Disc Fragments Research Articles

Suprapedicular Retrocorporeal Technique of Transforaminal Full-Endoscopic Lumbar Discectomy for Highly Downward-Migrated Disc Herniation

Anatomical barriers (e.g., pedicles, narrow foramina) can hinder direct access to, and removal of, disc fragments that have migrated far downward. Using transforaminal full-endoscopic lumbar discectomy (FELD), we devised a modified technique, the suprapedicular retrocorporeal approach, for herniations in which the disc has migrated to the axilla of the traversing nerve roots. In the present report, we have described our preliminary results. Soft, highly downward-migrated disc herniation was treated with transforaminal FELD through the suprapedicular retrocorporeal approach in 22 patients from June 2017 to May 2019. The clinical outcomes were evaluated, including the preoperative and postoperative visual analog scale scores for the back and leg, Oswestry disability index, and MacNab criteria for surgical success. The affected discs were at L4-L5 in 14 patients, L3-L4 in 6 patients, and L5-S1 in 2 patients. In each case, the affected disc was successfully removed using the suprapedicular retrocorporeal approach. The mean follow-up was 18.1 ± 5.7 months. The mean visual analog scale scores for back and leg pain improved significantly (P < 0.05 for both). The mean Oswestry disability index had decreased from 62.5 ± 14.2 preoperatively to 10.5 ± 5.9 postoperatively (P < 0.05). Using the MacNab criteria, 13 patients reported excellent outcomes and 9, good outcomes. No complications or recurrence developed during follow-up. The suprapedicular retrocorporeal technique is a feasible and effective surgical option in transforaminal FELD for the treatment of herniation in which the disc has migrated to the axilla of the traversing nerve roots.

Modified Interlaminar Endoscopic Lumbar Discectomy for Highly Upmigrated Disc Herniation: A Proctorship Description of the Technique via Translaminar Route.

Lumbar disc herniation (LDH) comprises one of the most common causes of low back pain. 35%–72% of LDH is associated with disc fragment migration. The migration of the disc fragments can be high-grade up, low-grade up, high-grade down, and low-grade down. Spine surgeons deal with unique challenges during surgical management of migrated discs. Operational challenges with open surgery include extensive lamina excision, pars excision, and potential for iatrogenic instability without fixation. In contrast, rigid instruments and poor visualization are the challenges with transforaminal endoscopic spine surgery (ESS). Hence interlaminar approach with ESS is an excellent choice with these migrated LDH. The creation of a translaminar crater in the cranial lamina without dealing with the interlaminar window or ligamentum flavum could be an excellent option to deal with these herniations face front. The lamina is the only anatomical barrier between the endoscope and the migrated disc fragment. Hence with a translaminar approach, unnecessary flavectomy can be avoided. In this technical report and video, we demonstrate the surgical technique of performing the translaminar ESS for highly upmigrated LDH with the preservation of optimal natural anatomy.

TORAKOLOMBER BİLEŞKE DİSK HERNİASYONLARININ CERRAHİ TEDAVİSİNDE POSTEROLATERAL TRANSKAMBİN YAKLAŞIM

Objective: The optimal surgical approach for treatment of thoracolumbar junction disc herniations (TLJDH) remains controversial. Anterolateral retroperitoneal, anterior transthoracic, posterolateral, lateral and transforaminal endoscopic approaches are used in current surgical treatment of TLJDH. In a posterolateral transcambin approach, a small piece of bone is removed from the pars interarticularis and facet joints, and decompression is achieved by discectomy without causing instability. The transcambin approach has advantages such as discectomy without advanced neural tissue retraction, short recovery time and less postoperative complications. Methods: The eight patients with 3 T12-L1 and 5 L1-2 TLJDH who were operated on using the posterolateral transcambin approach between 2016-2018 in our clinic were presented retrospectively. The study included patients with extruded or sequestrated disc herniation that had far lateral, foraminal, and paramedian extension, and caused cauda equina syndrome, conus medullaris syndrome, and radiculopathy. A skin incision and fascia opening were done from midline. The exiting root was revealed at laterally of pars interarticularis by subperiosteally stripping of paravertebral muscles and the removal of disc fragments were targeted. Results: Three male and five female patients with a mean age of 45.1 (32-66). Mean operation time was 57.8 minutes. Preoperative VAS values were 8.75±0.51 and postoperative VAS values were 1.25±0.65. According to the MacNab classification, 62.5% excellent, 25% good and 12.5% were fair. There was no neurological injury, cerebrospinal fluid (CSF) fistula, pneumothorax, or operation field hematoma.Conclusion: The transcambin approach was found to be useful in terms of a relatively short operation time, low morbidity probability, and less postoperative pain in patients with TLJDH.&nbsp;

Cauda Equina Syndrome after Sequestered Disc Herniation Migrating to the Dorsal Epidural Space: Case Report and Review of the Literature

Background: Posteriorly migrated epidural disc fragments (PMEDF) presenting with cauda equina syndrome are relatively common. These cases are sometimes inaccurately identified on MRI as; epidural tumors, abscesses, hematomas and or facet cysts. Proper description and identification are key to be able to provide effective and safe management. Currently we are presenting the case of a patient with cauda equina syndrome secondary to a posterior mass compression intraoperatively identified as a PMEDF. Case Description: 45-years-old male presenting with insidious low back pain that progressed to urinary retention and bilateral foot drop. An MRI of the lumbar spine showed a posteriorly located epidural lesion. That appeared to be dependent on a left facet cyst. The patient was treated with a decompressive laminectomy and multiple disc fragments were identified under the ligamentum flavum and over the posterior epidural space. Conclusion: Posterior epidural migration of a lumbar disc fragments (PEMLDF) are not a common presentation of intervertebral disc herniations and their differential diagnosis and treatment might require a different surgical approach; fusion vs decompression. PEMLDFs should be suspected on those patients presenting with sudden cauda equina syndrome and posteriorly located epidural lesions on MRI.

Stochastic Fragmentation in Protoplanetary Disks under External Irradiation

Abstract It has been shown that disk fragmentation within several tens of au from the star is very difficult when the gravitational instability and cooling time criterion are considered. However, in the stochastic fragmentation scenario, things may be different. We investigate stochastic fragmentation in protoplanetary disks. In the stochastic fragmentation model, we consider the effects of the external irradiation on the fragmentation process. For the stochastic fragmentation, owing to the probability of generating bound fragments at longer cooling times relative to the critical value and the short collapsing times in the external irradiation region, the inner boundary of the fragmentation region extends inward to 19 au. We find that the required self-gravitating lifetime for fragmentation in the external irradiation region is far less than the self-gravitating lifetime of the disk. Therefore, once a radius is in the external irradiation region, the fragmentation probability increases quickly to 1 after gravitational instability sets in, and fragmentation occurs within a short period of time. We also find that the self-gravitating lifetime required for fragmentation decreases significantly as the radius increases in the external irradiation region.

Biportal endoscopic spine surgery (BESS): considering merits and pitfalls.

The biportal endoscopic spine surgery allow us to use conventional spine surgical instruments in the endoscopic procedure like open surgery. And protection of the neural structures with assistant retractor make this procedure safer than the uniportal endoscopic spine surgery. The authors present a novel technique in treating degenerative spinal diseases in variable access angle different from the conventional uniportal endoscopic spine surgeries. The main objective of this report is presenting two approaches for central and extraforaminal stenosis using an assistant retractor. Both central and foraminal stenosis were well decompressed and a migrated disc fragment was removed successfully with this minimal endoscopic procedure without major complications in these cases.

Microendoscopic anterior cervical foraminotomy: a preliminary series of 76 cases

BackgroundAnterior cervical foraminotomy represents a relatively recent minimally invasive approach that can potentially preserve the intervertebral disc and thus the functional motion segment.ObjectiveThis study aims to evaluate the clinical outcome of microendoscopic anterior cervical foraminotomy (MACF) for patients with cervical unilateral radiculopathy due to single level soft disc herniation or hard disc-osteophyte complex (DOC).MethodsIn the period between August 2009 and March 2015, 76 consecutive patients with symptomatic unilateral cervical radiculopathy were included in this study. There were 40 left-sided cervical radiculopathy cases and 36 right-sided; of those, 42 had soft disc fragment herniation, 18 had DOC, 12 had a migrated disc fragment whether cranial or caudal, and four had far lateral (foraminal) disc herniation. In all cases, MACF with root decompression was performed. Cervical magnetic resonance imaging (MRI), computed tomography (CT) scan, and plain X-rays were performed for all patients and then repeated postoperatively. All patients were followed-up for at least a year. Clinical and functional outcomes were assessed using visual analogue scale (VAS) and Odom’s criteria.ResultsAccording to VAS score, there was an improvement in neck pain from 6.4 (range 5–10) to 1.5 (1–5) and in arm pain from 7.2 (range 6–10) to 1.2 (0–4) at final follow-up (P < 0.05). Functional outcomes according to Odom’s criteria were excellent in 59 (78%) cases, good in ten (13%), fair in six (8%), and poor in one (1%) case. Success of surgery was considered to be achieved in 91% (excellent + good) of cases. Mean operating time was 81 min, and mean intraoperative blood loss was 21 ml. Most significant complications included a dural tear in one case, transient postoperative dysesthesia in six cases, excess bony work resulting in unintended uncinectomy in three cases, fracture of transverse process in one case, unintended near total discectomy in two cases, infective discitis in one case, and persistent radicular pain due to incomplete osteophyte removal in one case.ConclusionsThis preliminary report suggests that MACF yields overall excellent results in selected patients with unilateral cervical radiculopathy. The technique potentially can preserve the functional motion segment, thus patients typically experience immediate postoperative neck mobility and do not need to wear a cervical collar.

Clinicopathologic Features of Thoracolumbar Interdural Disc Herniations: A Retrospective Case Series with a Systematic Literature Review

Transdural disc herniations represent about 0.3% of all herniated discs. Preoperative imaging rarely demonstrates this condition. Therefore, diagnosis of transdural disc herniation is usually made intraoperatively. We describe the clinicopathologic features of extremely rare cases of thoracic and lumbar interdural disc herniations mimicking spinal intradural en plaque tumors. This is a retrospective case series with a systematic literature review. Clinical presentation, imaging, differential diagnosis, intraoperative microsurgical findings, and possible pathogenesis were reviewed according to published guidelines. All patients underwent a posterior approach for microsurgical excision of disc herniation, but no epidural lesion was found. At intradural exploration, a tumor-like en plaque lesion was discovered. The surface of the lesion was incised, and multiple friable, cartilaginous white-yellow fragments were removed to achieve complete intralesional excision. The postoperative course was characterized by progressive neurologic improvement in all cases. In peculiar anatomic (adhesions between the anulus fibrosus, posterior longitudinal ligament, and ventral surface of dura mater) and pathologic (calcified giant disc herniation, spinal canal stenosis, previous lumbar spine surgery) conditions, penetration of disc fragment in the thickness of spinal dura mater can occur. Interdural disc herniations constitute a rare pathologic condition characterized by the migration of the herniated disc in neither the epidural nor the subdural spinal space, but rather in the thickness of the spinal dura mater. Further advances are necessary in neuroradiologic investigations to achieve a correct preoperative diagnosis, which is essential, as spine surgeons must be aware of these rare pathologies.

Pregnancy Associated Plasma Protein A (PappA) Knockout Mice: In Vivo Disc Study

INTRODUCTIONPast research in disc biology has highlighted the beneficial effects of growth factors, such as BMPs and IGF‐1, in vitro. Based on this research, it was proposed that exogenous IGF‐1 be used as a therapy for intervertebral disc degeneration (IDD). In the aging research field, suppressing the IGF‐1‐mediated signaling pathway has consistently decreased the incidence of age‐related disorders and increased lifespan of mammals and rodents. One model using PappA knockout mice has shown decreasing IGF‐1 signaling leads to positive effects on aging and longevity. Active PappA protease cleaves IGF binding protein 4 (IGFBP4), releasing active IGF‐1 which can bind to its receptor and exert downstream signaling effects. When you genetically remove PappA, IGF‐1 stays bound to IGFBP4. Here, we examined the discs of aged PAPPA−/− mice versus wild type (WT) to determine whether there was an effect on age‐associated IDD.METHODSThis study was conducted according to IACUC approved protocols at University of Pittsburgh. Genetic deletion of PAPP‐A protease in mice with a mixed C57BL/6‐129SV/E background was achieved by deletion of both alleles of PAPP‐A. Spine segments were harvested from WT and PAPPA−/− mice at 23 months. Disc proteoglycan content was assessed by safranin‐O‐histology and DMMB assay was used to quantify sulfated glycosaminoglycans (GAG) in lumbar NP tissue. Western blotting was performed to measure the disc aggrecan proteolytic fragments, and the catabolic markers MMP‐3 and ADAMTS‐4. Levels of disc cellular senescence (loss of lamin B1expression) was assessed by immunohistochemistry. Student’s t‐test was used to test significance between groups (p&lt;0.05). Average values (n=4 mice) were shown with SEM.RESULTSCompared to WT, PAPPA−/− mice had decreased proteoglycan content and two times less disc GAG content (Figure 1). PAPPA−/− mice also had significantly decreased aggrecan fragmentation and decreased protein levels of MMP‐3 and ADAMTS‐4 in their discs compared to WT mice (Figure 2). Additionally, greater level of disc lamin B1 was seen in PAPPA−/− compared to WT mice, suggesting reduced disc cellular senescence in PAPPA−/− mice.DISCUSSIONThe role of IGF‐1 in disc health and aging is currently unresolved. PAPPA−/− mice have reduced matrix content but the aggrecan matrix present after aging appears to be less fragmented based on our findings. Lowered disc fragmentation corresponded to a decrease in disc catabolic factors MMP‐3 and ADAMTS‐4 protein in PAPPA−/− mice. Lamin B1 staining suggests there are less disc senescent cells in old PAPPA−/− mice compared to normally aged mice. Further studies are needed to determine the mechanism for the decreased disc catabolism and more full length aggrecan in aged PAPPA−/− mice compared to aged WT mice. Additionally, further studies should confirm whether young PAPPA−/− mice also have decreased GAG content or this loss occurs during the aging process.SIGNIFICANCEThe results of this study suggest the net effect of IGF‐1 regarding both anabolic and catabolic effects must be examined to fully understand if IGF‐1 is beneficial for disc homeostasis during age‐associated IDD.Support or Funding InformationR01‐AG044376‐01 &amp; Ferguson Foundation GrantQualitative and quantitative results show decreased disc proteoglycan content, including aggrecan, in aged PAPPA −/− mice.Figure 1Despite less proteoglycan content, aged PAPPA −/− mice had less fragmented aggrecan and lower levels of catabolic markers, MMP‐3 and ADAMTS‐4 compared to aged WT mice.Figure 2

The Birth of a Massive First-star Binary

Abstract We study the formation of massive Population III binary stars using a newly developed radiation hydrodynamics code with the adaptive mesh refinement and adaptive ray-tracing methods. We follow the evolution of a typical primordial star-forming cloud obtained from a cosmological hydrodynamics simulation. Several protostars form as a result of disk fragmentation and grow in mass by the gas accretion, which is finally quenched by the radiation feedback from the protostars. Our code enables us, for the first time, to consider the feedback by both the ionizing and dissociating radiation from the multiple protostars, which is essential for self-consistently determining their final masses. At the final step of the simulation, we observe a very wide (≳104 au) binary stellar system consisting of 60 and 70 M ⊙ stars. One of the member stars also has two smaller mass (10 M ⊙) companion stars orbiting at 200 and 800 au, making up a mini-triplet system. Our results suggest that massive binary or multiple systems are common among Population III stars.

13CH3OH Masers Associated With a Transient Phenomenon in a High-mass Young Stellar Object

Abstract We report the first detection of isotopic methanol (13CH3OH) maser emission in interstellar space. The emission was detected toward the high-mass young stellar object G358.93-0.03 during monitoring of a flare in the 6.7 GHz methanol (CH3OH) maser emission in this source. We find that the spectral and spatial distribution of the 13CH3OH masers differs from the CH3OH masers imaged at the same epoch, contrary to expectations from similarity of their pumping. This conclusively demonstrates that isotopic methanol masers are bright under different physical conditions and suggests that they can provide additional, complementary information to the CH3OH masers from the same source. We detect a rapid decay of the 13CH3OH maser lines suggesting that they are transient phenomena (masing for only a few months), likely associated with rapid changes in radiation field due to an accretion burst induced by massive disk fragmentation. Changes in the line flux density are faster than required to achieve equilibrium in the energy level populations, indicating that the pumping of these masers is likely variable.

Spiral arms and instability within the AFGL 4176 mm1 disc

We present high-resolution (30 mas or 130 au at 4.2 kpc) Atacama Large Millimeter/submillimeter Array observations at 1.2 mm of the disc around the forming O-type star AFGL 4176 mm1. The disc (AFGL 4176 mm1-main) has a radius of ∼1000 au and contains significant structure, most notably a spiral arm on its redshifted side. We fitted the observed spiral with logarithmic and Archimedean spiral models. We find that both models can describe its structure, but the Archimedean spiral with a varying pitch angle fits its morphology marginally better. As well as signatures of rotation across the disc, we observe gas arcs in CH3CN that connect to other millimetre continuum sources in the field, supporting the picture of interactions within a small cluster around AFGL 4176 mm1-main. Using local thermodynamic equilibrium modelling of the CH3CN K-ladder, we determine the temperature and velocity field across the disc, and thus produce a map of the Toomre stability parameter. Our results indicate that the outer disc is gravitationally unstable and has already fragmented or is likely to fragment in the future, possibly producing further companions. These observations provide evidence that disc fragmentation is one possible pathway towards explaining the high fraction of multiple systems around high-mass stars.

Are viruses associated with disc herniation? A clinical case series

BackgroundThere is some limited evidence for the presence of viruses in herniated disc material including a previous case series that claimed to provide “unequivocal evidence of the presence of herpes virus DNA in intervertebral disc specimens of patients with lumbar disc herniation suggesting the potential role of herpes viruses as a contributing factor to the pathogenesis of degenerative disc disease”. This study has not been replicated. The objective of our study was to determine if viruses were present in herniated disc fragments in participants with a prior history of back pain.MethodsWe recruited fifteen participants with a history of prior low-back pain prior to undergoing disc herniation surgery in the lumbar spine. Harvested disc samples were subject to next generation sequencing for detection of both RNA and DNA viral pathogens. Additionally, samples were analysed by a broadly reactive PCR targeting herpesviral DNA. Ethics approval was granted by the Human Research Ethics Committees of both Murdoch University, and St John of God Hospital, Western Australia.ResultsOf the fifteen research participants, 8 were female. Mean age was 49.4 years (SD 14.5 yrs) with a range of 24–70 years. All participants had prior back pain with mean time since first ever attack being 8.8 years (SD 8.8 yrs). No samples contained significant DNA sequences relating to known human viral agents. Inconsequential retroviral sequences were commonly found and were a mixture of putative animal and human retroviral protein coding segments. All samples were negative for herpesvirus DNA when analysed by pan-herpesvirus PCR.ConclusionsThis study found no viral pathogens in any intervertebral disc fragments of patients who had previous back pain and underwent discectomy for disc herniation and thus it is unlikely that viruses are associated with disc herniation, however given the contradiction between key studies enhanced replication of this experiment is recommended.

Minimally invasive anterior foraminotomy for cervical radiculopathy: how I do it.

The standard treatment for cervical radiculopathy is anterior discectomy and fusion. The authors describe a minimally invasive anterior cervical foraminotomy as a surgical option for direct nerve root decompression in cervical radiculopathy. Through a modified Smith-Robinson approach, the prevertebral fascia is mobilized laterally, displacing the sympathetic chain with it. A thumbnail size portion of the longus colli muscle is removed. A tubular retractor is placed, centered over the index uncovertebral joint. The lateral part of the joint is progressively drilled towards the foramen. After exposure of the intervertebral foramen, the perivascular ligamentous tissue is opened. Removal of disc fragments and osteophytes allows direct visualization and direct decompression of the nerve root. Anterior cervical foraminotomy is a safe "motion preserving" procedure for direct nerve decompression in selected patients with cervical radiculopathy that does not require cervical fusion.

Planet formation around M dwarfs via disc instability

Context. Around 30 per cent of the observed exoplanets that orbit M dwarf stars are gas giants that are more massive than Jupiter. These planets are prime candidates for formation by disc instability. Aims. We want to determine the conditions for disc fragmentation around M dwarfs and the properties of the planets that are formed by disc instability. Methods. We performed hydrodynamic simulations of M dwarf protostellar discs in order to determine the minimum disc mass required for gravitational fragmentation to occur. Different stellar masses, disc radii, and metallicities were considered. The mass of each protostellar disc was steadily increased until the disc fragmented and a protoplanet was formed. Results. We find that a disc-to-star mass ratio between ~0.3 and ~0.6 is required for fragmentation to happen. The minimum mass at which a disc fragment increases with the stellar mass and the disc size. Metallicity does not significantly affect the minimum disc fragmentation mass but high metallicity may suppress fragmentation. Protoplanets form quickly (within a few thousand years) at distances around ~50 AU from the host star, and they are initially very hot; their centres have temperatures similar to the ones expected at the accretion shocks around planets formed by core accretion (up to 12 000 K). The final properties of these planets (e.g. mass and orbital radius) are determined through long-term disc-planet or planet–planet interactions. Conclusions. Disc instability is a plausible way to form gas giant planets around M dwarfs provided that discs have at least 30% the mass of their host stars during the initial stages of their formation. Future observations of massive M dwarf discs or planets around very young M dwarfs are required to establish the importance of disc instability for planet formation around low-mass stars.

An Unusual Intraoperative Lumbar Disc Herniation Migrating into the Posterior Epidural Space

Background: The migration of a herniated fragment of the intervertebral disc towards posterior epidural space remains an exceptional phenomenon and Its clinical presentation is not unequivocal. Its diagnosis in modern imaging can cause confusion with other lesions of the posterior epidural space. We report an unusual migration of a herniated disc fragment into the posterior epidural. Method: we describe a case of an unusual migration of disc fragment into the posterior epidural space admitted in Neurosurgery department of University Teaching Hospital of Cotonou in 2019. Result: A 33-year-old man was admitted for progressive bilateral radiculopathy, gait disturbances and constipation. The clinical examination noted a moderate perineum and right buttock hypoesthesia, a flaccid paraparesis, bilatéral straight leg raising limitation (45°). The right patellar and achilean reflexes were depressed. MRI of the lumbar spine showed a right L4L5 herniated disc and its migration into the anterolateral epidural space. Surgery was performed with posterior approach. After an L4 and L5 laminectony, we discovered a very compressive large fragment of L4L5 intervertebral disc. The fragment was delicately dissociated from its dural adhesions. Histological examination confirmed the fibrocartilaginous nature of the sample. The post-operative period was uneventful. Three months post-operatively, he had regained his autonomy with a strength score of 5/5 in both pelvic limbs. Conclusion: Migration of intervertebral disc fragment into the posterior epidural space is a rare phenomenon. Diagnosis errors are possible. In case of posterior migration with cauda equina syndrom, we recommend laminectomy with removal of herniated disk fragment. This approach remains a simple and secure.

Concealed Intradural Disc Herniation: A Case Report

Introduction: We present a case of a concealed intradural lumbar disc herniation following a previous discectomy with adhesions of the ventral dura to the posterior longitudinal ligament. Case Presentation: A 40-year-old Asian male with a lumbar discectomy 2 years ago presented to our emergency department with over the last few days rapidly progressing neurological symptoms of the lower limbs. The patient was admitted and MRI was performed on an emergency basis. Due to severe pain, and as a result the patient inability to lie down to complete the MRI examination, the MRI scan was incomplete. However, it showed an occupying mass at the level L4/5 with suspected recurrent disc herniation. Intraoperative only a small herniation was found. A new MRI, performed shortly after the 1st surgery, revealed an intradural herniation that could be addressed by microscopic durotomy and sequestrectomy. Because of persisting weakness and pain a new MRI scan was done and revealed a recurrent intradural hernia proximal to the durotomy. Revision surgery was indicated and performed successfully. The 6 months follow-up MRI scan revealed no signs of recurrence. The clinical examination, 6 months postoperatively, showed almost complete remission of the preoperative weakness and pain with restoration of the walking ability. Discussion: Most literature addressing the pathophysiology of intradural lumbar disc herniation are cadaveric studies. Currently only few case reports or series discuss this pathology. Different theories including ‘mechanical compression’ and ‘adhesions’ theories have been discussed. A solid proof couldn’t be provided. Our patient had a previous discectomy at the same segment two years ago. The MRI scans could clearly show scar tissue on this level with a direct connection of the lumbar disc to the intradural compartment. We believe that extradural adhesions provided an access, through which disc fragments could migrate intradurally. Conclusion: Intradural disc herniation is a rare presentation and its diagnosis can be challenging. With rapidly progressing neurological symptoms and positive history for previous spinal surgery, intradural disc herniation should be kept in mind as an important differential diagnosis. Careful postoperative monitoring, and possibly early follow-up MRI, is needed to avoid missing a recurrent herniation or missed intradural disc fragments.

Percutaneous Endoscopic Transforaminal Approach for Far Lateral Lumbar Discectomy: 2-Dimensional Operative Video.

The conventional surgical approach to far lateral lumbar disk herniations is a paraspinal Wiltse approach. During the Wiltse approach, it is sometimes necessary to resect some of the facet or pars interarticularis to achieve an adequate exposure. The endoscopic transforaminal route can be of benefit in far lateral disk herniations due to direct access to the epidural space through Kambin's triangle, without the need for any bony removal or nerve retraction. In this video, we describe a percutaneous endoscopic transforaminal approach for far lateral discectomy in a patient presenting with a left L4 radiculopathy due to a far lateral L4-5 disk herniation. We describe Kambin's triangle anatomy and its relevance to the transforaminal route. The steps of the procedure are then described: dissection of soft tissue and removal of free disk fragments on the inferior aspect of the foramen far from the compressed exiting nerve route above to decrease the risk of retraction injury, gentle maneuvering of endoscope superiorly with removal of further compressive disk fragments, exposure of the exiting nerve root superiorly after adequate decompression is achieved and removal of any remaining fragments in close proximity to the nerve, and finally evaluation of traversing nerve root for any compressive lesions. The presentation ends with postoperative imaging confirming decompression of the far lateral disk herniation.

Migration of Giant Gaseous Clumps and Structure of the Outer Solar System

New data on the distribution of distant trans-Neptunian objects and on the properties of comets indicate the importance of dynamical processes in the outer part of the protoplanetary disk in the formation of the observed structure of the Solar system. In this paper, we examined the possible action of giant gaseous clumps, resulting from gravitational instability and fragmentation of circumstellar disks, on the orbital distribution of the population of small bodies in the outer Solar system. Basically, we studied those features of migration and gravitational interaction of giant clumps that were found previously by Vorobyov and Elbakyan (2018). Our modeling showed that the main features of the distribution of small bodies resulting from the gravitational influence of giant clumps are consistent with the observed orbital distribution of distant trans-Neptunian objects. The studied dynamical process associated with a single giant clump is very short-time event (no more than several tens of thousands of years). The main factor affecting the orbital distribution of small bodies is close encounters with giant clumps. A significant part of small bodies (comets) is very quickly transferred to distant orbits with large eccentricities, which allows them to avoid mutual collisions.

A New High-Speed Shielded Curved Device Allowing Safe Posterior Thoracic Discectomy Through a Modified Transforaminal Thoracic Interbody Fusion Approach: Technique Description and Case Series.

The appropriate approach for surgical removal of thoracic disc herniations is controversial. The posterior approach historically acquired a bad reputation due to high rates of neurologic deterioration subsequent to spinal cord manipulation. The anterior approach has consequently gained popularity but entails a larger magnitude of surgery if open and is technically demanding if approached thoracoscopically. Approaching the thoracic disc posteriorly following unilateral facetectomy and pediculectomy was suggested in 1978. This study presents a technique for posterior unilateral thoracic discectomy through a hemilaminectomy, unilateral facetectomy, and hemipediculectomy, facilitated by a novel curved dorsally shielded high-speed device. Introducing the device ventral to the dural sac allows removal of calcified and soft disc fragments without relying on forceful manual maneuvers and avoiding manipulation of the spinal cord. The maximal disc protrusion side is approached through a hemilaminectomy, unilateral facetectomy, and hemipediculectomy removing the superior half of the pedicle and exposing the disc transforaminally, allowing its removal using the device. Pedicle fixation and fusion concluded all procedures (TTIF). Between June 2014 and November 2018, 12 patients (6 men and 6 women) ages 23 to 74 years underwent posterior thoracic discectomy applying the above approach. The affected levels were D3 to D4 (1), D5 to D6 (1), D7 to D8 (1), D9 to D10 (1), D10 to D11 (3), D11 to D12 (4), and D12 to L1 (1). All patients presented with neurologic deterioration and all but 2 with pyramidal signs. All procedures were uneventful, without dural tears. None of the patients deteriorated neurologically. Average back pain visual analog scale scores decreased by 1.2, from 6.6 to 5.4. Average leg pain visual analog scale scores decreased by 2.2, from 6.6 to 4.4. Improvement was noted in Oswestry Disability Index scores and 6 SF-36 metrics. The new curved device and approach allow for a faster, safer thoracic disc herniation removal. The proposed technique allows a safer treatment for thoracic disc herniations, reducing complication rates and improving patient outcome.