Key words
Low backache, keyhole-surgery, daycare-surgery, Discectomy, Endoscopic Indication, Inter-laminar, Transforaminal.
Conflicts of interest
No conflicts of interest have been declared.
ABSTRACT
Background
Low back pain is a major clinical problem that results in an important socioeconomic burden. The percutaneous endoscopic lumbar discectomy technique developed by Yeung, also known as PELD, is currently the flagship of minimally invasive transforaminal decompression. Kambin and Gellman first introduced PELD in 1983. PELD has been further developed with the Yeung endoscopic spine system and transforaminal endoscopic spine system.
Statement of Problem
Patient apprehension towards open surgery and risk of complications with anaesthesia in patients with multiple comorbidities have led us to conduct a review on how the endoscopic technique differs from conventional open lumbar discectomy in terms of patient satisfaction.
Objective
PELD surgery- short term results and follow-up of 230 patients, reporting patient satisfaction, in terms of duration of surgery and early recovery.
Methods
A prospective study was performed on all 230 patients who had undergone PELD between September 2018 and July 2019 at Aster Mims Kottakkal. This included patients who presented with intervertebral disc prolapse, both central and paracentral disc herniation, or radiculopathy. A narrative review was conducted to outline the basic principles, surgical techniques, and clinical outcomes of lumbar and cervical disc herniation.
Results
PELD allows intra-operative protection of the nerve roots, and communication with the patient under local anaesthesia. However, the learning curve for PELD is steeper than that of conventional microsurgery, and proper surgical indications and a good working channel position are important. PELD approaches should be tailored to remove disc fragments specific to various types of HD.
We observed 184 successful cases (80%) and 3 infected patients (1.3%) with discitis, one of which relapsed, the other two being converted to open surgery. We observed 2 cases of impending cauda equina syndrome and 10 cases of degenerative lumbar canal stenosis. Radiculitis patients (n=7, 3%), were effectively treated with oral steroids. The complication rate was <5%, similar to that of conventional open techniques.
Conclusions
PELD may be an ideal surgical technique for LDH. Preliminary results demonstrate a high efficacy rate, with few surgical complications. Given recent technical advancements, surgical indications for endoscopic spine surgery are still expanding and the clinical results have become more practical and reliable.
Introduction
Low back pain is a major clinical problem, that results in an significant socioeconomic burden.1 Its incidence appears to be increasing, despite technical and therapeutic advances in diagnosis and treatment. Surgery is advantageous over conservative treatment in most cases of back pain caused by lumbar spinal stenosis.2 Over recent years, various percutaneous, minimally invasive intradiscal techniques have been developed, directed at the mechanical process of discus herniation, with the underlying aim of capitalizing on the advantages of operative therapy, with as few of the disadvantages as possible.
Posterolateral Selective Endoscopic Discectomy (SED) and radiofrequency (RF) thermal annuloplasty, a percutaneous endoscopic technique developed by Yeung,3,4 also known as PELD, is currently the flagship of minimally invasive transforaminal decompression. Kambin and Gellman first introduced PELD in 1983 to remove affected disc material under local anaesthesia, for direct neural decompression.5 PELD was further developed with the Yeung endoscopic spine system (YESS) and transforaminal endoscopic spine system (TESSYS) techniques, and thereby became a feasible alternative for lumbar disc herniation (LDH) treatment.
In contrast to traditional open surgical techniques, PELD involves a lateral rather than midline approach, introducing an endoscope to the disc space through the foramin, thus avoiding damage to the vital lumbar structures. The annulus is cut and prolapsed disc material retrieved through the annular tear, keeping the dural tube free from compression, and therefore providing immediate relief to the patient.
Patient apprehension towards open surgery, and the complications of anaesthesia associated with patients with multiple comorbidities (including CAD, CKD, diabetes and reliance on antiplatelets), for whom open surgery and regional and general anaesthesia pose a risk, yet we can easily perform endoscopic surgery under local anaesthesia, have led us to conduct a review on how the endoscopic technique differs from conventional open lumbar discectomy.
Here, we analyse the short term results of percutaneous endoscopic transforaminal lumbar discectomy in terms of patient satisfaction, based on a cohort of 230 patients treated at Aster Mims Kottakkal during the period of September 2018 to July 2019.
OBJECTIVE
To review the results from short term follow-up of 230 patients receiving PELD surgery, reporting patient satisfaction in terms of duration of surgery and likelihood of early recovery.
MATERIALS AND METHODS
A prospective study review was performed on all 230 patients who underwent PELD between September 2018 and July 2019, performed by a team of 5 doctors. This included patients who presented with intervertebral disc prolapse, or both central and paracentral disc herniation. All patients had radiculopathy, which was resistant to medical treatment. The height and width of the foramen, LDH type, and positional relationship between LDH and the foramen were radiologically evaluated prior to surgery.
All cases underwent PELD on a single vertebral level, based on standard indications, with patients in the prone position. Chart review was carried out, and preoperative, intraoperative, and postoperative radiographic reviews were performed. Patient satisfaction was defined as a maintained reduction in pain and absence of recurrence within a 24 month period, with no further surgery being necessary.
A literature search of the transforaminal approach to LDH was carried out, with a focus on surgical indications for percutaneous endoscopic discectomy and corresponding clinical outcomes in the lumbar region and spine, in cases involving percutaneous or full endoscopic discectomy, carried out with a working channel endoscope.
Statistical comparisons of proportions were performed using Fisher’s exact test. P values less than 0.05 were considered statistically significant.
RESULTS
Review of reported Outcomes of PELD
There are a range of studies available which indirectly or directly compare open surgical patient outcomes to PELD and other endoscopic outcomes. Five such studies were systematically reviewed in 2016 by Peng et al.,9 which report similar clinical outcomes across a range of different measures, yet greater patient satisfaction with PELD, with 91% of patients being satisfied with their surgeries.
Among more recent studies, a single centre study of 10,228 patients by Choi et al. over a 12 year period showed a successful post-operative outcome rate of 95.7%.10 Positive outcomes were judged by indications for reoperation within 6 weeks. The most common cause of failure was incomplete removal of the herniated disc, with a third of these cases the result of incorrect positioning of the working channel, highlighting the importance of tailoring the PELD approach in each case based on pre-operative indications.
A study by Choi et al,11 comparing satisfaction in 23 patients with large LDH (>50% of spinal canal occupied) undergoing open lumbar microdiscectomy (OLD), and 20 receiving PELD, measured significantly higher patient satisfaction in the PELD group, as reported using a pain and movement questionnaire. Additionally, a loss of disc height in the OLD group was avoided with PELD. The frequency of recurrence or reoperation within 24 months was 10%. However, a longitudinal study made in Korea showed no difference in the reoperation rates observed with OLD and PELD between 1973 and 2018.12
Song et al. compared PELD outcomes of 30 patients to those of 30 patients receiving microendoscopic discectomy (MED), which also uses an endoscope, but does not integrate radiofrequency technology.13 Clinical markers of operative success were similar across both groups, with the PELD group having a faster post-operative recovery.
Indications for PELD were as follows- Song et al. included patients with MRI and MR imaging indications, differential pain in the waist and lower limb(s) in conjunction with positive results for either the femoral or sciatic nerve stretch tests,13. Choi et al. also included patients with MRI imaging indications,10,11 and used imaging results used to infer the optimal approach. Wildermuth et al. demonstrate similar accuracy with MRI imaging and functional myelography in identifying measurements of the lumbar dural sac.14
Hirano et al. suggest inclusion of patients with recurrent disc herniation after microdiscectomy, who are high risk for general anaesthesia, have LDH at L3-4 or above, or are emergency cases.15 They do not recommend PELD with limited accessibility to the disc space, bony canal stenosis, large and hard herniated nucleus pulposus (HNP), or HNP with a vertical migration of more than 10 mm.
A steep learning curve is described for PELD, as explored by Lee et al;16 Hirano et al also describe lessons learned from early procedures, in which 16% of patients experienced unfavourable outcomes,6,15 yet these became rare events with increasing surgical experience. Specifically, Hirano et al. describe the following difficulties regarding PELD training6: (1) Posterior procedures have been performed for decades by spine surgeons, so they are familiar with posterior anatomy. However, PELD is a posterolateral approach, and the intervertebral foramen anatomical structure is relatively new to surgeons; (2) Anatomical landmarks are absent, and (3) tissue differences between the annulus fibrosus and posterior longitudinal ligament (PLL), or the PLL and dura matter, are vague.
Case post-surgical outcomes
The demographics and surgical approaches of case patients are shown in Table 1. Two patients presented with impending cauda equina syndrome and 10 with degenerative lumbar canal stenosis.
80% of patients who returned for one and two-year follow-ups reported successful outcomes requiring no further treatment, with an average 90% reduction in reported pain, and early ambulation. Three patients had an infection (discitis), of which one had a relapse. The other two cases were converted to open surgery. Sterilization methods were revised, and all instruments autoclaved. These patients were managed post-operatively with IV antibiotics for 24 hours, followed by oral antibiotics for 1 week. On the initial post-operative follow up, we recorded no permanent complications.
The overall complication rate was <5%, including transient dysesthesia, the most common postoperative complaint, which occurred in approximately 5%-15% of cases. Dysesthesia is almost always transient. Three patients had post-surgical radiculitis, which was effectively treated with oral steroids. With these exceptions, all patients were satisfied with their results, received relief of pre op pain and experienced early recovery. Our rates of reoperation, and combined reoperation and recurrence, are similar to those of other studies reporting results from earlier years of PELD implementation (P>0.05, Figure 1), and are congruent with the 95.7% of 10,228 patients considered to have had successful outcomes by Choi et al. at 6 weeks post-surgery (P>0.05), although this study includes all negative outcomes reported within 24 months.
Based on the observations of this study and the literature, we propose the following inclusion and exclusion indications for PELD surgery:
Include:
1) Single level disc prolapse, ideally with unilateral radiculopathy.
2) Foraminal stenosis with claudication.
3) Revision cases- in this study, patients seeking consultation following a transient successful or partially successful or unsuccessful translaminar discectemy were offered endoscopic discectomy.
Exclude:
1) Multilevel bilateral foraminal stenosis- for such cases, the procedure must be staged, with an inter-surgery interval varying from 3 weeks to 3 months.
2) Patients with psychomotor symptoms (even if they are indicated to be under adequate cover of antidepressants and are receiving suitable counselling).
3) Central bony-canal stenosis is an absolute contraindication to the procedure.
DISCUSSION
Preliminary results with PELD surgery demonstrate a high efficacy rate, with few surgical complications.6,9,10,11,13 The indications for operative discectomy are larger discus protrusions, and extrusions that show signs of nerve root compression on MRI. Smaller, focal protrusions, without nerve root compression, appear to be less apt to spontaneously resorb, and have a less favorable natural resolution. In comparison with open surgery, minimally invasive spinal surgery has repeatedly shown short-term benefits, including shorter operation and lower complication rates.9-11 By preserving paraspinal muscle, and avoiding iatrogenic facet injury, PELD gives superior patient outcomes in comparison with conventional OLD, in terms of a shorter hospital stay,9,10 often with same-day discharge, less postoperative pain,10 and reduced intraoperative blood loss.9
Proper surgical indications and a good working channel position are important for successful PELD.6,8,15,16 The “surgeon factor” is critical, as each endoscopic surgeon needs to possess a wide range of surgical experience and skills to determine the procedures and techniques that work best, limited only by their own surgical experience and ability. The learning curve of PELD is perceived to be longer and steeper than that of conventional microsurgery,6,15,16 due to the unfamiliarity of most surgeons with the anatomy of the intervertebral foramen. Despite these complications, some studies report an acceptable PELD learning curve with sufficient preparation and pre-operative training, such as attending seminars, hands-on training, or learning at advanced surgical centres.17
PELD has a number of advantages over OLD. Firstly, that it can be performed under local anaesthesia, which supports communication between patients and surgeons during the operation and is beneficial to intraoperative protection of the nerve root and rapid mobilization postoperatively. Secondly, approach-related complications, such as dural tear and cerebrospinal fluid fistulas,7 are minimised in patients receiving PELD. Finally, PELD retains the motor segment, and thus decreases the incidence of fusion diseases such as adjacent segment disease.
Some patients are particularly suited to PELD. PELD is the simplest way to remove foraminal stenosis when encountered, removing the need for fusion. In this study, foraminal stenosis was present in 4.3% of patients, and the benefits of PELD are likely to be greater in this subgroup. Most patients suffering from LDH are elderly, with various medical comorbidities. A shorter operative time and reduced blood loss have been demonstrated to help in reducing potential complications in such cohorts.6 PELD has also shown promise for treating serial multilevel LDH.19
Theoretically, PELD is assumed to be superior in terms of postoperative low back pain, because normal paraspinal structures are more likely to be preserved.18 However, PELD also poses several challenges, such as higher incidences of postoperative chronic low back pain and recurrence. Within a 12 month follow-up period, two patients underwent reoperation at the operated level or another lumbar level after PELD. No further reoperation was required within 24 months, suggesting the follow-up period was sufficient to capture most complications. The rate of reoperation was similar to that seen with conventional procedures, and to that reported across similar single and multi centre studies. We therefore consider that PELD for recurrent disc herniation yielded favorable outcomes within our centre.
Conclusion
Our results suggest that PELD that avoids the occurrence of iatrogenic normal-tissue injury may be an ideal surgical technique for addressing LDH. The procedure is effective for preservation of the facet joint. Based on the preservation of normal anatomic structure, its usefulness could be maximized in patients with serial multilevel LDHs. Given recent technical advancements, the number of surgical indications for endoscopic spine surgery are increasing, and clinical results have become more practical and reliable. PELD techniques should be tailored to remove disc fragments in various forms of HD.
PELD allows a short hospital stay, which reduces total costs and results in a direct economic advantage. As most patients suffering from LDH are elderly, with various medical comorbidities, a shorter operative time and reduced blood loss are clear advantages.
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