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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 3  |  Issue : 2  |  Page : 238-242

Learning curve of tubular micro-endoscopic decompression in patients with degenerative lumbar canal stenosis over 200 cases


Department of Orthopedics and Spine, Bombay Hospital and Medical Research Centre, Mumbai, Maharashtra, India

Date of Submission17-Apr-2019
Date of Decision24-May-2019
Date of Acceptance23-Oct-2019
Date of Web Publication13-Jul-2020

Correspondence Address:
Dr. Sanyam Jain
Department of orthopedics and spine, Bombay Hospital and Research Centre, Marine Lines, Mumbai, Maharashtra.
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/isj.isj_24_19

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  Abstract 

Introduction: Tubular micro-endoscopic decompression is a technically demanding surgical technique involving familiarity of microscope handling with surgical and radiographic anatomical planning. Understanding the learning curve is necessary to delineate the problems faced during initial cases to reduce the complication rates and set guidelines for safe spine surgery through educational and training programs on bone-saw models and organizing workshops to enhance the standard of health care with improvement in surgical skills. Aims and Objectives: The aim of this study was to evaluate the learning curve of tubular micro-endoscopic decompression in patients with degenerative lumbar canal stenosis based on surgical and clinical parameters and delineate the challenges faced in early cases in long series of patients. Materials and Methods: Study design. Retrospective analysis of prospectively collected data. Study cohort. Data of first 220 consecutive patients with single-level degenerative lumbar canal stenosis managed with tubular micro-endoscopic decompression surgery from 2010 to 2016 with a minimum two-year follow-up were retrieved. Methodology. First 200 patients available at the final follow-up were divided into quartiles (50 each) as per the date of surgery with each consecutive group serving control for prior. Preoperatively and postoperatively clinical parameters (pain scores: visual analog scale [VAS]; functional disability: oswestry disability index [ODI] score), perioperative (operative time, blood loss, and hospital stay), technical issues (guide wire migration, tube docking-related problems, and dural tear), and postoperative complications (postoperative leg pain, neural injury, infection, and recurrence) were evaluated. Statistical analysis. The logarithmic curve-fit regression analysis and analysis of variance test were used to find the asymptote. Results: The mean age of patients was 61.81 years (ranging from 39 to 85) with male-to-female ratio of 121:79 with no significant difference among the quartiles. Statistically significant differences (P < 0.005) were noted in mean operative time (q1 = 109 min, q2 = 69.4 min) and mean blood loss (q1 = 110.6 mL, q2 = 69.6 mL) between the first and second quartiles with no further significant reduction in the third and fourth quartiles.Statistically significant differences (P < 0.005) in clinical parameters (VAS preoperative/postoperative 6.7/1.43; ODI preoperative/postoperative 39.08/12.63) were noted but were not associated with surgical experience. Hospital stay time did not show any significant difference among the quartiles.Guide wire-migrated issues, neural injury, dural tear, and tube docking-related problems significantly reduced after q1. However, recurrence occurred at any phase. Infection occurred in one patient in the first quartile.Although blood loss and operative time showed a declining trend, it was not significant after the second quartile. Therefore, asymptote lay in the first quartile; however, we recommend that novice surgeon should perform 50–100 cases to achieve mastery in this technique as different surgeons have different learning abilities. Conclusion: For mastering the art of tubular micro-endoscopic decompression for lumbar canal stenosis and to reduce its learning curve, novice surgeons can avoid the challenges and problems faced during initial cases with improvement in surgical skills by doing practice on cadavers and bone-saw models following certain recommendations that we came through our learning curve of surgical experience so that the results of their initial surgery are similar to the results that we had after achieving asymptote. Familiarity with instrumentation, communication between surgical team, and defined expectations from radiology technician are the keys to reduce the learning curve.

Keywords: Lumbar canal stenosis, micro-endoscopic decompression, operative time


How to cite this article:
Jain S, Kundnani V, Kire N, Merchant ZA, Patel J. Learning curve of tubular micro-endoscopic decompression in patients with degenerative lumbar canal stenosis over 200 cases. Indian Spine J 2020;3:238-42

How to cite this URL:
Jain S, Kundnani V, Kire N, Merchant ZA, Patel J. Learning curve of tubular micro-endoscopic decompression in patients with degenerative lumbar canal stenosis over 200 cases. Indian Spine J [serial online] 2020 [cited 2020 Oct 30];3:238-42. Available from: https://www.isjonline.com/text.asp?2020/3/2/238/289649




  Introduction Top


Lumbar canal stenosis (LCS) is a fairly common spinal disorder in an aging society, where the dural sac and nerve roots are compressed by the combination of degenerative processes such as hypertrophy of ligamentum flavum, facet joint arthropathy, disc degeneration, and osteophytes[2],[3],[4],[5] resulting in neurogenic claudication, back pain, buttock, or lower extremity pain with problems in ambulation. The main aim of the surgery is to get relief from leg pain with improvement in walking ability by decompression of dural sac and nerve roots.

There have been a number of lumbar spine decompression procedures described over the past decades. The standard, conventional open decompression[6] procedure was laminectomy including flavectomy, medial facetectomy, and foraminotomy that involved stripping of deep spinal muscles away from the spinous process with retraction to expose the lamina resulting in disturbed blood supply and multifidus atrophy, which can cause chronic low back pain postoperatively and also associated with high intraoperative blood loss with potential for iatrogenic instability of spinal segment.[7],[8],[9]

The indications for micro-endoscopic decompression (MED) for lumbar spine, first reported by Foley and Smith[1] as discectomy for lumbar disc herniation, have now expanded to include LCS. This minimally invasive muscle dilating technique with the tubular retractor system[7],[8],[9] provides visualization through microscope and allows bilateral decompression via a unilateral approach through an enlarged laminotomy and partial resection of base of spinous process, thereby preserving supraspinous and interspinous ligaments and contralateral musculature with reduced tissue trauma and morbidity.[10] This approach is not using resection of facet joint as carried out in conventional decompression especially when distance between spinous process and facet joint is small as at upper lumbar levels. We also do discectomy in some patients who significantly suffer from one side radicular leg pain more in comparison to other leg and magnetic resonance imaging (MRI) shows significant inter vertebral disc bulge as a part of LCS. Minamide et al.[11] reported that micro-endoscopic laminotomy was a safe and very effective approach for the treatment of degenerative LCS according to their two-year follow-up results.

Although the learning curve of micro-endoscopic discectomy has been mentioned in the past,[12],[13],[14],[15] each report presented too few cases. Moreover, the learning curves of the tubular MED for LCS over large series of patients with challenges and problems associated in initial cases were seldom discussed in the literature.[16],[17] Also, guidelines for safe spine surgery in MED are lacking.

Thus, the purpose of our study was to show the learning curve of tubular MED in degenerative LCS and to delineate the challenges encountered during initial cases in the large series of patients with some recommendations to avoid these problems.


  Materials and Methods Top


After permission from the hospital board, data of first 220 consecutive patients with single-level degenerative LCS operated by tubular MED between 2010 and 2016 by a single surgeon at a single institute with a minimum two-year follow-up period were retrieved.

Following strict inclusion and exclusion criteria as mentioned below, 200 patients formed the study cohort. These patients were arranged in sequence of their dates of surgery and divided into four quartiles with 50 patients each and each consecutive group serving as control for prior. Preoperatively and postoperatively clinical parameters (pain scores: VAS; functional disability: ODI score), perioperative (operative time, blood loss, and hospital stay), technical issues (guide wire migration, tube docking-related problems, and dural tear), and postoperative complications (postoperative leg pain, neural injury, infection, and recurrence) were evaluated.

Inclusion criteria

The inclusion criteria of the study were as follows:

  1. Single-level degenerative LCS.


  2. Patients with a minimum two-year follow-up period.


Exclusion criteria

The exclusion criteria of the study were as follows:

  • Radiological signs of instability/deformity.


  • Surgery of revision cases.


  • >=2 level involved.


  • Patients with degenerative scoliosis or spondylolisthesis.


  • Patients requiring concomitant fusion or instrumentation.


  • Acute spinal fracture, tumor, or infection.


Operative procedure

Under general anesthesia, the patient was positioned prone on a radiolucent table with bolsters below the chest and pelvis keeping the abdomen free and head on soft jelly pad with head end raised and pressure points well padded. Using AP/lateral fluoroscopy imaging, 18-gauge spinal needle was inserted at the diseased level 1cm lateral to midline at spino-laminar junction. Then, 10-cc normal saline was inserted through needle into soft tissue and needle was withdrawn. Subsequently, 2cm incision was made at the needle site till the fascia just 1cm lateral to midline. The blunt end of guide wire was inserted under fluoroscopic guidance at spino-laminar junction targeted at the center of disc involved. The initial dilator was inserted over the guide wire and the wire was removed. Then, sequential dilators were inserted separating the muscles while palpating the bony landmarks. The final tubular retractor either 18mm or 20mm in diameter was docked at the final working channel centering over the disc at base of spinous process at spino-laminar junction. The operating microscope was then bought into the field. Muscles covering the lamina were carefully resected and the bony structures were exposed. The midline was confirmed first by resecting the base of the spinous process with 4-mm high-speed burr. Ipsilateral side decompression was carried out by flavectomy, laminotomy, medial facetectomy, and foraminotomy with discectomy if indicated. Then, the tubular retractor was pulled out halfway and slanted medially and over the top decompression was done. The epidural bleeding was controlled using bipolar cautery or gelfoam with neurosurgical patty. The thoracolumbar fascia and subcutaneous tissue were closed by 2-0 vicryl suture. The skin was closed using 3-0 monocryl suture.

A single dose of intravenous antibiotic was given preoperatively and postoperatively as a standard protocol and most of the patients were discharged within 24–48 h post-surgery. The patients were followed up at 12–14 days post-surgery for removal of stitches and allowed to resume daily activities except lifting heavy weight and bending forward for three weeks. Gradual back muscles strengthening exercises were started at three weeks.

The patients were followed up at regular intervals (six weeks, three months, six months, and yearly) and evaluated for clinical outcomes by VAS for leg pain and ODI questionnaire and technical issues such as tube docking-related problems, guide wire migration issues, and postoperative complication. The parameters in different quartiles were compared using analysis of variance test. The logarithmic regression curve fit analysis was used to find the asymptote. A value of P < 0.005 was considered statistically significant.


  Results Top


The mean age of patients was 61.81 years (ranging from 39 to 85) with male-to-female ratio of 121:79. Of 200 patients, the levels operated were L4–L5 in 123 and L5–S1 in 77 cases. The cohort of each quartile was homogenous and comparable with regard to demographics.

The mean operative time was 76.37 min. The cases carried out in the first quartile took longer time; however, after gaining experience, till the second quartile the average time taken for surgery was less than the mean average (mean q1 = 109 min, q2 = 69.4 min, q3 = 65.1 min, and q4 = 62 min), that is, a significant difference (P < 0.005) was seen between the first and second quartiles.

The average blood loss was 77.62 mL (mean q1 = 110.6 mL, q2 = 69.6 mL, q3 = 66.7 mL, and q4 = 63.6 mL). The cases carried out in the first quartile bled more as compared with the second quartile (P < 0.005), which was significant. But after achieving mastery in the procedure, although it showed a declining trend in successive quartiles, there was no significant difference.

Dural punctures occurred in four cases (three in the first quartile and one in the second quartile) in our study. All cases were treated with water tight closure of the wound. No delayed cerebrospinal fluid (CSF) leaks or pseudomeningoceles developed. Five patients developed postoperative leg pain but completely recovered within four months of surgery.

Tube docking-related problems occurred in four patients in the first quartile and in one patient in the second quartile. Guide wire migration issues occurred in four patients in first quartile. One patient in the first quartile had deep wound infection. The patient needed debridement, antibiotics with serial dressings, and recovered completely without further complications. Two patients showed recurrence, one in the first quartile and other in the third quartile, indicating that recurrence can occur at any phase even after gaining experience in the procedure. Two patients showed neural injury in the first quartile with both showing complete recovery at final follow-up.

The mean VAS scale for leg pain improved significantly from a preoperative value of 6.7 to 1.43 postoperatively (P < 0.05). The mean ODI changed significantly from 39.08 to 12.63 (P < 0.05), but there was no significant difference between the quartiles as extent of decompression and technique followed was same in all patients. The mean hospital stay was 31.98 h with no significant difference among quartiles.


  Discussion Top


The common difficulties faced by the new learners in mastering MED technique include not taking true AP/lateral images, guide wire migration complication, tube docking-related issues, and inappropriate tube length insertion and requiring greater demand of hand-eye coordination with manipulation fineness. Therefore, there is need to understand the learning of this technique benefiting the new learners and clinical spine fellows, to avoid repeated errors faced during initial cases.

The asymptote of any operation is determined by the operative time, intraoperative blood loss, operation effectiveness through clinical parameters, intraoperative, and postoperative complications.

In the case of MED, Nowitzke[12] reported that the asymptote of operating time was reached at 30 cases. In another report about the learning curve for MED, the operation time and blood loss tended to become steady after the first 20 cases, and then they declined gradually.[13] Although the operating time and intraoperative blood loss showed declining trend throughout our study, they decreased gradually along a natural logarithmic function in the first quartile achieving asymptote there and became steady after the second quartile that was similar to above studies. However, we recommend that for achieving mastery in tubular technique, novice surgeon should perform 50–100 cases as we divided our study in successive quartiles comparing results with each other.

The steep decline in the operating time and blood loss during initial cases till the second quartile in our study may be attributable to the accurate placement of a tubular retractor at the desired level. Tubular dilator should be exactly at the center of the disc level involved at base of spinous process at spino-laminar junction.

We did not use guide wire in the second quartile after gaining enough experience, leading to reduction in all guide wire-migrated complications such as dural tear, neural injury, postoperative leg pain that ultimately leads to reduced blood loss, and operative time.

The surgeon required 15 min for tubular retractor placement in early cases, but it decreased to 2–4 min for the same procedure after the first quartile. We used to do same side decompression followed by over the top decompression in initial cases, but after the second quartile we tend to do opposite side decompression first followed by the ipsilateral side noticing that it helped us in controlling the bleeding intraoperatively more and producing clear blood less field vision, which ultimately lead to reduction in operative time and blood loss.

At the start of surgery, normal saline was injected through spinal needle at the level involved that helps in dilatation of the soft tissue with the tubular dilator.

Technical problems such as tube docking and guide wire migration issues significantly reduced after the first quartile as we stopped using guide wire and we became much aware of taking true AP/lateral images in fluoroscopy during tube docking [Figure 1]A and B.
Figure 1: (A) True AP X-ray view showing that end plates should be parallel with tube docking at spino-laminar junction. (B) True lateral X-ray view showing that tube docking should be in parallel to disc involved

Click here to view


Of four patients in the first quartile who had tube docking-related problems, two patients had facet joint violation diagnosed intraoperatively and in two patients, superior docked tube leads to difficulty in identifying the anatomical landmarks. In all the patients, we removed all the tubes and reinsert them at correct position that indirectly increased our surgical time and blood loss intraoperatively. One patient in the second quartile had inferior docked tube because of more inclination of lamina in that patient.

Dural punctures occurred in three cases in q1 and one case in q2 because of guide wire migration. Our study showed 2% dural tear, which was comparable to others.[17 None of the patients developed postoperative CSF leak due to very minimal dead space and water tight closure in the tubular technique.

Five patients developed postoperative leg pain. We found conjoint roots in one case in q1 and one case in q2 causing leg pain. Three patients in q1 with postoperative leg pain had guide wire migration, which completely recovered at final follow-up of two years.

Two patients showed neural injury postoperatively in the first quartile because of guide wire migration. One patient developed foot drop and one patient had extensor hallucis longus/extensor digitorum longus weakness. Both the patients were managed conservatively and had complete recovery at final follow-up.

Two patients showed recurrence of symptoms in our study. One patient in the first quartile showed residual compression of spinal canal diagnosed with MRI and one patient in the third quartile showed recurrent disc herniation diagnosed with computed tomography myelogram, indicating that recurrence can occur at any phase even after gaining experience in the procedure. Both patients were considered for re-surgery.

Length of the tube used is of utmost importance. Longer tube length leads to increase in working length of the instruments intraoperatively and shorter tube length leads to continuous soft-tissue herniation through the tube. In initial cases, we used shorter length tube causing continuous soft-tissue herniation through the tube with more blood loss and increased operative time.

In addition, during initial cases, surgeon found difficulties in handling the microscope with less hand-eye coordination but became efficient after certain cases.

Therefore, many pitfalls that beginners encounter in this procedure can be avoided easily while considering certain technical points during surgery such as

  • True AP/lateral image in fluoroscopy.


  • Infiltrating the tissues with normal saline for easy dilation of muscles resulting in reduced blood loss.


  • Guide wire should not be used.


  • Tube should be in line with the center of disc involved in lateral view.


  • Dock the tube at the base of spinous process at spino-laminar junction.


  • Contralateral decompression first, then ipsilateral.


  • Avoid soft-tissue herniation through the tube by using appropriate length of the tube.


  • Surgeon should practice in handling the microscope on models for better hand-eye coordination.


  • The limitations of our study included its retrospective nature; however, database was constructed prospectively. Certain nonmodifiable confounding factors were present, which include individual surgeons learning ability as some surgeons are slow, whereas some are quick learners and other minimal invasive surgey procedures performed by the surgeon during the period. The number of operations carried out per month by surgeon has also an effect on the final outcome.


      Conclusion Top


    For mastering the art of tubular MED for LCS and to reduce the learning curve, novice surgeons can avoid the challenges, and problems faced during initial cases and improve surgical skills by doing practice on cadavers and bone-saw models by following the above guidelines. Familiarity with instrumentation, communication between surgical team, and defined expectations from radiology technician are keys to reduce the learning curve.

    Financial support and sponsorship

    Nil.

    Conflicts of interest

    There are no conflicts of interest.



     
      References Top

    1.
    Foley KT, Smith MM. Microendoscopic discectomy. Tech Neurosurg 1997;3:301-7.  Back to cited text no. 1
        
    2.
    Bartynski WS, Lin L. Lumbar root compression in the lateral recess: MR imaging, conventional myelography, and CT myelography comparison with surgical confirmation. AJNR Am J Neuroradiol 2003;24:348-60.  Back to cited text no. 2
        
    3.
    Andreisek G, Imhof M, Wertli M, Winklhofer S, Pfirrmann CW, Hodler J, et al; Lumbar Spinal Stenosis Outcome Study Working Group Zurich. A systematic review of semiquantitative and qualitative radiologic criteria for the diagnosis of lumbar spinal stenosis. AJR Am J Roentgenol 2013;201:W735-46.  Back to cited text no. 3
        
    4.
    Ben-Eliyahu DJ, Rutili MM, Przybysz JA. Lateral recess syndrome: Diagnosis and chiropractic management. J Manipulative Physiol Ther 1983;6:25-31.  Back to cited text no. 4
        
    5.
    Winkler PA, Zausinger S, Milz S, Buettner A, Wiesmann M, Tonn JC. Morphometric studies of the ligamentum flavum: A correlative microanatomical and MRI study of the lumbar spine. Zentralbl Neurochir 2007;68:200-4.  Back to cited text no. 5
        
    6.
    Issack PS, Cunningham ME, Pumberger M, Hughes AP, Cammisa FP Jr. Degenerative lumbar spinal stenosis: Evaluation and management. J Am Acad Orthop Surg 2012;20:527-35.  Back to cited text no. 6
        
    7.
    Cook JA, Ramsay CR, Fayers P. Statistical evaluation of learning curve effects in surgical trials. Clin Trials 2004;1:421-7.  Back to cited text no. 7
        
    8.
    Righesso O, Falavigna A, Avanzi O. Comparison of open discectomy with microendoscopic discectomy in lumbar disc herniations: Results of a randomized controlled trial. Neurosurgery 2007;61:545-9.  Back to cited text no. 8
        
    9.
    Palmer S, Turner R, Palmer R. Bilateral decompression of lumbar spinal stenosis involving a unilateral approach with microscope and tubular retractor system. J Neurosurg 2002;97:213-7.  Back to cited text no. 9
        
    10.
    Nomura K, Yoshida M. Microendoscopic decompression surgery for lumbar spinal canal stenosis via the paramedian approach: Preliminary results. Global Spine J 2012;2:87-94.  Back to cited text no. 10
        
    11.
    Minamide A, Yoshida M, Yamada H, Nakagawa Y, Kawai M, Maio K, et al. Endoscope-assisted spinal decompression surgery for lumbar spinal stenosis. J Neurosurg Spine 2013;19:664-75.  Back to cited text no. 11
        
    12.
    Nowitzke AM. Assessment of the learning curve for lumbar microendoscopic discectomy. Neurosurgery 2005;56:755-62.  Back to cited text no. 12
        
    13.
    Rong LM, Xie PG, Shi DH, Dong JW, Liu B, Feng F, et al. Spinal surgeons’ learning curve for lumbar microendoscopic discectomy: A prospective study of our first 50 and latest 10 cases. Chin Med J (Engl) 2008;121:2148-51.  Back to cited text no. 13
        
    14.
    Nomura K, Yoshida M, Kawai M, Maio K, Nakao S. Microendoscopic discectomy as a minimally invasive surgery for lumbar disc herniation: Technical training and learning curve. J Jpn Soc Spine Surg Relat Res 2009;20:649-52.  Back to cited text no. 14
        
    15.
    Ohashi M, Yamazaki A, Watanabe K. Learning curve for microendoscopic lumbar discectomy: A comparative study among 3 spinal surgeons. J Spine Res 2011;2:1342-5.  Back to cited text no. 15
        
    16.
    Mannion RJ, Guilfoyle MR, Efendy J, Nowitzke AM, Laing RJ, Wood MJ. Minimally invasive lumbar decompression: Long-term outcome, morbidity, and the learning curve from the first 50 cases. J Spinal Disord Tech 2012;25:47-51.  Back to cited text no. 16
        
    17.
    Nomura K, Yoshida M. Assessment of the learning curve for microendoscopic decompression surgery for lumbar spinal canal stenosis through an analysis of 480 cases involving a single surgeon. Global Spine J 2017;7:54-8.  Back to cited text no. 17
        


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