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Percutaneous Transforaminal Endoscopic Discectomy

Surgical Indications, Technique, and Patient Outcomes

The emergence of endoscopic techniques in spine surgery represents more than 5 decades of surgical innovation.[1] While these techniques have been historically limited by low-quality imaging, the advancement of appropriate surgical instrumentation and ancillary camera systems in recent years has led to the increasing utilization of endoscopic approaches in spine surgery.

Percutaneous transforaminal endoscopic discectomy (PTED) is one such technique that has been investigated as a potential alternative to tubular microdiscectomy (TM). Although TM is still considered the gold standard for minimally invasive treatment of symptomatic lumbar disc herniation (LDH), PTED has been shown to offer several advantages regarding iatrogenic morbidity. These include minimal muscle dissection and soft tissue damage, decreased removal of bony structures, and negligible manipulation of neural elements allowing for reduced blood loss, rapid recovery, and preservation of segmental stability.[1,2]

Surgical Indications and Considerations

Utilization of PTED is warranted for patients presenting with signs of radiculopathy and nerve root tension due to LDH after 12 weeks of failed conservative therapy. However, several patient-level factors must be considered prior to surgical intervention. While PTED has been shown to effectively treat extruded LDHs, far migrated or sequestered discs have been reported as potential contraindications. A disc that has migrated upward or downward may necessitate a pediculectomy or translaminar approach.[2] Likewise, in patients with a steep iliac crest above the mid-L5 pedicle in lateral radiography, insertion of the cannula through the intervertebral foramen may prove difficult. Prior reports have recommended foraminoplasty for transforaminal access in these cases.[3,4] PTED with foraminoplasty has likewise been introduced as a potential treatment for patients with concomitant spondylolisthesis, in comparison to traditional laminectomy and fusion. However, PTED alone should not be used for patients presenting with spondylolisthesis with segmental instability.[5] Patients with a prior history of conventional microdiscectomy and recurrent LDH may additionally have associated scar formation that alters local anatomy, obscures visualization, and is challenging to address with a transforaminal approach. Dissection of scar tissue from the medial facet joint via percutaneous interlaminar endoscopic discectomy has been suggested as a potential alternative.[6] As such, there are several conditions surgeons should be wary of when considering PTED for treatment of LDH.

Surgical Technique

Preoperatively, a reference line is drawn from the superior articular process to the midpoint of the superior endplate once the level of LDH is determined. Prior to incision, the patient is placed in the lateral decubitus position or traditional prone position on a Wilson frame.[7,8]

The primary incision should be made within 8 to 12 cm lateral to the midline depending on the operated level. Operations at L2-L3, L3-L4, and L5-S1 should have incisions made 8 cm, 10 cm, and 12 cm from the midline, respectively.[7] An 18-gauge needle is subsequently inserted through Kambin’s triangle. The angle of needle insertion should be approximately 55° to 65° in the craniocaudal direction and 30° to 40° on both the anteroposterior and axial views. The disc material is then stained to aid in visualization when utilizing the endoscope. Next, the guidewire is inserted through the needle. Dilation of the neuroforamen up to 8mm is conducted using dilators of varying sizes to prevent irritation of the exiting nerve root. Following dilation, the insertion of the cannula and endoscope may commence. The surgeon must be able to visualize the intradiscal space and previously stained disc material through the endoscope. The high-resolution endoscopic camera system permits comprehensive visualization of the spine with an angled field view ranging from 20° to 90°.[9] A rongeur is then used to grasp and remove the disc material through the working channel of the endoscope. The procedure is deemed sufficient once mobilization of the nerve root and pulsations in line with the heart rate are achieved.[10] The disc space is then visualized to ensure that no loose disc material remains. Corticosteroids may be applied around the nerve root to reduce pain.[7,9] Finally, the endoscope is withdrawn, hemostasis is achieved, and closure is performed.

Outcomes

A systematic review comparing outcomes between PTED and open microdiscectomy determined that there is a slightly increased risk of LDH recurrence among patients treated with PTED. However, PTED was also associated with a significantly decreased length of hospital stay and trended toward improved leg pain, functional recovery, and operative time.[11] Another study implementing the American College of Surgeon’s National Surgical Quality Improvement Program database compared 175 patients undergoing endoscopic discectomy to 38,322 patients undergoing open discectomy and found that endoscopic discectomy resulted in a significantly shorter length of stay (0.81 vs. 1.15 days) and lower rate of adverse events (0.6% vs. 3.4%).12 Although previous studies have primarily focused on comparing open discectomy to MIS approaches, few have compared endoscopic to tubular techniques. One of the primary advantages of endoscopy is the ability to extract foraminal discs without removing bony components. Unlike endoscopy, removal of the foraminal disc using tubular techniques requires a facetectomy, thus necessitating subsequent fusion. Liu et al evaluated 60 PTED and 60 TM patients across a 20-month period and similarly found that the PTED group exhibited less intraoperative blood loss (18.0 mL vs 39.83 mL, p < 0.001), shorter length of stay (5.4 days vs 10.6 days), and lower incidence of paresthesia (6.67% vs 16.67).[13]

Conclusion

PTED is an innovative technique aimed at reducing tissue damage when treating LDH. Unlike open and tubular microdiscectomy, PTED eliminates the need for muscle dissection, bone removal, and nerve root retraction by accessing the disc space through the intervertebral foramen. Despite concerns raised by spine surgeons regarding the potential risks of PTED due to the narrow working corridor and uncertainty regarding successful decompression, research has demonstrated that PTED is a safe and effective treatment option for LDH among patients who meet the appropriate operative criteria.

References

1. Jang JW, Lee DG, Park CK. Rationale and advantages of endoscopic spine surgery. Int J Spine Surg. 2021;15(suppl 3):S11-S20.

2. Kapetanakis S, Gkasdaris G, Angoules AG, Givissis P. Transforaminal percutaneous endoscopic discectomy using transforaminal endoscopic spine system technique: pitfalls that a beginner should avoid. World J Orthop. 2017;8(12):874-880.

3. Lee SH, Kang HS, Choi G, et al. Foraminoplastic ventral epidural approach for removal of extruded herniated fragment at the L5-S1 level. Neurol Med Chir (Tokyo). 2010;50(12):1074-1078.

4. Choi KC, Park CK. Percutaneous endoscopic lumbar discectomy for L5-S1 disc herniation: consideration of the relation between the iliac crest and L5-S1 disc. Pain Physician. 2016;19(2):E301-308.

5. Li XF, Jin LY, Lv ZD, et al. Efficacy of percutaneous transforaminal endoscopic decompression treatment for degenerative lumbar spondylolisthesis with spinal stenosis in elderly patients. Exp Ther Med. 2020;19(2):1417-1424.

6. Kim CH, Chung CK, Jahng TA, Yang HJ, Son YJ. Surgical outcome of percutaneous endoscopic interlaminar lumbar diskectomy for recurrent disk herniation after open diskectomy. J Spinal Disord Tech. 2012;25(5):E125-133.

7. Gadjradj PS, Harhangi BS. Percutaneous transforaminal endoscopic discectomy for lumbar disk herniation. Clin Spine Surg. 2016;29(9):368-371.

8. Kapetanakis S, Gkasdaris G, Angoules AG, Givissis P. Transforaminal percutaneous endoscopic discectomy using transforaminal endoscopic spine system technique: pitfalls that a beginner should avoid. World J Orthop. 2017;8(12):874-880.

9. Yue JJ, Long W. Full endoscopic spinal surgery techniques: advancements, indications, and outcomes. Int J Spine Surg. 2015;9:17.

10. Lee SG, Ahn Y. Transforaminal endoscopic lumbar discectomy: basic concepts and technical keys to clinical success. Int J Spine Surg. 2021;15(suppl 3):S38-S46.

11. Zhang B, Liu S, Liu J, et al. Transforaminal endoscopic discectomy versus conventional microdiscectomy for lumbar disc herniation: a systematic review and meta-analysis. J Orthop Surg Res. 2018;13:169.

12. Page PS, Ammanuel SG, Josiah DT. Evaluation of endoscopic versus open lumbar discectomy: a multi-center retrospective review utilizing the American College of Surgeons’ National Surgical Quality Improvement Program (ACSNSQIP) database. Cureus. 14(5):e25202.

13. Liu L, Xue H, Jiang L, et al. Comparison of percutaneous transforaminal endoscopic discectomy and microscope-assisted tubular discectomy for lumbar disc herniation. Orthop Surg. 2021;13(5):1587-1595.

Omri Maayan, BS

Anthony Pajak, BS

Maximilian K. Korsun, BS

Pratyush Shahi, MBBS, MS (Ortho)

Sravisht Iyer, MD

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