Based on a T2-weighted MRI Classification system for the LEPLs and a lumbar spine QCT scanning for vBMD measurements, the associations between LEPLs and LDH, LDD, and lumbar vBMD were investigated in a healthy cohort of Chinese adults. LEPLs were common findings in the male lumbar spine, particularly in the lower lumbar region. The presence of endplate lesions was associated with several factors, but these associations only remained lumbar herniation and male hipline after adjusting for the effects of age, BMI, waistline, lumbar vBMD, and disc degeneration.
Our study showed remarkable gender differences not only in characteristics data and lumbar vBMD but also in the prevalence of lumbar disc lesions. Male gender is associated with a higher positive incidence for LEPLs than females whether from the prevalence of EPLs and the number of the lesioned endplates, in which men often do harder physical labor than women [19], which might explain for a larger hipline accompanies and exacerbates the advance of LEPLs. Hormonal factors may play some as yet consequential role in the development of EPLs [7]. Moreover, our study finds that except for one level, the incidence of EPLs was lower in males than in females, and the incidence of other 2–5 levels was higher in males than in females.
Our results showed that LEPLs involved 263 (64.9%) general people, 1072 (28.6%) discs, and 1500 (20.0%) lumbar endplates, and this is corresponding with the previous study[4, 5, 9]. However, Wang et al. observed 1148 vertebral endplates (L1–S1) from the cadaveric spines of 136 men and found 45.6% of lumbar vertebral endplates with lesions [20]. Although, it is unexceptional that the prevalence of LEPLs is higher in men than women and even the whole cohort, the difference can be accounted for that the medical imaging is not on a par with the pathological examination, and the two methods should not compare immediately without segregation in clinical studies and diagnoses.
Brayda-Bruno[5] et al. researched that “notched” was the most common type of EPLs followed by “Schmorl’s node” observed in patients with low back pain, our studies reveal that the most common EPLs are “Wavy/irregular” and “notched”. This difference could account for our subjective population being the general people without low back pain conditions occur that can be severe enough to affect normal work and activity. Based on the fact that “Wavy/irregular” & “notched” are more common in general people, and “notched” & “Schmorl’s node” are more common in a person with low back pain, we can preliminarily infer that “Wavy/irregular” is physiological, while “notched” & “Schmorl’s node”, especially the latter, are more likely to be symptomatic or even pathological. At least, "Notched" and "Schmorl's Nodes" are risk factors for low back pain. This is also consistent with Chen’s finding that focal defects were statistically significantly associated with the presence of back pain over the past 12 months (OR = 2.10, P = 0.009)[4]. Moreover, we find that the fracture is most involved in L3-4 inferior endplate. This may be because the stress distinctiveness of L3-4 intervertebral discs at the boundary between the upper and lower lumbar spine is predisposed to mechanical failure.
Proteoglycan molecules are critical for the control of solute transport and maintenance of water content in the disc, and consumption of proteoglycans from the endplate cartilage is associated with loss of proteoglycans from the nucleus [8]. Then, a finite element analysis concludes that variations in proteoglycan content of the disc were associated with variations in high tensile strains in the endplates, which is responsible for vertebral compressive strength [21]. As a result, we found that LDH and LDD are associated with LEPLs, and LDH is one of the risk factors for LEPLs progression and is following previous studies[5, 9, 22, 23]. Moreover, Sahoo has identified that endplate lesions are commonly associated with symptomatic LDH, and bony lesions are affiliated with adverse outcomes [24].
This is the first study determining the role of lumbar vertebral vBMD in the severity and advancement of LEPLs among healthy Chinese cohorts. As the conjunct structure, the endplate is vital for maintaining the integrity of the vertebral trabeculae and disc. Damage to the endplate may impair not only the adjacent disc but the vertebra. Fujiwara et al. [6] have shown that EPLs are associated with vertebral fractures and the healing of osteoporotic vertebral fractures. We find that the relationship between lumbar vBMD and LEPLs vanished after adjustment for covariates, suggesting that changes in BMD are not a protective or risk factor for LEPLs both in women and men. This is consistent with the result of Gungor that there was no significant relationship between the total number of Schmorl’s nodes per patient and the mean vBMD (p = 0.156) [11], and different from the result of Okano that higher TEPS (score 10 − 12, b = 14.2, p༜0.001) was shown to be independent contributors to vBMD [12]. The age difference demographic variance maybe accounts for this non-conformity.
In 2018, two common and certified nomenclature systems for endplate lesions had been almost recommended simultaneously by Brayda-Bruno [5] and Feng [9], respectively. Although Wang’s team contributed to the lumbar spine study both in vivo and cadaveric spines for many years [20, 25], Feng et. al considers that the different types of endplate defects differed in morphology, distribution patterns, and strength of association with disc degeneration, suggesting they represent different pathologies[9]. Nevertheless, the classification systems of Brayda-Bruno suppose that same as Pfirrmann’s classification of lumbar intervertebral disc degeneration, lesion grade from lower to higher is a progressive or continuous process. And our results using Brayda-Bruno’s classification also show that people with higher grades of lesions are older both men and women. Although the etiology of LEL is blear, our study is in line with the known theory that the majority of endplate lesions are asymptomatic, and is frequently incidental by radiological, and can partly suggest that the occurrence and development of LEL is a cumulative process. And the monistic study of the disease may reduce unnecessary controversy and confusion.
Although we used the more accurate strategy, QCT to measure vBMD in a large cohort of 750 healthy subjects, there are several limitations to this study. First, we executed a cross-sectional study, whereas endplate and disc disorders, and decreasing BMD being a continuing occurrence needs a longitudinal follow-up study to elaborate further on their relationship, which was not done in this study. Second, our study population was drawn from community-dwelling adults in the city of Beijing and might underestimate the prevalence of LEPLs in the general population, because LEPLs are associated with physical activity and economic well-being. Third, the loss of older people would likely have reduced the chance of showing significant relationships between evaluations of LEL and other variates.
In summary, EPLs are also the common findings on lumbar MRIs in general people, particularly in men. The present results suggest that the presence and advance of LEPL could be mainly attributed to LDH, and hipline in men, suggesting that treatment of LDH and avoidance of inappropriate physical activity may delay the progression of LEPLs. However, further studies are needed to evaluate the clinical implication of endplate lesions and remission of the back pain it causes.