Both groups of patients showed significant improvement in pain scores and functional status at follow-ups of 1 day, 1 month, and 1 year, consistent with the results of previous studies. The modified MacNab criteria indicated that patient satisfaction in both the herniation of cartilaginous endplates group and the non-herniation of cartilaginous endplates group was acceptable, demonstrating that the use of PELD to treat LDH is equally effective, regardless of the presence or absence of herniation of cartilaginous endplates.

Our research found that the average age of patients with herniation of cartilaginous endplates (n = 45) was greater than that of patients without herniation of cartilaginous endplates (n = 81), with the difference being statistically significant (P < 0.05). However, the relevant literature notes that it is more common in young people and during the growth period [8, 9]. In all probability, the late presentation may be the reason for an acute exacerbation on a chronic basis. The thickness of the vertebral endplate and bone mineral density (BMD) showed no significant correlation with age, suggesting that the physical properties of the endplate might not undergo significant changes with aging. However, vertebral endplates adjacent to intervertebral discs with a higher degree of degeneration exhibited greater thickness, indicating a certain correlation between disc degeneration and structural changes in the endplate [10]. During our data collection process, we also observed that patients with herniation of cartilaginous endplatess were more likely to experience disc degeneration. Numerous studies have found a significant correlation between disc degeneration and age [11, 12], Endplate changes may be a characteristic or result of the disc degeneration process, and vice versa, these changes can affect the nutrient supply to the disc and further the process of degeneration [13]. This could explain why patients in the endplate protrusion group have a higher average age than those in the non-endplate protrusion group. Furthermore, Modic type 2 changes, in particular, have a strong association with disc degeneration. This may be because this type of change reflects a longer-term and chronic process related to alterations in fat metabolism [14].

Our research shows that patients with intervertebral disc protrusion accompanied by cartilage herniation of cartilaginous endplates exhibit significant differences in back VAS scores at early postoperative stages (1 day and 1 month) and in leg VAS scores at 1 day postoperatively compared to the group without cartilage herniation of cartilaginous endplates (P < 0.05). However, there were no statistically significant differences in back VAS scores at 1 year postoperatively and in leg VAS scores at 1 month and 1 year postoperatively (P > 0.05). Previous studies have suggested that cartilage herniation of cartilaginous endplates is closely related to Modic changes, and the presence of the cartilage endplate seems to affect the absorption of the protruding intervertebral disc. In their research, cases with the presence of cartilage pieces showed less neovascularization of inflammatory granulation tissue and macrophage infiltration, which could lead to the failure of natural remission of clinical symptoms [15]. This explains why patients with cartilage herniation of cartilaginous endplates have higher VAS scores in the early postoperative period, as the inflammatory response may be more significant during this period.

Feng et al. noted that cartilage endplate tears are associated with adjacent Modic changes and endplate defects, and patients with cartilage endplate tears are more likely to experience residual back and leg pain during a 2-year postoperative follow-up. Histological characteristics reveal that the torn cartilage endplates present multiple defects, significant inflammation, and nucleus pulposus invasion, along with the upregulation of IL-1β, caspase-1, and the NLRP3 inflammasome [16]. These factors may be related to the significant differences in early postoperative VAS scores, but these differences gradually decrease over time as the inflammatory response subsides. In the early postoperative period, the inflammatory response may exacerbate pain, especially in patients with cartilage endplate damage [17]. However, over time, this inflammatory response may gradually alleviate, leading to an improvement in pain scores. This explains why, at 1 year postoperatively, there was no statistically significant difference in VAS scores between patients in the herniation of cartilaginous endplates group and those in the non-herniation of cartilaginous endplates group.

Postoperative back pain VAS scores showed significant differences between the two groups on the 1st day and 1st month after surgery (P < 0.05), while differences in postoperative leg pain VAS scores were statistically significant only on the 1st day, with no significant differences at 1 month or 1 year (P > 0.05). Kawaguchi et al. [18] investigated the characteristics of newly developed Modic changes after lumbar disc herniation surgery and their impact on early postoperative residual lower back pain. It was found that at 6 months, 28% of patients with cartilage protrusion developed new Modic changes. These patients had higher back pain VAS scores within 6 months post-surgery, but no significant difference was observed at the one-year follow-up regarding the presence or absence of Modic changes, suggesting that Modic changes may be related to early postoperative lower back pain, but this impact may decrease over time. In our Table 3, patients with Modic changes had higher postoperative back pain VAS scores compared to those without Modic changes, and the difference in back pain VAS scores at 1 month postoperatively between the two groups was statistically significant. The research on these aspects is still controversial, with some studies suggesting no significant difference in postoperative pain or functional outcomes between patients with and without Modic changes [19, 20]. In our study, six lumbar MRI features were used as criteria for diagnosing herniation of cartilaginous endplates, including Modic changes at the endplate and posterior corners, which were part of the diagnostic criteria. We believe that patients with herniation of cartilaginous endplates accompanied by Modic changes experience a higher degree of postoperative lower back pain compared to those without herniation of cartilaginous endplates, explaining why patients in the herniation of cartilaginous endplates group suffer from longer-term lower back pain after surgery.

Furthermore, We divided patients with endplate protrusions into two groups based on the presence or absence of Modic changes. The Visual Analogue Scale (VAS) is of utmost importance for assessing patients' pain on the first day after surgery. However, we observed no significant difference in the VAS scores between the two groups on the first day after surgery (P > 0.05). We believe that the pain variations caused by the presence or absence of endplate protrusions might have diminished the differences in pain caused by Modic changes, leading to no significant difference in VAS scores between the groups. Nevertheless, the significant differences in the Oswestry Disability Index (ODI) (P < 0.05) scores between the two groups indicate that the presence of Modic changes does impact the immediate functional recovery of patients post-surgery. A prospective MRI study explored the significance of Modic changes, osseous endplate injuries, and intervertebral disc degeneration as predictors of chronic lower back pain (LBP). The study found that over a 1-year follow-up period, pain decreased in most patients but increased or persisted in 36% of patients. Changes in Modic types 1 and 2 and osseous endplate injuries were associated with changes in pain intensity, while changes in Modic type 1 and osseous endplate injuries were associated with changes in ODI [21], consistent with our observations.

Some studies [22] suggest that for cases with endplate damage, PRAF, and failure at the endplate junction, the endpoint of decompression changes. Among the surgical patients participating in this study, the endpoint of surgical decompression was consistent. During the 1-year follow-up period after surgery, Most patients experienced reduced pain, but 36% of the patients had increased or persistent pain. These patients required a more aggressive surgical decompression endpoint to fully remove the endplate damage. With continuous improvements in endoscopic equipment, optical systems, surgical tools, and safety, along with enhanced diagnostic and classification methods for different spinal pathologies, Full Endoscopic Spine Surgery (FESS) techniques [23] have been able to be applied to more complex spinal lesion treatments. For patients with endplate herniation, choosing FESS might provide a better surgical view and postoperative recovery outcome.

With the enhanced recovery and aggressive surgical outcome assured, we need to identify factors which mass the initial recovery pattern. Rajasekaran et al. [24] discovered that Lumbar Disc Herniation (LDH) is more often caused by endplate junction failure (EPJF) than by annulus fibrosus rupture. The effectiveness of surgical treatments for EPJF remains an area for further research. Calcified intervertebral discs significantly [25] influence the choice of surgical method and the outcome of post-operative recovery. For Calcified Lumbar Disc Herniation (CLDH) leading to Calcified Ventral Stenosis (CVS), Posterolateral Endoscopic Lumbar Discectomy (PELD) has been proven to be a comprehensive, safe, and effective surgery.

This study faced several notable limitations, chiefly its retrospective design, which could potentially introduce biases in the selection of patients and the collection of data. As it was conducted at a single center, the generalizability of its findings to broader populations or different surgical practices remains uncertain. Additionally, the study was constrained by both its sample size and the duration of follow-up, which may undermine the strength and longevity of the conclusions reached. The lack of a control group for comparison with alternative surgical approaches or conservative management further limits the thoroughness of the results. Moreover, the primary reliance on MRI findings for categorizing patients may not fully capture the clinical subtleties associated with Lumbar Disc Herniation cases. Future studies could overcome these limitations by adopting a prospective, multicenter design with larger patient groups, longer follow-up periods, and the inclusion of control groups undergoing various treatments. Relying solely on the Oswestry Disability Index (ODI) to assess the recovery of patients' postoperative activities is limited. Other evaluation methods such as the Prolo rating for lumbar disc herniation efficacy and the Japanese Orthopaedic Association scoring system should also be adopted. Regarding the issue of whether patients undergoing surgery for cartilage endplate protrusion face an increased risk of postoperative recurrence, this is a key factor in preoperative planning and postoperative management. However, the potential impact of cartilage endplate herniation on the risk of postoperative recurrence was not addressed in this study. This issue could be a focus of future research. This would pave the way for a more definitive and broadly applicable understanding of the effects of herniation of cartilaginous endplates and Modic changes on postoperative outcomes.