Cauda equina syndrome due to intradural lumbar disc herniation

Cauda equina syndrome due to intradural lumbar disc herniation

Intradural lumbar disc herniation is rare, with an incidence of 0.3%-1%, but has been well reported in the literature. Transdural migration of the disc penetrating both ventral and dorsal dura is extremely rare, and there is a dearth of literature in the pathophysiology and surgical management of transdural herniation. Lack of knowledge on this type of presentation can cause intraoperative surprises and inadvertent cauda equina root injuries and lead to prolonged operative time. 1).

Diagnosis

Intradural disc prolapse remains a diagnostic dilemma as it is very difficult to diagnose all the cases preoperatively. The presence of MRI findings of mass effect in the form of displacement of the traversing nerve roots due to large central disc with crumble disc sign were suggestive of early evidence of intradural disc herniation. Y sign in ventral dura due to splitting of ventral dura and arachnoid mater by disc material was a good diagnostic sign to suspect intradural extra-arachnoid disc. The presence of hypointense structure inside the dura with no continuity with the adjacent intervertebral disc on MRI was highly suggestive of an intradural disc, in patients having the large central disc on MRI, especially at L4-L5 levels, should raise suspicion of intradural herniation of disc. 2).


Ducati et al. described five cases of this pathology and review the literature as well as some considerations about the difficulties in the preoperative diagnostic issues and the surgical technique.

They concluded that for intradural disc herniations the diagnosis is mainly intraoperative, and the surgical technique has some special aspects 3).


A female patient with lumbosciatic pain who developed an incomplete cauda equina syndrome. An asymmetric discopathy of the L2-L3 space and a gas bubble with disc material within the spinal canal was noticed in the radiologic explorations. The literature and the authors’ experience are reviewed with the aim of confirming the frequency of intradural herniation in association with gas in the spinal canal.

A laminoarthrectomy of the involved space was performed followed by direct intradural examination, which revealed a disc fragment that was excised. An instrumented L2-L3 arthrodesis was performed. Postoperative evolution was satisfactory. To date, the authors have found this association in 2% of the patients with intraspinal gas.

The potential presence of an intradural disc herniation must always be considered when performing an open discectomy on a patient whose CT scan study shows the presence of epidural gas. This association is particularly striking given the relative rarity of intradural herniations and intraspinal gas. In the event that no clear disc herniation was found, an intradural examination may be indicated to justify clinical signs and symptoms or previous radiologic studies 4).

Treatment

Intradural exploration and/or transdural sequestrectomy avoids traction on already compromised nerve roots and is often safer than extradural sequestrectomy. The onset of bladder paralysis is a most important indication for immediate surgery. The cases presented show that there is a highly significant difference in the outcome of those cases operated on within 24h of bladder paralysis compared to those operated on after this period 5).

Case series

Sharma et al. presented a case series of six cases of intradural disc herniation at L4-L5 level diagnosed on the basis of intraoperative findings.

All the cases, on preoperative magnetic resonance imaging (MRI) were reported as having diffuse annular bulge with large posterocentral extrusion. The study comprised patients in age group of 30-60 years. Four cases out of six presented with cauda equina syndrome. In three cases, cauda equina was associated with sudden deterioration in the power of lower limb muscle groups.

They suspected that intradural herniation of disc was synchronous with cauda equina syndrome in these cases, which was very well documented in one of the cases. On retrospective analysis, MRI findings of mass effect in the form of displacement of the traversing nerve roots due to large central disc with crumble disc sign were suggestive of early evidence of intradural disc herniation. Y sign in ventral dura due to splitting of ventral dura and arachnoid mater by disc material was a good diagnostic sign to suspect intradural extra-arachnoid disc. The presence of hypointense structure inside the dura with no continuity with the adjacent intervertebral disc on MRI was highly suggestive of an intradural disc.

Intradural disc prolapse remains a diagnostic dilemma as it is very difficult to diagnose all the cases preoperatively. The presence of above-mentioned radiological signs on MRI in patients having the large central disc on MRI, especially at L4-L5 levels, should raise suspicion of intradural herniation of disc. 6).


Ducati et al. described five cases of this pathology and review the literature as well as some considerations about the difficulties in the preoperative diagnostic issues and the surgical technique.

They concluded that for intradural disc herniations the diagnosis is mainly intraoperative, and the surgical technique has some special aspects 7).

Case reports

Intradural lumbar disc herniation is rare, with an incidence of 0.3%-1%, but has been well reported in the literature. Transdural migration of the disc penetrating both ventral and dorsal dura is extremely rare, and there is a dearth of literature in the pathophysiology and surgical management of transdural herniation. Lack of knowledge on this type of presentation can cause intraoperative surprises and inadvertent cauda equina root injuries and lead to prolonged operative time. Pedaballe et al. reported 1 such case, described the surgical experience, and discussed the pathological mechanisms and signs.

A 30-year-old woman presented to outpatient clinic with chronic cauda equina syndrome due to massive L4-L5 disc herniation. L4-L5 decompression and transforaminal lumbar interbody fusion were planned. Unexpectedly, however, surgery revealed a transdural herniation, which was effectively managed with laminectomy, extension of durotomydiscectomy, repair of both dorsal and ventral dura, and interbody fusion, but at the expense of prolonged surgical time.

Transdural herniation of a lumbar disc is very rare presentation. It can be effectively managed with laminectomy, extension of durotomydiscectomy and repair of both dorsal and ventral dura. It can be diagnosed by magnetic resonance imaging preoperatively only if read with suspicion of such presentation. 8).


A 56-year-old man who developed cauda equina syndrome after several episodes of severe Valsalva maneuver.

The patient was found to have developed subacute urinary retention and leg weakness. Magnetic resonance imaging findings were concerning for an unusual-appearing lesion extending cranially at L2-3. Urgent decompression via an L2 laminectomy, exploration, and subsequent discectomy was performed. The patient recovered exceptionally well, regaining bladder function and ultimately being able to ambulate without assistance.

Cranially extending intrathecal disc herniations are a rare phenomenon and exceptionally uncommon above L3. The clinician should have a high level of suspicion for herniation when looking at the clinical and historical information consistent with such a diagnosis even in the presence of ambiguous imaging findings 9)


Nagaria et al. presented a case with intermittent symptoms and signs of cauda equina compression. They were unable to find in the literature, any previously described cases of intermittent cauda equina compression from a herniated intradural disc fragment leading to a “floppy disc syndrome” 10).


A 73-year-old male presented with a rare dorsally sequestrated lumbar disc herniation manifesting as severe radiating pain in both leg, progressively worsening weakness in both lower extremities, and urinary incontinence, suggesting cauda equina syndrome. Magnetic resonance imaging suggested the sequestrated disc fragment located in the extradural space at the L4-L5 level had surrounded and compressed the dural sac from the lateral to dorsal sides. A bilateral decompressive laminectomy was performed under an operating microscope. A large extruded disc was found to have migrated from the ventral aspect, around the thecal sac, and into the dorsal aspect, which compressed the sac to the right. After removal of the disc fragment, his sciatica was relieved and the patient felt strength of lower extremity improved 11).


Mailleux et al. described a case of anterior transdural L4-L5 disc herniation presenting as a partial cauda equina syndrome without related back pain or history of back pain. MRI allowed presurgical diagnosis showing an irregular intradural mass that did not enhance. That lack of enhancement could be related to the fact that the disc herniation was relatively recent 12).


A female patient with lumbosciatic pain who developed an incomplete cauda equina syndrome. An asymmetric discopathy of the L2-L3 space and a gas bubble with disc material within the spinal canal was noticed in the radiologic explorations. The literature and the authors’ experience are reviewed with the aim of confirming the frequency of intradural herniation in association with gas in the spinal canal.

A laminoarthrectomy of the involved space was performed followed by direct intradural examination, which revealed a disc fragment that was excised. An instrumented L2-L3 arthrodesis was performed. Postoperative evolution was satisfactory. To date, the authors have found this association in 2% of the patients with intraspinal gas.

The potential presence of an intradural disc herniation must always be considered when performing an open discectomy on a patient whose CT scan study shows the presence of epidural gas. This association is particularly striking given the relative rarity of intradural herniations and intraspinal gas. In the event that no clear disc herniation was found, an intradural examination may be indicated to justify clinical signs and symptoms or previous radiologic studies 13).


A 59 year-old man with ILDH. It was the only case of ILDH among 960 patients surgically treated, during the period 1989-1996. Clinically the patient demonstrated an acute cauda equina syndrome. The diagnosis was established by radiculograms, which showed a total block at the L3-L4 level. There was a 3 days time interval between the diagnosed syndrome itself and the operation. At surgery the L3-L4 level was intact, whereas dense adhesions were found between the L4-L5 disc and the dura. Root retraction to expose the nucleus pulposus mass was impossible. A laminectomy of the L4 was undertaken. An incision was made in the dura and arachnoid, revealing an extruded discal mass, lying between the roots of the cauda equina. It was carefully removed. The state of the patient at follow-up 1 year after surgery was unsatisfactory. The patient has moderate flaccid paraparesis, bladder dysfunction improved. The prognosis appeared to be linked to the preoperative duration of symptoms 14)


One case of intradural lumbar disc herniation at the L3-L4 disc level with cauda equina syndrome is reported. Myelo-CT demonstrated an intradural tumor-like lesion with complete block. An intradural fragment of sequestrated disc material was found intraoperatively. Accurate preoperative diagnosis of the intradural nature of the disease and prompt surgical treatment resulted in a smooth recovery 15).


A case of intradural disk herniation at L4-5 observed in a patient with longstanding low back pain and sciatica due to a herniated disk. After having undergone various surgical procedures for this disorder, the patient developed a multiradicular syndrome of the cauda equina 16)

References

1) , 8)

Pedaballe AR, Mallepally AR, Tandon V, Sharma A, Chhabra HS. An Unusual Case of Transdural Herniation of a Lumbar Intervertebral Disc: Diagnostic and Surgical Challenges. World Neurosurg. 2019 Aug;128:385-389. doi: 10.1016/j.wneu.2019.05.103. Epub 2019 May 20. PubMed PMID: 31121367.
2) , 6)

Sharma A, Singh V, Sangondimath G, Kamble P. Intradural Disc a Diagnostic Dilemma: Case Series and Review of Literature. Asian J Neurosurg. 2018 Oct-Dec;13(4):1033-1036. doi: 10.4103/ajns.AJNS_55_17. PubMed PMID: 30459862; PubMed Central PMCID: PMC6208249.
3) , 7)

Ducati LG, Silva MV, Brandão MM, Romero FR, Zanini MA. Intradural lumbar disc herniation: report of five cases with literature review. Eur Spine J. 2013 May;22 Suppl 3:S404-8. doi: 10.1007/s00586-012-2516-4. Epub 2012 Sep 27. Review. PubMed PMID: 23014741; PubMed Central PMCID: PMC3641279.
4) , 13)

Hidalgo-Ovejero AM, García-Mata S, Gozzi-Vallejo S, Izco-Cabezón T, Martínez-Morentín J, Martínez-Grande M. Intradural disc herniation and epidural gas: something more than a casual association? Spine (Phila Pa 1976). 2004 Oct 15;29(20):E463-7. Review. PubMed PMID: 15480124.
5)

Dinning TA, Schaeffer HR. Discogenic compression of the cauda equina: a surgical emergency. Aust N Z J Surg. 1993 Dec;63(12):927-34. PubMed PMID: 8285904.
9)

Tempel Z, Zhu X, McDowell MM, Agarwal N, Monaco EA 3rd. Severe Intradural Lumbar Disc Herniation with Cranially Oriented Free Fragment Migration. World Neurosurg. 2016 Aug;92:582.e1-582.e4. doi: 10.1016/j.wneu.2016.06.024. Epub 2016 Jun 16. PubMed PMID: 27318310.
10)

Nagaria J, Chan C, Kamel M, McEvoy L, Bolger C. Episodic cauda equina compression from an intradural lumbar herniated disc: a case of ‘floppy disc’. J Surg Case Rep. 2011 Sep 1;2011(9):6. doi: 10.1093/jscr/2011.9.6. PubMed PMID: 24950507; PubMed Central PMCID: PMC3649298.
11)

Kim JS, Lee SH, Arbatti NJ. Dorsal extradural lumbar disc herniation causing cauda equina syndrome : a case report and review of literature. J Korean Neurosurg Soc. 2010 Mar;47(3):217-20. doi: 10.3340/jkns.2010.47.3.217. Epub 2010 Mar 31. PubMed PMID: 20379476; PubMed Central PMCID: PMC2851086.
12)

Mailleux R, Redant C, Milbouw G. MR diagnosis of transdural disc herniation causing cauda equine syndrome. JBR-BTR. 2006 Nov-Dec;89(6):303-5. PubMed PMID: 17274584.
14)

Bayassi S. [Intradural lumbar disk herniation (ILDH). Case report and literature review]. Neurol Neurochir Pol. 1998 Sep-Oct;32(5):1295-301; discussion 1301-2. Polish. PubMed PMID: 10463243.
15)

Fang CM, Huang TJ, Chen WJ, Lee ST, Hsu RW. Intradural lumbar disc herniation–a case report. Changgeng Yi Xue Za Zhi. 1994 Sep;17(3):297-300. PubMed PMID: 7954013.
16)

Borgogno G, Fontanella C, La Camera V. [Herniated intradural lumbar disk: a clinical case]. Arch Putti Chir Organi Mov. 1991;39(1):87-91. Italian. PubMed PMID: 1842495.

Lumbar spinal stenosis risk factors

Lumbar spinal stenosis risk factors

Risk factors for the disease include some comorbidities such as obesity or smoking, daily habits such as an active lifestyle, but also genetic factors that are not completely elucidated yet 1).

Lumbar spinal stenosis (LSS) is frequently observed in obese patients and the elderly especially due to the aging of the spine.

Increased Spinal inclination angle (SIA) and Body Mass Index BMI might be the most relevant risk factors for LSS 2).

DM and low ankle-brachial index values (ABI)s are significantly associated with sLSS in patients with moderate radiographic stenosis. Neither factor is associated with sLSS in patients with severe stenosis. Notably, the effects of intrinsic factors on symptomology may be masked when anatomic stenosis is severe 3).


Kitab et al., performed a re-analysis of data from their previously reported prospective MRI-based study, stratifying data from the 709 cases into 3 age categories of equal size (instead of the original < 60 vs ≥ 60 years). Relative lumbar spinal canal dimensions, as well as radiological degenerative variables from L1 to S1, were analyzed across age groups in a multivariate mode. The total degenerative scale score (TDSS) for each lumbar segment from L1 to S1 was calculated for each patient. The relationships between age and qualitative stenosis grades, TDSS, disc degeneration, and facet degeneration were analyzed using Pearson’s product-moment correlation and multiple regression.

Multivariate analysis of TDSS and spinal canal dimensions revealed highly significant differences across the 3 age groups at L2-3 and L3-4 and a weaker, but still significant, association with changes at L5-S1. Age helped to explain only 9.6% and 12.2% of the variance in TDSS at L1-2 and L2-3, respectively, with a moderate positive correlation, and 7.8%, 1.2%, and 1.9% of the variance in TDSS at L3-4, L4-5, and L5-S1, respectively, with weak positive correlation. Age explained 24%, 26%, and 18.4% of the variance in lumbar intervertebral disc (LID) degeneration at L1-2, L2-3, and L3-4, respectively, while it explained only 6.2% and 7.2% of the variance of LID degeneration at L4-5 and L5-S1, respectively. Age explained only 2.5%, 4.0%, 1.2%, 0.8%, and 0.8% of the variance in facet degeneration at L1-2, L2-3, L3-4, L4-5, and L5-S1, respectively.

Age at presentation correlated weakly with degeneration variables and spinal canal morphometries in LSS segments. Age correlated with upper lumbar segment (L1-4) degeneration more than with lower segment (L4-S1) degeneration. The actual chronological age of the patients did not significantly correlate with the extent of degenerative pathology of the lumbar spinal stenosis segments. These study results lend support for a developmental contribution to LSS 4).

References

1)

Bagley C, MacAllister M, Dosselman L, Moreno J, Aoun S, El Ahmadieh T. Current concepts and recent advances in understanding and managing lumbar spine stenosis. F1000Res. 2019 Jan 31;8. pii: F1000 Faculty Rev-137. doi: 10.12688/f1000research.16082.1. eCollection 2019. Review. PubMed PMID: 30774933; PubMed Central PMCID: PMC6357993.
2)

Hirano K, Imagama S, Hasegawa Y, Muramoto A, Ishiguro N. Impact of spinal imbalance and BMI on lumbar spinal canal stenosis determined by a diagnostic support tool: cohort study in community‑living people. Arch Orthop Trauma Surg. 2013 Nov;133(11):1477-82. doi: 10.1007/s00402-013-1832-4. PubMed PMID: 23959069.
3)

Maeda T, Hashizume H, Yoshimura N, Oka H, Ishimoto Y, Nagata K, Takami M, Tsutsui S, Iwasaki H, Minamide A, Nakagawa Y, Yukawa Y, Muraki S, Tanaka S, Yamada H, Yoshida M. Factors associated with lumbar spinal stenosis in a large-scale, population-based cohort: The Wakayama Spine Study. PLoS One. 2018 Jul 18;13(7):e0200208. doi: 10.1371/journal.pone.0200208. eCollection 2018. PubMed PMID: 30020970; PubMed Central PMCID: PMC6051614.
4)

Kitab S, Habboub G, Abdulkareem SB, Alimidhatti MB, Benzel E. Redefining lumbar spinal stenosis as a developmental syndrome: does age matter? J Neurosurg Spine. 2019 May 17:1-9. doi: 10.3171/2019.2.SPINE181383. [Epub ahead of print] PubMed PMID: 31100722.

Lateral lumbar interbody fusion (LLIF)

Lateral lumbar interbody fusion (LLIF)

E.g. XLIFDLIFOLIF. Approach through psoas muscle (XLIF, DLIF) or anterior to psoas muscle (OLIF) through a lateral or anterolateral approach. Can distract the vertebral bodies by increasing the height of the disc space and thereby indirectly decompressing the neural elements. If bone quality is good, and there is no instability nor spondylolisthesis > Grade I, a standalone procedure (i.e. without screw instrumentation) may be an option if cage width of at least 22 mm (or preferably 26 mm) in the AP dimension is used.

LLIF was more effective than TLIF for spondylolisthesis reduction, likely due to the higher profile cage and ligamentotactic effect. In addition, LLIF showed mechanical stability of the reduction level by using a cage with a larger footprint. Therefore, LLIF should be considered a surgical option before TLIF for patients with unstable DS 1).

Advantages

Lateral lumbar interbody fusion (LLIF) is a minimally invasive technique first described by Ozgur et al. 2). LLIF allows the surgeon to access the intervertebral space via a minimally invasive direct lateral approach through the psoas muscle. The advantage of LLIF over the traditional anterior approach is the avoidance of exposure of the abdominal viscera, large vessels, and sympathetic plexus. Injury to the nerve roots and dura, and perineural fibrosis, which can occur after PLIF or TLIF, are minimized with this technique 3)4).

Indications

Used to treat leg pain or back pain generally caused by degenerative disc disease.

LLIF has been utilized to treat a variety of pathologies including adult degenerative scoliosis, central and foraminal stenosis, spondylolisthesis, and adjacent segment degeneration

They have become an increasingly popular surgical technique due to the benefits of minimal tissue disruption, excellent disc visualization, ability to insert a large intervertebral cage to lessen subsidence, and faster recovery times 5) 6).

Position

The LLIF procedure differs from other lumbar procedures in that the patient is positioned in the lateral decubitus position, often times utilizing bending the bed near the iliac crest region in order to facilitate access to the L4-5 disc space.

In awake volunteers, the pressure at the iliac crest or greater trochanter at the break of the bed increases by increasing the bed angle. Women with a lower BMI had high VAS pain scores when their greater trochanter was at maximal bed break. Men with higher BMI had high VAS pain scores when their iliac crest was at maximal bed break. An awareness of the iliac crest or greater trochanter at the break of the bed should be considered to prevent pain and increased pressure based on the patient’s sex and BMI 7).

As with most minimally invasive spine procedures, lateral lumbar interbody fusion (LLIF) requires the use of biplanar fluoroscopy for localization and safe interbody cage placement. Computed tomography (CT)-based intraoperative spinal navigation has been shown to be more effective than fluoroscopic guidance for posterior-based approaches such as pedicle screw instrumentation.

Use of an intraoperative cone-beam CT with an image-guided navigation system is feasible and safe and appears to be accurate, although a larger study is required to confirm these results 8).

Complications

Cost effectiveness

TLIF and LLIF produced equivalent 2-year patient outcomes at an equivalent cost-effectiveness profile 9).

Systematic reviews

Transpsoas lateral interbody fusion is one of the Lateral Lumbar Interbody Fusion minimally invasive approaches for lumbar spine surgery. Most surgeons insert the interbody cage laterally and then insert pedicle or cortical screw and rod instrumentation posteriorly. However, standalone cages have also been used to avoid posterior instrumentation.

The literature on comparison of the two approaches is sparse.

Alvi et al., performed a systematic review and meta-analysis of the available literature on transpsoas lateral interbody fusion by an electronic search of the PubMedEMBASE, and Scopus databases using PRISMA guidelines. They compared patients undergoing transpsoas standalone fusion (TP) with those undergoing transpsoas fusion with posterior instrumentation (TPP).

A total of 28 studies with 1462 patients were included. Three hundred and seventy-four patients underwent TPP, and 956 patients underwent TP. The mean patient age ranged from 45.7 to 68 years in the TP group, and 50 to 67.7 years in the TPP group. The incidence of reoperation was found to be higher for TP (0.08, 95% confidence interval [CI] 0.04-0.11) compared to TPP (0.03, 95% CI 0.01-0.06; p = 0.057). Similarly, the incidence of cage movement was found to be greater in TP (0.18, 95% CI 0.10-0.26) compared to TPP (0.03, 95% CI 0.00-0.05; p < 0.001). Oswestry Disability Index (ODI) and visual analog scale (VAS) scores and postoperative transient deficits were found to be comparable between the two groups.

These results appear to suggest that addition of posterior instrumentation to transpsoas fusion is associated with decreased reoperations and cage movements. The results of previous systematic reviews and meta-analysis should be reevaluated in light of these results, which seem to suggest that higher reoperation and subsidence rates may be due to the use of the standalone technique 10).


A systematic and critical review of recent literature was conducted in accordance with PRISMA guidelines. The sources of the data were PubMed, MEDLINE, Embase, Cochrane and Scopus. Key search terms were “transpsoas”, “interbody fusion”, “LLIF”, “XLIF” and “spondylolisthesis”. Papers included in the review were original research articles in peer-reviewed journals. The articles were thoroughly examined and compared on the basis of study design, outcomes, and results. Only studies which met the eligibility criteria were included. Eight studies were included in the qualitative and quantitative analysis (three retrospective, four prospective, one randomized controlled trial). A total of 308 patients (227 females) (pooled age 64.5 years) and a total of 353 operated levels were analyzed. Mean follow up time ranged from 6.2 to 24 months. There were no reported cases of durotomies or pseudarthrosis in any study. All neurologic complications were reported to be transient with no permanent deficits. Mean improvement in ODI scores ranged between 19.5 (38.6%) to 36 (54.5%). Mean improvement in slip ranged from 47 to 67.5%. Three studies also reported that patient satisfaction and willingness to undergo the procedure again approached 90%. Minimally invasive transpsoas interbody fusion possibly leads to favorable clinical and radiological outcomes while avoiding the possible complications of its more traditional open and minimally invasive counterparts. Further studies are needed to better establish its role in the management of low grade degenerative lumbar spondylolisthesis 11).

Case series

References

1)

Ko MJ, Park SW, Kim YB. Correction of Spondylolisthesis by Lateral Lumbar Interbody Fusion Compared with Transforaminal Lumbar Interbody Fusion at L4-5. J Korean Neurosurg Soc. 2019 May 8. doi: 10.3340/jkns.2018.0143. [Epub ahead of print] PubMed PMID: 31064044.
2) , 3)

Ozgur BM, Aryan HE, Pimenta L, Taylor WR. Extreme lateral interbody fusion (XLIF): a novel surgical technique for anterior lumbar interbody fusion. Spine J. 2006;6:435–443.
4)

Rodgers WB, Gerber EJ, Patterson J. Intraoperative and early postoperative complications in extreme lateral interbody fusion: an analysis of 600 cases. Spine (Phila Pa 1976) 2011;36:26–32.
5)

Rodgers WB, Gerber EJ. Outcomes of MIS spinal fusion: 12 and 24 months. The Spine Journal. 2010;10(9):S141.
6)

Isaacs RE, Hyde J, Goodrich JA, et al. A prospective, nonrandomized, multicenter evaluation of extreme lateral interbody fusion of the treatment of adult degenerative scoliosis: perioperative outcomes and complications. Spine. 2010;15(35):S322–30.
7)

Tatsumi RL. Lateral Pressure and VAS Pain Score Analysis for the Lateral Lumbar Interbody Fusion Procedure. Int J Spine Surg. 2015 Sep 28;9:48. doi: 10.14444/2048. eCollection 2015. PubMed PMID: 26512342; PubMed Central PMCID: PMC4610324.
8)

Park P. Three-Dimensional Computed Tomography-Based Spinal Navigation in Minimally Invasive Lateral Lumbar Interbody Fusion: Feasibility, Technique, and Initial Results. Neurosurgery. 2015 Mar 23. [Epub ahead of print] PubMed PMID: 25812070.
9)

Gandhoke GS, Shin HM, Chang YF, Tempel Z, Gerszten PC, Okonkwo DO, Kanter AS. A Cost-Effectiveness Comparison Between Open Transforaminal and Minimally Invasive Lateral Lumbar Interbody Fusions Using the Incremental Cost-Effectiveness Ratio at 2-Year Follow-up. Neurosurgery. 2016 Apr;78(4):585-95. doi: 10.1227/NEU.0000000000001196. PubMed PMID: 26726969.
10)

Alvi MA, Alkhataybeh R, Wahood W, Kerezoudis P, Goncalves S, Murad MH, Bydon M. The impact of adding posterior instrumentation to transpsoas lateral fusion: a systematic review and meta-analysis. J Neurosurg Spine. 2018 Oct 1:1-11. doi: 10.3171/2018.7.SPINE18385. [Epub ahead of print] Review. PubMed PMID: 30485206.
11)

Goyal A, Kerezoudis P, Alvi MA, Goncalves S, Bydon M. Outcomes following minimally invasive lateral transpsoas interbody fusion for degenerative low grade lumbar spondylolisthesis: A systematic review. Clin Neurol Neurosurg. 2018 Apr;167:122-128. doi: 10.1016/j.clineuro.2018.02.020. Epub 2018 Feb 16. Review. PubMed PMID: 29476935.
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