Discectomy decreases facet joint distance and increases the instability of the spine: A finite element study

PLGA/BK microspheres targeting the bradykinin signaling pathway as a therapeutic strategy to delay intervertebral disc degeneration

Intervertebral disc degeneration(IVDD) is a common spinal condition with limited effective treatments available. This study aims to investigate the impact of poly(lactic-co-glycolic acid)/Bradykinin (PLGA/BK) microspheres on IVDD and its underlying mechanisms. We collected nucleus pulposus samples from both healthy and degenerated human intervertebral disks and conducted immunohistochemical analyses, revealing reduced BK expression in degenerated tissues. Subsequently, we used BK to treat nucleus pulposus cells and conducted Bulk RNA sequencing (RNA-seq), identifying BK's involvement in cellular senescence, extracellular matrix metabolism, and the PI3K signaling pathway. Further experiments using tert-butyl hydroperoxide (TBHP)-induced cell senescence showed that BK treatment reduced senescence, enhanced extracellular matrix synthesis, and inhibited degradation, along with activation of the PI3K pathway. These effects were mediated through B2R (BK receptor 2) and the downstream PI3K pathway. Following this, we developed sustained-release BK microspheres with an optimized manufacturing process. In vitro co-culture experiments showed no observable toxicity. We established an IVDD model in rat tail vertebrae through fine needle puncture, administering local injections of BK sustained-release microspheres. Using various experimental methods, including X-ray, MRI, histopathology, and immunohistochemistry, we found that these microspheres could slow the progression of IVDD. This study highlights the potential of injectable PLGA/BK microspheres to regulate cellular senescence and extracellular matrix metabolism via the B2R and PI3K pathways, ultimately delaying IVDD.

A comparative study of the effect of facet tropism on the index-level kinematics and biomechanics after artificial cervical disc replacement (ACDR) with Prestige LP, Prodisc-C vivo, and Mobi-C: a finite element study

INTRODUCTION

Artificial cervical disc replacement (ACDR) is a widely accepted surgical procedure in the treatment of cervical radiculopathy and myelopathy. However, some research suggests that ACDR may redistribute more load onto the facet joints, potentially leading to postoperative axial pain in certain patients. Earlier studies have indicated that facet tropism is prevalent in the lower cervical spine and can significantly increase facet joint pressure. The present study aims to investigate the changes in the biomechanical environment of the cervical spine after ACDR using different prosthese when facet tropism is present.

METHODS

A C2-C7 cervical spine finite element model was created. Symmetrical, moderate asymmetrical (7 degrees tropism), and severe asymmetrical (14 degrees tropism) models were created at the C5/C6 level by adjusting the left-side facet. C5/C6 ACDR with Prestige LP, Prodisc-C vivo, and Mobi-C were simulated in all models. A 75 N follower load and 1 N⋅m moment was applied to initiate flexion, extension, lateral bending, and axial rotation, and the range of motions (ROMs), facet contact forces(FCFs), and facet capsule stress were recorded.

RESULTS

In the presence of facet tropism, all ACDR models exhibited significantly higher FCFs and facet capsule stress compared to the intact model. In the asymmetric model, FCFs on the right side were significantly increased in neutral position, extension, left bending and right rotation, and on both sides in right bending and left rotation compared to the symmetric model. All ACDR model in the presence of facet tropism, exhibited significantly higher facet capsule stresses at all positions compared to the symmetric model. The stress distribution on the facet surface and the capsule ligament in the asymmetrical models was different from that in the symmetrical model.

CONCLUSIONS

The existence of facet tropism could considerably increase FCFs and facet capsule stress after ACDR with Prestige-LP, Prodisc-C Vivo, and Mobi-C. None of the three different designs of implants were able to effectively protect the facet joints in the presence of facet tropism. Research into designing new implants may be needed to improve this situation. Clinical trials are needed to validate the impact of facet tropism.

Influence of foot excitation and shin posture on the vibration behavior of the entire spine inside a seated human body

Due to ethical issues and simplification of traditional biomechanical models, experimental methods and traditional computer methods were difficult to quantify the effects of foot excitation and shin posture on vibration behavior of the entire spine inside a seated human body under vertical whole-body vibration. This study developed and verified different three-dimensional (3D) finite element (FE) models of seated human body with detailed anatomical structure under the biomechanical characteristics to predict vibration behavior of the entire spine inside a seated human body with different foot excitation (with and without vibration) and shin posture (vertical and tilt posture). Random response analysis was performed to study the transmissibility of the entire spine to seat under vertical white noise excitation between 0 and 20 Hz at 0.5 m/s2 r.m.s. The results showed that although the foot excitation could reduce the fore-aft transmissibility in the cervical spine (23% reduction), it could significantly increase that in the lumbar spine (52% increase), which resulted in complex alternating stresses at lumbar spine and made the lumbar spine more vulnerable to injury in long-term vibration environment. Moreover, the shin tilt posture made the maximum fore-aft transmissibility in the lumbar spine move to the upper lumbar spine. The study provided new insights into the influence of foot excitation and shin posture on the vibration behavior of the entire spine inside a seated human body. Foot excitation exposed the lumbar spine to complex alternating stresses and made it more vulnerable to injury in long-term whole body vibration.

Percutaneous endoscopic transforaminal vs. interlaminar discectomy for L5-S1 lumbar disc herniation: a retrospective propensity score matching study

OBJECTIVE

Percutaneous endoscopic lumbar discectomy (PELD) is a safe and effective minimally invasive surgery for treating lumbar disc herniation (LDH); however, the comparative clinical efficacy of percutaneous endoscopic transforaminal discectomy (PETD) and percutaneous endoscopic interlaminar discectomy (PEID) in treating L5-S1 LDH remains unclear. This study compared the clinical advantages of PEID and PETD for treating L5-S1 LDH.

METHODS

This was a single-centre retrospective study analysing clinical data from 120 patients with L5-S1 LDH between February 2016 and May 2020. Propensity score matching (PSM) was used to adjust for imbalanced confounding variables between the two groups. Perioperative data were recorded, and clinical outcomes, including functional scores and imaging data, were compared between groups. Functional scores included visual analogue scale (VAS) for back and leg pain, Oswestry disability index (ODI), and modified MacNab criteria. Imaging data included disc height index (DHI), ratio of greyscale (RVG), and range of motion (ROM) of the responsible segment.

RESULTS

After PSM, 78 patients were included in the study, and all covariates were well balanced between the two groups. In the matched patients, the PEID group showed significantly shorter surgical time (65.41 ± 5.05 vs. 84.08 ± 5.12 min) and lower frequency of fluoroscopy (2.93 ± 0.63 vs. 11.56 ± 1.54) compared with the PETD group (P < 0.001). There were no statistically significant differences in intraoperative blood loss, postoperative hospital stay, total incision length, and incidence of complications between the two groups (P > 0.05). After surgery, both groups showed significant improvement in back and leg pain based on VAS and ODI scores (P < 0.05). There were no statistically significant differences in clinical functional scores and imaging data between the two groups at various time points after surgery (P > 0.05). According to the modified MacNab criteria, the excellent and good rates in the PEID group and PETD group were 91.89% and 89.19%, respectively, with no statistically significant difference (P > 0.05).

CONCLUSION

PEID and PETD have similar clinical efficacy in treating L5-S1 disc herniation. However, PEID is superior to PETD in reducing operation time and frequency of fluoroscopy.

Long-Term Radiographic and Clinical Outcomes in Patients Undergoing Transforaminal Endoscopic Lumbar Discectomy: A Propensity Score Matching Study

Background

Our study aims to investigate the long-term clinical and radiographic effects of transforaminal endoscopic lumbar discectomy (TELD) on lumbar disc herniation.

Patients and Methods

Radiographic and clinical data of patients undergoing TELD in our institution from January 2015 to January 2019 were retrospectively collected. LDH outpatients who had not received surgical treatment during the same period were 1:1 matched by propensity score matching as the conservative group. The radiographic parameters of the two groups at baseline and at the last follow-up (≥24 months) were analyzed.

Results

The study included 47 patients in the TELD group, matched with 47 patients in the conservative group. The disc height of the TELD group at the last follow-up was lower than that at the baseline (P < 0.001), and lower than that of the conservative group at the last follow-up (P < 0.05). The disc degeneration grade of the TELD group at the last follow-up was greater than that at the baseline, and greater than that of the conservative group at the last follow-up. There was no significant difference in the facet joint degeneration in the TELD group between the baseline and the last follow-up, and between the TELD group and the conservative group at the last follow-up (P > 0.05). The pain intensity and disability score in the TELD group at 3-month follow-up and at the last follow-up were significantly lower than those at the baseline (P < 0.001). Six patients in the TELD group required additional surgery during the follow-up period.

Conclusion

Our long-term follow-up data shows that the disc height of the operated level was significantly reduced and the disc degeneration was significantly aggravated in TELD-treated patients; in contrast, the facet joint degeneration did not show significant aggravation.

Visible trephine-based foraminoplasty in PTED leads to asymmetrical stress changes and instability in the surgical and adjacent segments: a finite element analysis

This study aimed to construct a multi-segment lumbar finite element model (FEM) of PTED surgery to analyze the changes in stress and ROM after visible trephine-based foraminoplasty. The CT scans of a 35-year-old healthy male were used to develop a multi-segment lumbar FEM with Mimic, Geomagic Studio, Hypermesh and MSC.Patran. Different foraminoplasty was performed on the model, and these were grouped into normal group (A), the ventral resection group (B), the apex resection group (C), the ventral + apex + isthmus resection group (D), and the SAP + isthmus + lateral recess resection group (E). A vertical load of 500N and a torque of 10N·M were applied to the upper surface of the L3 vertebral body to simulate the biomechanical characteristics under the motion of flexion, extension, lateral bending, and rotation. The von Mises stress maps of the intervertebral f, vertebral body, facet joints, and the ROM of the L3-S1 intervertebral disk were calculated and analyzed. The changes of peak stress on the vertebral body for each group were not significant in the same motion state. Significant stress differences were observed in the L4/5 intervertebral disks, while no obvious stress changes were observed for the L3/4 and L5/S1 intervertebral disks. The stress of the L3/4 and L5/S1 facet joints decreased after L4/5 foraminoplasty, while the stress of L4/5 facet joints displayed an overall increasing trend. Significant asymmetrical stress changes of bilateral facet joints were observed in all three segments, particularly during bilateral rotation movements. The ROM of L3-S1 gradually increased from Group A to Group E, especially during flexion, left lateral bending, and right rotation, with the highest elevation observed for the L45 ROM. Our FEM indicated that enlarged resection and exposure of the articular surface could lead to significant asymmetrical stress changes in the bilateral facet joints and ROM instability of the surgical and adjacent segments. These findings suggested that unnecessary and excessive resection should be avoided in PTED to reduce the incidence of low back pain and the risk of postsurgical degeneration.