Residual Disc Research Articles

Comparison of Percutaneous Endoscopic Transforaminal Discectomy, Chemonucleolysis, Microdiscectomy, and Microendoscopic Discectomy for Symptomatic Lumbar Disc Herniation: One-year Follow-up Clinical Results and Disc Degeneration.

This study compared the 1-year clinical outcomes and disc degeneration rates after transforaminal full-endoscopic lumbar discectomy (TF-FED), condoliase injection, open discectomy (OD), and microendoscopic discectomy (MED) for lumbar disc herniation (LDH). In total, 279 patients with LDH were divided into four treatment groups: TF-FED, OD, MED, and condoliase injection. Outcomes were evaluated on the basis of the complication rate, Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ), visual analog scale (VAS) scores, and the modified MacNab criteria. Surgical and hospital costs were assessed. Disc degeneration and endplate bone marrow edema were evaluated using magnetic resonance images. The mean postoperative JOABPEQ, VAS, or modified MacNab scores among the four groups had no significant differences. Additionally, the nerve injury or reoperation rate among the TF-FED, OD, and MED groups had no significant difference. However, the reoperation rate with condoliase injection was high because of residual disc herniation. Surgical and hospital costs were lower with condoliase injection and higher with OD and MED than those with TF-FED. With TF-FED and condoliase injection, the Pfirrmann grade progressed, and the disc height was significantly smaller than that with OD and MED. Endplate bone marrow edema was more common with condoliase injection and TF-FED. All groups had good outcomes. TF-FED and condoliase injection may reduce the burden of surgery because they can be performed under local anesthesia with little blood loss and low medical costs but tend to be associated with disc degeneration and endplate bone marrow edema. A randomized controlled study with a larger sample is needed.

Can optic disc vessel density help in cases of residual disc elevation after shunt surgery in cases of idiopathic intracranial hypertension?

AimTo detect if we can use the reduction in the optic disc vessel density as an indicator to the reduction in intracranial tension in patients with residual optic disc elevation after shunt surgery as fundus examination in those cases is not conclusive.Patients and method21 patients with papilledema due to idiopathic intracranial hypertension underwent shunt surgery. Full neurological and ophthalmological assessments were done. The optic disc vessel density was measured before and 3 months after surgery. Patients were then divided according to the resolution of papilledema into 2 groups: 1) Residual disc elevation group. 2) Completely resolved disc edema group. CSF pressure was measured via lumber puncture preoperative for all patients and 3 months post-operative only for patients with residual disc edema. A comparison between both groups was done.ResultsThere was a highly statistically significant difference between the two groups as regard the papilledema grade (the residual disc elevation group had a higher grade of papilledema) with P-value=0.000. As regard the difference in the preoperative optic disc vessel density between the two groups, there were statistically significant differences (optic disc vessel density was more in the residual disc elevation group). As regard the postoperative optic disc vessel density, there were non-significant differences between the two groups in whole image, inside disc and peripapillary vessel density (either in macro or microvasculature).ConclusionThe optic disc vessel density decreased with normal postoperative CSF opening pressure in cases with residual disc elevation postoperatively. Thus, in cases of residual optic disc swelling after shunt surgery, we can detect the reduction of intracranial pressure by the reduction in the optic disc vessel density which is a safe non-invasive technique. That may help in cases of residual disc elevation.

Transforaminal endoscopic lumbar discectomy with two-segment foraminoplasty for the treatment of very highly migrated lumbar disc herniation: a retrospective analysis.

The surgical resection of very highly migrated lumbar disc herniation (VHM-LDH) is technically challenging owing to the absence of technical guidelines. Hence, in the present study, we introduced the transforaminal endoscopic lumbar discectomy (TELD) with two-segment foraminoplasty to manage VHM-LDH and evaluated its radiographic and midterm clinical outcomes. The present study is a retrospective analysis of 33 consecutive patients with VHM-LDH who underwent TELD with two-segment foraminoplasty. The foraminoplasty was performed on two adjacent vertebrae on the basis of the migration direction of disc fragments to fully expose the disc fragments and completely decompress the impinged nerve root. The operation duration, blood loss, intra- and postoperative complications, and recurrences were recorded. Additionally, imageological observations were evaluated immediately after the procedure via magnetic resonance image and computerized tomography. Clinical outcomes were evaluated by calculating the visual analog scale (VAS) score and Oswestry Disability Index (ODI). The MacNab criterion was reviewed to assess the patients' opinions on treatment satisfaction. The resection rate of bony structures were quantitatively evaluated on postoperative image. The segmental stability was radiologically evaluated at least a year after the surgery. Additionally, surgery-related and postoperative complications were evaluated. The average age of the patients was 56.87 ± 7.77 years, with a mean follow-up of 20.95 ± 2.09 months. The pain was relieved in all patients immediately after the surgery. The VAS score and ODI decreased significantly at each postoperative follow-up compared with those observed before the surgery (P < 0.05). The mean operation duration, blood loss, and hospital stay were 56.17 ± 16.21min, 10.57 ± 6.92 mL, and 3.12 ± 1.23 days, respectively. No residual disc fragments, iatrogenic pedicle fractures, and segmental instability were observed in the postoperative images. For both up- and down- migrated herniation in the upper lumbar region, the upper limit value of resection percentage for the cranial SAP, caudal SAP, and pedicle was 33%, 30%, and 34%, respectively; while those in the lower lumbar region was 42%, 36%, and 46%, respectively. At the last follow-up, the satisfaction rate of the patients regarding the surgery was 97%. Surgery-related complications including dural tear, nerve root injury, epidural hematoma, iatrogenic pedicle fractures, and segmental instability were not observed. One patient (3%) suffered from the recurrence of LDH 10 months after the initial surgery and underwent revision surgery. The TELD with two-segment foraminoplasty is safe and effective for VHM-LDH management. Proper patient selection and efficient endoscopic skills are required for applying this technique to obtain satisfactory outcomes.

Use of minimally invasive ultrasound transducer during tubular microdiscectomy.

Minimally invasive ultrasound during tubular microdiscectomy is novel. The authors report the technique during surgery for L5-S1 herniated disc. Ultrasound provided real-time visualization of the pathology and neural elements. After discectomy and tactile assessment, ultrasound showed decompression of the thecal sac and traversing nerve root. The patient tolerated the procedure well, with resolution of preoperative pain and strength improvement. Postoperative MRI revealed a residual asymptomatic disc fragment that was retrospectively identified on ultrasonography. Minimally invasive ultrasound could become a useful supplement to direct visual and tactile assessment during tubular microdiscectomy, but further experience with surgical anatomy on ultrasound is required. The video can be found here: https://stream.cadmore.media/r10.3171/2024.1.FOCVID23206.

Lumbar percutaneous transforaminal endoscopic discectomy: a retrospective survey on the first 172 adult patients treated in Denmark

PurposeTo evaluate patient demographics, surgery characteristics, and patient-reported clinical outcomes related to the implementation of lumbar PTED in Denmark by surgeons novice to the PTED technique.MethodsAll adult patients treated with a lumbar PTED from our first surgery in October 2020 to December 2021 were included. Data was generated by journal audit and telephone interview.ResultsA total of 172 adult patients underwent lumbar PTED. Surgery duration was a median of 45.0 (35.0–60.0) minutes and patients were discharged a median of 0 (0–1.0) days after. Per operatively one procedure was converted to open microdiscectomy due to profuse bleeding. Post operatively one patient complained of persistent headache (suggestive of a dural tear), two patients developed new L5 paresthesia, and three patients had a newly developed dorsal flexion paresis (suggestive of a root lesion). Sixteen patients did not complete follow-up and 24 (14.0%) underwent reoperation of which 54.2% were due to residual disk material. Among the remaining 132 patients, lower back and leg pain decreased from 7.0 (5.0–8.5) to 2.5 (1.0–4.5) and from 8.0 (6.0–9.1) to 2.0 (0–3.6) at follow-up, respectively (p < 0.001). Additionally, 93.4% returned to work and 78.8% used less analgesics. Post hoc analysis comparing the early half of cases with the latter half did not find any significant change in surgery time, complication and reoperation rates, nor in pain relief, return to work, or analgesia use.ConclusionClinical improvements after lumbar PTED performed by surgeons novel to the technique are satisfactory, although the reoperation rate is high, severe complications may occur, and the learning curve can be longer than expected.

Binary Coalescences as Sources of Ultrahigh-Energy Cosmic Rays.

Binary coalescences are known sources of gravitational waves (GWs) and they encompass combinations of black holes (BHs) and neutron stars (NSs). Here we show that when BHs are embedded in magnetic fields (B's) larger than approximately 10^{10} G, charged particles colliding around their event horizons can easily have center-of-mass energies in the range of ultrahigh energies (≳10^{18} eV) and become more likely to escape. Such B-embedding and high-energy particles can take place in BH-NS binaries, or even in BH-BH binaries with one of the BHs being charged (with charge-to-mass ratios as small as 10^{-5}, which do not change GW waveforms) and having a residual accretion disk. Ultrahigh center-of-mass energies for particle collisions arise for basically any rotation parameter of the BH when B≳10^{10} G, meaning that it should be a common aspect in binaries, especially in BH-NS ones given the natural presence of a B onto the BH and charged particles due to the magnetosphere of the NS. We estimate that the number of ultrahigh center-of-mass collisions ranges from a few up to millions before the merger of binary compact systems. Thus, binary coalescences may also be efficient sources of ultrahigh energy cosmic rays (UHECRs) and constraints to NS/BH parameters would be possible if UHECRs are detected along with GWs.

A rare case of intervertebral disc calcification combined with ossification of the posterior longitudinal ligament in a child: a case report and literature review

BackgroundIntervertebral disc calcification (IDC) combined with calcification in children has been sporadically reported, while ossification of the posterior longitudinal ligament (OPLL) in the cervical spine in pediatric patients is exceedingly rare. The aim of this study is to investigate the potential prognosis and outcomes associated with this condition.Case presentationWe present an unusual case involving a 10-year-old Chinese child diagnosed with calcified cervical disc herniation and ossification of the posterior longitudinal ligament. Conservative treatment measures were implemented, and at the 1-month and 6-month follow-up, the patient's pain exhibited significant improvement. Subsequent cervical MRI and CT scans revealed the complete disappearance of OPLL and substantial absorption of the calcified disc. During the three-month follow-up, CT demonstrated slight residual disc calcification, however, the patient remained asymptomatic with no discernible limitation in cervical motion.ConclusionsWe conducted a comprehensive review of several cases presenting with the same diagnosis. It is noteworthy that IDC combined with OPLL in children constitutes a rare clinical entity. Despite imaging indications of potential spinal canal occupation, the majority of such cases demonstrate complete absorption following conservative treatment, with OPLL exhibiting a faster absorption rate than calcified discs.

Intraoperative changes of surgical approach and a second surgery after percutaneous endoscopic surgery for lumbar spinal stenosis

ObjectiveTo investigate the reasons for a second surgery after Percutaneous Endoscopic Surgery (PES) for lumbar spinal stenosis and to provide references for the choice of indications and appropriate surgical approach. MethodA total of 426 patients received PES for lumbar spinal stenosis. The postoperative, intraoperative, and postoperative data of the subjects were analyzed. The reasons for intraoperative difficulties, poor outcomes after surgery, and a second surgery were analyzed. ResultThe surgical approach was changed in four out of 426 patients (0.94 %) during surgery, and 6 patients (1.4 %) received a second surgery; 3 out of 4 patients were intraoperatively shifted to PIED using the Delta endoscope, and 1 shifted to ordinary PIED. The reasons for the intraoperative change of surgical approach included severe hyperplasia and obscure anatomic structure in 3 patients and a dural sac tear with neural outflow in 1 patient. The reasons for a second surgery in 19 patients were as follows: nerve entrapment by bone fragments in 1 patient; nerve injury in 3 patients; lumbar instability in 3 patients; untreated or residual Lumbar Intervertebral Disc Herniation (LIDH) in 4 patients; recurrent LIDH in 1 patient; and inadequate decompression in 7 patients. ConclusionSevere hyperplasia, obscure anatomic structure, lumbar instability, and nerve injury are the common reasons for a second surgery after PES for lumbar spinal stenosis. Appropriate indications and surgical approaches can be chosen based on the patient's situations and technical conditions.

Video telescope operating monitor-assisted surgery is equivalent to conventional surgery in treatment of cervical intervertebral disc herniation in dogs.

To compare the use of the video telescope operating monitor (VITOM) and use of a conventional unassisted surgical method for treatment of cervical intervertebral disc herniation in dogs. 39 dogs with cervical intervertebral disc disease. Prospective study. Dogs were prospectively nonrandomly assigned to either the VITOM (n = 19) or conventional surgery (20) group depending on VITOM system availability. Signalment and preoperative neurologic status were recorded for all dogs. Preoperative and postoperative CT myelography was performed to compare intervertebral space location, spinal cord dimensions at the decompression level, ventral slot dimensions, and residual disc material. Surgical complications and postoperative neurologic outcomes were recorded. Data were compared between the 2 groups using fixed-effects or mixed-effects models to consider double reading of CT myelography images. No significant differences were noted between the 2 groups regarding the decompression ratio (P = .85), vertebral length body ratio (P = .13), ventral slot width ratio (P = .39), residual disc material (P = .30), and sinus bleeding (P = .12). No significant differences were found between the 2 groups regarding postoperative neurologic grade (P = .17). VITOM-assisted ventral slot decompression is equivalent to conventional surgery in treatment of cervical intervertebral disc herniation in dogs. The use of VITOM remains a good alternative to the conventional surgical method.

Anterior cervical discectomy and fusion for the treatment of giant cervical disc herniation

ObjectiveGiant cervical disc herniation (GCDH) was defined as a herniated intervertebral disc that accounted for more than 50% of the spinal canal. The purpose of this study was to analyse the feasibility of anterior cervical discectomy and fusion (ACDF) for the treatment of GCDH.MethodsPatient demographic and imaging data, clinical results, and perioperative complications were analysed retrospectively.ResultsA total of 23 patients were included in the study. Spinal cord recovery pulsation was observed under a microscope in all cases. Postoperative magnetic resonance imaging showed complete decompression of the spinal cord and no residual intervertebral disc. The patients were followed up for 12 to 18 months. The average visual analogue scale score and Neck Disability Index decreased from 8.6 ± 0.5 and 86.0 ± 2.7% to 2.2 ± 0.2 and 26.7 ± 2.0%, respectively, three days after surgery. The average Japanese Orthopedic Association score increased from 6.9 ± 2.1 to 13.9 ± 1.1. The cervical spinal cord function improvement rate was 69.3%. No neurological complications after surgery were observed.ConclusionThis study shows that ACDF is feasible for the treatment of GCDH disease. The results indicate that this approach can be used to safely remove herniated disc fragments, effectively relieve compression of the spinal cord, and improve neurological function.

MLP-Res-Unet：MLPs and residual blocks-based U-shaped network intervertebral disc segmentation of multi-modal MR spine images.

Intervertebral disc degeneration (IVD) is now the most prevalent disease in the world; thus, precise intervertebral disc segmentation is essential for the assessment and diagnosis of spinal diseases. Multi-modal magnetic resonance (MR) imaging is more multi-dimensional and thorough than unimodal imaging. However, manual segmentation of multi-modal MRI not only imposes a huge burden on physicians but also has a high error rate. In this study, we propose a new method that can efficiently and accurately segment intervertebral discs from multi-modal MR spine images, providing a reproducible usage scheme for the diagnosis of spinal disorders. We suggest a network structure called MLP-Res-Unet that reduces the amount of computational load and the number of parameters while maintaining performance. Our contribution is two-fold. First, a medical image segmentation network that fuses residual blocks and a multilayer perceptron (MLP) is proposed. Secondly, we design a new deep supervised method and pass the features extracted from the encoder to the decoder through the residual path to achieve a new full-scale residual connection. We evaluate the network on the MICCAI-2018 IVD dataset and obtain Dice similarity coefficient equal to 94.77 (%) and Jaccard coefficient equal to 84.74 (%), while we reduce the amount of parameters by a factor of 3.9 and computation by a factor of 2.4 compared to the IVD-Net. Experiments show that MLP-Res-Unet improves segmentation performance and creates a simpler model structure while reducing the number of parameters and computation.

The effect of subcutaneous fat and skin-to-lamina distance on complications and functional outcomes of minimally invasive lumbar decompression.

Minimally invasive lumbar decompression (MIS) in obese pzatients is technically challenging due to the use of longer tube retractors. The purpose of this study was to evaluate the impact of the thickness of the soft tissue and subcutaneous fat on complications, revisions, and patient-reported functional outcomes after MIS. This is a retrospective analysis of 148 consecutive patients who underwent minimally invasive lumbar decompression at our institute between 2013 and 2017 and had at least one year of follow-up. Analysis was performed five times, each time the study group was defined by another measure of adiposity: BMI > 30, skin to lamina distance at the site of surgery and at L4 > 6 cm, and subcutaneous fat thickness at the site of surgery and at L4 > 3 cm. Outcomes included intraoperative complications (durotomy or neurological deficit), possibly inadequate decompression (residual disc, reoperation), length of stay, return to the emergency room or readmission, postoperative medical complications, and functional outcomes: visual analog scores for back and leg pain, and Oswestry Disability Index (ODI). Patients with a thicker layer soft tissue had a significantly higher burden of comorbidities than controls, including higher prevalence of cardiovascular disease (p = 0.002), diabetes (p < 0.001), hypertension (p < 0.001) and higher ASA scores (p = 0.002). Nevertheless, there was no significant difference between the patient groups in surgical and medical complications, functional outcomes, and other assessed outcomes. Our results indicate that minimally invasive lumbar decompression is safe and effective for patients with a thick layer of soft tissue and subcutaneous fat.

A case of Takayasu's arteritis and thoracic-abdominal pseudoaneurysm with vertebral destruction.

A 27-year-old woman presented to our institution with diagnosis of Takayasu’s arteritis and thoracic-abdominal pseudoaneurysm with vertebral destruction. Computed tomography revealed a giant 8 × 8 × 14 cm pseudoaneurysm with erosions of thoracic vertebrae 10, 11, and 12 (Figure 1 Panel A to C show CT image reconstruction; yellow arrow shows the pseudoaneurysm; arrow in Panel B shows the vertebral erosions in Figure 1 Panel C shows the ventral compensatory circulation caused by severe stenosis of the aorta). After a 4-week corticosteroid therapy, the descending thoracic-abdominal aorta grafting was performed. Intraoperatively serious vertebral body erosion was observed. More interestingly, the erosions on intervertebral disc were relatively mild which was rarely mentioned before (Figure 1 Panel D shows the direct vision of vertebral destruction; arrow shows the residual intervertebral disc). It suggested that compared with well-vascularized vertebral body, the avascular intervertebral disc with intact fibrous ring showed better erosion resistance. Considering this patient’s general condition, vertebral reconstruction was performed 3 weeks later, and patient discharged uneventfully in 2 weeks.

Development and Designing an Adjustable Metal Cut off Machine

Nowadays metal-cutting equipment is in demand in the market because of the different construction process not only on this infrastructure but also on the training process of different schools that offer qualification under the metals and engineering sector. Cutting these metals may also affect the budgetary cost of the output. Cut off machines are commonly used for this purpose. Cut off machines that are produced in the industry seem to be more expensive not just because of the parts but also because of the use of the consumption of the disc. Cut off machines uses #14 cut off disc. After using it there is always a residual disc that is having a diameter of 12 cm. This residual disc is almost the size of the disc of an angle grinder which is having a #7 cutting discs that almost cost 80 pesos. Also, this cut off machine cannot cut at your desired angle. Upon this issue, the researcher came up with developing and designing an adjustable metal cutter that can maximize the use of the disc and can cut at a different angle, As the result of the project almost 6 cm diameter was the maximum size of the waste disc. This machine can be used in the metals and engineering sector, specifically in SMAW, welding shops, construction companies, and others related to metal workings. This has also become economical because some parts of the machine are recyclable materials. A full factorial design of the experiment is selected for experimental planning and the analysis of variance (ANOVA) has been employed. Upon the evaluation, the adjustable metal cut off machine passed the level of (1) acceptability (2) functionality and (3) safety of the product.

Clinical and radiologic outcomes of biportal endoscopic lumbar discectomy in obese patients: a retrospective case-control study

BackgroundObese patients have a higher risk of complications during spinal surgery than non-obese patients. To the best of our knowledge, no studies have examined the differences in clinical and radiological outcomes after biportal endoscopic lumbar discectomy (BELD) between obese and non-obese patients. The study evaluated the association between obesity and outcomes after BELD in patients with lumbar disc herniation.MethodsThis was a retrospective case-control study conducted from March 2017 to March 2021 at two hospitals with 360 patients who underwent BELD after showing no improvement with conservative treatment. Clinical and radiologic outcomes were retrospectively analyzed after BELD in the non-obese (body mass index [BMI] < 30 kg/m2) and obese (BMI ≥ 30 kg/m2) groups. Demographic data and surgery-related factors were compared between the two groups. Clinical outcomes were followed up for 12 months after surgery and analyzed for differences.ResultsA total of 211 patients were enrolled in this study, and through case-control matching, the data of 115 patients (29, obese group; 86, non-obese group) were analyzed. The two groups showed no significant differences in Oswestry Disability Index, European Quality of Life-5 Dimensions (EQ-5D), and visual analog scale scores measured immediately after BELD and 12 months after surgery. After surgery, back pain, radiating leg pain, and EQ-5D scores improved. However, there was no significant difference in improvement, residual herniated disc, hematoma, or recurrence between the groups.ConclusionsObese patients who underwent BELD for lumbar disc herniation showed no significant difference in clinical and radiologic outcomes compared with non-obese patients.

Radiation Exposure during Fluoroscopy-Guided Ozone Chemonucleolysis for Lumbar Disc Herniation.

Introduction: Radiation exposure is a frequent drawback of spinal surgery, even if X-ray guidance plays a pivotal role in improving the accuracy and safety of spinal procedures. Consequently, radiation protection is essential to reduce potential negative biological effects. The aim of this study was to evaluate patients’ radiation exposure, the radiation dose emission during fluoroscopy-guided ozone chemonucleolysis (OCN), and the potential role of patient characteristics. Methods: The radiation dose emission reports were retrospectively evaluated in patients who underwent single-level OCN for lumbar disc herniation. A generalized linear model (GLM) with a gamma distribution and log link function was used to assess the association between radiation emission and patients’ characteristics such as age, sex, BMI, level of disc herniation, disc height, and site of disc herniation. Results: Two hundred and forty OCN cases were analyzed. A safe and low level of radiation exposure was registered during OCN. The median fluoroscopy time for OCN was 26.3 (19.4−35.9) seconds, the median radiation emission dose was 19.3 (13.2−27.3) mGy, and he median kerma area product (KAP) was 0.46 (0.33−0.68) mGy ⋅ m2. The resulting KAP values were highly dependent on patient variables. In particular, sex, obesity, and residual disc height < 50% significantly increased the measured KAP, while levels of disc herniations other than L5-S1 reduced the KAP values. Conclusions: The radiation exposure during OCN is low and quite similar to a simple discography. However, patient characteristics are significantly related to radiation exposure and should be carefully evaluated before planning OCN.

Can scallop-shell stars trap dust in their magnetic fields?

ABSTRACT One of the puzzles to have emerged from the Kepler and TESS missions is the existence of unexplained dips in the light curves of a small fraction of rapidly rotating M dwarfs in young open clusters and star-forming regions. We present a theoretical investigation of one possible explanation – that these are caused by dust clouds trapped in the stellar magnetic fields. The depth and duration of the observed dips allow us to estimate directly the linear extent of the dust clouds and their distances from the rotation axis. The dips are found to be between 0.4 and 4.8 per cent. We find that their distance is close to the co-rotation radius: the typical location for stable points where charged particles can be trapped in a stellar magnetosphere. We estimate the charge acquired by a dust particle due to collisions with the coronal gas and hence determine the maximum grain size that can be magnetically supported, the stopping distance due to gas drag, and the time-scale on which dust particles can diffuse out of a stable point. Using the observationally derived magnetic field of the active M dwarf V374 Peg, we model the distribution of these dust clouds and produce synthetic light curves. We find that for 1μm dust grains, the light curves have dips of 1–3 per cent and can support masses of order of 1012 kg. We conclude that magnetically trapped dust clouds (potentially from residual disc accretion or tidally disrupted planetesimal or cometary bodies) are capable of explaining the periodic dips in the Kepler and TESS data.

Reduction of the Mass of the Main Asteroid Belt and the Mars Zone due to Solar Radiation and the Influence of Jupiter—II: Scenario of the Evolution of the Residual Disk Density

Reduction of the Mass of the Main Asteroid Belt and the Mars Zone due to Solar Radiation and the Influence of Jupiter—II: Scenario of the Evolution of the Residual Disk Density

Gap opening by planets in discs with magnetized winds

ABSTRACT Planets open deep gaps in protoplanetary discs when their mass exceeds a gap opening mass, Mgap. We use one- and two-dimensional simulations to study planet gap opening in discs with angular momentum transport powered by MHD disc winds. We parametrize the efficiency of the MHD disc wind angular momentum transport through a dimensionless parameter αdw, which is an analogue to the turbulent viscosity αv. We find that magnetized winds are much less efficient in counteracting planet tidal torques than turbulence is. For discs with astrophysically realistic values of αdw, Mgap is always determined by the residual disc turbulence, and is a factor of a few to ten smaller than usually obtained for viscous discs. We introduce a gap opening criterion applicable for any values of αv and αdw that may be useful for planet formation population synthesis. We show that in discs powered by magnetized winds growing planets detach from the disc at planet masses below $\sim 0.1{\, {\rm M}_{\rm J}}$ inside 10 au. This promotes formation of super-Earth planets rather than gas giants in this region, in particular precluding formation of hot jupiters in situ. On larger scales, ALMA gap opening planet candidates may be less massive than currently believed. Future high-resolution observations with instruments such as the extended ALMA, ngVLA, and SKA are likely to show abundant narrow annular features at R &amp;lt; 10 au due to ubiquitous super-Earth planets.

Ultrasonic spine surgery for every thoracic disc herniation: a 43-patient case series and technical note demonstrating safety and efficacy using a partial transpedicular thoracic discectomy with ultrasonic aspiration and ultrasound guidance.

Thoracic disc herniations (TDHs) are a challenging pathology. A variety of surgical techniques have been used to achieve spinal cord decompression. This series elucidates the versatility, efficacy, and safety of the partial transpedicular approach with the use of intraoperative ultrasound and ultrasonic aspiration for resection of TDHs of various sizes, locations, and consistencies. This technique can be deployed to safely remove all TDHs. A retrospective review was performed of patients who underwent a thoracic discectomy via the partial transpedicular approach between January 2014 and December 2020 by a single surgeon. Variables reviewed included demographics, perioperative imaging, and functional outcome scores. A total of 43 patients (53.5% female) underwent 54 discectomies. The most common presenting symptoms were myelopathy (86%), motor weakness (72%), and sensory deficit (65%) with a symptom duration of 10.4 ± 11.6 months. A total of 21 (38.9%) discs were fully calcified on imaging and 15 (27.8%) were partially calcified. A total of 36 (66.7%) were giant TDHs (> 40% canal compromise). The average operative time was 197.2 ± 77.1 minutes with an average blood loss of 238.8 ± 250 ml. Six patients required ICU stays. Hospital length of stay was 4.40 ± 3.4 days. Of patients with follow-up MRI, 38 of 40 (95%) disc levels demonstrated < 20% residual disc. Postoperative Frankel scores (> 3 months) were maintained or improved for all patients, with 28 (65.1%) patients having an increase of 1 grade or more on their Frankel score. Six (14%) patients required repeat surgery, 2 of which were due to reherniation, 2 were from adjacent-level herniation, and 2 others were from wound problems. Patients with calcified TDHs had similar improvement in Frankel grade compared to patients without calcified TDH. Additionally, improvement in intraoperative neuromonitoring was associated with a greater improvement in Frankel grade. The authors demonstrate a minimally disruptive, posterior approach that uses intraoperative ultrasound and ultrasonic aspiration with excellent outcomes and a complication profile similar to or better than other reported case series. This posterior approach is a valuable complement to the spine surgeon's arsenal for the confident tackling of all TDHs.