate comparison of patients between mild-to-moderate and severe disc degeneration groups

Variable	Mild-to-moderate group (N = 509)	Severe group (N = 1509)	χ2/t value	P-value
Male/Female(n)	325 / 184	633 / 876	73.222	< 0.001
Age (years)	37.69 ± 13.30	60.37 ± 12.50	−33.74	< 0.001
BMI (kg/m2)	25.98 ± 4.49	26.18 ± 3.58	−0.891	0.373
Smoking status (No/Yes)	427/82	1306/203	2.216	0.137
MVB-CT HU (HU)	197.33 ± 49.19	134.29 ± 47.50	25.223	< 0.001
MCranEpi-CT HU (HU)	409.18 ± 69.84	405.53 ± 69.84	1.019	0.308
MCaudEpi-CT HU (HU)	370.12 ± 57.68	372.93 ± 53.69	−0.966	0.334
MCranEBQ	2.73 ± 0.69	3.18 ± 0.81	−12.184	< 0.001
MCaudEBQ	2.72 ± 0.69	3.13 ± 0.82	−10.973	< 0.001

Correlation and multivariate analysis

Linear regression and Spearman correlation analyses revealed that the severity of lumbar disc degeneration was significantly associated with age, mean vertebral body CT attenuation value, cranial EBQ, and caudal EBQ (all P < 0.05), as detailed in the scatter plots (Fig. 3).

Fig. 3.

Scatter plots and fitted curves showing the associations between mean Pfirrmann grade and imaging parameters

Scatter plots depict the relationships between mean Pfirrmann grade and A age, B mean vertebral body CT attenuation (HU), C mean cranial EBQ score, and D mean caudal EBQ score. Each panel shows a fitted linear regression line and the Spearman correlation coefficient (ρ) with the corresponding P value

Binary logistic regression further confirmed that female sex, advanced age, lower mean vertebral body CT attenuation values, and higher cranial EBQ scores were independent risk factors for severe disc degeneration (Table 4).

Table 4.

Results of binary logistic regression analysis for the occurrence of severe disc degeneration

Variable	B	SE	P-value	OR	95% CI
Male/Female*	0.519	0.14	< 0.001	1.680	1.277–2.211
Age (years)	0.089	0.005	< 0.001	1.093	1.081–1.105
MVB-CT HU (HU)	−0.012	0.002	< 0.001	0.988	0.985–0.991
MCranEBQ	0.211	0.101	0.036	1.235	1.014–1.505

*Female = 1

Sex subgroup analysis

To clarify the differences between males and females, a sex subgroup analysis was performed. The basic characteristics of the male and female subgroups are presented in Table 5. Subsequently, univariate comparisons between the mild-to-moderate and severe degeneration groups were conducted separately for male and female subgroups (Table 6). The results indicated that in both subgroups, patients with severe degeneration were older, had lower mean CT attenuation values, and had higher EBQ scores. Binary logistic regression analysis was performed separately for the male and female subgroups based on variables that were significant in the univariate analysis (Table 7). The results showed that advanced age and low vertebral body CT attenuation values were common risk factors for both sexes. Additionally, within the female subgroup, higher BMI (OR = 1.086) and cranial EBQ score (OR = 1.665) were also identified as independent risk factors.

Table 5.

Comparison of baseline characteristics among patients of different sex

Variable	Male group	Female group	χ2/t value	P-value
Age (years)	51.69 ± 17.55	57.34 ± 14.09	−7.913	< 0.001
BMI (kg/m2)	26.20 ± 3.73	26.06 ± 3.92	0.856	0.392
Smoking status (No/Yes)	689/269	1044/16	292.91	< 0.001
MVB-CT HU (HU)	160.26 ± 52.48	141.09 ± 56.02	7.933	< 0.001
MCranEpi-CT HU (HU)	419.06 ± 71.23	395.05 ± 66.57	7.800	< 0.001
MCaudEpi-CT HU(HU)	379.18 ± 54.50	365.93 ± 54.19	5.466	< 0.001
MCranEBQ	2.91 ± 0.73	3.20 ± 0.84	−8.314	< 0.001
MCaudEBQ	2.87 ± 0.73	3.17 ± 0.85	−8.630	< 0.001
MPG	3.47 ± 0.74	3.76 ± 0.65	−9.438	< 0.001

Table 6.

Univariate comparison between mild-to-moderate and severe degeneration patients within different sex subgroups

	Male Group		χ2/t	Female Group		χ2/t
	Mild-to-Moderate	Severe		Mild-to-Moderate	Severe
Age (years)	34.59 ± 11.77	60.47 ± 12.95	−31.127*	43.19 ± 14.10	60.30 ± 12.17	−15.268*
BMI(kg/m2)	26.63 ± 4.15	25.99 ± 3.48	2.371*	24.84 ± 4.85	26.31 ± 3.65	−3.884*
Smoking status (No/Yes)	246/79	443/190	3.465	181/3	863/13	0.022
MVB-CT HU (HU)	197.00 ± 49.67	141.39 ± 43.08	17.141*	197.93 ± 48.44	129.15 ± 49.85	17.42*
MCranEpi-CT HU (HU)	403.09 ± 71.45	427.26 ± 69.77	−4.997*	419.93 ± 65.73	389.82 ± 65.59	5.649*
MCaudEpi-CT HU(HU)	367.08 ± 59.81	385.39 ± 50.49	−4.721*	375.49 ± 53.46	363.93 ± 54.15	2.661*
MCranEBQ	2.77 ± 0.66	2.99 ± 0.76	−4.631*	2.66 ± 0.75	3.32 ± 0.82	−10.719*
MCaudEBQ	2.76 ± 0.65	2.92 ± 0.76	−3.374*	2.65 ± 0.76	3.28 ± 0.83	−10.134*

*P < 0.05

Table 7.

Results of multivariate logistic regression analysis for the occurrence of severe disc degeneration within different sex subgroups

Variable	B	SE	P-value	OR	95% CI for OR
					Lower	Upper
Male subgroup
Age(years)	0.109	0.008	< 0.001	1.116	1.099	1.133
MVB-CT HU (HU)	−0.014	0.003	< 0.001	0.987	0.981	0.992
Female subgroup
Age(years)	0.06	0.008	< 0.001	1.062	1.045	1.08
BMI(kg/m2)	0.082	0.024	< 0.001	1.086	1.036	1.138
MVB-CT HU (HU)	−0.011	0.002	< 0.001	0.989	0.985	0.993
MCranEBQ	0.51	0.136	< 0.001	1.665	1.276	2.171

Analysis by lumbar segment

Univariate analyses were performed separately for each lumbar segment (L1/2 to L4/5) (Table 8). The analyses revealed segment-specific differences in demographic and imaging indicators between the mild-to-moderate and severe degeneration groups across segments. A separate scatter plot was generated for the L4/5 segment (Fig. 4). The results of multivariate analysis indicated that the predominant associated factors differed among segments, suggesting the possibility of segment-dependent mechanisms (Table 9).

Table 8.

Univariate comparison between mild-to-moderate and severe degeneration groups for each lumbar segment (L1/2 to L4/5)

Variable	Mild-to-moderate group	Severe group	χ2/t value	P-value
L4/5
Sex (M/F, n)	160/124	798/936	10.417	0.001
Age (years)	44.79 ± 17.33	56.28 ± 15.27	−10.516	< 0.001
BMI (kg/m2)	26.41 ± 3.93	26.13 ± 3.80	1.296	0.196
Smoking status (No/Yes)	249/35	1484/250	0.882	0.348
Upper Vertebral Body CT (HU)	177.29 ± 58.31	141.98 ± 55.24	9.46	< 0.001
Lower Vertebral Body CT (HU)	181.19 ± 56.97	149.58 ± 56.80	8.618	< 0.001
Cranial Endplate CT (HU)	476.14 ± 129.84	433.64 ± 92.91	5.326	< 0.001
Caudal Endplate CT (HU)	380.62 ± 82.94	364.55 ± 77.85	3.075	0.002
Cranial EBQ Score	2.72 ± 0.84	3.08 ± 0.57	−6.82	< 0.001
Caudal EBQ Score	2.73 ± 0.78	3.06 ± 0.85	−6.518	< 0.001
L3/4
Sex (M/F)	448/254	510/806	115.329	< 0.001
Age (years)	43.67 ± 15.83	60.51 ± 12.81	−24.244	< 0.001
BMI (kg/m2)	26.00 ± 4.22	26.20 ± 3.61	−1.055	0.292
Smoking status (No/Yes)	591/111	1142/174	2.532	0.112
Upper Vertebral Body CT (HU)	175.93 ± 56.86	126.66 ± 50.01	19.313	< 0.001
Lower Vertebral Body CT (HU)	179.65 ± 55.63	129.80 ± 50.28	19.818	< 0.001
Cranial Endplate CT (HU)	429.16 ± 98.44	420.58 ± 93.42	1.898	0.058
Caudal Endplate CT (HU)	379.23 ± 71.70	385.36 ± 77.17	−1.78	0.075
Cranial EBQ Score	2.84 ± 0.78	3.14 ± 0.91	−7.624	< 0.001
Caudal EBQ Score	2.79 ± 0.75	3.07 ± 0.90	−7.211	< 0.001
L2/3
Sex (M/F)	582/404	376/656	103.211	< 0.001
Age (years)	46.34 ± 15.79	62.61 ± 11.75	−26.162	< 0.001
BMI (kg/m2)	25.85 ± 4.17	26.40 ± 3.46	−3.204	0.001
Smoking status (No/Yes)	837/149	896/136	1.554	0.213
Upper Vertebral Body CT (HU)	175.55 ± 55.63	124.37 ± 47.24	22.228	< 0.001
Lower Vertebral Body CT (HU)	169.46 ± 56.17	119.28 ± 47.13	21.692	< 0.001
Cranial Endplate CT (HU)	391.80 ± 80.23	393.01 ± 80.20	−0.337	0.736
Caudal Endplate CT (HU)	365.01 ± 70.41	369.77 ± 72.33	−1.499	0.134
Cranial EBQ Score	2.93 ± 0.80	3.25 ± 0.84	−8.779	< 0.001
Caudal EBQ Score	2.85 ± 0.80	3.18 ± 0.88	−8.837	< 0.001
L1/2
Sex (M/F)	683/673	275/387	13.902	< 0.001
Age (years)	50.34 ± 16.47	63.50 ± 10.78	−21.481	< 0.001
BMI (kg/m2)	26.10 ± 4.00	26.18 ± 3.47	−0.454	0.65
Smoking status (No/Yes)	1164/192	569/93	0.005	0.946
Upper Vertebral Body CT (HU)	168.29 ± 57.87	129.80 ± 47.65	15.846	< 0.001
Lower Vertebral Body CT (HU)	162.84 ± 57.74	121.83 ± 46.11	17.224	< 0.001
Cranial Endplate CT (HU)	372.94 ± 68.65	366.25 ± 72.68	1.976	0.048
Caudal Endplate CT (HU)	374.74 ± 65.22	367.71 ± 71.54	2.131	0.033
Cranial EBQ Score	3.00 ± 0.77	3.30 ± 0.90	−7.308	< 0.001
Caudal EBQ Score	3.01 ± 0.81	3.29 ± 0.91	−6.762	< 0.001

For each disc level, the cranial endplate refers to the inferior endplate of the cranial (upper) vertebra, and the caudal endplate refers to the superior endplate of the caudal (lower) vertebra

Fig. 4.

Scatter plots and fitted curves for the L4/5 segment showing segment-specific associations

Scatter plots depict the relationships between L4/5 Pfirrmann grade and A cranial endplate CT attenuation (HU), B caudal endplate CT attenuation (HU), C cranial EBQ score, D caudal EBQ score, E age, F cranial (L4) vertebral body CT attenuation (HU), and G caudal (L5) vertebral body CT attenuation (HU)

Table 9.

Results of multivariate logistic regression analysis for severe disc degeneration for each lumbar segment

	Variable	B	P-value	OR	95% CI for OR
					Lower	Upper
L4/5	Age (years)	0.041	< 0.001	1.041	1.033	1.05
	Cranial Endplate CT (HU)	−0.004	< 0.001	0.996	0.995	0.997
	Cranial EBQ Score	0.362	< 0.001	1.436	1.217	1.696
L3/4	Male/Female	0.843	< 0.001	2.323	1.864	2.896
	Age (years)	0.057	< 0.001	1.059	1.05	1.068
	Lower Vertebral Body CT (HU)	−0.009	< 0.001	0.991	0.989	0.993
L2/3	Male/Female	0.71	< 0.001	2.033	1.643	2.516
	Age (years)	0.061	< 0.001	1.063	1.054	1.073
	BMI (kg/m2)	0.081	< 0.001	1.085	1.054	1.116
	Upper Vertebral Body CT (HU)	−0.011	< 0.001	0.989	0.987	0.992
L1/2	Age (years)	0.05	< 0.001	1.052	1.042	1.062
	Lower Vertebral Body CT (HU)	−0.013	< 0.001	0.987	0.981	0.993

Discussion

By analysing imaging data from 2018 patients, this study revealed a close association between the bone quality of the lumbar vertebral bodies and endplates and the severity of intervertebral disc degeneration. Our results showed that advanced age, female sex, lower mean vertebral body CT attenuation value, and higher cranial EBQ score were all independent risk factors for severe disc degeneration. Clinically, these findings suggest that a combined CT–MRI assessment (vertebral HU plus EBQ) may provide an opportunistic, imaging-based approach for identifying individuals at higher risk of lumbar degenerative disease and may support earlier risk stratification and targeted prevention strategies.

Independent association and mechanisms of the endplate bone quality score

A key finding of this study was the significant positive correlation between the EBQ score and grade of disc degeneration. The EBQ primarily reflects the composite status of subchondral bone and adjacent marrow composition in the region immediately beneath the endplate. An elevated EBQ typically indicates fatty marrow replacement and altered marrow composition/microstructure in the subendplate region [14].

The vertebral endplate serves as a crucial connecting region between the intervertebral disc and the vertebral body, and its bone quality directly influences the stress distribution and nutrient supply to the disc [15]. Patients with osteoporosis exhibit reduced BMD in the bony end plate, leading to decreased mechanical strength and load-bearing capacity. This weakening of the bony endplate makes it more prone to damage, such as endplate defects. Previous studies have suggested that abnormalities in endplate structure may lead to altered internal stress distribution within the intervertebral disc, thereby accelerating the degenerative process [16, 17]; furthermore, basic research has confirmed that a decrease in subchondral bone density in the lumbar endplate indeed accelerates disc degeneration [18].

Segmental analysis further revealed that in the L4/5 segment, a high-prevalence site for degeneration, an elevated cranial EBQ was a significant independent risk factor. This may be explained by segment-specific loading characteristics: during upright posture and daily activities, the cranial endplate often bears and transmits substantial axial loads. Thinning of the subchondral bone plate, sparseness of the trabeculae, and reduced mineralisation may lead to a significant decline in stiffness and strength, thereby preventing effective stress dispersion. Consequently, loads become abnormally concentrated locally, increasing the peak stress borne by the underlying disc, accelerating microtears in the annulus fibrosus, and causing mechanical wear of the nucleus pulposus [19–21]. In parallel, fatty marrow replacement and microvascular changes in the subchondral region may impair nutrient exchange and waste clearance across the endplate–disc interface, exposing disc cells to a persistently adverse microenvironment [22, 23]. These factors collectively contribute to an accelerated progression of disc degeneration.

Pathological significance and mechanisms of reduced vertebral body CT attenuation value

Decreased mean vertebral body CT attenuation is a quantitative local manifestation of systemic bone metabolic abnormalities in the lumbar spine. The results of this study showed a significant negative correlation between the mean vertebral body CT attenuation value and disc degeneration grade. The underlying mechanisms are likely multifaceted. First, in the osteoporotic state, abnormal bone remodelling (excessive osteoclastic bone resorption over osteoblastic bone formation) leads to trabecular bone thinning, microarchitectural deterioration, and a weakened mechanical foundation of the vertebral body [24]. Under a continuous load, the vertebral body becomes more susceptible to microfractures or deformation, thereby altering the stress state of the adjacent endplates and indirectly affecting the stress environment of the intervertebral disc. Second, the vascular channels within the vertebral body traverse the trabecular network. Bone loss and structural disruption may compress or distort these nutrient vessels, interfering with blood perfusion in the vertebral body, which in turn jeopardises the intervertebral disc, which relies on diffusion through the endplate for nutrition. Osteoporosis is often accompanied by a chronic low-grade inflammatory state and fatty marrow transformation. Pro-inflammatory mediators may diffuse across the endplate–disc interface and contribute to catabolic changes in disc tissue, thereby accelerating degeneration [25, 26].

Potential explanation for sex differences

This study found a more pronounced correlation between osteoporosis and disc degeneration in the female population, which may be related to the sharp decline in oestrogen levels after menopause in women. Oestrogen promotes osteoblast activity and inhibits osteoclast function; its deficiency directly leads to rapid bone loss [27]. Concurrently, oestrogen has a protective effect on the anabolic metabolism of the extracellular matrix in intervertebral discs [28]. Therefore, the loss of this dual protective effect of oestrogen after menopause may exacerbate the processes of declining bone quality and disc degeneration [29]. Notably, in the female subgroup, BMI also emerged as an independent risk factor, which may reflect additional mechanical loading and metabolic influences that warrant further investigation in prospective studies.

Limitations of this study

First, as a cross-sectional study, it establishes a correlation but cannot infer strict causation. Future prospective cohort studies are required to verify whether declining bone quality predicts the progression of degeneration. Second, the sample was derived from a symptomatic population, which may have introduced a selection bias. Third, despite efforts to standardise the ROI selection, the thin and curved nature of the endplate region indicates that CT attenuation value measurements may be affected by partial volume effects. Fourth, although smoking status was recorded and medications affecting bone metabolism within the past six months were excluded, several potential confounders could not be fully obtained or quantified due to the retrospective design, including physical activity history, occupational mechanical loading, and comorbidities influencing bone metabolism (e.g., thyroid-related disorders). These factors were not included in the model for adjustment, which may lead to residual confounding and affect the interpretation of the results. Finally, although inter-observer agreement was good to excellent, EBQ and HU measurements remain partly operator dependent, and external validation across centres and imaging platforms is needed.

Conclusions

This study found a significant association between bone quality indicators of the lumbar vertebral bodies and endplates and the severity of intervertebral disc degeneration, and this association was more pronounced in female patients. These findings suggest that bone quality assessment may help identify individuals at higher risk of more severe disc degeneration and may contribute to imaging-based risk stratification. In clinical practice, for patients with moderate to severe lumbar disc degeneration, particularly women, incorporating indicators such as CT attenuation values (HU) and MRI-based endplate bone quality (EBQ) during routine imaging examinations—when feasible—may serve as a useful adjunct to conventional assessment. This approach could enable a more comprehensive assessment of bone health status and degeneration risk, providing additional objective information to support personalised follow-up and management strategies.

Abbreviations

BMI

Body Mass Index

CT

Computed Tomography

HU

Hounsfield Units

MRI

Magnetic Resonance Imaging

EBQ

Endplate Bone Quality

LDD

Lumbar Disc Degeneration

OP

Osteoporosis

DEXA

Dual-energy X-ray Absorptiometry

VBQ

Vertebral Bone Quality

MPG

Mean Pfirrmann Grade

MVB-CT HU

Mean vertebral body CT attenuation (HU)

MCranEpi-CT HU

Mean cranial endplate CT attenuation (HU)

MCaudEpi-CT HU

Mean caudal endplate CT attenuation (HU)

MCranEBQ

Mean cranial EBQ score

MCaudEBQ

Mean caudal EBQ score

ROI

Region of Interest

PACS

Picture Archiving and Communication System

CSF

Cerebrospinal Fluid

OR

Odds Ratio

CI

Confidence Interval

SPSS

Statistical Package for the Social Sciences

BMD

Bone Mineral Density

Author contributions

Conceptualization, WG; methodology, WG; software, ST; validation, HW; formal analysis, YW; investigation, WG; data curation, ST; writing—original draft preparation, WG; writing—review and editing, XM and HZ. All authors have read and agreed to the published version of the manuscript.

Funding

The present study was supported by the Taishan Scholars Program of Shandong Province (No. tstp20230664).

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Institutional Review Board of The Affiliated Hospital of Qingdao University (QYFY WZLL 30933).

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.