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 Table of Contents  
SYMPOSIUM - MINIMALLY INVASIVE SPINE SURGERY
Year : 2020  |  Volume : 3  |  Issue : 1  |  Page : 54-65

Transforaminal endoscopic surgery in lumbar spine: Technical aspects, current status, and evolving scope


1 Department of Spine Services, Columbia Asia Hospital, Gurugram, Haryana, India
2 Spine Department, Deena Nath Mangeshkar Hospital, Pune, Maharashtra, India
3 Department of Orthopedics, Maulana Azad Medical College and Hospital, New Delhi, India
4 Department of Physiology, Indraprastha Dental College, Sahibabad, Ghaziabad, Uttar Pradesh, India

Date of Submission08-Apr-2019
Date of Decision13-Aug-2019
Date of Acceptance16-Oct-2019
Date of Web Publication05-Feb-2020

Correspondence Address:
Dr. Arun Bhanot
Dr. Arun Bhanot, Department of Spine Services, Columbia Asia Hospital, Gurugram, Haryana.
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/isj.isj_29_19

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  Abstract 

Study Design: This study is comprehensive literature review. Aims and Objectives: This study aimed to evaluate the effectiveness of transforaminal endoscopic technique for managing symptomatic lumbar disc herniations and foraminal/extraforaminal/lateral recess stenosis and to assess the comparative status vis-à-vis existing treatment methods. Materials and Methods: A comprehensive systematic literature search of PubMed, Embase, and Cochrane library databases was performed for articles, including case series, randomized controlled trials (RCTs), controlled clinical trials (CCTs), reviews, and metanalysis with the following search terms: transforaminal endoscopic disc surgery, full endoscopic transforaminal surgery, selective endoscopic discectomy, percutaneous endoscopic lumbar discectomy, transforaminal endoscopic surgery for lumbar stenosis, and endoscopic surgery for foraminal stenosis in various combinations. Results: Results were analyzed in terms of efficacy, safety, complications, recurrence rate, and learning curve in comparison with standard preexisting open procedures. Overall, the reviewed literature pointed toward the following observations: the endoscopic techniques had shorter operating times, less blood loss, less operative site pain, faster postoperative rehabilitation, shorter hospital stay, faster return to work than the microsurgical techniques, although some of the observations were limited in their scope. Endoscopic foraminal stenosis decompression could help avoid facetectomy and fusion procedures. Conclusion: Full endoscopic transforaminal surgeries for lumbar disc herniations and foraminal stenosis are safe and effective alternative to open surgery. Similar clinical outcomes as compared with conventional open surgeries can be reached with lesser incidence of complications and better opportunities for revision surgeries, if and when needed.

Keywords: Full endoscopic lumbar discectomy, percutaneous endoscopic lumbar discectomy, transforaminal endoscopic lumbar discectomy


How to cite this article:
Bhanot A, Raiturker PP, Kashyap A, Arora M. Transforaminal endoscopic surgery in lumbar spine: Technical aspects, current status, and evolving scope. Indian Spine J 2020;3:54-65

How to cite this URL:
Bhanot A, Raiturker PP, Kashyap A, Arora M. Transforaminal endoscopic surgery in lumbar spine: Technical aspects, current status, and evolving scope. Indian Spine J [serial online] 2020 [cited 2020 Feb 27];3:54-65. Available from: http://www.isjonline.com/text.asp?2020/3/1/54/277805




  Introduction Top


Lumbar disc herniation causing radicular pain is one of the most common reasons for patients to seek help from a spine specialist. Most of the literature recommends surgery for pain relief after a certain period of conservative treatment or for neurological deficit. Maximum number of surgeries are still performed for relief of persistent and disabling pain not improving with nonoperative methods.[1]

Microdiscectomy (MI) has hitherto been considered gold standard to remove the herniated disc, though there are sufficient reports not endorsing this assumption beyond doubt.[1],[2],[3],[4],[5] Although it has proven to be quite a reliable and reproducible technique across the globe with a fairly high percentage of success, it has been fraught with some serious complications and failures. Some of the failures and complications are innately linked to the surgical approach (denervation of paraspinal muscles, epidural scarring due to breach of barrier of ligamentum flavum, handling of thecal sac and nerves that can expose them to risk of dural tears, CSF leaks with their antecedent complications, approach-related instability if the bony resection goes beyond a certain point, and so on).[6],[7],[8],[9],[10],[11],[12]

Transforaminal endoscopic approach to remove a disc herniation intuitively appears to be an excellent technique to address the problem of herniated disc surgery avoiding most of the complications encountered in posterior MI technique. However, it can become acceptable only when it can achieve similar or better outcomes as compared with the well-established previous techniques whether one accepts them as gold standard or not. Hijikata[13] and Kambin and Brager[14],[15] were the earliest to consider the role of transforaminal approach to treat disc pathologies by mechanical tools in early seventies. Kambin and Brager[15] also defined the safe triangular zone to allow for safe access to the lumbar disc protecting the exiting nerve root. However, the initial days of transforaminal spine surgery were limited to central disc decompressions.[16] Later, Yeung[17] and Yeung and Tsou[18] refined the transforaminal approach by using good quality working channel endoscope to remove the disc pathology under local anesthesia calling it as selective endoscoic discectomy (SED). Various authors further contributed towards refinement of the full endoscopic (FE) transforaminal technique to make it applicable to a variety of disc-related pathologies from simple to complex disc herniations as well as foraminal/extraforaminal stenosis.[19],[20],[21],[22],[23]

The term “full endoscopic transforaminal technique” means the use of a working channel rigid rod lens-type endoscope introduced inside the spinal canal through the transforaminal approach. The surgery is carried out under constant saline irrigation so that the saline serves as the medium of visualization. The surgical decompression is carried out under constant endoscopic visualization through the same working channel endoscope without having to create any extra portal for insertion of working instruments. The working cannula is also introduced completely percutaneously without stripping or cutting through any of the posterolateral structures in the back. Transforaminal technique has been called by several names such as SED, percutaneous endoscopic lumbar discectomy (PELD), full endoscopic discectomy (FED), and transforaminal endoscopic discectomy (TED). Essentially all the names apply to introduction of a working channel rigid endoscope into the concerned disc or spinal canal through the intervertebral foramen and address the incriminating pathology.


  Purpose of this review article Top


This review has been undertaken with a purpose to analyze the current status of transforaminal surgery for lumbar disc herniation on its technical aspects, its evolution, expanding the scope to pathologies other than disc herniation, and evidence available in literature on the efficacy of this technique. The review also focuses on limitations of the technique, if any and the reasons thereof.


  Materials and Methods Top


An online search was done using the following keywords: transforaminal endoscopic disc surgery, FE transforaminal surgery, SED, PELD, transforaminal endoscopic surgery for lumbar stenosis, and endoscopic surgery for foraminal stenosis. This search was carried on databases such as PubMed, Cochrane, Embase for articles, reviews, case series, and metanalysis. The articles were retrieved from peer reviewed journals and the selection criteria were identified. Simple case reports were not included for assessment in this study except when it highlighted some special surgical technique variation for a special indication or unusual complication. A total of 83 articles were initially retrieved and later filtered to 28 with the stress on below-mentioned criteria. For the sake of authenticity, an attempt was made to focus on large case series from renowned and experienced authors. Comparative studies, review articles, and metanalysis were mainly taken into consideration for writing this review. However, valuable literature from other sources was also considered wherever suitable.


  Surgical Technique Top


Equipment

TED is usually done with a working channel endoscope where a single port is used for visualizing and use of hand instruments. The endoscope has an in built channel through which various hand instruments can be introduced [Figure 1]. With the working channel endoscope, this surgery is done under a coaxial vision and does not require any triangulation technique.
Figure 1: A working channel endoscope depicting optical fiber, two irrigation and drainage ports, and a larger port for insertion of working hand instruments

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Preoperative planning

Preoperative planning is preferable so as to dock the working tube as close to the hernia mass as possible,[24] as well as to anticipate any bony hindrances during the surgery (such as high iliac crest, narrow foramen, and hypertrophied facet). Many techniques have been cited to calculate the correct skin entry point for transforaminal approach. Various methods have been propagated by leading authors based on radiological measurement on preop magnetic resonance/computed tomography (MR/CT) images as well as intraoperative methods based on C-arm fluoroscopic guidance.[18],[25],[26] The needle entry into the annulus varies according to the location of the disc herniation (more medial annular puncture for central disc and relatively lateral annular puncture points as the disc herniation moves from central to paracentral to foraminal/extraforaminal).[25]

Surgical Procedure

Inside–out and outside-in techniques have been propagated by various authors depending upon whether they remove the hernia mass indirectly by pulling it within the disc space first and then retrieving it or removing it directly by docking the working cannula in the epidural space, respectively.[18],[19],[27] We believe that this technical difference is fast becoming irrelevant as surgeons gain experience with this technique. The central idea is to keep the working cannula tip as close to the disc hernia as possible. For a disc herniation that stays at the level of disc without much migration, it would be better to dock the cannula in the posterior most annulus. On the contrary, if the disc fragment is migrated, then it is wise to keep the working tube tip close to the base of the fragment in the epidural space. The patient is positioned prone on Jackson table or radiolucent bolsters. The image intensifier is brought in. The centre as well as alignment of the disc is checked in true anteroposterior and lateral images. Care is taken to visualize both the end plates of the disc as parallel. Skin markings are done as per preoperative plan.

A 16-G-long spinal needle is introduced through the intervertebral foramen into the concerned disc under image intensifier guidance. Some authors perform a discogram using a mixture of radio opaque dye (omnipaque 300) and indigo carmine mixed in a ratio of 2:1, before inserting the guide wire. They claim the discogram reveals morphological pattern of disc herniation as well as selectively stain the nucleus pulposus blue for easier identification under the endoscope. A 0.9-mm guide wire, a blunt conical obturator, and a beveled working cannula are introduced along the needle track one after another. The working cannula can either be anchored into the posterior annulus for inside out technique (half and half: [Figure 2A]–[C]) or it can be positioned in the epidural space for the outside in technique (used for sequestered or migrated disc fragments). The working channel endoscope is introduced through the working cannula. The surgery is done under constant saline irrigation. The optical medium is saline in this surgery as opposed to an air medium in other types of endoscopic assisted or microscopic spine surgeries. The irrigation fluid helps to keep the endoscopic view clear of any small bleeding points by flushing out the minor bleeding and debris. After achieving hemostasis using flexible bipolar coagulation, the tear in the posterior annulus is identified through which the nucleus pulposus has herniated and a cuff of the annular tissue/posterior longitudinal ligament around the herniated fragment is released [Figure 3A] and [B]. This can be done by using either the trigger flex probe, annular cutter or a side firing Ho:YAG laser under endoscopic visualization. Once mobilized, the fragment is removed by using the endoscopic grasping forceps. After removal of the fragment, one can see the free movement of the annular flaps or upon partial withdrawal of the working cannula, even the pulsatile thecal sac and traversing nerve root can be visualized [Figure 4A] and [B]. This usually confirms the adequacy of the decompression and marks the end point of the surgery. The endoscope along with working cannula is withdrawn and wound is closed with a single suture and dressed.
Figure 2: (A) C-arm AP view showing the tip of the beveled working cannula centered over midline at the level of spinous process. (B) C-arm lateral view taken at the same time as [Figure 1A], showing the tip of the beveled working cannula anchored in posterior annulus and a part of the bevel opening into the epidural space behind the posterior vertebral border. (C) An animated version of the “half and half” technique of working cannula placement

Click here to view
,
Figure 3: (A) Endoscopic view with cannula position at “half and half” level, showing herniated disc fragment going toward epidural space at 12 O’clock position, cuff of posterior longitudinal ligament (PLL) and annulus, and the hollowed out disc space beneath the PLL. (B) Endoscopic view after the cuff of PLL is released, showing the undersurface of the herniated fragment that is seen pushed into epidural space toward 12 O’clock position

Click here to view
,
Figure 4: (A) Endoscopic view showing well-decompressed nerve root after removal the herniated fragment. (B) C-arm picture showing the position of cannula at the same time as shown in [Figure 3A]. Note the sub-facetal position of the cannula opening

Click here to view


Postoperatively, the patient can be mobilized within a few hours after the surgery and discharged either the same or the next day.

One can do check magnetic resonance imaging (MRI) in the immediate postoperative period or later to confirm the adequacy of neural decompression [Figure 5A] and [B]; [Figure 6A]–[C].
Figure 5: (A) Preoperative MRI showing a large right paracentral disc herniation at L4-5. (B) Three-month postoperative MRI of the same patient, showing well-decompressed neural elements and no evidence of any postoperative scarring or evidence of a surgery having been conducted on this patient

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,
Figure 6: (A) MRI showing an upmigrated sequestered, L4-5 disc herniation, lying besides the L4 pedicle. (B) C-arm showing the floating position of the round cannula. Note the cannula tip is kept on the posterior surface of disc space and subtly advanced cranially to catch hold of upmigrated fragment. (C) Postoperative MRI of same patient showing complete removal of the upmigrated, sequestered fragment

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Foraminal stenosis decompression technique

Foraminal stenosis decompression is indicated for foraminal/extraforaminal stenosis [Figure 7]. In this technique, the working cannula is docked over the lateral surface of the hypertrophied facet [Figure 8A] and [B]. The lateral aspect of the facet can be reamed with mechanical hand reamers under fluoroscopic guidance initially, followed by introduction of the endoscope. Subsequently, the tip of the facet along with its medial part and foraminal ligaments can be removed under endoscopic visualization after identifying and protecting the exiting nerve root [Figure 9][Figure 10][Figure 11]. Endoscopic drill is quite useful to do the foraminal decompression. One can confirm the adequacy of decompression by doing postoperative CT scan [Figure 12].
Figure 7: Preoperative MRI showing a left L5-S1 extraforaminal stenosis impinging the exiting L5 nerve root

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,
Figure 8: (A) C-arm view showing position of working cannula in AP view. (B) C-arm view showing position of working cannula in lateral view

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,
Figure 9: Endoscopic view of the drilled lateral surface of superior articular process of S1 vertebra

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,
Figure 10: Endoscopic view with a flexible bipolar probe under the inferior surface of exiting L5 nerve root

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,
Figure 11: Endoscopic view showing decompressed L5 exiting nerve root

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,
Figure 12: Postoperative CT scan showing drilled lateral surface of left S1 facet and decompressed extraforaminal space

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Lateral stenosis affecting the extraforaminal region, foraminal region, and lateral recess narrowing can all be addressed using this technique. The endoscope and working cannula need to be advanced according to the desired goal of the surgery. For lateral recess stenosis, the undersurface of superior articular facet along with a part of ligamentum flavum overlying the facet needs to be removed right up to medial margin of the facet. The lateral recess stenosis decompression is checked by visualizing the traversing nerve root and its free movement.


  Results Top


Yeung and Tsou[18] reported his series of 307 patients treated by SED for disc herniations. He advocated a geometrical method of drawing lines on the back under AP and lateral fluoroscopic views to calculate the optimum skin puncture point. He used inside out technique that allowed to inspect the annular tear through which the disc herniation had occurred. The results were reported as 89.3% satisfactory and 10.7% poor. Several poor results were attributed to previous history of laminectomy and discectomy. Yeung and Tsou[18] mentioned the use of side firing Ho:YAG laser to release tough annular adhesions/fibrous tissue but not for debulking the nucleus tissue. His advocacy of local anesthesia was endorsed by the fact of finding furcal nerves in the foraminal/extraforaminal region, though he did mention about inadvertently damaging those furcal nerves many times with no major clinical sequelae.

Hoogland[27] reported on use of chymopapain before doing PELD and reported less degree of early recurrence besides noticing more than 90% good and fair outcomes at the end of two years. Chymopapain’s use did not lead to any serious long term negative effects in his series. Though this combined technique has not been used at many other centers since then.

Ruetten et al.[19] published a prospective study on 463 patients treated by transforaminal approach. A significant number of their patients were treated under general anesthesia. They did not find any difference in risk of neurological injury using general anesthesia though they switched over to general anesthesia after gaining sufficient experience and confidence in transforaminal approach under local anesthesia. Recurrence rate of 7% was reported by them with majority of recurrences occurring during first five months of index surgery. Most of their recurrences were managed by using the same technique if needed. They also noted encountering an end plate fragment in about 75% of their recurrences. They observed a 5% failure rate for relief of preoperative symptoms. Satisfaction level measured by choice of patients to reconsider the same procedure if suffered again was noted to be 88% but these criteria improved to 96% if patients with recurrence were excluded from the series. Reduction in operating time, tissue traumatisation, and complications such as dural injury, nerve damage, bleeding, or infections was reported.[28],[29],[30],[31],[32],[33],[34],[35]

Choi et al.[21] published on PELD technique for extraforaminal disc herniations. They advocated a direct approach to the herniated disc without needing to work intradiscally. The benefit of transforaminal technique over other available methods to treat these disc herniations cannot be overemphasized as this obviates the need for any amount of facet or bone resection. They reported a success rate of 92% as satisfactory at around three years of follow-up and 8% unsatisfactory. They noted much less incidence of dysesthesia due to handling of dorsal root ganglion and no case of reflex sympathetic dystrophy that is seen in other open surgical techniques.

Ahn et al.[36] reported using PELD for high-migrated herniations. They advocated the use of navigable instruments such as semiflexible forceps, articulating forceps, curved forceps, and flexible curved probe that could reach the remote site more easily and take out the sequestered fragment without additional bone resection or foraminoplasty.

Gu et al.[26] reported on 209 consecutive cases treated by TED without any exclusions such as cauda equina syndrome, high iliac crest, extruded or sequestered herniations, and calcified/recurrent herniations. They used an entry point on the posterolateral surface of skin where the horizontal skin of the back changes to the lateral skin surface of the flank and named it Gu’s point. They also recommended widening of the foramen by reaming the anterior part of superior articular facet as earlier recommended by Hoogland to provide easier access to the disc herniation located in epidural space. Their high success rate of more than 95% was marred by poor outcomes only when they were treating calcified disc herniation. Utility of this posterolateral approach was especially noted to treat recurrent disc herniation where no case of dural injury, CSF leak, or pseudomeningocele was noticed as compared with open MI where such complications have earlier been reported in about 10% cases.[37]

Kim et al.[38] published a comparative series of 295 patients undergoing PELD with 614 patients undergoing open MI for a single-level disc herniation. This was a retrospective review and excluded high down-migrated herniations as well as L5-S1 herniations with very high iliac crest and poor foraminal access. They noted similar outcomes between two groups in terms of excellent/good results as well as complications, reoperation rates, and blood loss. They concluded that the endoscopic discectomy was as safe and effective as previously existing MI technique.

Ruetten et al.[39] published a comparative series between conventional MI and FE discectomy using both transforaminal and interlaminar techniques. Postoperative pain and pain medication were significantly reduced in the FE group. The mean postoperative work disability in the FE group was 25 days versus 49 days in the MI group. They concluded that a new technique (FE) should be able to match up to or improve upon the previous established standard of care while minimizing the complications and long-term sequelae. Less postoperative scarring and ease of doing revision surgeries with minimal complications clearly was noticed with FE group as compared with microscopic group because there is a 10% or more incidence of complications noted in revision surgery done after microsurgical techniques.

Gibson et al.[40] published a randomized controlled trial comparing 143 patients operated for lumbar disc herniation either undergoing endoscopic or microscopic discectomy. Recurrent herniations and large sequestered migrations besides upper lumbar disc herniations were excluded. Results were based on patient reported outcome measures such as Oswestry Disability Index (ODI), Visual Analogue Score (VAS) scale, and 36-Item Short Form Health Survey questionnaire (SF-36) form whose scores were converted into SF-6D to calculate Quality Adjusted Life Years (QALYs). They reported statistically significant shorter hospital stay, better affected leg pain score at two years of follow-up for endoscopic group as compared with microscopic group. However, reoperation rates were marginally higher in their endoscopic group that was noticed more during early part of the study duration. There was no significant difference in QALYs among both the groups.

Lv et al.[41] published a meta analysis of comparison between PELD and open fenestration discectomy (FD). Twenty-four trials were included (17 retrospective cohorts and 7 RCTs), involving 1795 patients: 914 cases treated by PELD and 881 cases by (FD). Their analysis found that PELD could offer benefits in terms of blood loss, incision length, and bed rest time, but FD, being a conventional operation had shorter operation time. Two years final ODI results were superior in PELD groups than in FD groups. In terms of efficacy and complications, both the groups were found to have similar results.

Kim et al.[42] published another metaanalysis of comparison between PELD and open-lumbar discectomy groups studying seven papers based on Korean patients. PELD has often been mistrusted to have higher recurrence rate or higher re-operation rate. This metaanalysis did not find any difference on these two parameters between open and endoscopic surgeries. However, they did find a statistically significant difference for shorter hospital stay, shorter operation time, final VAS scores, and ODI for endoscopic group.

Ahn et al.[43] published the radiation hazard and safety rules for PELD. According to them, with standard PELD procedure, following all precautions, a surgeon could safely carry out 620 such procedures annually. However, the radiation hazard for PELD was found to be less as compared with other MIS surgeries such as MIS TLIF, and MIS pedicle screw insertion and was significantly less as compared with vertebroplasty and kyphoplasty. The importance of using protective gears for hands and eyes besides the regular lead apron and thyroid shield cannot be underestimated.

Lewandrowski[23] reports a large series (860/1869 endoscopic procedures for various indications) of foraminal/lateral recess stenosis managed by transforaminal endoscopic decompression using various hand tools such as endoscopic chisels, hand reamers, and endoscopic drill/burr system. They mentioned a 75% rate of good/fair outcomes with minimal complications such as two dural tears and postoperative foot drop in two cases. The major complication was failure to achieve good immediate postoperative relief of preoperative symptoms.

Li et al.[44] and Ahen et al.[47] in different publications citing comparison of endoscopic technique versus open MI found equal or superior results for lumbar disc herniation in the endoscopic groups.[44],[45],[46],[47]

Nellensteijn et al.[48] published a review on the evidence of effectiveness of transforaminal endoscopic surgery by reviewing controlled randomized as well as nonrandomized studies along with some observational series for various indications for endoscopic discectomy. They did not find a strong evidence for effectiveness of this surgery based on design flaws in the studies reviewed. They could not find any difference in the outcome of patients operated endoscopically or with conventional MI. That establishes the fact that endoscopy is as effective if not superior to MI. Because of lack of sufficient evidence, a firm conclusion about its superiority was not drawn in their study.

Birkenmaier et al.[1] reviewed literature comparing FE technique versus conventional MI technique. They witnessed fewer complications with the endoscopic techniques as compared with the standard techniques and in two of the five studies, these differences reached statistical significance.[39],[49] The difference in serious complications was 21% versus 6%, in favor of the endoscopic approach especially when considered in the context of recurrent herniations. With endoscopy, obvious benefits were shorter operating times and less blood loss (even if not statistically evaluated) in all five studies. Three of the five studies claimed significantly less pain at the surgical site immediately postoperative and less use of pain medication. Most importantly and at least in the five studies that could be considered for this review, these benefits do not appear to come at the cost of increased complication rates or lesser efficacy.

Ahn[50] in his review article on role of endoscopic technique in lumbar stenosis mentioned the application of this technique for foraminal and extraforaminal stenosis. Central stenosis has not been recommended as a suitable condition to be treated by transforaminal technique. Definitive compression of a single nerve root of a narrow neural foramen usually causes more pain and discomfort than a diffuse intracanal spinal stenosis and is suitable for focal decompression surgery.[51] However, foraminal/extraforaminal stenosis clearly seems to have an advantage of addressing the stenosis pathology along the tract of working cannula without any need of cutting the facet/fusion.[52]

Knight et al.[53] reported results of foraminal decompression on 79/114 patients using endoscope and side firing laser probe for indications of foraminal stenosis and failed back surgery syndrome patients. He would dock the working cannula at or within the safe zone in the foramen, widen the foraminal dimensions and mobilize the nerve root. His 10-year follow-up revealed 72% excellent and good outcomes with another 10% having satisfactory outcome after the procedure.

Epstein,[55] Garrido and Connaughton,[56] and Haher et al.[57] used PELD technique in addressing foraminal/extraforaminal stenosis for claudicant symptoms on patients with no associated spinal instability.[54] Excellent and good outcomes in 89/91 patients were noted. They recommended endoscopic foraminal decompression for select group of patients to avoid total/partial facetectomy with its inherent disadvantages as earlier reported by various authors.

Lee et al.[58] reviewed a series of 55 operative failures of PELD of a group of 1586 operated cases. They found that high canal compromise >50% in central herniations and high migrations of herniated fragment beyond the measured height of the disc space in either direction were associated with a statistically significant higher rate of failure (15%). On the contrary, nonmigrated herniations and low-migrated herniations did not have any significant difference for failure rates.

Lewandrowski[59] reported a retrospective review of 2076 levels operated on 1839 patients to study the load of complications during transforaminal endoscopic decompression. Grade I complications (any deviation from normal postoperative course treated with observation) occurred in two patients who immediately developed foot drop postoperatively on the surgical side (0.11%) and in another two patients (0.11%) with incidental durotomy. Grade II complications (any deviation with pharmacological interventions) occurred in 11 patients due to chronic obstructive pulmonary disease exacerbation, and in another 2 patients due to infections.The latter were successfully treated with antibiotics. Grade III complications (any deviation requiring surgical, endoscopic, or radiological intervention under general anesthesia) occurred in nine patients with re-herniations of extruded discs within the first three postoperative months (recurrence rate 2.7%).

Grade IV (organ failure) and grade V (death) complications did not occur.


  Discussion Top


TED has evolved from its early days of intradiscal decompression to removal of the sequestered and migrated disc herniations with reasonable reliability. The earlier literature and its reviews talked about the limitations of the technique and higher reoperation rates as well as recurrences. However, with the passage of time and surgeons gaining experience in this technique along with the improvement in surgical equipments and tools, the transforaminal technique has not only expanded to address most of the disc herniation pathologies (e.g., classical indications of contained paracentral herniation to sequestered/migrated as well as foraminal and extraforaminal disc herniations), but it has also been applied to diagnose and address less recognized and undertreated pathology of foraminal/extraforaminal herniation and stenosis compressing the exiting nerve root. However, large down-migrated disc herniations still remain a bit of challenge for this approach.

An analysis of the current available literature reaffirms that TED has reached a level of equal results as compared with the previously assumed gold standard of MI in terms of efficacy for intent to treat. This equivalent status has been reported by several of the authors across various geographical locations and over a large number of operated patients. Several of the published papers also noted a statistical significance in terms of lesser operative time, shorter hospital stay, lesser complication rate, and ease of subsequent revision surgeries, if needed. Going by the logic of a new technique reaching the earlier established standard of care, transforaminal surgery seems to have already measured up to that expectation. However, its superiority over preexisting techniques is still to establish beyond doubt.

A steep learning curve has always been cited as a disadvantage for transforaminal technique. Hsu[60] reported that a surgeon with short observation and cadaver practice can reach a reasonable level of proficiency in transforaminal technique by 10 cases, thus implying rapid acquisition of skills and a good thing for the beginners.

Ruetten et al.[19] observed a comparatively high return to the occupational and athletic level of activities following FED. Criteria such as gender, age, height, weight, educational status, insurance status, or status in the job market had no influence on the outcome with FED. Subsequent endoscopic or conventional procedures can be performed without difficulty and show none of the extended operating time described.

Endoscopic surgery attempts to bridge the gap between injection techniques and open surgery as it attempts to perform the decompression required via the most minimized surgical approach possible, which is the placement of an instrument of just a few millimeters in diameter over the spinal needle that otherwise would have been used to perform a selective nerve root block or a different type of injection.[1]

Use of local anesthesia is much talked about and promoted by several authors. The main claimed advantages are an ability to see and ablate the pain generators that are claimed to lie mostly in the foraminal area. The pioneer surgeons initially promoted it, but nowadays hardly anybody actually uses this part of the surgery. Most surgeons focus on removal of the herniated fragment and shrinkage of the annular tear. These two goals can be comfortably achieved even under general anesthesia. Therefore, insistence on use of local anesthesia need not be that strict. Certain authors have amply shown the safety of transforaminal approach under general anesthesia, thus allowing the comfort factor to the patient.[19] However, surgeons in the early part of their practice might get benefit from use of local anesthesia to help them identify and differentiate various anatomic structures under endoscopic visualization. Patients who are not so suitable for general anesthesia due to advanced age or other comorbid medical conditions can definitely benefit from endoscopic discectomy under local anesthesia.

Earlier studies during evolution of endoscopic discectomy could not find any significant advantage over the previously existing techniques. This could be attributed to lesser experience with a newly evolving technique as well as limitation in endoscopic equipments. However, considering the literature published during last decade from large number of senior authors with significant experience in the usage of these techniques, outcomes have consistently been shown to improve and match those of preexisting techniques. In fact, some of the outcome measures such as shorter operative time, less blood loss, early recovery period, less postoperative work disability, lesser rate of complications, and epidural scarring, thus facilitating easy revision surgeries as and when indicated, clearly point toward a better acceptance of the endoscopic techniques and their potential large usage in the coming times.

Despite reviewing extensively the published literature, the authors feel that there is still a paucity of valuable literature such as several randomized controlled trials originating from multiple centers across the world, to lend authenticity to the positive observations noted by many senior authors and surgeons. Future availability of such studies may be able to provide conclusive evidence for wider acceptance and adaptation of these minimally invasive endoscopic techniques.


  Conclusion Top


TED has come a long way from its earlier days of central disc decompression done for contained disc herniations. Various advancements in tools have widened the scope of transforaminal endoscopic techniques to permit its usage across wide range of indications, with a high percentage of success that matches the pre-existing techniques. Advantages in terms of shorter operating time, less rate of complications, early recovery period, less postoperative disability, and ease of doing revision surgeries, if needed, are clear pointers toward a potential wider acceptance of this technique in the future.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Christof B, Martin K, Hansjorg FL, Bernd W, Sebastian R. The current state of endoscopic disc surgery: Review of controlled studies comparing full-endoscopic procedures for disc herniations to standard procedures. Pain Physician 2013;16:335-44.  Back to cited text no. 1
    
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Gibson J, Waddell G. Surgical interventions for lumbar disc prolapse. Spine (Phila Pa 1976) 2007;32:1735-47.  Back to cited text no. 2
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12]



 

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