|
 
 |
| SYMPOSIUM - MINIMALLY INVASIVE SPINE SURGERY |
|
| Year : 2020 | Volume
: 3
| Issue : 1 | Page : 66-77 |
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Full-endoscopic interlaminar surgery of lumbar spine: Role in stenosis and disc pathologies
Pramod V Lokhande
Department of Orthopaedics, Smt. Kashibai Navale Medical College and General Hospital, Pune, Maharashtra, India
| Date of Submission | 31-Mar-2019 |
| Date of Decision | 27-May-2019 |
| Date of Acceptance | 07-Dec-2019 |
| Date of Web Publication | 05-Feb-2020 |
Correspondence Address:
Dr. Pramod V Lokhande
Prof. Dr. Pramod Vasant Lokhande, Department of Orthopaedics, Smt. Kashibai Navale Medical College and General Hospital, S.No. 49/1, Mumbai Pune Bypass Rd, Narhe, Pune, 411041, Maharashtra.
India
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/isj.isj_22_19
The aim of this study was to evaluate the effectiveness of full-endoscopic interlaminar operations for symptomatic lumbar disc herniations and lumbar canal stenosis and to compare their results with conventional open procedures. A comprehensive systematic literature search of PubMed, Embase, and Cochrane Library databases was performed for articles, including randomized trials (RCTs), controlled clinical trials (CCTs), reviews, and meta-analysis with the following search terms: full-endoscopic discectomy, also known as percutaneous endoscopic lumbar discectomy, interlaminar discectomy, endoscopic, and percutaneous stenosis decompression in various combinations. Results were analyzed for their effectiveness, safety, complications, recurrence rate, and learning curve, and compared with standard open procedures. Overall, the endoscopic techniques had shorter operating times, less blood loss, less operative site pain, and faster postoperative rehabilitation/shorter hospital stay/faster return to work than the microsurgical techniques for both disc herniation and lumbar spinal stenosis surgeries. The advantages and disadvantages of variations in techniques and choice of anesthesia are discussed. This comprehensive literature review shows that full-endoscopic surgeries for lumbar disc herniations and lumbar spinal stenosis are safe and effective alternative to open surgery. These can achieve the same clinical results with added benefits of minimally invasive spine surgeries. Keywords: Discectomy, full endoscopy, interlaminar, review, stenosis decompression
How to cite this article:
Lokhande PV. Full-endoscopic interlaminar surgery of lumbar spine: Role in stenosis and disc pathologies. Indian Spine J 2020;3:66-77 |
| Introduction | |  |
The treatment of symptomatic lumbar disc herniations is mainly conservative with analgesics and epidural steroids. Surgery is advised only when conservative management is ineffective. Open lumbar microdiscectomy has been the gold standard with good clinical outcomes.[1],[2],[3],[4],[5],[6],[7] The disadvantage of conventional surgeries are epidural scarring, caused by removal of ligamentum flavum (LF), which is symptomatic in 10% cases.[8],[9],[10],[11],[12],[13],[14],[15] Excessive muscle stripping beyond the lateral border of facet joints can damage branches of dorsal nerve roots and denervating multifidus,[9],[16],[17],[18] leading to loss of stabilization and coordination system, thereby hampering locomotion.[11],[14],[15] Excessive bone resection involving facet, lamina, or pars, especially at upper lumbar levels, can lead to iatrogenic instability.[7],[19],[20],[21],[22],[23],[24],[25] All these factors may be considered as primary reasons for postdiscectomy syndrome.[10],[11],[18],[26] Revision surgery in such patients poses problems such as difficulty in separating neural structures from scar tissue to identify herniated fragment. Additional bone removal during this process causes instability necessitating need for fusion.[20],[22],[27],[28]
The aim of minimally invasive spine (MIS) surgeries is to minimize these “access portal” related injuries to these normal anatomical structures. Full-endoscopic discectomy (FED), also known as percutaneous endoscopic lumbar discectomy (PELD), can be considered as one of the most sophisticated forms of MIS surgeries. FED was introduced in 1971 by Kambin[29],[30],[31] and Hijikata et al.[32] Although transforaminal (FED-TF) was the first endoscopic approach described for lumbar discectomy, interlaminar approaches have added versatility to the indications of surgery.
Full-endoscopic interlaminar technique has certain advantages over other MIS techniques such as METRx and Destandeu. Because of its small size, the incision size has been reduced from 20–25mm to 8mm. Secondly, continuous saline irrigation keeps the visual field clean and also has a hemostatic effect.
Ruetten[33] first reported full-endoscopic interlaminar discectomy (FED-IL) technique in 2005. After its successful outcomes, the indications were extended to management of lumbar canal stenosis (LSS). This was possible due to technological advancements[34],[35] such as better optics, increase in the working channel size of endoscope, and development of better instruments such as endoscopic drill, Kerrison rongeurs, and articulated instruments.
| Review of Database | | |
A comprehensive systematic literature search of PubMed, Embase, and Cochrane Library databases was performed for articles, including randomized trials (RCTs), controlled clinical trials (CCTs), reviews, and meta-analysis with the following search terms: full endoscopic, PELD, interlaminar discectomy, endoscopic, and percutaneous stenosis decompression in various combinations. The articles were retrieved from peer-reviewed journals; their eligibility criteria were identified and categorized. A total of 128 articles related to uniportal full-endoscopic interlaminar surgeries were reviewed, of which 112 articles were regarding lumbar disc and 16 articles were regarding endoscopic stenosis decompression.
| Discectomy Technique | | |
Surgical Approach and Technique
Surgery is performed in prone position under general anesthesia. An 8-mm incision is taken close to the spinous process in the center of the interlaminar space of the affected level. A dilator is inserted through the incision till it reaches the LF. Its position is checked in anteroposterior and lateral views of fluoroscopy. A beveled working channel is inserted over the dilator. Endoscope with attached irrigation fluid flow is inserted through the working channel [Figure 1]. Some muscle fibers are removed to expose the LF. If the interlaminar space is large like at L5-S1 level, then flavum is directly cut with a 2.5-mm punch forceps, layer by layer, till the epidural space is opened. If the interlaminar space is narrow, then some medial portion of the facet is removed with an endoscopic drill to widen the space, before cutting the flavum. Flavum cutting is continued laterally till facet is reached and lateral border of nerve root is seen. The working channel is then pushed forward to reach the disc and is rotated in 180° to retract the nerve root. Disc is identified, and herniated fragments are removed by cutting annulus with a punch forceps. Hemostasis during the procedure is achieved using a radio-frequency bipolar trigger-flex [Figure 1],[Figure 2],[Figure 3]–[Figure 4]. | Figure 1: Basic steps of insertion of endoscope: (A) marking of the inter laminar space, (B) insertion of obturator, (C) insertion of cannula over obturator, (D) final cannula position, and (E) position of video trolley and handling of endoscope
Click here to view |
,  | Figure 2: (A) First view after the insertion of the endoscope. Some muscle and fat needs to be removed to expose the ligamentum flavum. (B) Exposed ligamentum flavum. (C) Opening of epidural space. (D) Extending the cut in flavum laterally towards facet. (E) Exposed disc fragment. (F) Decompressed nerve root after removal of disc
Click here to view |
,  | Figure 3: Illustrative case 1. (A) Preoperative MRI images of L5-S1 left paracentral disc herniation. (B) Immediate postoperative MRI images after full-endoscopic interlaminar discectomy showing complete removal of disc herniation with well-decompressed nerve root and dural sac. We can appreciate that there is negligible damage to the posterior musculature and ligaments
Click here to view |
,  | Figure 4: Illustrative case 2. (A) Preoperative MRI images of L5-S1 left-sided down-migrated extruded disc herniation. (B) Immediate postoperative MRI images after full-endoscopic interlaminar discectomy showing completely removed extruded fragment with well-decompressed nerve root and dural sac. A small slit (red arrow) can be seen in the ligamentum flavum, which was made to access and remove the herniation
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Stenosis Decompression Technique
A 5.7-mm large working channel endoscope is used for stenosis decompression. Once the endoscope is inserted, LF is completely exposed till bony margins are seen from all sides. Bony resection is done with an oval burr with side protection starting from tip of descending facet, continuing upwards towards superior lamina till the tip of ascending facet and then finally inferior lamina. Complete flavectomy is done using punch and a Kerrison rongeur. Decompression of the contralateral side is done by tilting the endoscope under the spinous process. Flavum is removed from the underside. Undersurface of the contralateral facet is drilled if necessary to decompress the contralateral nerve root [Figure 5] and [Figure 6]. | Figure 5: Stenosis decompression––ipsilateral and contralateral. (A and B) The vertical position of the endoscope during ipsilateral decompression. (C and D) The tilted position of the endoscope for contralateral decompression. The endoscope passes over the dural sac and under the spinous process to reach the opposite side
Click here to view |
,  | Figure 6: Illustrative case of stenosis decompression: (A) preoperative and (B) postoperative axial MRI images showing good decompression by over the top technique
Click here to view |
| Analysis of Reported Outcomes | | |
Efficacy of full-endoscopic interlaminar discectomy
We studied 128 articles related to FED, of which 13 articles were found to be important and were reviewed. There were four prospective and five retrospective studies, two comprehensive reviews, and two meta-analyses.
Ruetten et al.[34] prospectively analyzed the results of 331 patients with lumbar disc herniation who underwent interlaminar decompression with minimum follow-up of 2 years. They performed surgeries in prone position under general anesthesia. 82% patients reported complete relief and 13% had only occasional pain at final follow-up. The recurrence rate was 2.4%. They concluded that the results were equivalent to those of conventional procedures with added benefit of reduced trauma to the access pathway and the spinal canal structures. Epidural scarring was also minimized.
Choi et al.[36] retrospectively analyzed 67 patients with L5-S1 soft disc herniation treated with interlaminar PELD with more than 1.6 years of follow-up. Surgeries were performed under local anesthesia and conscious sedation in lateral position by a complete percutaneous approach. 90.8% patients showed favorable results. Mean hospital stay was 12h. Average time to return to work was 6.79 weeks. Complications included two cases of dural injury with cerebrospinal fluid leakage, nine cases of transient dysesthesia, and one case of recurrence. Two patients required conversion to open procedure at the initial operation. They concluded that interlaminar PELD is a safe and viable alternative to conventional open surgery.
Chumnanvej et al.[37] reported 91.6% excellent outcomes in their prospective analysis of 60 patients with 26 months of follow-up. There were two cases of recurrent herniations, which were reoperated by the same method with resolution of symptoms. They concluded that FED-IL is a safe and effective procedure with advantages of less postoperative pain, early recovery, and a short period of work absence. However, the learning curve is steep, necessitating proper surgical training and careful patient selection in the early cases.
Comparison with conventional techniques
There are two prospective RCTs and one meta-analysis comparing results of FED to standard open procedures.
Ruetten et al.,[38] in his prospective RCT compared endoscopic interlaminar and transforaminal lumbar discectomy to the conventional microsurgical technique.The key findings were a reduced operating time (22 vs. 43min on average) and a faster return to work (25 vs. 49 days) with endoscopic technique. Clinical outcome was similar, but there were less complications and less need for fusions with the endoscopic technique.
Zhiming et al.[39] reported similar advantages of FED-IL or micro endoscopic discectomy (MED). Although no statistical difference was found, the complication rate seemed lower in FED-IL procedure. They found that the challenges for beginners were early recurrence and a steep learning curve. They recommended proper choice of cases in the early stages.
A literature review by Birkenmaier et al.[40] comparing the clinical outcomes and complication rates of FED-IL to the microsurgical standard procedures identified only four RCTs and one controlled study that could be considered to originate from experienced investigators. The studies show that FED-IL can achieve the same clinical results without any higher complication rates. But the limitation of this review was that all the RCTs came from the same group. This created ambiguity regarding reproducibility of results by less-experienced surgeons.
Sah et al.[41] reported that postoperative leg pain improvement was similar, but improvement of back pain was higher in the endoscopy group than microdiscectomy group.
A meta-analysis by Lin et al.[42] compared the effectiveness and safety of endoscopic discectomy (ED) with open discectomy (OD). There was no significant difference in the clinical outcomes and operating time, but there was significantly longer hospital stay and greater blood loss volume in the OD group. Although the recurrence rates of ED group were slightly higher than OD group (5.04% vs. 3.35%, respectively), the reoperation rates were comparable (6.82% vs. 6.93%). There was higher patient satisfaction rate with comparable clinical outcomes with ED group. It was reported that, at the beginning of the learning curve, the poor depth perception possibly resulted in higher incidence of neural injuries and the restricted field of work decrease the chance of identifying and removing free fragments, ultimately leading to a higher incidence of recurrences.
Regarding cost effectiveness, one RCT found that minimally invasive procedures were significantly more expensive than OD.[43] However, they also argued that shorter length of hospital stay may ultimately lead to lower cost of treatment. Another study found endoscopic surgeries to be more cost-effective as compared to MED with no difference in cost-effectiveness among FED-TF, IFED-IL, and Biportal endoscopy.[44]
Another prospective RCT comparing endoscopic techniques with microdiscectomy for recurrent lumbar disc herniations reported reduced operating time (24 vs. 58min on average) and a faster return to work (28 vs. 52 days) with the endoscopic technique. Although the clinical outcomes were the same in both groups, there were less serious complications with the endoscopic technique.[45]
Comparison of transforaminal and interlaminar technique
A prospective RCT by Nie et al.[46] compared the efficacy and radiation exposure of the two techniques. They reported that transforaminal approach may be difficult at L5-S1 level, when there is high iliac crest or small foramen. On the contrary, wide interlaminar space facilitates easy access, even for migrated herniations. Interlaminar group also experienced significantly less radiation and operation time than transforaminal group. The advantages of FED-IL are as follows: (1) it uses the posterior approach that is familiar with all spine surgeons, (2) it can dissect extruded disc tissues under direct vision with manipulation of nerve root, (3) its interlaminar window at L5-S1 is very wide and can allow access to disc herniation without the need of bone resection, and (4) it can provide better mobility to remove the sequestered or migrated fragments without the limitation of bony foramen and blockage of pelvis.
Amato et al.[47] have also confirmed that FED-IL needs smaller amount and lesser duration of radiation exposure as compared to the FED-TF technique.
Variations in interlaminar technique
There were three variations of interlaminar technique reported in the literature. In Choi et al.’s[36] technique, a needle was inserted through the skin under fluoroscopy guidance passing through LF to enter the disc. Serial dilators were passed over the guide wire into the disc. Round tipped cannula was then passed till it reached the disc. In Ruetten’s[33] technique, an 8-mm small incision was made through which the dilator was inserted till it reached the LF. A small cut was made in the flavum under direct endoscopic vision to enter the epidural space. A third variation was reported by Kim and Chung[48], in which LF was split with a dissector under endoscopic vision. The tip of working cannula was used to retract and create wide opening in the LF to enter epidural space. Hwang et al.[49] used a contralateral approach to remove sequestrated or migrated herniations, where the endoscope was passed over the dura by undercutting the spinous process to visualize the contralateral nerve root and disc fragment. This ipsilateral facet-preserving approach is recommended especially in patients with facet hypertrophy and narrow interlaminar space. Kim and Park[50] used annular sealing technique after discectomy. A radio-frequency probe was used to cauterize the margins of annulus intermittently at least 10 times to minimize the incidence of recurrence.
Song et al.[51] compared the intermittent (Gun Choi) technique with full endoscopy technique (Ruetten). They found that intermittent technique is more effective and economic because of its shorter surgical duration and lower hospitalization costs. Avoidance of intraoperative nerve injury is easier due to intraoperative feedback from patients. It also causes less damage to LF. Lee et al.[52] found that opening of LF under visual control was safer.
Choice of anesthesia
Depending on surgeon preference, FED was performed with local anesthesia with conscious sedation (LA), epidural (EA), or general anesthesia (GA). Successful use of LA has been mainly reported by studies advocating transforaminal technique. Its use is not commonly reported for interlaminar approach. LA has the following advantages: Feedback from an awake and conscious patient prevents inadvertent injury to the nerve root during surgery. Use of neuromonitoring is not necessary.[53],[54] The patient can report relief of pain on the operating table following adequate decompression providing instantaneous feedback on the success of decompression. Trauma to anomalous nerves, such as furcal nerve, which are found in the “hidden zone” of Macnab, can lead to unpleasant dysesthesias. Local anesthesia can avoid this complication
Sairyo et al.[55] stated that the transforaminal PELD is possible for the elderly patients with poor general condition, in whom GA may not be safe. Henmi et al.[56] also reported good outcomes of transforaminal PELD under LA in elderly patients with combined spinal canal stenosis and disc herniation. Fang et al.[57] compared the effects of LA and EA in a retrospective analysis of 286 cases. No significant difference was noted between the two groups, although the satisfaction rate in postoperative patients was significantly greater in the EA group. Yoshikawa et al.[58] compared the effects of LA, EA, and GA during PELD. They concluded EA to be a useful option in patients undergoing PELD. However, these studies concluded that LA or EA was related to transforaminal approach.
Chen et al.[59] prospectively compared the results of LA and GA for interlaminar approach at L5-S1. The patients in the LA group usually felt discomfort in the low back and leg during intraoperative manipulation of the dural sac and nerve root, whereas they found the procedure comfortable under mild conscious sedation. Fewer transient postoperative dysesthesia occurred in the LA group (13.7%) than in the GA group (24%). LA was also associated with significantly shorter hospital stay. They concluded that LA is preferable to GA in FED-IL.
Learning curve and surgical outcome
Yörükoğlu et al.[60] observed that FED-IL has a steep learning curve and it is a difficult procedure to implement. Surgeons should be aware of complications that can occur with the FELD procedure, and in most cases these complications resolve spontaneously. Choi et al.[36] stated that supervision of an experienced endoscopic surgeon is necessary during the initial 10 cases.
According to Wang et al.,[61] there are two potential pitfalls with the FED-IL technique: one is anatomic orientation and the other is the amount of manipulation of neural elements within the spinal canal.
Misplacement of working portal during the exposure of the ligament flavum and difficulty in identifying anatomy are potential causes for conversion to open in the initial adoption of the technique. However, uncommon conditions such as variation of the nerve root origin can also result in conversion to open in experienced hands. Larger disc herniations and herniations with longer duration of symptoms can also be associated with a higher risk of complication.
A steep learning curve is a major concern for the initial adoption of this technique. To avoid complications, they recommended gaining extensive experience in microsurgical procedures before attempting the FED-IL procedure. They recommended minimum 30 cases for learning curve and also recommended to start with L5-S1 disc herniations where the interlaminar window is wide. After improvement in the surgical skills, non-migrated L4-L5 disc herniations were included as next surgical indications.
Meticulous attention paid towards accurate anatomic positioning, careful dissection and manipulation of the nerve root, and hemostasis are key factors to avoid complications and failures.
Passacantilli et al.[62] observed that proper case selection played an important role in avoiding complications during the learning phase. They suggested treating type A prolapse (shoulder-type herniations where nerve root is displaced medially) at the beginning of the learning curve and type B prolapse (axillary herniations where nerve root is displaced laterally) after sufficient experience in the use of the endoscopic burrs has been achieved to uncover the nerve root.
| Stenosis | | |
Introduction
LSS is predominantly a disease of the elderly.[63],[64],[65],[66],[67]. The symptoms occur because of narrowing of the vertebral canal due to varying degrees of disc herniation and/or bulging, facet joint hypertrophy and cyst formation, and LF hypertrophy with buckling. In some cases, there may be associated spondylolisthesis.[68],[69]
Symptomatic LSS can cause progressive neurogenic claudication, radicular pain, and weakness. Claudication pain occurs usually due to central canal stenosis and radiculopathy from lateral recess encroachment. The mechanical back pain which may occur is usually secondary to dynamic instability or spinal deformity.
Surgical decompression for symptomatic LSS is the most common indication for spine surgery in patients older than 65 years.[70],[71] It has been shown to improve pain, disability, and health-related quality of life.[72],[73],[74],[75],[76]
Open laminectomy for spinal stenosis is a safe and cost-effective procedure, with superior outcomes as compared to nonsurgical management.[75],[77],[78],[79] However, in some cases, the disadvantages are persistent postoperative back pain due to prolonged muscle retraction,[80],[81],[82],[83] increased risk of postoperative instability, and the subsequent need for secondary fusion surgery.[21],[84] This is again associated with additional risks and costs.[21],[85],[86],[87],[88],[89]
The incidence of postlaminectomy spondylolisthesis is 5.5%, with 1.8% of patients requiring a reoperation for instability.[90],[91] Patients with preoperative spondylolisthesis undergoing decompression alone are nearly 10 times more likely to undergo a subsequent additional stabilization procedure than their stenosis-only counterparts. Fusion is associated with increased cost and higher subsequent reoperation rates than decompression alone.[74],[92],[93],[94],[95]
To minimize these complications, multiple MIS approaches such as partial interspinous laminectomies,[95],[96] modifications of spinous process osteotomies;[97],[98],[99],[100],[101] bilateral laminotomy;[102],[103],[104],[105],[106],[107] and unilateral laminotomy have been described over many years.[17],[108],[109],[110],[111],[112],[113]
In 1988, Young et al.[114] introduced microscope-assisted bilateral laminotomy. In 1999, a less-invasive unilateral approach was introduced for bilateral decompression.[115] Along with these MIS techniques, changes in the retractor system from conventional to tubular further reduced traumatization of tissues.[113],[116],[117]
Unilateral laminotomy for bilateral decompression (ULBD) using tubular retractor is already an accepted technique. The advantage of this technique is that the paraspinal muscles are dissected only on one side, thereby preserving the functional integrity of the contralateral muscles and interspinous and supraspinous ligaments. This technique has better clinical outcomes with reduced chance of postoperative instability.[98],[118],[119] According to Arai et al.,[120] in multilevel decompressions, ULBD was superior to midline decompression procedure in terms of improvement of low back pain and lumbar function. However, Hugo et al.[121] reported that microscope-assisted tubular ULBD has higher chances of dural tears and incomplete decompression of the contralateral side leading to symptomatic residual stenosis. This is due to limited visual field available while performing contralateral decompression. A 25-degree lens endoscope can overcome this disadvantage by bringing the surgeon’s eye closer to the pathology.
| Analysis of Reported Outcomes | | |
A total of 11 articles were reviewed, which included three prospective RCTs and one meta-analysis.
Full-endoscopic operations for LSS were first reported by the Ruetten group, intially for lateral recess stenosis in 2009 and later for central stenosis in 2011. Full-endoscopic operations for LSS were first reported by the Ruetten group.[122],[123],[124] Both were prospective RCTs with minimum follow-up of 2 years. Their clinical outcomes were equal to those of conventional procedures with lower rate of complications.
A prospective RCT by Ruetten et al.[122] compared the results of full-endoscopic decompression (FI) to microsurgical laminotomy (MI). Among 135 patients, 72% had almost complete relief and 21.2% had occasional pain. The mean intraoperative and postoperative blood loss was 73mL in the MI group as compared to 15mL in FI group. The rate of complications and revisions was significantly reduced in the FI group. The operation in the FI group was technically feasible in all patients. An intraoperative switch to a conventional procedure was not necessary in any patient.
The mean operating time in the FI group was significantly shorter than in the MI group (42 vs. 64min). They concluded that full-endoscopic techniques brought advantages in areas viz. operation, complications, traumatization, and rehabilitation.
On the contrary, a retrospective analysis by McGrath et al.,[125] involving 95 patients, which again compared endoscopic-ULBD with MIS-ULBD, found that, although endoscopic-ULBD had reduced hospital length of stay and superior clinical outcomes in terms of leg pain and back pain, it was associated with significantly longer operative times.
Another retrospective study by Lim et al.[126] involving 450 patients with symptomatic LSS reported similar results to traditional techniques but with lower infection rates, which they attributed to small skin incision.
Finally, Lee et al.,[127] in his meta-analysis included five retrospective cohort studies. Two of these studies were of uniportal (technique of present review) and three studies of UBE (biportal) technique. According to them, the major concern of both techniques was incomplete decompression, mainly occurring at the cranial end of LF or the ipsilateral lateral recess, because of the limitation of vision and tools, such as drills and Kerrison rongeurs. The authors tried to overcome these limitations through a contralateral approach of the severely symptomatic side,[128] en bloc detachment of the LF,[129] and newly invented cannula.
| Discussion | | |
This comprehensive review of the literature reveals that all the studies unanimously corroborate that the clinical outcomes of FED surgeries are comparable to standard microsurgical techniques with added benefits of less postoperative pain, reduced bleeding, shorter duration of surgery, fewer complications, shorter hospital stay, early return to activity, and higher patient satisfaction rate. The recurrence rate of FED is also comparable to open surgeries.
There were no RCTs comparing cost-effectiveness of FED to open procedures. Although one study mentioned that FED was less cost-effective, the other study reported no difference in endoscopic and open surgeries. This probably could be explained by shorter hospital stay, which reduces the overall cost.
FED-IL proved to be more beneficial than FED-TF in the lower lumbar spine, especially at L5-S1, as it avoided the natural anatomical barriers. The wider interlaminar space makes it easy to access even high migrated herniations.
There were three variations reported in the approach of interlaminar technique. The flavum cutting approach under direct endoscopic visualization, in which the lateral border of nerve root is identified first, before entering inside the spinal canal, is found to be the safest technique, avoiding damage to neural structures especially in cases with intraoperative surprises such as congenital nerve root anomalies. The percutaneous approach, which uses guide wire and serial dilators to open the LF and enter the disc under fluoroscopic guidance, is a relatively blind technique with higher chances of neural injury, especially in the hands of less-experienced surgeons. Intraoperative neural retraction and manipulation can be reduced by using beveled tipped working channel, which does not occupy a lot of space inside the spinal canal, as compared to round channel. The rotation of beveled channel allows the surgeon to intermittently relieve the nerve retraction, further decreasing injury to the neural tissue. This reduces the incidence of intraoperative nerve injuries and postoperative dysesthesias.
Although some studies have highlighted the benefits of LA, we think that it is more tolerated during transforaminal endoscopy where manipulation of the nerve root is minimal. Neural retraction during FED-IL causes significant discomfort and pain especially in cases with very large disc herniations and inflamed nerve root. Secondly if the patient is anxious, less cooperative or when the operating time is extended, the procedure is less tolerated by the patient. Therefore, although the hospital stay is slightly extended, our preferred anesthesia is either epidural or general, as it increases the surgeon’s comfort during surgery. The learning curve of FED-IL is steep, which is substantiated by all the studies. FED-IL is a procedure, which is easy to understand but difficult to master. The learner surgeon should have significant microsurgical experience. Observing operations done by experienced surgeons, attending didactic courses regarding operative technique, and hands on cadaver training can help shorten the learning curve. A beginner should start with simple cases like a paracentral, non-migrated disc herniation at L5-S1 level with a wide interlaminar space, to get acquainted with the basic surgical steps and endoscope handling, and to develop confidence.
Although very few, all studies confirmed that endoscopic stenosis decompression is as effective as open surgery. Komp et al.[123] reported reduced operating time for endoscopic decompression as compared to open surgery whereas McGrath et al.[125] stated the operation time to be significantly longer. We feel that experienced surgeons who have passed their learning curve, can perform endoscopic decompression faster as compared to open surgery. One of the reasons is that the time taken for exposure and closure of surgical wound is significantly less in endoscopic approach. One study mentioned low rate of infection in the endoscopy group, which they attributed to small incision size. In our experience, continuous saline irrigation also plays an important role in reduced incidence of infection. One of the major concerns of incomplete decompression was raised by one study.[127] This is due to the limited field of endoscopic vision. It can be avoided by intraoperative use of fluoroscopy to confirm the extent of decompression.
| Conclusion | | |
This comprehensive literature review shows that full-endoscopic surgeries for lumbar disc herniations and LSS are safe and effective alternative to open surgery. They can achieve the same clinical results with added benefits of MIS surgeries.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
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