How Does intervertebral foramen surgical trephines Work?

Projections of the vertebra

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The articular process or zygapophysis (Greek: ζυγόν, romanized: zugón, lit.''yoke' + apophysis) of a vertebra is a projection that serves the purpose of fitting with an adjacent vertebra. The actual region of contact is called the articular facet.

Articular processes emerge from the junctions of the pedicles and laminae. There are two pairs: right and left, and superior and inferior. They protrude from a vertebra to lock with a zygapophysis on the adjacent vertebra, enhancing backbone stability.

• The superior processes or prezygapophysis project upward from a lower vertebra, with articular surfaces directed more or less backward (oblique coronal plane).
• The inferior processes or postzygapophysis project downward from a higher vertebra, with articular surfaces directed more or less forward and outward.

The articular surfaces are coated with hyaline cartilage.

In the cervical vertebral column, the articular processes collectively form the articular pillars, which are the bony surfaces palpated just lateral to the spinous processes.

Additional Images

• Cervical vertebra

• Median sagittal section of two lumbar vertebrae and their ligaments.

See Also

References

This article incorporates text in the public domain from page 97 of the 20th edition of Gray's Anatomy ()

1. ^

   Moore, Keith L. et al. () Clinically Oriented Anatomy, 6th Ed, p.442 fig. 4.2

Associated Data

Data Availability Statement

The research-related data used to support the findings of this study are restricted by the Ethics Committee of Honghui Hospital, Xi'an Jiaotong University, to protect patient privacy. Data are available from Zhong-Liang Deng, for researchers who meet the criteria for access to confidential data.

Abstract

Objective

To compare the clinical efficacy and complications of foraminoplasty at the tip or base of the superior articular process (SAP) in patients with lateral recess stenosis treated by percutaneous endoscopic lumbar discectomy (PELD).

Methods

Between January and January, 156 patients with lumbar disc herniation and lateral recess stenosis were treated with PELD in five tertiary hospitals and had a 2-year follow-up. Among them, 78 patients received foraminoplasty at the tip of SAP (group A), while the other 78 had it at the base of SAP (group B). Clinical efficacy was evaluated using the visual analog scale (VAS) for back and leg pain, the Oswestry Disability Index (ODI), and the 36-item Short-Form Health Survey (SF-36). Follow-ups occurred at 1 month, 3 months, 6 months, 1 year, and 2 years after surgery.

Results

Mean operative duration was shorter in group B (55 vs. 61 min, P = 0.047). One case in group A couldn't tolerate the neural irritation and required conversion to an open procedure. No dura tears, cauda equina syndrome, or infections were observed. Five patients in group A experienced transient dysesthesia at the exiting nerve, while no cases were reported in group B. Two cases of temporary motor weakness were observed in group A. Five cases required revision surgery due to recurrence, with three from group A. Significant improvements in VAS scores, ODI, and SF-36 were observed during the follow-up (P < 0.05). No statistical difference was found between the two groups after surgery (P > 0.05).

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Conclusions

For patients with lumbar disc herniation and lateral recess stenosis, our modified foraminoplasty technique at the base of SAP simplifies the puncture process in transforaminal PELD and reduces operation time, with no significant difference in symptom relief compared to the routine technique. The modified approach showed advantages in decreasing postoperative neural dysfunction.

1. Introduction

Since the introduction of percutaneous discectomy by Kambin, transforaminal percutaneous endoscopic lumbar discectomy (PELD) has become increasingly popular for treating lumbar disc herniation. Numerous studies have shown that PELD provides successful outcomes comparable to conventional open or microendoscopic surgery.

PELD offers advantages in controlling muscular trauma, shortening hospital stay, and maintaining spinal segment stability. As neural decompression is performed under a single port, establishing an ideal working cannula toward the targeted lesion is crucial.

The superior articular process (SAP) can obstruct the posterolateral rod-shaped endoscope and the anteromedial dura sac, especially in elderly patients with hypertrophic facet joints and lateral recess stenosis. To address this, endoscopic foraminoplasty using reamers, drills, or lasers has been proposed to widen the lumbar intervertebral foramen and facilitate the establishment of the working sheath.

However, complications like postoperative dysesthesia and motor weakness associated with nerve root injury remain concerns. The classical foraminoplasty, known as the Tessys technique, targets the tip of SAP. The modified technique shifts the foraminoplasty to the base of SAP, which is farther from the exiting nerve root, reducing the risk of nerve root dysfunction.

2. Method

Between January and January, 156 patients with lumbar disc herniation and lateral recess stenosis were treated with PELD in five tertiary hospitals, with a 2-year follow-up. The first 78 patients received foraminoplasty at the tip of SAP (group A), while the latter 78 were treated at the base of SAP (group B). Patient demographics and characteristics are summarized separately. The study was approved by the ethics committees of the hospitals, and informed consent was obtained from all patients.

3. Surgical Technique

All patients underwent PELD via a transforaminal approach under local anesthesia. Dexmedetomidine hydrochloride was used intravenously to improve surgical tolerance. The needle entry point was determined by the intersection of the horizontal and oblique caudal directional lines tangent to the tip of SAP.

A 16G spinal needle was used in the puncture process to adjust the trajectory in the strong back muscles. The spinal needle was first placed on the dorsal surface of the facet joint. A guide wire was then introduced, and a blunt guide rod was placed at the surface of SAP. The protective cannula was introduced along the guide rod, and topical anesthesia was applied as needed. A trephine was used to perform foraminoplasty via the transforaminal approach.

The protective cannula was replaced with a working cannula, and an endoscope was introduced. Additional manipulations enlarged the intervertebral foramen and lateral recess, enabling the removal of the protruded nucleus pulposus under endoscopic visualization. Annuloplasty was performed to prevent recurrent herniation.

4. Postoperative Management and Outcome Assessment

Patients were advised to wear a lumbar brace for approximately 4 weeks post-surgery to ensure the healing of the ruptured annular fibrosis. Pain intensity was assessed using the visual analog scale (VAS), while functional outcomes were measured using the Oswestry Disability Index (ODI) and SF-36. Follow-ups occurred at 1 month, 3 months, 6 months, 1 year, and 2 years post-surgery.

Clinical scores and physical examinations were performed by a surgeon who did not participate in the surgery. Complications, such as postoperative dysesthesia and motor weakness, were recorded. Postoperative MRI and CT scans were performed on all patients to detect any residual disc.

5. Statistical Analysis

Statistical analysis was performed using SPSS 11.5 software. Preoperative and postoperative VAS scores for back and leg pain, as well as ODI and SF-36 values, were analyzed with ANOVA. A P-value less than 0.05 was considered significant.

6. Results

Mean operative duration was shorter in group B (55 vs. 61 min, P = 0.047). Only one case in group A required conversion to an open procedure due to neural irritation. No dura tears, cauda equina syndrome, or infections were observed. Five patients in group A experienced transient dysesthesia, but none was reported in group B. Two cases of temporary motor weakness were observed in group A. Five cases required revision surgery due to recurrence, with three from group A. Significant improvements in VAS scores, ODI, and SF-36 were observed postoperatively (P < 0.05). No statistical difference was found between the two groups post-surgery (P > 0.05).

7. Discussion

Transforaminal PELD has been widely used for treating lumbar disc herniation (LDH) since the late 1990s. However, incomplete removal of disc fragments remains a common complication. Unsatisfactory working channel establishment and residual disc are the main reasons for PELD failure.

For complex LDH cases, like central, migrated, and axillary types, PELD failure rates without foraminoplasty are as high as 4.3% to 10.3%. The SAP can obstruct the surgical field and limit space to place the working channel through the intervertebral foramen. Foraminoplasty provides direct visualization of the anterior epidural space via thorough decompression, especially by undercutting the ventral part of SAP and removing the foraminal ligament.

The instruments used for foraminoplasty include endoscopic burr, side-firing laser, reamers, and trephines. While endoscopic burr and side-firing laser offer safety under visualization, their small size affects efficiency. Using high-speed tools can also induce vibration or thermal damage, posing a risk of nerve root injury.

Trephines and reamers are economical and time-saving equipment but carry risks without continuous visualization and protection. Li et al. modified foraminoplasty by targeting the base of SAP, reducing the risk of postoperative nerve root dysfunction. The protective cannula serves as a barrier, enhancing the safety of the procedure.

The design of the blunted guide rod simplifies the puncture procedure, reducing radiation exposure and operation time. The guide rod's shape facilitates sliding and anchoring into the intervertebral foramen, minimizing the risk of abdominal visceral perforation during the puncture process.

While excessive removal of the facet joints is associated with spinal instability, the modified foraminoplasty preserves ligamental and muscular structures, maintaining spinal stability. Dexmedetomidine hydrochloride was used in anesthesia, enhancing patient comfort during the procedure.

8. Conclusion

For patients with LDH and lateral recess stenosis, the modified foraminoplasty at the base of SAP simplifies the puncture process and reduces operation time. Although symptom relief was comparable to the routine technique, the modified approach lowered postoperative neural dysfunction incidence.

Acknowledgments

We thank the Key Project of Medical Research of Chongqing Municipal Healthy Bureau (no. ZDXM007 for Zhong-Liang Deng) and the Chinese National Natural Science Foundation (no. for Ding-Jun Hao) for their grant support.

Data Availability

The research data supporting this study are restricted by the Ethics Committee of Honghui Hospital, Xi'an Jiaotong University, to protect patient privacy. Data are available from Zhong-Liang Deng for researchers who meet the criteria for access to confidential data.

Conflicts of Interest

The authors declare no conflicts of interest.

Authors' Contributions

Lei Chu, Xiang-Fu Wang, Li-Min Rong, and Zhong-Liang Deng conceived the study design. Ke-Xiao Yu, Lei Shi, Zhen-Xing Zhang, Chien-Min Chen, and Rui Deng supervised data collection. Jun-Song Yang drafted the manuscript. Ding-Jun Hao and Zhong-Liang Deng contributed to revisions. Ding-Jun Hao is responsible for this article. Lei Chu, Jun-Song Yang, Chien-Min Chen, Xiang-Fu Wang, and Pei-Gen Xie contributed equally to this study.

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