En bloc resection of ligamentum flavum with laminotomy of the caudal lamina in the minimally invasive laminectomy: surgical anatomy and technique

Luis M. TumialánDepartment of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona

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OBJECTIVE

A CSF leak is a potential complication in a lumbar laminectomy. An analysis of the author’s surgical experience identified inadvertent durotomies that occurred when resecting the ligamentum flavum at its insertion into the superior aspect of the caudal lamina. Anatomical analyses of the lumbar canal diameter demonstrate that the insertion point of the caudal ligamentum flavum is the most constrained area of the canal. The surgical technique was modified to eliminate the need for direct action in that anatomical region after the author compared the efficacy of piecemeal resection of the ligamentum flavum with en bloc resection with a laminotomy of the caudal lamina beyond the insertion point of the ligamentum flavum in the lumbar laminectomy.

METHODS

An analysis of a single surgeon’s experience managing 147 consecutive patients with lumbar stenosis who underwent single-level lumbar hemilaminectomies over a 4-year period was performed. Patients were managed with either piecemeal resection (cohort 1) or en bloc resection with a laminotomy beyond the caudal insertion (cohort 2) of the ligamentum flavum.

RESULTS

Seventy-seven patients underwent piecemeal resection (cohort 1), and 70 underwent en bloc resection (cohort 2). There were 5 CSF leaks (6.4%) in cohort 1. There were no CSF leaks in cohort 2. There was a statistically significant difference in operative times between the two groups (p = 0.04), but there was no statistically significant difference in patient-reported outcomes at 6 months between the groups.

CONCLUSIONS

En bloc resection of the ligamentum flavum with a laminotomy below the caudal insertion point appears to decrease the risk of a CSF leak by working beyond the most constrained diameter of the lumbar canal to release the caudal insertion of the ligamentum flavum.

ABBREVIATIONS

ODI = Oswestry Disability Index; SPORT = Spine Patient Outcomes Research Trial; VAS = visual analog scale.

OBJECTIVE

A CSF leak is a potential complication in a lumbar laminectomy. An analysis of the author’s surgical experience identified inadvertent durotomies that occurred when resecting the ligamentum flavum at its insertion into the superior aspect of the caudal lamina. Anatomical analyses of the lumbar canal diameter demonstrate that the insertion point of the caudal ligamentum flavum is the most constrained area of the canal. The surgical technique was modified to eliminate the need for direct action in that anatomical region after the author compared the efficacy of piecemeal resection of the ligamentum flavum with en bloc resection with a laminotomy of the caudal lamina beyond the insertion point of the ligamentum flavum in the lumbar laminectomy.

METHODS

An analysis of a single surgeon’s experience managing 147 consecutive patients with lumbar stenosis who underwent single-level lumbar hemilaminectomies over a 4-year period was performed. Patients were managed with either piecemeal resection (cohort 1) or en bloc resection with a laminotomy beyond the caudal insertion (cohort 2) of the ligamentum flavum.

RESULTS

Seventy-seven patients underwent piecemeal resection (cohort 1), and 70 underwent en bloc resection (cohort 2). There were 5 CSF leaks (6.4%) in cohort 1. There were no CSF leaks in cohort 2. There was a statistically significant difference in operative times between the two groups (p = 0.04), but there was no statistically significant difference in patient-reported outcomes at 6 months between the groups.

CONCLUSIONS

En bloc resection of the ligamentum flavum with a laminotomy below the caudal insertion point appears to decrease the risk of a CSF leak by working beyond the most constrained diameter of the lumbar canal to release the caudal insertion of the ligamentum flavum.

The Spine Patient Outcomes Research Trial (SPORT) analysis on the surgical versus nonoperative treatment for lumbar spinal stenosis confirmed what spine surgeons have intuitively known for decades: Lumbar laminectomy for the management of symptomatic lumbar stenosis refractory to nonoperative management is one of the most reliable operations in a spine surgeon’s armamentarium.1,2 The SPORT study also confirmed that the rate of inadvertent durotomy was as high as 9%, consistent with other reports in the literature of similar rates ranging from 7% to 10%.1,3,4 Although several large studies have shown that an inadvertent durotomy does not affect long-term outcomes, it remains a complication that surgeons prefer to avoid under any circumstance.4,5

An analysis of the CSF leaks that occurred during a minimally invasive lumbar hemilaminectomy demonstrated that each leak occurred while undercutting the anterosuperior edge of the caudal lamina after piecemeal resection of the ligamentum flavum. The occurrence of the same complication in the same anatomical location prompted reconsideration of the technique employed. After a reexamination of the lumbar canal dimensions, two modifications were made for decompression of the thecal sac in minimally invasive lumbar laminectomies. The first was the elimination of piecemeal removal of the ligamentum flavum. Instead, the rostral and lateral insertion points at each facet were released while keeping the ligamentum flavum intact. The second modification was to avoid the anterosuperior edge of the caudal lamina, which anthropometric studies have demonstrated to be the most constrained aspect of the bony canal.6 Instead, the focus shifted to working on the midportion of the caudal lamina, where the canal dimensions could expand considerably. A laminotomy was then created beyond the insertion of the ligamentum flavum, the caudal insertion was released, and the entire ligamentum flavum was removed en bloc.

The purpose of this work is to present the surgical technique and a comparative analysis of patients who underwent piecemeal resection versus those who underwent the modified technique with en bloc resection.

Methods

An institutional review board approved this retrospective analysis of 147 patients who underwent a single-level minimally invasive hemilaminectomy performed by a single surgeon from September 2014 through April 2018. All patients presented with neurogenic claudication with or without a radicular component and demonstrated moderate to severe lumbar stenosis at one segment in the lumbar spine on sagittal and axial MRI. All patients had symptoms refractory to exhaustive nonoperative measures, which included a 6- to 12-week trial of epidural steroid injections and physical therapy. Patients with spondylolisthesis without evidence of instability on flexion and extension radiographs were included in this study. Patients who had undergone previous microdiscectomies or previous laminectomies at the symptomatic level were not included in this study. Patients with spondylolisthesis who had evidence of instability on flexion-extension radiographs were also not included. This study did not include patients needing treatment at 2 or more levels.

From September 2014 to July 2016, all patients underwent piecemeal resection of the ligamentum flavum after a laminectomy through a 16-mm minimal access port. After removal of the lamina and exposure of the ligamentum flavum, multiple actions with a Kerrison rongeur were used to decompress the thecal sac from insertion point to insertion point. In August 2016, the surgical technique was modified from piecemeal resection of the ligamentum flavum to an en bloc resection with the creation of a laminotomy in the midportion of the caudal lamina (described in Operative Technique below).

Demographic data, surgical technique, operative time, estimated blood loss, and length of hospital stay data were collected and analyzed. Preoperative and postoperative Oswestry Disability Index (ODI), visual analog scale (VAS)–back scores, and VAS-leg scores at 4 weeks, 3 months, 6 months, and 1 and 2 years (when available) were also collected and analyzed.

Operative Technique

With the patient positioned prone on a Jackson table atop a fully expanded Wilson frame, an 18-mm incision was planned for a 16-mm access port with fluoroscopic guidance. An incision was made 20 mm from the midline, the fascia was divided, and a series of dilators were passed onto the lamina, followed by placement of a 16-mm minimal access port with a medial angulation of 15° to 20° as previously described by Khoo and Fessler7 and Boukebir et al.8 The target for the first position of the access port was the rostral insertion of the ligamentum flavum, as seen in Fig. 1.

FIG. 1.
FIG. 1.

Lateral fluoroscopic image demonstrating the target for the access port that encompasses the rostral insertion point of the ligamentum flavum for an L4–5 laminectomy. A: Lateral fluoroscopic image demonstrating spinal needle in position. B: Artist’s rendering of the ligamentum flavum on the fluoroscopic image. C: Position of the access port at the base of the spinous process. Such a position allows undercutting the spinous process and reaching the contralateral recess. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

The patient is rotated away from the surgeon to optimize a trajectory to the contralateral recess, as emphasized by Boukebir and colleagues.8 Under the operating microscope, the lamina is exposed and drilled down to the ligamentum flavum, with particular attention to drilling the underside of the contralateral lamina (Fig. 2). The thinned lamina is then removed with a Kerrison rongeur until the rostral insertion of the ligamentum flavum is identified. In the piecemeal resection technique, resection of the ligamentum flavum begins at this point, and the entire ligamentum flavum in the field of view is resected. In the en bloc resection technique, the rostral insertion of the ligamentum flavum is completely detached, but no other part of the ligamentum flavum is resected at this time. The rostral insertion of the ligamentum flavum is released along with the lateral aspects of the ligamentum flavum on the ipsilateral and contralateral sides. Again, no ligamentum is resected for decompression, only for release from its insertion. In contrast, the piecemeal resection exposes the entire thecal sac within the field of view.

FIG. 2.
FIG. 2.

Technique for en bloc resection of the ligamentum flavum at L4–5. A: Illustration of the laminectomy performed. The lamina is first thinned using a drill and then removed with a Kerrison rongeur until the rongeur reaches beyond the insertion of the ligamentum flavum. Note the absence of the ligamentum flavum at the rostral-most aspect of the exposure, which represents the insertion point. B: Drilling the contralateral recess to gain access to the insertion of the ligamentum flavum beneath the contralateral pedicle. Rotating the patient away from the surgeon optimizes the line of sight and ergonomics of this task. C: A view from within the canal while drilling the contralateral recess. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

The access port is repositioned to place its diameter over the top of the superior aspect of the caudal lamina. Herein lies the significant departure from the piecemeal technique: the bone work performed on the caudal lamina. The position of the access port for the piecemeal resection does not need to be angled as far caudal because the target does not extend beyond the superior aspect of the rostral lamina. The position of the access port for the en bloc resection needs to be over the top of the midportion of the caudal lamina and over the midline. Recognizing the anthropometric dimensions reported by Panjabi and colleagues, the dimension of the lumbar canal is narrowest at the caudal insertion point of the ligamentum flavum, which is also at the superior aspect of the rostral lamina (Fig. 3).6 The new position of the access port places the field of view caudal to the insertion point.

FIG. 3.
FIG. 3.

The various dimensions of the lumbar canal. Using the anthropomorphic measurements reported by Panjabi et al.,6 a computer-generated model illustrates the varying diameters of the lumbar canal from L3 to L5. Left: The superior-most aspect of the lamina represents the most constrained dimension (magenta ring), whereas the caudal aspect of the lamina presents a larger dimension (turquoise ring). Right: The cross-sectional areas of the lumbar spine of the Panjabi model illustrate the displacement of the thecal sac with a number 2 Kerrison rongeur in the most constrained corridor (magenta ring) compared with the larger diameter (turquoise ring). Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

After repositioning the access port, the piecemeal technique is used to complete the resection by removing the remaining caudal insertion with a number 1 or 2 Kerrison rongeur. In performing this technique, the footplate of the Kerrison needs to pass beneath the superior aspect of the caudal lamina and remove the superior aspect of the caudal lamina and the remaining ligamentum flavum. The decompression proceeds in the rostral-to-caudal direction without a direct line of sight of the Kerrison footplate over the thecal sac. For the en bloc technique, the access port is angled over the middle aspect of the lamina and the base of the spinous process, which allows for a laminotomy to be created beyond the insertion of the ligamentum flavum. Such a position places the working corridor over a relative safe zone, where the diameter of the bony canal has widened compared with the rostralmost aspect of the lamina. Once a breach in the lamina is created, a tuft of epidural fat becomes evident. The epidural fat confirms the midline position of the access port, and a number 2 Kerrison rongeur is used to remove the lamina beyond the insertion of the ligamentum flavum, thereby releasing the caudal insertion point of the ligamentum flavum. Creating the breach in the midline allows for the actions of the rongeur to release the insertion points of the ligamentum flavum on the ipsilateral and contralateral laminae. After completion of the laminotomy, the thecal sac comes into view, and the insertion of the ligamentum flavum is removed in the caudal-to-rostral direction, with a direct line of sight to the thecal sac for every pass of the instrument (Fig. 4).

FIG. 4.
FIG. 4.

Illustration demonstrating the release of the caudal insertion of the ligamentum flavum with both the piecemeal and en bloc techniques. A: In the piecemeal resection technique, the release of the ligamentum flavum is completed from the rostral-to-caudal direction by passing the footplate of the Kerrison rongeur into the most constrained corridor of the lumbar canal. B: The en bloc technique creates a laminotomy into the midportion of the lamina, where the canal diameter is larger. The ligamentum flavum is resected in the caudal-to-rostral direction, with direct visualization of the thecal sac. C: A comparison view shows the greater depth of the Kerrison rongeur in a more constrained corridor for a rostral-to-caudal approach compared with working beyond the insertion of the ligamentum flavum for a caudal-to-rostral approach. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Finally, the access port is repositioned over the ipsilateral nerve root, the medial facet is removed, and the remaining ligamentum flavum overtop the ipsilateral nerve root is removed. In the piecemeal technique, the remaining ligamentum flavum is resected, and a foraminotomy is performed. In contrast, in the en bloc technique, the release of the lateral insertion allows for en bloc removal of the entire ligamentum flavum for the segment (Video 1).

VIDEO 1. Operative video demonstrating the rationale and technique for en bloc resection of ligamentum flavum in the minimally invasive lumbar hemilaminectomy. Used with permission from Barrow Neurological Institute, Phoenix, Arizona. Click here to view.

Statistical Analysis

Descriptive statistics were compiled on baseline variables, procedural characteristics, and endpoints. Continuous and ordinal variables are summarized by means and SDs or medians. Univariate between-group comparisons were performed using the chi-square test, Fisher exact test, or Student t-test, as appropriate. Multivariate logistic regression was performed using variables with p values < 0.1 in univariate analyses. All analyses were performed using IBM SPSS version 27 (IBM Corp.). Statistical significance was set at p < 0.05.

Results

Seventy-seven patients underwent the piecemeal resection technique (cohort 1), and 70 underwent the en bloc resection technique (cohort 2). The demographic and operative data for these patients are detailed in Table 1. The outcome data (ODI, VAS-back, and VAS-leg scores) are detailed in Table 2. Germane to this report is the incidence of incidental durotomies reported in Table 3. Cohort 1 had 5 such events (6%), whereas there were no incidental durotomies in cohort 2 (0%). No statistically significant difference surfaced in the outcome measures between cohorts 1 and 2, which is consistent with the reports in the literature concluding that CSF leaks did not affect outcomes.4,5 There was a statistically significant difference in operative time between the two cohorts (p = 0.04), but that difference did not remain when the 5 incidental durotomies were removed from the statistical analysis. Therefore, the additional time to address the durotomy explains the difference between the two operative times. There was also a statistically significant difference in length of stay, with cohort 1 averaging 23.4 hours (range 4–48 hours) and cohort 2 averaging 14.6 hours (range 3–28 hours). All patients who underwent durotomies were admitted for overnight observation. There was 88% follow-up at 1 year for cohort 1. Three patients in the original cohort of 77 required further surgery, 2 required further decompression and fusion at the same level as their laminectomy, and 1 required a laminectomy at L3–4 above their index surgery. There was 94% follow-up at 1 year for cohort 2. Two patients from that cohort required additional surgery; 1 required a microdiscectomy at L5–S1 below their laminectomy, and 1 required a laminectomy one level above L3–4. At the most recent follow-up, there were no conversions to fusions in cohort 2.

TABLE 1.

Demographic and operative data by resection technique

VariableCohort 1: Piecemeal ResectionCohort 2: En Bloc Resectionp Value
No. of patients7770
Age, yrs
 Mean69.268.9
 Range49–8952–86
Sex
 Male4746
 Female3024
Operated segments
 L1–200
 L2–324
 L3–41610
 L4–55856
 L5–S110
Op time, mins0.04
 Mean62.847.8
 Range42–8437–62
EBL, mL0.79
 Mean2735.8
 Range10–15010–75
Length of stay, hrs
 Mean23.414.60.04
 Range4–483–28

EBL = estimated blood loss.

Values represent the number of patients (%) unless stated otherwise.

TABLE 2.

Patient-reported outcome data by resection technique

VariableCohort 1: Piecemeal Resection (n = 77)Cohort 2: En Bloc Resection (n = 70)p Value
Mean ODI score
 Preop47490.58
 6 mos19*220.79
 1 yr2123§0.94
Mean VAS-leg score
 Preop88820.49
 6 mos1290.67
 1 yr14120.78
Follow-up, mos
 Mean16.414.2
 Range6–243–36

96% follow-up.

100% follow-up.

88% follow-up.

94% follow-up.

TABLE 3.

Complications by resection technique

VariableCohort 1: Piecemeal Resection (n = 77)Cohort 2: En Bloc Resection (n = 70)
Complication, n (%)
 Dural tear5 (6)0 (0)
 Epidural hematoma1 (1)2 (3)
 Infection0 (0)0 (0)

Discussion

In a 1982 commentary on a technical note by Lin, Weinstein identified the superior aspect of the rostral lamina as the area most susceptible to incidental durotomy during a lumbar laminectomy.9 Weinstein stated,

The rostral laminar edge is the site of greatest midline stenosis, especially in patients with a relatively vertical orientation of the laminar arch. The dura mater is often thinned when the sac has been compressed chronically, and considerable caution would be appropriate to avoid dural laceration while undercutting the anterosuperior edge of the lamina….

The 5 incidental durotomies that occurred in the piecemeal resection cohort in this series all occurred while manipulating a Kerrison rongeur to release the ligamentum flavum in precisely the area where Weinstein advised surgeons to take the greatest caution. Complication avoidance is the central tenet of any surgical technique. When the same complication recurred in the same anatomical area again and again, reconsideration of the technique for decompression of the caudal aspect of a segment and removal of the caudal insertion of the ligamentum flavum was indicated. Anatomical analysis of the well-reported anthropometric measurements of the lumbar canal ultimately led to the technique described in this work.

Surgical Anatomy

An analysis of the anthropometric measurements reported by Panjabi et al. demonstrated that the bony lumbar canal dimensions are narrowest at the superior aspect of the lamina, as suggested by Weinstein and illustrated in Fig. 3.6 The narrowest aspect of the canal also corresponds to the insertion of the ligamentum flavum. It is the location of the final actions of a Kerrison rongeur in a lumbar decompression. Given such a constrained corridor, the footplate of the Kerrison rongeur needs to pass beneath the laminar edge to remove the lamina and the insertion of the ligamentum flavum without damaging the thecal sac during removal. Modeling Panjabi’s anthropomorphic measurements led to the generation of a 3D model that readily identified a more plausible working channel. Because the canal diameter increases considerably distal to the caudal insertion of the ligamentum flavum, the midportion of the caudal lamina became a target for a laminotomy. By creating a breach beyond the ligamentum flavum insertion in the midportion of the lamina, a larger surgical corridor with direct visualization of the thecal sac becomes available. The surgeon can now pass a Kerrison rongeur into the breach and remove the lamina distal to the ligamentum flavum insertion. With the remaining insertion points of the ligamentum flavum released, the surgeon may now remove the ligamentum flavum en bloc. It is important to recognize that the drilling on the caudal lamina distal to the insertion point of the ligamentum flavum places the tip of the drill in an area where there is no ligamentum flavum to protect the dura. Ensuring that the access port has been secured over the lamina–spinous process junction places the working channel over a relative safe zone, where the dura of the thecal sac is at a distance from the innermost aspect of the lamina. When the drill creates a breach in the lamina in the midline, epidural fat is typically encountered.

Incidence of CSF Leaks in Lumbar Laminectomies

It would be unrealistic to expect the en bloc technique to eliminate the risk of a CSF leak in a lumbar laminectomy. The numbers in the series reported herein are relatively small, and it will only be a matter of time before future events, specifically incidental durotomies, will balance, to some extent, the apparent deviation from the incidence of CSF leaks reported in the literature. Despite these inevitable events, the question is whether the overall incidence has the potential to be lower by fully recognizing and avoiding the most constrained diameter of the canal and working beyond it. The incidence and consequence of incidental durotomies reported in the literature do not identify anatomically where these events occurred.1,4,5,10 It would be helpful to know precisely where they occurred to confirm the hypothesis that they occurred in the most constrained cross-sectional area of the lumbar canal that increases the risk of an incidental durotomy, as observed by Weinstein in 1982.9

There are two additional points to the en bloc technique that are worthy of mention. First, release of the insertions of the ligamentum flavum decreases the total number of actuations of the Kerrison rongeur needed and maintains a protective covering over the top of the dura throughout nearly the entire operation. Focusing on the insertion points also decreases the overall time of surgery. Second, maintaining the ligamentum flavum intact for nearly the entire procedure prevents the inevitable expansion of the thecal sac that occurs in a piecemeal decompression. As the thecal sac expands, it increases the risk to the dural edge by creating an even greater distance between the dural edge that has been decompressed and the dural edge that remains to be decompressed. Maintaining the thecal sac in the compressed state until all of the insertion points have been released prevents this circumstance.

Limitations

The retrospective nature of this report and the single-surgeon application of this technique are the main limitations of this report. Furthermore, this report did not include patients with previous microdiscectomies or laminectomies at the same level. An evaluation of the en bloc technique by multiple surgeons comparing the incidence of CSF leaks before and after would be needed to determine the impact this technique has on the incidence of incidental durotomies in patients undergoing lumbar laminectomy.

Conclusions

En bloc resection of the ligamentum flavum via a laminotomy at the caudal lamina decreased the risk of CSF leakage by allowing the surgeon to work beyond the most constrained diameter of the lumbar canal to release the caudal insertion of the ligamentum flavum. The en bloc resection technique reduces the number of Kerrison rongeur actuations and maintains a protective barrier over the thecal sac for nearly the entire procedure.

Acknowledgments

I thank the staff of Neuroscience Publications at Barrow Neurological Institute for assistance with manuscript and video preparation and Kevin Gosselin, PhD, for performing the statistical analysis.

Disclosures

Dr. Tumialán reported being an investor in LessRay, TrackX, Durastat, and Fusion Robotics and receiving royalties from Globus during the conduct of the study.

Supplemental Information

Videos

Video 1. https://vimeo.com/766114725.

Video Abstract. https://vimeo.com/778492106.

Previous Presentations

Portions of this work were orally presented at the University at Buffalo, Getzville, New York, Grand Rounds, July 28, 2022, and the Brazilian Neurosurgical Society Meeting in São Paulo, Brazil, August 4, 2022.

References

  • 1

    Weinstein JN, Tosteson TD, Lurie JD, et al. Surgical versus nonoperative treatment for lumbar spinal stenosis four-year results of the Spine Patient Outcomes Research Trial. Spine (Phila Pa 1976). 2010;35(14):13291338.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2

    Lurie JD, Tosteson TD, Tosteson A, et al. Long-term outcomes of lumbar spinal stenosis: eight-year results of the Spine Patient Outcomes Research Trial (SPORT). Spine (Phila Pa 1976). 2015;40(2):6376.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3

    Bydon M, Macki M, Abt NB, et al. Clinical and surgical outcomes after lumbar laminectomy: an analysis of 500 patients. Surg Neurol Int. 2015;6(suppl 4):S190S193.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4

    Herren C, Sobottke R, Mannion AF, et al. Incidental durotomy in decompression for lumbar spinal stenosis: incidence, risk factors and effect on outcomes in the Spine Tango registry. Eur Spine J. 2017;26(10):24832495.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5

    Desai A, Ball PA, Bekelis K, et al. SPORT: does incidental durotomy affect longterm outcomes in cases of spinal stenosis? Neurosurgery. 2015;76(suppl 1):S57S63.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6

    Panjabi MM, Goel V, Oxland T, et al. Human lumbar vertebrae. Quantitative three-dimensional anatomy. Spine (Phila Pa 1976). 1992;17(3):299306.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7

    Khoo LT, Fessler RG. Microendoscopic decompressive laminotomy for the treatment of lumbar stenosis. Neurosurgery. 2002;51(5 suppl):S146S154.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8

    Boukebir MA, Berlin CD, Navarro-Ramirez R, et al. Ten-step minimally invasive spine lumbar decompression and dural repair through tubular retractors. Oper Neurosurg (Hagerstown). 2017;13(2):232245.

    • Crossref
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    • Export Citation
  • 9

    Lin PM. Internal decompression for multiple levels of lumbar spinal stenosis: a technical note. Neurosurgery. 1982;11(4):546549.

  • 10

    Wong AP, Shih P, Smith TR, et al. Comparison of symptomatic cerebral spinal fluid leak between patients undergoing minimally invasive versus open lumbar foraminotomy, discectomy, or laminectomy. World Neurosurg. 2014;81(3-4):634640.

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  • Collapse
  • Expand

Illustration from Chan et al. (E2). © Andrew K. Chan, published with permission.

  • View in gallery
    FIG. 1.

    Lateral fluoroscopic image demonstrating the target for the access port that encompasses the rostral insertion point of the ligamentum flavum for an L4–5 laminectomy. A: Lateral fluoroscopic image demonstrating spinal needle in position. B: Artist’s rendering of the ligamentum flavum on the fluoroscopic image. C: Position of the access port at the base of the spinous process. Such a position allows undercutting the spinous process and reaching the contralateral recess. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

  • View in gallery
    FIG. 2.

    Technique for en bloc resection of the ligamentum flavum at L4–5. A: Illustration of the laminectomy performed. The lamina is first thinned using a drill and then removed with a Kerrison rongeur until the rongeur reaches beyond the insertion of the ligamentum flavum. Note the absence of the ligamentum flavum at the rostral-most aspect of the exposure, which represents the insertion point. B: Drilling the contralateral recess to gain access to the insertion of the ligamentum flavum beneath the contralateral pedicle. Rotating the patient away from the surgeon optimizes the line of sight and ergonomics of this task. C: A view from within the canal while drilling the contralateral recess. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

  • View in gallery
    FIG. 3.

    The various dimensions of the lumbar canal. Using the anthropomorphic measurements reported by Panjabi et al.,6 a computer-generated model illustrates the varying diameters of the lumbar canal from L3 to L5. Left: The superior-most aspect of the lamina represents the most constrained dimension (magenta ring), whereas the caudal aspect of the lamina presents a larger dimension (turquoise ring). Right: The cross-sectional areas of the lumbar spine of the Panjabi model illustrate the displacement of the thecal sac with a number 2 Kerrison rongeur in the most constrained corridor (magenta ring) compared with the larger diameter (turquoise ring). Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

  • View in gallery
    FIG. 4.

    Illustration demonstrating the release of the caudal insertion of the ligamentum flavum with both the piecemeal and en bloc techniques. A: In the piecemeal resection technique, the release of the ligamentum flavum is completed from the rostral-to-caudal direction by passing the footplate of the Kerrison rongeur into the most constrained corridor of the lumbar canal. B: The en bloc technique creates a laminotomy into the midportion of the lamina, where the canal diameter is larger. The ligamentum flavum is resected in the caudal-to-rostral direction, with direct visualization of the thecal sac. C: A comparison view shows the greater depth of the Kerrison rongeur in a more constrained corridor for a rostral-to-caudal approach compared with working beyond the insertion of the ligamentum flavum for a caudal-to-rostral approach. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

  • 1

    Weinstein JN, Tosteson TD, Lurie JD, et al. Surgical versus nonoperative treatment for lumbar spinal stenosis four-year results of the Spine Patient Outcomes Research Trial. Spine (Phila Pa 1976). 2010;35(14):13291338.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2

    Lurie JD, Tosteson TD, Tosteson A, et al. Long-term outcomes of lumbar spinal stenosis: eight-year results of the Spine Patient Outcomes Research Trial (SPORT). Spine (Phila Pa 1976). 2015;40(2):6376.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3

    Bydon M, Macki M, Abt NB, et al. Clinical and surgical outcomes after lumbar laminectomy: an analysis of 500 patients. Surg Neurol Int. 2015;6(suppl 4):S190S193.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4

    Herren C, Sobottke R, Mannion AF, et al. Incidental durotomy in decompression for lumbar spinal stenosis: incidence, risk factors and effect on outcomes in the Spine Tango registry. Eur Spine J. 2017;26(10):24832495.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5

    Desai A, Ball PA, Bekelis K, et al. SPORT: does incidental durotomy affect longterm outcomes in cases of spinal stenosis? Neurosurgery. 2015;76(suppl 1):S57S63.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6

    Panjabi MM, Goel V, Oxland T, et al. Human lumbar vertebrae. Quantitative three-dimensional anatomy. Spine (Phila Pa 1976). 1992;17(3):299306.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7

    Khoo LT, Fessler RG. Microendoscopic decompressive laminotomy for the treatment of lumbar stenosis. Neurosurgery. 2002;51(5 suppl):S146S154.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8

    Boukebir MA, Berlin CD, Navarro-Ramirez R, et al. Ten-step minimally invasive spine lumbar decompression and dural repair through tubular retractors. Oper Neurosurg (Hagerstown). 2017;13(2):232245.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9

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